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#47749 - 02/09/09 06:57 PM tossing around the idea of efi for my 235
drummin52 Offline
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Registered: 04/23/08
Posts: 104
Loc: Wapwallopen, Pa
After reading all these threads on here and a few other forums (stovebolt, hotrodders, etc) I began tossing around the idea of converting my 235 to electronic fuel injection. Currently I have a clifford 2/4bbl intake with a 4bbl adapter and holley 390cfm carb so I have the intake manifold covered for such a conversion. What parts would I need for this conversion. I would hope most of it would be able to come from donor vehicles as I live very close to a u-pull-it yard and can easily and very cheaply get almost any part needed. Is there a TBI unit that would bolt onto my intake manifold and be sized properly for a 235? Im good with electronics and wiring and have a good understanding of computerized engine controls so getting and making a ecm to work shouldn't be too much of a challenge.

List of current engine mods are clifford tube style headers and a H.E.I. Conversion (modified GM 250 distributor)
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47759 - 02/10/09 04:15 AM Re: tossing around the idea of efi for my 235 [Re: drummin52]
243 Offline
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Registered: 05/15/08
Posts: 4
Loc: TX
drummin,

Here is a link to a good article on retrofitting an AMC 258 with a GM TBI. I bought a complete 89 TBI 350 for my CJ and then, while mocking up the motor, trans and xfer case I said to myself, "if a 258 fell into my hands in the next two days I would use that." And two days later it happened. So the 350 will live under the bench until the next project and the TBI is for the 258.

It is very ironic that I turned my nose up at hundreds of I6 cars and trucks over the last 20 years because I wanted a V8, now I can't find the next project because everybody has converted them to a V8!

http://www.bustedjeep.com/projects/junkyardtbi.asp

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#47776 - 02/10/09 09:17 AM Re: tossing around the idea of efi for my 235 [Re: 243]
drummin52 Offline
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Registered: 04/23/08
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Loc: Wapwallopen, Pa
thanks that was very informing
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Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47785 - 02/10/09 04:52 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
Beater of the Pack Offline
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I just bumped a thread back up that has a list of what you need from a donor. Good luck!" TBI on A 250"
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#47787 - 02/10/09 05:47 PM Re: tossing around the idea of efi for my 235 [Re: Beater of the Pack]
drummin52 Offline
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Loc: Wapwallopen, Pa
thanks

looks like I will be waiting for the local yard to have a sale so I can get what I need even cheaper. Currently looking at about 50-60 for everything I would need. Includes TBI unit, computer, wiring harness and all sensors (not really charged for sensors). I already have a gm 250 distributor on my 235, I hopefully will be able to swap out the inner parts so the computer can control timing advance.

My brother has a engine computer diagnostic tool and a tuner program on the laptop so I mess around with the program if needed. I believe I read that the vss and egr program need to be removed.

I have a friend that runs a laser cutter that once I design the tbi adapter will be able to cut me out the adapter out of 1/2" steel or aluminum.

I currently have a brand new holley 390cfm carb on my 235 but if I get this to work I will put it away for a future project or see if I can find a taker for it. Its already modified (jets and nozzles) to work for a 235/261.
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47789 - 02/10/09 06:52 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
Beater of the Pack Offline
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Sounds like you're starting down the road I started on about a year or so ago. Wave when you go by! \:D


Edited by Beater of the Pack (02/10/09 06:53 PM)
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#47797 - 02/11/09 03:16 AM Re: tossing around the idea of efi for my 235 [Re: Beater of the Pack]
drummin52 Offline
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Registered: 04/23/08
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Loc: Wapwallopen, Pa
yeah hopefully its a good road to head down. I figured Im already doing alot of modifying to my 52 Chevy 3/4ton pickup, why not go a step further and add fuel injection to the 54 235 inline 6 thats in it. That should make it stand out just that much more at car shows and gatherings. 1 no v8, instead a engine, a inline 6 of the trucks era with a bunch of speeed parts and custom modifications like power steering and so on. Adding throttle body injection is just icing on the cake.
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47805 - 02/11/09 09:29 AM Re: tossing around the idea of efi for my 235 [Re: drummin52]
Nexxussian Offline
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drummin 52, welcome.

I read that you have an intake already and it's setup for a 4bbl.

