bad fuel pump?

[domano 68]

My 72 350 C10 died after 15 min or so of driving. Thought i ran out of gas so put a few gallons in 20 min later and srarted right up. Minute or so later it sputtered a bit then a min or so later sputtered again then a bit after that died like it was out of gas. So are we looking at a bad fuel pump? Thanks in advance.

[domano 68]

Originally Posted by domano 68

My 72 350 C10 died after 15 min or so of driving. Thought i ran out of gas so put a few gallons in 20 min later and started right up. Minute or so later it sputtered a bit then a min or so later sputtered again then a bit after that died like it was out of gas. So are we looking at a bad fuel pump? Thanks in advance.

Forgot to mention it turns over but does not ever start. I tried the next day and does the same thing.

[domano 68]

Found the positive battery cable half way hanging out from the terminal. Definitely loose. Would this cause the truck to die? I can see that it would cause the truck not to start if it does not have a solid connection. And the fuel pump looks somewhat new and probably replaced by the previous owner at some point in the recent past. Thanks in advance.

[flashed]

Have you checked all your soft fuel lines especially the short one right at the top of the gas tank ?

[Gromit]

This is to recommend checking your oil for any fuel smell (via the dipstick) before running the motor any more.

Assuming you have the mechanical (stock type) fuel pump; it is my understanding that those can leak fuel into the crankcase if their diaphragm fails.

If this occurs, your crankcase oil will quickly get whipped into a yogurt like foam or fuel/oil emulsion and all the bearings and piston rings will be prematurely worn and need replacement if you run the motor with the oil in that condition.

The fuel pumps are cheap, often less than $25 and easy to replace, so if yours is more than ten years old and has 100,000 miles you wouldn't exactly be throwing money away if you replaced it and it turned out to be some other problem.

Most people on this forum hate those glass $15 fuel filters but one thing they are useful for is diagnosis. If you install one at the upper connection just temporarily you can see right away if your pump is pumping fuel - easy to pop on and off with a couple 3/8 hose clamps.

Speaking of fuel filters if you have the Holley with the internal inlet filters - that could be clogged.

[domano 68]

Yes they look fine but I am no expert. Fuel is getting to the carburetor so would this rule out the fuel pump?

[Gromit]

Please explain a little more regarding "they look fine" Do you mean the small vent hoses at the top of each side of the tank?

I recently had a similar problem with my '70 C10 and it turned out I just needed to put a few more gallons in the tank - I had put just four or five gallons into an empty tank and the pump didn't like that very much.

it would idle fine and the glass fuel filter would stay full with no bubbles or air showing while idling; but if I drove the truck a few miles and then quickly stopped and jumped out and opened the hood I could see that the fuel filter was almost empty..

Do check your oil for fuel smell..

[domano 68]

Looking at the center of the top of the tank; these hoses look ok to me. What exactly am I looking for there?

The truck does only have a few gallons in it but that is how I have always run it since I do not drive it much.

What would it mean or not mean if I smelled gas in the oil?

[hugger6933]

Lets talk about the other end, exhaust. If there is a severe restriction, it could run fine for a few minutes then smother out and die. If you have a exhaust restriction it could set for a while and the back pressure is equaled out then start and run again for a little bit and die again. If indeed you have ruled out the pump and are still looking for problems that might be an answer.
You said you have fuel to the carb, the other thing to check would be the short rubber lines to make sure they are not getting sucked shut that would stop the flow to the carb but yet you could have gas there from before it shut off.
I would probably as a maintenance issue change the rubber hoses and then the pump itself and DOUBLE check the oil to make sure it has NO gas smell to it at all. If it does change the oil while doing the changing of parts.
Also a little helper hint on changing the pump there is a 3/8 bolt in the front of the block that has direct access to the pump push rod, take it out it is real short like 1/2 inch or less then push the rod as far up towards the cam as you can, then install a little bit longer bolt say 1 inch long then tighten it ever so lightly to hold the push rod out of the way while you install the new pump. Don't forget to change it back or problems will abound!!
With a new pump and new hoses and oil and making sure you don't have a rats nest or the like in the tailpipes you should be ready to ride.
You can check the pipe simple enough just feel back there as the truck is dying for a strong exhaust feel or you can put a vacuum gauge on it to see how it reacts. Jim

[domano 68]

Been able to get out and put the new battery cable on between these ice cold rain showers. Truck started right up, and strong. I let it run for 10 minutes or so and got 14.2 Volts on the battery while the engine is running. So the alternator is charging good.

Five minutes later, the truck slowly dropped rpms and died as I was coming back outside to check on it. I immediately started her right back up, turned it off, started right back up again like a champ with strong revs coming from the engine.

So who says the battery cable fixed this issue? But then why did it die? Perhaps the battery is weak/needs replaced?

For those who say the new battery cable did not fix the issue, I bet you say there is an intermittent electrical issue with the ignition system (distributor, coil, etc)?

Cap, rotor, plugs and wires were all changed out a few months back.

[Gromit]

Sounds like it is either slowly flooding, or slowly starving for fuel; as in a vapor lock. Or the fuel pump is clogged with rust flakes or debris from the tank.

Did your truck ever have auxiliary tanks?

Right after it stalls; check the rubber part of the fuel supply line running from the steel fuel line along the frame rail where it connects to the fuel pump - is the tubing collapsed like it has suction on it with nowhere to go?

Then check the rubber line connecting the pump to the fuel rail - (that one has positive pressure whereas the supply line is under negative pressure) is it constricted or folded or pinched? Also might want to open you gas cap and listen carefully for an in-rush of air - or just leave the cap loose and see if the problem persists.

Those are just things I would try but I am decidedly an amateur compared to most people on this site.

If you can post a photo of your engine I'd suggest that - there are people on this site who have seen it all ten thousand times and can take one look at a photo and see many things that need attention on these motors that the average enthusiast would never notice.

[Ozzy2013]

Check your fuel filter and hoses mine did it it was the stone filter filling with ultra fine rust particles .

[domano 68]

Never had auxillary tanks as far as I know.

The truck has a fuel filter hanging right off the fuel pump. I doubt this is how it came from the factory. I am sure there is one on the carb but haven't looked yet. I will change these out next.

If it stalls again, I'll check to see if hoses are collapsed and open the gas cap and listen for the vaccuum sound. If it is "vapor lock" how is this fixed? Vented cap?

[Valarius_Starchaser]

Originally Posted by Gromit

This is to recommend checking your oil for any fuel smell (via the dipstick) before running the motor any more.

Assuming you have the mechanical (stock type) fuel pump; it is my understanding that those can leak fuel into the crankcase if their diaphragm fails.

I lost a 383 that way checked the oil level to late wasted a lot of time checking everything else and the bearings had already washed out 2200 in machining bills and parts later had it fixed right up

[domano 68]

Thinking about this more, after it stalled initially, pulled the gas cap off and put gas in the tank. So that could have relieved the vacuum and explains why it started back up. So what causes vapor lock or this condition? Need a vented cap?
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