It sounds to me like the fuel pumps rubber diaphragm is failing. The pump is easy to replace too.

 

Well, I took the truck out again today and reproduced the same situation - after driving and warming up, I pulled up to a drive through, let it idle for about 5 mins and it began to cut out, then wouldn't get any fuel pass the fuel pump.

I disconnected the fuel line from the pump, there was a little gas there, but not much. Reconnected the line allowing the vacuum that was present between the pump and tank to subside. Still no fuel to the carb. Removed the gas cap, heard no hissing, so I knew there wasn't negative pressure working against the pump to cause problems.

Disconnected the fuel line again, and blew through it until I got a steady stream of air out to the tank, then let the fuel run back up the line - there was a stronger stream of gas coming out the line this time. Reconnected the line, and within a few revolutions there was gas to the carb and I was running fine again.

So, I think if the pump was the problem, blowing through the line wouldn't change a thing, right? Odd part is, I can't for the life of me figure out what could be causing the fuel blockage. It's a brand new, clean tank, new sending unit and filter...the whole deal. It's been running clean up through my carb filter for months now.

Anyway, looks like I may have to drop the tank. Problem is, I've got 3/4 of a tank of gas! Anyone have a clue what could cause the problem? And it's quite odd, too, that it only does it after it either sits after being driven a while or after idling in a stationary position.


Happy Friday!

Justin

 

It's entirely up to you, of course...but I'd listen to Mil1ion on this one. Grab a gas can and some rubber hose...hook the fuel pump up the gas can and just turn the truck on and let it idle for awhile...see what happens.

 

Yeah, it's worth a shot - especially if it saves me from having to drop the tank. I'll have to replicate the situation exactly, though - driving enough to get it hot, sitting stationary and idling for about 5 mins straight. My gut feeling says though, that it's most likely a blockage somewhere in th tank, otherwise I don't think that adding gas to the tank or blowing through the lines would have alleviated the problem.

 

Also check to make sure someone didnt add another fuel fillter between the tank and pump. Friend of mines truck had one added and it was his problem.

 

Blowing the fuel back into the tank has nothing to do with the fuel pump. The fuel pump can die slowly or at once. They're only about 15 bucks and 10 minutes to change. You should probably have a spare anyhow.

I bet a dollar to a donut that it is the fuel pump since the issue is intermittent - just like a perforated rubber diaphragm inside a fuel pump...

Unless there is a sock type filter on the fuel sending unit in the tank and it is extremely clogged, I would not suspect that component. Taking that tank off is more time consuming and less likely to be the culprit.

Fuel pumps on the other hand are moving components and fail far more often than the tank units. Go for the most logical and easiest approach first is my experience.

 

My 79 gets that way. My fuel gauge dosen't work, but I've driven it enough to keep as in it (ran out once..............Once) but my gas cap wasn't a vented type. I could remove the cap to put fuel in it and it had enough vacume built up that when I removed the cap to fill it, fuel would come spilling out.

 

Thanks Shamus. It's probably best to try that pump before I go through the trouble of pulling (cutting?) off those filler hoses and dropping the tank - the memory of that course of action is burned into my consciousness.

Dialed up a local auto parts store and they can get me one for 18 bucks. 18 bucks and 15 minutes sounds better than dropping that tank and siphoning the gas before we take the hass to Cincinnati.

I'll update ASAP. Prob. ordering/buying the pump tomorrow, installing Sunday.

Thanks again guys.

Justin

 

You never said if you checked for that intermediate rubber hose.

Also, double, maybe triple check you have the correct gas cap as well.

The next time, instead of undoing the input hose, disconnect the output and see how much fuel you can catch in a can while cranking the engine over.

 

Just checked that intermediate hose, walls of the hose are still strong, no leaks. The tank hose was replaced when I did the tank, so know it's good. I'm gonna go with the fuel pump for now, just trying to get one under 20.00!

I'll post back soon.

 

[QUOTE=jfarcas;6037560]Just checked that intermediate hose, walls of the hose are still strong, no leaks. QUOTE]


Not that I doubt you, but I have seen hoses that looked perfectly good, didn't leak and yet allowed air to be sucked in. Just ran into this with a Sakai Roller Compactor. Machine ran great for 10 minutes then would sputter, replace the fuel filter and it would run great for 10 minutes. Sputter. Double checked the hoses, yadda yadda yadda still ran like crap.

Replaced the supply and return fuel hoses and now it runs like a champ.

Just something to think about.

Josh

 

Thanks Josh. Yeah, I'm planning on replacing the intermediate and front hoses when I do that fuel pump. I pick up the part tomorrow morning. Pretty easy fix, right? I'm assuming you line up the engine at TDC, swap pumps, and you're ready to go?


Grrr...the problem happened again today. Luckily I was in a parking lot and could blow through the line to get fuel pressure up to the pump again. It's like the pump can't self prime at idle after the truck gets a thorough warm-up. That sound plausible?

Also noticed that my gas gauge began working much more accurately after I relieved the pressure in the fuel tank and blew through that line.

 

You know I have never really paid attention when I have swapped pumps...

and I just checked two of my manuals and neither say anything specific about where to have the engine when removing/ installing the fuel pump

Happy Motoring!

 

It's easier to swap the pump when the motor isn't pushing down on the pump arm, but it doesn't matter where the motor is at when you put the new one in. Usually good to grease the arm, and then just bolt it in. They're really easy to do, and take almost no time.

 

It has to do with the position of the eccentric.

Just keep turning the engine until there is no pressure on the pump arm.