I thought I should forward that it was suggested to me that if I wanted a few more style points I could do more or less the same thing with the substitution of 2 single barrel throttle bodies on a multi carb manifold (ie offy dual carb).

It was suggested that if you wired one throttle body up with the idle air control, plugged it off in the other you could run straight linkage between the two TBI units the computer wouldn't know the difference.

I mention this as you spoke of astetics being one of your motivating factors (since 2 'carbs' look cooler than 1 ).

If you are interested I will try to find where I was told that (it was on here).

I haven't tried this, I have a 1950 Jimmy with the OE 228 I have been toying with the idea of doing this with. That and moving that smelly gas tank out of the cab.

Of course that's not happening any time soon (too much other stuff going on at the moment).
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My, what a steep learning curve. Erik II#5155

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#47809 - 02/11/09 11:31 AM Re: tossing around the idea of efi for my 235 [Re: Nexxussian]
drummin52 Offline
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Loc: Wapwallopen, Pa
I agree, two 2bbl tbi units on a dual intake would look awesome, in fact this person is currently doing that. But since I already spent the money on the clifford intake and such, that is what I will stay with. Plus it will be easier to just have 1 unit instead of two and cheaper as I know the local yard has tons of 4.3L's with throttle body injection and the vehicles to get the wiring, sensors and computer off of.

Luckly I already removed the gas tank from the cab and installed a summit fuel cell under the bed, behind the rear axle. Another plus is I already have 10AN steel braided fuel line running up to the mechanical pump on the 235. All I would need is a external mounted pump somewhere inline and a little changing around under the hood to bypass the mechanical pump. Maybe mount the pressure regulator down by the mechanical pump, like on the frame, with a steel line for the return. I'm going to try to set everything up where I do not have to butcher my current setup so that if I go back to carburated I don't need to redo what is alread done.
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47824 - 02/11/09 10:54 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
efi-diy Offline
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A couple of notes..

1) mount the pump as close to the tank as you can with a EFI fuel filter before and after the pump (unless the tank has a pickup strainer - if so then omit the inlet filter. If your get the Earls AN to snaginaw adapters then you can use the GM TBI fuel filters same type that on the donor.

2) GM TBI's have the pressure regulator built in :).

3) The 4.3 TBI should be fine if you can tune the ECM. If you run the GM ECM it'll probably idle rich until its tuned.. kind of like Tom's truck when we did the impromptu EFI conversion at B'Ville last year. the cause was was a horrible vacuum leak that caused the MS to think the throttle was near WOT when it wasn't so it was dumping fuel in. It took some fast fingers to lean it out before it stalled.

4) holley sells a TBI to 4bbl adapter for about $30.

5) Er -6 line is plenty big. For low buck use a single braid hydraulic hose.. no need to spend $$$ on the fancy stuff. Both the feed and return need to be braided in case the return line ever plugs up the line pressure will rocket up > 50 psi.

Have you consider what your going to run for the ECM?

If you decide to run a MS with the GM '747 adapter board it just plugs into the GM harness with no modes and you can tune it with a laptop much much faster than guessing at a change and then burning eproms. :(-

Ask either Tom or myself if you need help...


Edited by efi-diy (02/11/09 11:20 PM)
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#47827 - 02/12/09 04:51 AM Re: tossing around the idea of efi for my 235 [Re: efi-diy]
drummin52 Offline
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Loc: Wapwallopen, Pa
So I can go directly from the post fuel filter directly to the tbi unit? And then another line, size ?" comes out and runs back to the tank???

For the adapter I may just make my own as the clifford intake is quite simple, just 4 allen key screws hold the plate on. Just need to remove my 4bbl adapter. I have some 1/2" aluminum plate that I can have a friend cut the adapter out of for nothing except the cost to ship it to and from his work. I work daily on AutoCAD so a design like this should take 5 minutes at the most.

Oh and reading back through my previous post I noticed I said the wrong steel braided line size that I have, I ment to say 8an which I imagine will work just fine. The inner diameter is 0.438", 6an is somewhere around 0.343".

The eprom is the removeable chip correct? I will make sure I grab a few of them when I go to the yard.

For now I will try to run using just the computer that I get the TBI unit out of, if I manage to sell the holley carb to get some of what I spent back, I will look into getting MS.

