Grain truck starting issue

Milk · Mar 16, 2020

I have an older gmc grain truck with a 427 gasoline engine that has been sitting all winter long in storage shed that won t start! It fired over once, now it s not firing at all! I replaced all spark plugs,still won t fire unless I pour a little gasoline down carburetor. I took gas line apart coming up from the pump, nothing coming out or into the fuel pump, plenty of gasoline in the tank also. As a last resort I tried sucking on the gas line coming into the fuel pump, cannot suck any gas. Any help or recommendations would be greatly appreciated!! Thanks!

cole in mo. · Mar 16, 2020

Is there a filter someplace along the frame that could be plugged, you could remove the gas cap, and use some compressed air at the fuel pump end to blow back to the tank.

Olliejunkie · Mar 16, 2020

Maybe blow some air back to the tank. If theres any rubber lines in between they could be collapsed also.

rustred · Mar 16, 2020

you have it narrowed down then from fuel pump back to tank. try a bit of air blowing back to tank. then try from tank ahead. is that those saddle tanks? and one or two? it could be the change over valve also. get a long rubber hose and throw it in the tank and hook it to pump to see if the pump will suck. it should start.

Milk · Mar 16, 2020

Yes,there?s a filter in between the tank and fuel pump. There isn?t any gasoline coming into the filter from the tank. How does gasoline move from the top of the tank to the fuel pump? Seems like there should be an electric pump to get gasoline out of the tank to the pump, but I can?t see any electric pump!Gas is drawn from top of the tank , goes through the filter, coming out of the filter to the pump, then out of the pump up to the carburetor. Is all the sucking action coming from the fuel pump? I am going to try a new fuel pump, but I am not confident that it is going to help! Thanks for the reply!!

old · Mar 16, 2020

Take the line loose at the carb and rig up a small gas tank like a lawn mower tank and see if it will run that way. Be sure to also rig up way for gas coming out of the fuel pump to go some place safe. The fuel pump maybe bad or it need a bit of time to pull fuel out of the tank

Milk · Mar 16, 2020

Yes, does have saddle tanks but I only use the main tank. No gasoline coming up from the tank into the filter. I sucked on gas line pretty good, couldn?t get a taste of gasoline, just fumes!!
Is there any danger in blowing air back to the tank or vise versa?

Angle Iron · Mar 16, 2020

(quoted from post at 16:06:19 03/16/20) Yes, does have saddle tanks but I only use the main tank. No gasoline coming up from the tank into the filter. I sucked on gas line pretty good, couldn?t get a taste of gasoline, just fumes!!
Is there any danger in blowing air back to the tank or vise versa?

re your tank change over valves manual or electric? Are you sure you are on the correct tank?

72supr · Mar 16, 2020

You could take the line off the pump put your finger over the hole and have someone crank the engine and see if there is any suction.

Farmer Rock · Mar 16, 2020

I would give the carburator a really good clean.mysterious things happen with a bad/dirty carburator.also I would think the carburator should be sucking fuel at sime point especially at start up,I have had this happe more times than I care to say,and all it takes was cleaning and some cases a little adjusting.

Rock

Milk · Mar 16, 2020

It has always,as long as I have had the truck, been drawing gas from
the main tank. I am sure that nothing has changed!

Tech 7 · Mar 16, 2020

There IS gas in the tank right?

Milk · Mar 16, 2020

Does carburetor suck fuel or is fuel pushed up from the pump into the carburetor? I always thought that the fuel pump sucks the gasoline from the tank,then pushes gas up to the carburetor! Didn?t think that the carburetor had any sucking action! Thanks for the reply!

Bob Bancroft · Mar 16, 2020

If you're going to spend money on a fuel pump, don't waste it on an engine mounted mechanical one. Get yourself an electric pump and mount it as close to the tank as you can.

Milk · Mar 16, 2020

First thing I checked! Half full of gasoline!

marloweg · Mar 16, 2020

old truck might have a rust hole in fuel line .blow some air in to tank and see if the line is leaking

VADAVE · Mar 16, 2020

Maybe you should check.
Then disconnect the fuel line from the pump and the carb. Put your air compressor against one end and blow the trash out of the line.
That'll get a clear line.

Milk · Mar 16, 2020

Is there a danger of getting the WRONG size electric fuel pump? I have been thinking about doing this too but haven?t needed to but now it?s a different story!

