Inliners International Forums General Discussion Engines fuel troubles?

still having carb troubles. 250 1 brrl when sitting still with choke on will run smooth. driving must have choke on and yet it still stalls when you get on the gas, makes sort of a sucking sound through the carb. noticed that when i turn the truck off there is little to no fuel in the filter. just put on a new fuel pump same thing. any thoughts carb????

I had a '77 Chev pu with a 250 and a monojet that would idle perfect but not drive, it was the filter in the carb's fuel inlet plugged up. Also check that you don't have a bent or clogged line from the tank to the pump, and that the tank outlet is clear. Take an air hose and blow back from the fuel pump inlet fitting with the gas cap off to check for free flow, sometimes sediment will accumulate in the tank.

Tim

ok did some trouble shooting this weekend problem is that carb is not getting enough fuel. when the fuel line is disconnected at the carb. the pump is pumping fuel like it should. when you connect it back to the carb its like there is back pressure or something and the pump is not able to pump the fuel from the tank to the carb. i have a rebuild kit for the carb plan on tearing it apart today and seeing if i can fix. any other thoughts?

Where the fuel line hooks to the carburetor, the fitting on the carb itself should take about a 1" wrench. Remove the fuel line then remove the large fitting. Inside there should be a small filter that is probably clogged.

Tim

tim, i took that little filter out some time ago it got so clogged from a rust issue i had in my old fuel tank. so there is no filter at all in that port. the only filter i have is in the line right before the fuel pump. anything else inside the carb that could be the issue?

I think I would check to see if there is a clog where the filter was, it sounds to me like it has more rust in there. At this point it sounds like you have to pull the top off the carb and clean the fuel bowl and check the needle/seat also. Then put a new filter, that's your last chance to keep debris out.

Tim

Well there you go. I would bet that your filter sock in the tank is plugged, and/or the filter is plugged.

One way to TEST this theory is to put a new filter on it, stick a piece of hose over the line from the tank and BLOW AIR into the gas tank. That should clear crap off the pickup sock for a little while. If that "fixes" it you really ought to drop the tank and clear it out before it become so rusted you can't repair it.

Most factory service manuals will spec how much gas the pump will deliver in a minute of cranking. Hose into a coffee can and measure! Nothing like numbers...

"old fuel tank" ?

Does that mean you have a new(er) fuel tank in there now?

yes i have a new tank setup in the truck now. i have a buit-in tool box in the bed of the truck and one side of the box has a plastic fuel cell in it.

Dear Skirk;

With your "fuel cell" higher than'
the fuel pump, there should be a
'free flow' to it, corrct??

Now; replace your filter, making
sure the pump is pumping/holding
pressure as well.

Good luck.

Yes there is free flow to the fuel pump. The filter between the tank and the pump is new, i put on a new pump as well. If you disconnect the line from the carb it will pump correctly. When you hook that line back up it will pump all the fuel that is in the filter out but the filter wont fill back up. It is a clear filter and you can see some tiny amounts of fuel flowing in it but not much at all. I have the carb off, going to install a rebuild kit this weekend hopefully that will solve the issue. the thing that really bugs me is that it was running fine until i let it set for about two days with the front end up on ramps while i changed the clutch. then when i started it and backed it down thats when the troubles started.

Dear Srick;

Is your (clear) filter going the
correct direction?? If It's the
bowl type; Is it facing down??

Is it after the fuel pump??

Is your "fuel cell" vented??
-----

You shouldn't need two (2) filters
with a new tank/cell and the one in
front of the pump may be restricting
flow. Can't say W/O seeing.

Good luck.

Is your tank vented? 1 OL REDNECK

Dear Darrell;

Yes a vent is required for the fuel
to dispense properly.

In aircraft; the fuel cells can't
collapse W/O one. A check valve is
closed when inverted/steep angles.

On the sealed (SMOG cars) the tank is
vented via the vacuum canister device.