Thanks Guys


Edited by drummin52 (02/12/09 05:09 AM)
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47837 - 02/12/09 11:48 AM Re: tossing around the idea of efi for my 235 [Re: drummin52]
efi-diy Offline
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Drummin

The EARLS GM adapters to AN adapters are only available for -6 line.

There are 2 removable chips in the GM electronics

- eprom
and
- calpack

both have to be from a 6 cylinder app. otherwise the ecm will get pissed off.

I'd grab some eproms and calpaks from a 2.8TBI v6 and the 4.3 - with the 2.8 calibration and the 4.3 TBI it might be the best combo. Just make sure they are both from a '747 or '746 ECM.

fuel flow is... tank - pickup sock/inlet filter - pump - outlet filter - TBI (all -6) then TBI - submerged fuel return << very important or the fuel will flash when it enters the tank causing high pressue build up! return needs to be -6 as well.

Bring the TBI & fuel filter in with you when you get the adapters.



Edited by efi-diy (02/14/09 11:24 AM)
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Can't solved today's problems using the same technology/thinking that created them

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#47852 - 02/12/09 05:06 PM Re: tossing around the idea of efi for my 235 [Re: efi-diy]
drummin52 Offline
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Registered: 04/23/08
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Loc: Wapwallopen, Pa
out of what vehicle (hopefully a 80's or 90's) can I get a externally mounted fuel pump from.
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47877 - 02/13/09 05:15 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
drummin52 Offline
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Loc: Wapwallopen, Pa
what should the specs be for the fuel pump (psi and flow amount)?

Im looking for a external mounted electric pump that I can get at the local yard.
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47878 - 02/13/09 05:49 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
efi-diy Offline
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Look in a mid to late '80's ford - they typically had external pumps.

90#/hr @ 20 PSI is lots for your app. (good for 180 HP NA).

Once important note EFI pumps like to push fuel, but are very poor at sucking - so the pump needs to be below the fuel level and as far back as possible. Some times the factory will put a low pressure boost electrical pump ahead of the efi pump to ensure the efi pump gets the fuel out of the tank. Look under VW jettas/golf's for this type of setup.


Edited by efi-diy (02/14/09 11:17 AM)
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Can't solved today's problems using the same technology/thinking that created them

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#47883 - 02/13/09 07:36 PM Re: tossing around the idea of efi for my 235 [Re: efi-diy]
pinebluffdude Offline
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Registered: 04/13/08
Posts: 196
Loc: Pine Bluff, Arkansas
Thanks for this thread. I just rebuilt the carb on my 81 GMC 250
It has caused me aggrivation and I was just today wishing I could figure out a Fuel Injection Set up for that rascal.
Contrary to popular belief... Fuel Injection was not invented in the 1950s for the Corvette. In the Navy I ran a diesel generator that was designed in 1938 and it had TWO fuel injectors for each cylinder.
Good Luck with your projects. If I learn anything I will post it here.
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250 Integrated Head / 1981 C-10 Pick up.

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#47885 - 02/13/09 08:22 PM Re: tossing around the idea of efi for my 235 [Re: pinebluffdude]
Beater of the Pack Offline
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Trust what efi-diy is telling you. Last year at Speed Week we converted my carbed 270 GMC to Megasquirt controlled GM TBI in about an hour! Had it not been for a vacuum leak and a fuel line attachment problem we would have been cruzing Wendover! I'm closing in on my 292 project and it is only taking so long because I am learning it all at once, but I am learning it
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"I wonder if God created man because he was disappointed in the monkey?" Mark Twain

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#47902 - 02/14/09 10:38 AM Re: tossing around the idea of efi for my 235 [Re: Beater of the Pack]
drummin52 Offline
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Registered: 04/23/08
Posts: 104
Loc: Wapwallopen, Pa
Yeah I read that thread, one of the ones that pushed me towards doing the conversion in the first place.

Im putting a list of everything I need to do this conversion and so far looking at a total of just under $150.
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47904 - 02/14/09 11:10 AM Re: tossing around the idea of efi for my 235 [Re: drummin52]
efi-diy Offline
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It will be interesting to know if the GM ECM can adapt itself enough with out a tune (real painful with eproms) to run one of these motors.


