Starting to stall at low idle - Injection pump?

[basilbowman]

Hey guys, I brought the truck back from Atlanta to Kentucky on Sunday, and around Chatty it started to stall if the rpms dropped below 1200 or so. I brought it the rest of the way up to Kentucky, and about 40% of the time it would stall when I had to stop, the other times it would just idle like regular, not even rough or anything. I'm going to run some diesel purge through it, with a return and intake into a jug so as to really flush it through the engine, but could it even be a stuck valve in the IP, or is it most probably just my IP going bad?

 

[Cincinnati Guy]

Pull off your fuel filter, is it full or half full? Then go from there.

 

[The Warden]

Does the engine go down to a low RPM them come back to idle RPM? If so, it might be a metering valve in the pump.

Diesel Purge can't hurt, and certainly check/replace your fuel filter and check your lift pump output pressure, but you may want to be prepared to replace the pump...

 

[Cincinnati Guy]

Always start with the cheapest/easiest first.

 

[basilbowman]

I just changed the filter 400 miles before, and I've had some intrusion problems, so there might be air in the lines somewhere. The engine would start a bit hard, like it needed some goosing on the throttle, even when it was hot, and then if you let off the gas, it would just go out. I will start it and check the filter once it stalls tomorrow, see if that's the issue.

If it is an IP, where should I start looking for a new/rebuilt one?

 

[Cincinnati Guy]

I think uhaul may still have a few stock pumps. Or talk to Agnem if your looking for something performance.

 

[CaptTom]

I just changed the filter 400 miles before, and I've had some intrusion problems, so there might be air in the lines somewhere. The engine would start a bit hard, like it needed some goosing on the throttle, even when it was hot, and then if you let off the gas, it would just go out. I will start it and check the filter once it stalls tomorrow, see if that's the issue.

If it is an IP, where should I start looking for a new/rebuilt one?

Fuel filter would've been my first choice as it was yours.... but also my second choice on a sitting truck. There could be a lot of dirt in those tanks... did you drain the filter and inspect the crud??

Don't want to be mr. obvious or derogatory, but what about return caps??

Leaking injectors would be my first inclination after filter inspections indicating clean. Sitting o-rings don't like to sit and rot/crack away pretty easily. Real bad cap rings will also cause bad idle and hard starts....also cheap fix. No back pressure to help injectors fire.

I'm assuming you're talking about Big Blue? The one I'm ******* after. IIRC, that truck had sat for a lotta years....all indicators of dirty fuel and bad rubber/seals. Look at the supply side of the fuel pump too... leakie heaven there too.

Best guesstimate... hope it's that simple.

Total cost for me to do all the above on my sitter buy... $50.00 in parts and shipping. Filters, o-rings, olives and a hose clamp(although need to replace hose,band-aided for now).

 

[Shadetreemechanic]

Air intrusion first, sticky metering valve second.....new ip way down the list.

 

[typ4]

Sticky metering valve first if on a warm engine, loads of diesel kleen.

 

[RANOVRU]

Fuel filter first then go from there...

Mine did the same thing when it was time to be replaced (fuel filter).

 

[basilbowman]

I run SVO, and have to change my filters every 1500 miles, or when they get clogged up. The filter in it right now has less than 400 miles on it. Return lines were all done in the fall, as were filter lines, check valves, and damn near everything else, all the way back to the tanks, which I've pulled and had off four times now. The fuel lines are all solid and brand new, as is the lift pump. I don't know anything about everything after the filterhead other than the return lines, but everything before that is basically new and solid, I think. I've got some minor intrusion, as I could tell by the clear lines I've swapped in trying to track down the last little bit, but it's not real clear where it's coming from.
It did it both on low and on full tanks, on both tanks - so I'm thinking a sticky valve. The only reason I jumped to IP is because a buddy of mine once told me about getting an extra thousand miles out of his by just setting the idle higher and higher and that sounded like what I was going to have to do.
I'm going to try to clean the valves tomorrow - when I do that, should I run it hard and hot or idle it through?

 

[Black dawg]

if you let it run off of the cleaner, I would make it screw up but try to keep it running.

 

[basilbowman]

I've heard that the way to run diesel purge through an IP is to pull the line off the lift pump and off of the return lines and drop them both in a big jug of the stuff and let it run until it burns it all up - sound right?

 

[Black dawg]

yes, but I usually mix it 50/50 with diesel.

 

[basilbowman]

Gotcha - just to stretch it further, or because it won't burn right and keep the engine running if there's not something burnable in there?