My truck just quit running today while we were towing another vehicle. It seemed as if there was no fuel getting to the carb, so I loosened the fuel line nut where it enters the carb and turned her over; no fuel. I figured the fuel pump must be bad, so I removed it. When I got it off, I manually pumped it and fuel "shot" out just fine and under good pressure.

Since I already had a replacement pump there, I went ahead and put it in. Cranked the engine, no fuel to the carb??? Does this mean the fuel pump eccentric has failed? If so, is there a way to be sure without pulling the cam?

Any insight or this-happened-to-me stories will be appreciated. Thank you.

 

standing on your head with a flashlight you can see the eccentric....

first things first tho.
Put the pump on the engine. Remove suction fuel line. Stick it in a bucket of fuel. See if that works.
if no, look into eccentric, if yes, in terms of simplicity first:

1. Make sure fuel tank is venting (for starters, take off fuel cap, and check the lil vent line on the top of the tank).
2. Make sure the fuel hose from tank to pump is in good condition.
3. Do you have duel tanks? I've seen many of the Fuel switching valves stick, try switching tanks.
4. Possible obstruction in the fuel line, blow out with 3-4psi air pressure with fuel tank cap off.
5. Remove fuel tank pickup and check for debris clogging the pickup.


best of luck,
Drew

 

the one thing you didn't mention.... where is your fuel filter?
If it is between the pump and carb, check that first.

 

Thanks guys; all good advice. I hadn't thought about the cap not venting. We did get fuel through the line (up to the fuel pump input) by just blowing into the tank neck filler, so I do not think there is a restriction up to that point although it may act differently under suction than it does under pressure (might collapse a weak rubber line on suction).

To answer the question about the filter, it has the canister type filter integral to the pump, but as I mentioned, manually moving the pump lever moves fule just fine.

It does have dual tanks but the reserve tank has always leaked and I never use that tank or mess with the tank switching valve.

I will run a hose from a gas can directly to the input side of the pump and see if I get fuel up to the carb. If that doesn't work, I am going to install an electric fuel pump just to get her home.

 

I had an intermittent problem that was a piece of plastic junk that would occasionally hang up in the fuel pickup.
Nothing wrong with an electric pump, but I'd try the running from a bucket first.

As long as you don't use the Aux fuel tank, you should probably bypass the Fuel switching valve... I've had them get clogged with random bits.

best of luck
Drew

 

Did you happen to check the oil level when it died, or smell the oil to see if there were gas in it?

It's fairly common for a bad pump to dump fuel into the crankcase.

 

There was no fuel in the oil. Since the pumps (both the new and old) are pumping fuel when operated by hand, I do not suspect a ruptured diaphram at this point. I'll be sure to update this posting when I resolve the problem.

 

The only similar problem I had was no fuel getting to carb. After installing an electric pump I realize it was a 45 year old cracked rubber line right where it ran into the mechanical pump so it was just sucking air. But you said you got it to pump gas by hand so that wouldn't be it. The only other thing I can think is that if your getting fuel out of the pump, something is stopping it from getting into your fuel bowls on your carb. Its a long shot but if a little price of debris made it past the filter it may have plugged your jets. I know, long shot, but stranger things have happened. Plus its easy to check on a autolite 2100 / 4100. Best of luck man.

 

I've never seen an eccentric fail, but it sure sounds like it in this case. You shouldn't have to pull the cam as the eccentric bolts to it. Now that I think about it... I wonder if the timing chain failed and it not turning the eccentric?? Please post what you find.

 

Holy dead thread batman....BUT did you ever find the problem Wagonerkl? I'm having the same problem. Pump works fine outside of truck but once hooked up, I can't get fuel to the carb. My buddy was telling me tho the pump arm doesn't usually travel a lot under normal operation and I was pushing the arm as far as it would go to get gas pumping. So I'm thinking the pump is on its way out and I plan to buy a new one just thought I'd double check to see what you found

 

I am afraid I do not remember and in fact no longer own that truck. As I recall, it had a dual tank system with a manually operated tank switch. Seems like I ended up replacing the rubber fuel lines from the tank to the fuel pump. Sorry I cannot be more help.

 

Hook a hose to the fuel pump and stick the other end in a jug of fuel, then crank the engine and see if it pumps fuel from the jug.
Fuel pumps can and do go bad, eccentrics can come loose (personally I've never seen it happen), 95% of the time the problem is between the tank and the fuel pump.

If you have one of the old vacuum/pressure gauges you can check the pump with that, it should pull vacuum on the suction side and make pressure on the output side.

 

Yeah i have another thread open in the 73/79 section. I have tried a lot of things. Just confused on why the pump works off the truck but not On. I am thinking it is just the pump on the way out and too weak to work on the truck but hand pumping still works. I have a new pump ordered so we will see if that solves the problem... fingers crossed.

 

So did you try the pump using fuel from a different source or just hook everything back up and not get fuel?

 

I hooked up the inlet to a gas can, cranked, no gas reached the carb
I hooked up the outlet to an empty can, tried running off a gas can and the truck tank, no gas entered the empty can.
I blew out the lines, could here bubbles going into tank when blowing on the line at the pump. All rubber lines have been replaced (pump to carb, fuel line to pump, gas tank to filler, gas tank to fuel line right under cab)
Tried running the truck with the gas cap off the tank.
Took the pump off, hooked up hoses to it and used two gas cans, after about 5-7ish pumps gas starting transferring at a pretty good rate. I was having to push the arm all the way down tho to get it to pump gas. Hooked it back up to the truck ran through all those tests again and no fuel was reaching the carb.