Edited by efi-diy (02/14/09 11:22 AM)
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Can't solved today's problems using the same technology/thinking that created them

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#47907 - 02/14/09 02:54 PM Re: tossing around the idea of efi for my 235 [Re: efi-diy]
drummin52 Offline
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Loc: Wapwallopen, Pa
 Originally Posted By: efi-diy
One important note EFI pumps like to push fuel, but are very poor at sucking - so the pump needs to be below the fuel level and as far back as possible. Some times the factory will put a low pressure boost electrical pump ahead of the efi pump to ensure the efi pump gets the fuel out of the tank. Look under VW jettas/golf's for this type of setup.


now this I will need to work out. My current line has a up hill run before it gets to the filter. I have the stock mechanical pump for the carb which does fine at sucking the fuel from the tank all the way behind the rear axle. A rerouting of my fuel lines looks like it will be needed. I also will have to see if I can raise my tank a bit.

http://i175.photobucket.com/albums/w124/rockfan1815/fuel%20tank/100_0091.jpg
this pictures show what I mean. I would also need to fasten the fuel line to the bottom of the frame rail to decrease the up hill run.

I was also thinking of rotating the tank so the outlets are pointing towards the rear and mounting the pump on the frame to the side of the tank. I might use some 1.5" square tubing and cut 4 blocks so I can raise the tank up a little bit.


Edited by drummin52 (02/14/09 02:57 PM)
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47908 - 02/14/09 03:05 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
drummin52 Offline
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Loc: Wapwallopen, Pa
Another thing I have to figure out is the return and how Im going to do that. The 6an fitting on top is for a return, I have to check but I think there isn't a line down to the bottom of the tank. I could try and see if a I can get a plastic tube to fit through the fitting and reach the bottom of the tank, worth a try. The tank I got has a block of foam in it to prevent fuel slosh and splashing. Not sure if a tube would even be needed.

If I can't get the return to go back in through the tank, I have a few other ideas. 1 is to put a Tee in the line before the pre-filter and feed the return in before the filter. I could also use the second fitting on the bottom for the return, but I was wondering if it would be a problem with the fuel flowing back up through the return when the pump is off. I don't think there would but I figured Id ask.


Edited by drummin52 (02/14/09 03:10 PM)
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

Top
#47910 - 02/14/09 07:04 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
efi-diy Offline
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Can you get your arm into the tank and remove the fuel return fitting? If so maybe replace it with a -6 m-m bulkhead fitting then after getting it into the tank use a -6 to 3/8 line adapter and install a length of 3/8 steel line to 1/2 off the bottom of the tank.

Hard to judge from the pix, it appears that if you mounted the fuel pump under the frame rail behind the rear axle it should be low enough. If its within say 3 inches of the tank bottom you should be ok.


Edited by efi-diy (02/14/09 07:09 PM)
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Can't solved today's problems using the same technology/thinking that created them

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#47912 - 02/15/09 04:28 AM Re: tossing around the idea of efi for my 235 [Re: efi-diy]
drummin52 Offline
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Loc: Wapwallopen, Pa
I think that will work once I raise the tank up a bit

I will see what I can do with the return
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47922 - 02/15/09 01:29 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
drummin52 Offline
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Posts: 104
Loc: Wapwallopen, Pa
I took some 2inch square tubing and cut out 4 blocks. My plan will be to rotate the tank so the discharge is towards the rear. I will use the blocks I made to raise the tank up. The pre-filter (a -8an filter that I already have on the truck) will be mounted directly to the discharge of the tank with a -8an 90deg fitting, from there a piece of -8an hose with two -8an hose ends to the fuel pump, with a -8an to 3/8"npt fitting. From out of the pump I will use a 3/8"npt to 3/8" hose barb fitting and a short length of 3/8" fuel hose (rated up to 50psi working pressure, and 175 psi max pressure) to a post filter. From out of the post filter I will run some more 3/8" hose up to the engine compartment were I will use a piece of 3/8" steel hard line to run up along the firewall to the 4.3L TBI unit.

For the return, I will use another piece of 3/8" steel hard line in the engine compartment to run along the firewall (from the TBI unit, on the driver side, to passenger side, down to near the frame rail. From there some more 3/8" rubber fuel line along the frame rail to the return fitting on the tank.

