VCCA Home Forums TECHNICAL - GENERAL Trucks and Vans '37 half ton - Crud in the fuel line

Hi All,
I have had my gas tank well cleaned in my '37 half tone pick-up. But I'm still suffering from unreliable operation. It tends to stall alot and wont start. While this could be many things, after cleaning the carburator the probem seems to go away.

I seem to be having persistent troubles with the carburetor clogging up with "gunk". Assuming that the tank is clean, how likely is it that there could be "gunk" residing in the fuel pump or in the forward fuel line itself? We didn't really get into those to clean them out.

My symptoms are these: frequent stalling, eventually it wont start - behaving very much like it has a clogged fuel line filter.

When I had work done on it last year we throughly cleaned the tank but left the fuel pump in tact as well as the hard fuel line from the fuel pump to the carb.

Anyone have advice on how I can get to the bottom of apparently clogged carb/stalling issues?

I'm proposing to replace the fuel pump. The one I have is not original anyway. No glass bowl.

Thanks

Bruce

You might consider removing the gas cap, disconnect the fuel line at the fuel pump and use an air hose to blow back toward the tank. That will clean out the fuel line. Now remove the line from the carb and fuel pump and blow that line out. Hook everything up and give her a try.

Ray,
Though a little more difficult to do, it is far better to disconnect the fuel line at the tank and also at the fuel pump. Then blow either way to clear out the fuel line. If you have crud in the line and blow back to the tank it just puts the crud into the fuel tank. It will return sometime unless the tank is cleaned again.

If you still have a problem after cleaning the line it may be in the pickup tube in the tank. You will need to blow that back into the tank or take off the gas cap and put a few lbs pressure on the tank to blow it of the line and tank. Be sure to have the fuel line to pump disconnected so you don't put it into that line too.

Bruce,

When you cleaned the tank, you may have knocked some debris loose that remained in the tank got into your fuel line. The tank drain valve is a choke point where debris can get trapped. Before blowing out your fuel line, as suggested by Ray, I recommend you drain the fuel tank, then remove and disassemble the fuel tank drain valve. Caution--the stock drain valve has a short nipple on it that screws into the bottom of the tank with 1/8" pipe threads, however, it is possible that someone in the past may have soldered it to prevent it from leaking. Don't over-torque the valve in attempting to remove it and risk breaking it off. If it wont loosen, unscrew the valve stem packing nut, then back the valve stem clear out of the valve body and make sure there is a clear passage through the valve body and the nipple into the tank. With the valve removed or diassembled and disconnected from the fuel line, disconnect the fuel line at the fuel pump and, using compressed air, blow back through the line from the fuel pump toward the tank. If you leave the fuel line connected to the tank drain valve and blow back into the tank, if there is any debris in the line or the valve, you'll blow it back into the tank, where it will eventually end up back in your fule line again. Once the line is clear, reassemble/reinstall the drain valve and re-connect the fuel line to the valve and to the fuel pump.

I suggest you also install an in-line fuel filter just before the carburetor.

Mark

Check the hose going from the fuel line to the pump as they can swell up on the inside when they go bad.

Hi All,
It's been a while since my last post and request for advice. In my '37 half ton pickup I continue to suffer from poor performance and unreliable operation. What I am experiencing is frequent stalling unless I pull out the throttle knob in the dash. I am not familiar enough with the carburetor to clean it my self but when I had it done last time. My mechanic said they cleaned out the "idle circuit" and the truck ran great for about two days. Then slowly it started to run rough and eventually would not start at all. I'm fairly well convinced that there is some sort of debris finding its way into the carb.

My question is as follows. (1) how can I determine the source of the material clogging the carb? (2) Even though I have an inline filter could debris be getting through from the tank? And (3) what is the best course of action to deal with it so I can get this truck running reliable enough so I can take it further than the back yard?

In other details: I have recleaned the tank, I have been replacing in line filters between the tank and the fuel pump ( but they haven't looked all that bad). I have not yet attempted to replace the lines from the tank to the fuel pump and the lines from the pump to the carb. I'm wondering if it would be worthwhile to replace pump and lines all together.

Any assistance would be greatly appreciated.
Thanks.

First off to clean out the low speed jet so it will idle place #3 spark plug wire on #4 cylinder and #4 wire on #3. Remove air cleaner, start engine and quickly floor the gas peadal several times. The back firing will blow the dirt out of the low speed jet.
You will find dirt will get past the best gas filter.
I would make sure the tank is clean, blow-out the lines and replace the fuel pump.
Then disassemble the old fuel pump and see what king of crud is hiding inside. May give a clue.

Another method is put trans in top gear and roll the car backwards against compression with the throttle closed and ignition off. This will force air through the idle passages of the carb. This will only shift the crud but will still need to lift the top to clean it out properly.
Tony

Thanks. I'll give it a try.

Mark,
I am thinking an in line filter before the card may be a worthwhile option. Thanks.

So how much of a problem is it to disassemble and rebuild a fuel pump for this struck?

Thanks

If you have a complete repair kit, it is something that you can do in your home workshop. Your 1937 shop manual will also be a great help as well.