Brown Swiss · Mar 16, 2020

I've got an old 79 chevy with
427 and once in while the
electric fuel pump won't go!

rustred · Mar 16, 2020

use common sense with the air just give it a small shot not 100 lbs all at once. plus have the cap off. have someone there watching and listening. also yes it sucks from the top because it has a stand pipe from the top to bottom of tank. if I remember that is the fuel guage also. plus that line im sure has a sock on it that could be plugged. long time since I worked on one. but if you do as I say that will show you the truck will run if your saying the fuel pump is good. if u throw a hose into the tanks fill hole and hook the other end to the fuel pump it will suck fuel to the carb and start. I don't know why people don't believe good advise that works. then you know where the problem is you have to fix. I used to work on these trucks in the 1970's and early 1980's. overhaul the diff's , overhaul trans, the 5+ 4's replace engines, on gravel trucks and water trucks.

Bob Bancroft · Mar 17, 2020

You don't need, indeed don't want a high pressure one. 5 psi is plenty.

Milk · Mar 17, 2020

Will try the long hose going to the tank to the pump, that should tell me if pump is bad.Just didn?t know if gas is moving by an electric pump or gravity. Thanks for good advice!

RobCons · Mar 17, 2020

If you can suck air/fumes through the fuel line going to the tank I would look for a leak in that line. Maybe it has rubbed against something, came unhooked, a hole rusted in the metal sections, etc. Might be in the pickup tube inside the tank. Try blowing through it to make sure your on the tank you think your on.

Davidj · Mar 17, 2020

Hole in the fuel line? I had an '81 Chev pickup that the fuel line went bad. Ran it with a 5 Gal. jerry can tied to the inner fender.

Milk · Mar 17, 2020

Will try today!!Thanks

mudcreek183 · Mar 17, 2020

There should be a cartridge filter on the frame check that also my was plugged changed it and it solved all my problems

Bob · Mar 17, 2020

(quoted from post at 11:02:24 03/17/20) There should be a cartridge filter on the frame check that also my was plugged changed it and it solved all my problems

It's NOT uncommon for those frame-mounted filters to get a rust pit or several in the canister, that allows air in, and the fuel pump can't suck fuel from the tank.

Milk · Mar 17, 2020

Bob,
Can you take the filter out and try getting it started without the filter
for a short time?

Milk · Mar 17, 2020

Will check!

Bob · Mar 17, 2020

(quoted from post at 13:30:23 03/17/20) Bob,
Can you take the filter out and try getting it started without the filter
for a short time?

I meant the steel canister that holds the filter can get rust holes in it.

And while you COULD try to start it without a filter in the canister, I wouldn't.

Nothing to be gained, and might lead to rust and debris getting to the fuel pump and beyond.

My suggestion is to disconnect the line that comes from the filter to the fuel pump, then stick a blowgun into the tank fill tube and wrap a rag around the blowgun and wad it up over the tube and hold it tight with your hand while giving a REASONABLE puff of air from the blow gun.

It shouldn't take much to flow fuel out of the the disconnected line.

That will prove that the lines are open, and you can also look at the fuel lines and the filter canister for any wet spots that would indicate pinholes/leaks.

If you get fuel that far, next thing would be to connect the pump inlet line back up, take off the outlet line and see if the pump pumps fuel during cranking.

Also, I believe it was mentioned that there's more than one tank and a fuel valve, sure wouldn't be the first time one of those floor-mounted valves got kicked to a different position (or halfway there), or somebody monkeyed with it.

If there IS a fuel valve in the floorboards, there's several hoses to plumb it in, and they are well above the level of gasoline in the tank and can dry out and crack, allowing air to enter so the pump can't suck fuel.

Do some checking, and think this out logically, there's no reason to just start blindly throwing parts at it.

Papaw8 · Mar 17, 2020

If the truck had ethanol in it you may have a lot of rust in the tank and steel lines. Also the fuel pump diaphragm or check valves may be bad because of
the ethanol.if you sAck on the suction line at the fuel pump you should get gas. If you get air the line is cracked somewhere. If you don't get gas or air
something is plugged from there back th the tank.

Milk · Mar 17, 2020

Thanks for the reply, I blew air in the tank and found that the rubber fuel line that crosses over the main frame over to saddle tanks was cracked and letting air escape! Ran out of time to plug all back together today, will finish tomorrow. Hopefully it will start.

Grain truck starting issue

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