I could run everything along the driver side frame rail, but Im trying to keep everything for the TBI on the passenger side, incase I ever have to change back to the carb. Im also keeping the computer on the passenger side kick panel so the fuel pump relay will be near there too.

Sorry for the long posts, I like writing/typing stuff out, helps me sort things out better.


Edited by drummin52 (02/15/09 01:41 PM)
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47928 - 02/15/09 05:10 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
Beater of the Pack Offline
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You are a doer and a problem solver. If it takes a little space to do show and tell so what? We read what we want here, there is no required reading. ( except my posts )
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#47946 - 02/16/09 07:11 AM Re: tossing around the idea of efi for my 235 [Re: Beater of the Pack]
big bill I.I.#4698 Offline
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If you have a fuel filler neck that is connected to the tank with rubber hose you can weld/braze/solder a steel line into the filler neck that is long enough to reach the bottom of the tank then connect the return line to it. This keeps you from welding on a used fuel tank.
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#47948 - 02/16/09 07:39 AM Re: tossing around the idea of efi for my 235 [Re: big bill I.I.#4698]
drummin52 Offline
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Loc: Wapwallopen, Pa
no welding here, its a poly tank.

I will reach in the tank to see if I can feel a line running down to the bottom from the return fitting. If not I will come up with something. I would think just getting a piece of plastic/rubber tubing with a outer diameter the same as the inner diameter of the -6an return fitting and shoving the hose down from the top till it reached the bottom of the tank would work fine.
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47962 - 02/16/09 05:11 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
Nexxussian Offline
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I think he meant into a remote filler neck (like maybe at the fender / bedside where you would actually stick the fuel nozzle).

Are you running a trap door through the bed as it is now (to fill the tank)?
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#47965 - 02/16/09 05:34 PM Re: tossing around the idea of efi for my 235 [Re: Nexxussian]
drummin52 Offline
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Posts: 104
Loc: Wapwallopen, Pa
Yeah when I finish the bed, my plan is to use a trap door, but just to access the top of the tank as it has a fill cap on it.
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47968 - 02/16/09 06:57 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
big bill I.I.#4698 Offline
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Yes guys I am talking about a metal remote fill tube that your fuel cap goes on and the remote fill tube is then fastened to the tank with a hose. such as you would find on many cars and some trucks. If you are using a racing type fuel cell with a direct fill this won't work.
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#47971 - 02/16/09 07:52 PM Re: tossing around the idea of efi for my 235 [Re: big bill I.I.#4698]
drummin52 Offline
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Loc: Wapwallopen, Pa
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Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47974 - 02/16/09 10:05 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
efi-diy Offline
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The fuel pump needs a dedicated 20 amp fuse. Also the ground wires need to connected to the block to ensure a good ground. Other wise looks good.


Edited by efi-diy (02/16/09 10:18 PM)
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51 GMC 4.2 turbo
Can't solved today's problems using the same technology/thinking that created them

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#47976 - 02/17/09 05:05 AM Re: tossing around the idea of efi for my 235 [Re: efi-diy]
drummin52 Offline
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Registered: 04/23/08
Posts: 104
Loc: Wapwallopen, Pa
here is a question, what is a electronic vacuum regulator valve. Im guessing something with the exhaust gas recirculation system as it shares the same wires. For my diagrams Im following a diagram for a 89 gm truck. I also have a diagram for a 90 s10 with the 4.3L which is similar as far as where the wires go on the connectors but has a few extra items on the diagram.
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#47982 - 02/17/09 09:28 AM Re: tossing around the idea of efi for my 235 [Re: drummin52]
efi-diy Offline
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The S10 uses a inlet air temperature (IAT or MAT )sensor. The rest of the connections are for emissions purposes - not needed.


Edited by efi-diy (02/17/09 09:28 AM)
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#48029 - 02/19/09 06:37 PM Re: tossing around the idea of efi for my 235 [Re: efi-diy]
drummin52 Offline
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Registered: 04/23/08
Posts: 104
Loc: Wapwallopen, Pa
ok forgot the hot fuel module??? on my diagram, thats where I guess the 20A fuse goes to.

http://i175.photobucket.com/albums/w124/rockfan1815/TBI%20CONVERSION/TBIWIRING-1.jpg
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Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#48030 - 02/19/09 07:01 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
efi-diy Offline
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Registered: 11/21/04
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Loc: Calgary Alberta Canada
ftp://ftp.diy-efi.org/pub/gmecm/manuals/1227747/

Most installs don't need the hot fuel module. I installed a TBI 350 in a '83 malibu (my first efi effort) after 1 week I tossed the hot fuel module.