BTW: they now have a special (SMOG)
test for that in California now. FUBAR
-------

The OP has multiple problems I'm thinking.

tank is vented, it is actually a 12 gallon outboard marine tank that i am using temporarily. filter is not the bowl type just the round clear type like can be bought at walmart. It is installed facing the right direction and is between the fuel pump and tank. That is the only filter in the line. there is not one inside the port where the fuel line attaches to carb.

Trash in the needle valve? Bad float or wrong float adjustment? Beater

now gone from confused to just plain frustrated. Done a complete rebuild on the carb put it back on yesterday still same problem. It will run with the choke on but without it off it is starved for fuel. what the heck am i missing here???

What is the year model of your truck? Have you explored other possibilities like a cracked, leaking or dislodged power brake or vaccuum hose, pcv tube to the carb base, loose intake manifold, etc. All your descriptions really sounded like a restriction between the pump and the float bowl to me tho'.

Good luck,

Tim

Plugged main jet?
Did you ever get heat to the manifold?

Titen, its a 1966 c10, no vacuum on the brakes "old school" pvc tube is good, intake is tight in fact i took it off and put on a new gasket just to be sure, and when i put it back on i even put a little gasket sealer on it. i agree still sounds like a restriction somewhere but where? float seems to be working properly needle valve seems ok??? heat to the carb base didnt seem to help

What kind of fuel line runs from the tank to the filter? Check for a crack or leak in that line and all fittings from thank to pump. It could be sucking air which is easier than moving fuel. If the line is soft it might collapsing under a load. Beater

I'd try hooking up a manual fuel pressure gauge, manual vacuum gauge to the intake and drive it. And after checking those readings, move the vacuum gauge to distributor vacuum advance line and see what is happenning there when driving. If you're not sure what the gauges should be reading, then I'm sure that the info is in a GM service manual. Also, I tried 'rebuilding' my original 1 barrel carb and I discovered, after I took the carb to carb only guy, that installing a carb kit is not actually rebuilding it. After installing the same carb that was repaired by the carb guy, my float angle was well out of whack, it worked perfect.

Beater, they are solid lines only a small piece of rubber line. i have replaced all lines with new just in case. last night i checked intake and all hoses, carb base etc. for vacuum leaks all is good. took the top off the carb last night, i think the reason the fuel is not pumping into the carb is because the needle valve is closed. however the fuel bowl in the carb is full so the float is raised closing the needle valve. this leads me to thing that the problem is the carb is getting fuel but not getting rid of it. i.e. a jet problem or something??

Well, it's got to be something! It could be clogged passages from the bowl to the venturies. At this point I would take the top off of the carb and have someone else turn the engine over while I moved the float up and down just enough to make sure fuel flows through the needle valve. If it does I make sure the float level is set correctly. If that is done it would seem that there must be a restriction in the carb body. I'd also check the compression just to make sure. I'm still bothered by the filter not refilling. That seems to indicate a problem between it and the tank. This is nuts. Beater

your right beater its just plain crazy. took carb off this evening ran some small wire through the vac ports and the jet cleaned real good with carb cleaner, made a minor adjustment to the throttle plunger, said lots of prayers for the thing and it is now working better, not perfect but better. can now open the choke about 3/4 way before it starts to stumble. i am thinking that may improve with driving. it does have an issue with the icing condition at the base so i am thinking that may have something to do with it not getting enough fuel when the choke is all the way open. if that is the issue it may clear on up once i drive it for 8-10 miles and get the intake real warm. anyway thank God it is running better. thanks to all for the suggestions.

I hope it gets better. A can of Seafoam in the tank might help too. Good luck and let us know. Beater

If you think it might be related to carb icing you could duct hot air from the outside of the exaust manifold to the air cleaner for the wintertime.

I think I would swap carbs just to verify the problem.

Also, in my experience, very few few filters are completely full, with no air pocket, when sitting. I think it is because they usually sit horizontal and don't bleed out the air properly, I also think that is why most filters aren't clear (so you can't see this).

Tim

Gee Tim, Changing the carb would be too easy. That might solve the problem too quickly and we'd have nothing to talk about. Tom