Pump Issue??

[rattleonby]

Hello fellow OB members and idi owners!!

I have a recent issue with my truck that has me scratching my head just a tad. Now the goods...

Symptom:

My truck will stall if i abruptly let off the skinny pedal at an idling standstill (Like if you were to test for bad motor mounts) but it will do it regardless if you hold the brake pedal or not. It will not do it if im rolling over lets say 10 mph.

I've ruled out the pickup pump fuel pressure at the filter head, pressure is fine. Fuel filter is only 1k old and has had only diesel ran through it.
It will do it cold or warmed up but not on fast idle obviously because of the raised idle speed.

I almost thought maaaybe a dragging torque converter but it will also do it in neutral or park. If it was that most of the time i see that the truck will stall as soon as you put it in gear....So thats ruled out.

I AM running additive in the truck to maybe see if it was a fuel quality issue or possibly gelling. It has been getting down to 20-30 degrees here in PA. It does it on both tanks also so its not a shower head or selector valve issue nor is it fuel quality....So thats also ruled out.

I'm left staring at the possibility of maybe the idle circuit on the injection pump?? Or maybe someone has seen the engine torquing slightly pulling on the engine harness causing the shutoff solenoid to lose its power??

Just wanted to see if anyone here has experienced this problem that im having....Other than that the truck runs great and has all its power..


Thanks, Merlin

 

[Wellused]

What rpm is your tack reading @ idle? I had a 6.5 that did that.I set idle up ever so slightly and it stopped.

 

[rattleonby]

Probably a hair above the 500 mark. So for arguments sake lets say 550-600? Its too cold out to go look at the valve cover sticker haha.

 

[Wellused]

That seems kinda low.I dont know how accurate the tach is in mine but it says 675 or so

 

[OLDBULL8]

Is the idle set at 650-675 RPM? Check the mechanical advance arm on the IP, stuck or broke. Winter fuel blend won't gel, maybe at -10*. How many miles on the IP? Is it original OEM?

 

[Wellused]

Oldbull..Delphos..my old stomping grounds If you were ever in hot rod scene in you area..my uncle was quite the icon up there

 

[rattleonby]

Idk where the idle is set. She's been idling the same ever since ive owned it for bout a year now. Always runs good starts right the hell up. Pump is oem yes with 143k on it. Guess ill check the arm when i have light tommorow.

 

[Wyreth]

It's prolly just a sticky valve in the IP.

The ATF in the Filter Trick (tm):
Dump fuel out of the filter, fill it with ATF. Or diesel kleen, your preference. Make sure to fill the filter only from the outer ring of holes so everything the pump sees is filtered. Start the truck and let it idle for about 30ish seconds. You'll hear it mellow out just a little when it starts to burn the ATF. Shut it down immediately, and let it sit overnight. Next morning start it, let it warm up, and hammer it hard for a few miles. Should fix it.

 

[rattleonby]

Hmm I like that idea. I was leaning toward something sticking in the pump, just never knew a decent way of goin about fixin it. Thanks for the advice guys.

 

[HammerDown]

It's prolly just a sticky valve in the IP.

The ATF in the Filter Trick (tm):
Dump fuel out of the filter, fill it with ATF. Or diesel kleen, your preference. Make sure to fill the filter only from the outer ring of holes so everything the pump sees is filtered. Start the truck and let it idle for about 30ish seconds. You'll hear it mellow out just a little when it starts to burn the ATF. Shut it down immediately, and let it sit overnight. Next morning start it, let it warm up, and hammer it hard for a few miles. Should fix it.

Just a question, but would come out of a ATF bottle that would be dirty and require filtering?

 

[Leeland]

Second adjusting your idle. Don't forget that along with the advance you have the solenoid keeping the throttle from returning fully. Start simple.

 

[gandalf]

It's prolly just a sticky valve in the IP.

The ATF in the Filter Trick (tm):
Dump fuel out of the filter, fill it with ATF. Or diesel kleen, your preference. Make sure to fill the filter only from the outer ring of holes so everything the pump sees is filtered. Start the truck and let it idle for about 30ish seconds. You'll hear it mellow out just a little when it starts to burn the ATF. Shut it down immediately, and let it sit overnight. Next morning start it, let it warm up, and hammer it hard for a few miles. Should fix it.

Wyreth is right in both diagnosis and fix procedure. It sounds like a sticking metering valve in the IP. Soaking the IP with ATF will usually fix that, though not always. Every now and again there is just too much damage of one sort or another, which will require further action or even a new IP. Usually, though, the ATF will fix that metering valve.

Let us know how it works.

 

[Agnem]

DO NOT dump fuel out of your fuel filter! That is an easy way for dirty fuel to make its way onto the clean side of the fuel filter, and then get to your pump. If your going to try such things, use a NEW filter, or shut off your fuel supply and run the filter dry by drawing the fuel out of it. I sell those filters for about $25, and your probably due to change it anyway, so why chance it? Your going to need a new filter with a new IP anyway.

 

[icanfixall]

mel makes a good point. if you want to fill any fuel filter please pour fuel or whatever into only the small outside ring of holes in filter. pour it down the center big hole and dirt gets to the pump. the filter is not doing its job by filtering ..avoid the big easy hole if you do this. and using a new clean filter is a great idea. a cheap filter costs 25 times less than a new pump..