Normally the orange wire (power feed from the battery)to the fuel pump relay has a 20A fuse in series with the relay. My GM manual shows a 20 amp fuse.


Edited by efi-diy (02/19/09 08:32 PM)
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51 GMC 4.2 turbo
Can't solved today's problems using the same technology/thinking that created them

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#48033 - 02/20/09 06:55 AM Re: tossing around the idea of efi for my 235 [Re: efi-diy]
drummin52 Offline
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Registered: 04/23/08
Posts: 104
Loc: Wapwallopen, Pa
So delete the hot fuel module (and assosiated wires) and wire the fuel pump to the same terminal on the relay that the gray wire comes out of and goes to the computer. Then change the fuse on the orange wire to a 20amp fuse, or do you mean make the orange wire to the relay seperate from the orange wire to the computer, and put a 20A fuse on that.

What is a hot fuel module? looks like a special type of relay to me.

So in total only two fuses are needed to do this conversion. A 10A hot in start and run and a 20A hot all the time.


Edited by drummin52 (02/20/09 07:04 AM)
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#48034 - 02/20/09 09:30 AM Re: tossing around the idea of efi for my 235 [Re: drummin52]
efi-diy Offline
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Registered: 11/21/04
Posts: 1684
Loc: Calgary Alberta Canada
Fuel pump wiring - power side

battery > 20 amp fuse > orange relay wire > relay > relay tan/white wire > fuel pump. The orange fuel pump relay wire does not connect to the ecm or anywhere else except the 20 amp fuse that goes to the batery.

You need 5 fuses to make this work correctly with a GM ECM:

a) 20 amp > fuel pump
b) 3 amp(sometimes GM used a 10 amp) ECM fuse connected to B1 & C16 hot at all times. This keeps the RAM memory alive when you turn the key off so the learned values are kept.
c) 10 amp fuse switched hot in run/crank connected to A6.
d) 10 amp switched hot in crank/run to power the injectors.
e) from the fuel relay tan/white wire a 1 amp fuse going to B2 << this tells the ECM the fuel pump power is on.

With megasquirt you need 3 fuses:

1) 20 amp for the fuel pump
2) 3 amp switched hot in crank/run going to A6 ( this assumes your using the GM to MS adapter board).
3) 10 amp switched hot in crank/run to power the injectors.



Edited by efi-diy (02/20/09 09:34 AM)
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51 GMC 4.2 turbo
Can't solved today's problems using the same technology/thinking that created them

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#48122 - 02/25/09 08:55 AM Re: tossing around the idea of efi for my 235 [Re: efi-diy]
drummin52 Offline
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Registered: 04/23/08
Posts: 104
Loc: Wapwallopen, Pa
Thanks diy-efi, changed my drawings to show what you said. might post it later if I remember.


I am still planning to do the switch over, just waiting for a nice weekend (50's or higher and sunny) and/or a sale to go to the local yard and get what I need. I made a list of everything I should need from both the yard and summit racing.com

Total so far comes to about $200.

Good news, my brothers programmer/tuner already came with everything I will need (program/file wise) to make the changes needed to the computer. The 747 and 746 computer must be very popular unit. From what I read I need to take out the vss and egr.
_________________________
Chris
1952 Chevy 3600 (3/4 ton) pickup w/54 235
Clifford Intake w/ holley 4bbl carb

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#48123 - 02/25/09 12:12 PM Re: tossing around the idea of efi for my 235 [Re: drummin52]
efi-diy Offline
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Registered: 11/21/04
Posts: 1684
Loc: Calgary Alberta Canada
Yep the '746 & '747 came on just about everything that was TBI from GM.

For sure the EGR needs to go, not sure on the VSS though. Are you running an automatic?
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51 GMC 4.2 turbo
Can't solved today's problems using the same technology/thinking that created them

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