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98 K2500HD runs rough, possible IP?

well folks, she is fixed!! (in this issue anyways)

Before I got too wild, I remembered that the fuel lines would still rotate even with the fittings torqued.

All it turned out to be was a mis- machined Delphi lift pump that the PO installed. Ran out of threads before it was tight, so it was sucking air around the fitting.

I didnt even change the line, installed a new AC Delco made in USA EP158 LP, and problem solved! :)

Love it when its simple!

Now for more fun, got oil oozing out of a oil cooler port on the block, and out of the crimps up front. She won't leave the cement pad in from of the shop till I get that changed. Amazed it did not let loose on the PO.

Looks to have a reman t-case, its painted black and nothing else is underneath, new tailshaft sensor, and perfect oil level, so pretty pleased about that.

Might have a power steering leak that needs dealt with.

Has a bad block heater and blocked open t-stats. might run it for a little while this way since its winter and wont overheat, but judging by the buildup of crap between the radiator and condenser, I probably should address it sooner than later.
 
"wont come on after shutting off then trying to fire right back up, but will come on on initial key on"

This is because the ECM does not completely power off for like 30 seconds after key off. You can read out the ECM sensor data at the ALDL for this amount of time. Seriously I could read the APPS moving after key off...

Any Key Off I did and then waited till the data quit the SES and STS lights would properly bulb check by coming on. If I Key Off and back on quickly the bulbs were random and usually didn't turn on. the SES was the most often one to come on and stay on. STS was completely random.
 
ak diesel driver said:
air in fuel will cause it to stumble. saw one recently that only had air in the system at about 2k plus rpm. no air at idle. it also held 3 psi at the same time. bypassed the entire fuel system and still had air. evidently a failing IP can make it's own air.

a bad crank sensor won't cause it to die as it will run on the OS. it can make it stumble buck and snort in no particular order tho.
Click to expand...

Did you ever look at the 'last ditch screen' to see if it plugged on the IP making it's own air?
 
WarWagon said:
Did you ever look at the 'last ditch screen' to see if it plugged on the IP making it's own air?
Click to expand...

Yes, IIRC I put a new last ditch screen on (old one had a few specks).

never did get around to a clear line, but that was the next step after LP.

Essentially I had Leroy's hose and fittings and was ready to delete the steel line, then figured that the line probably should not be able to rotate in the pump with the fittings tight, so I investigated from there.
 
Depending on how much of the fuel system was bypassed: Not thinking of the screen in the FFM but the one on the DB2 IP nose just before the rotary vane pump. That's maybe a IP shop repair only anyway. Plugged anything will vapor lock boil diesel from the vac the pump can pull.

I don't think the DS4's have a screen in them?
 
GM Guy said:
well folks, she is fixed!! (in this issue anyways)

Before I got too wild, I remembered that the fuel lines would still rotate even with the fittings torqued.

All it turned out to be was a mis- machined Delphi lift pump that the PO installed. Ran out of threads before it was tight, so it was sucking air around the fitting.

I didnt even change the line, installed a new AC Delco made in USA EP158 LP, and problem solved! :)

Love it when its simple!.
Click to expand...

I use the Airtex E3158 made in USA too perhaps the best lift pump I've used.
 
well, apparently the truck is not wanting to go to work :), put a fresh set of braided cooler lines from Leroy on, and fire it up, and now its missing again.

I did hear the LP change tone like it did the last time. (sucking air)

Methinks sliding the suction line back and forth hooking it up, the old rubber at the crimped connection didn't like the flexing and went to sucking air.

I will bypass it with rubber like originally planned and try again.
 
Ok, more fun, bypassing the tank and fuel line entirely (got hose and fittings from leroy, end stuck in a 2.5 gallon jug of diesel) still results in rough running.

Yesterday's sequence of events was to fire it up, and drive it over to a combine on the other side of the yard I had just bought, and the PO used Road diesel exclusively, no blend at all.(So I gotta drain it out and replace with red farm diesel, not going to let that road tax go to waste on farm equipment! :) ), so with the pickup pretty low on fuel, I rigged up a funnel and some hose, and filled the tank till overflowing with diesel, shaking the truck to get as much air bubbles out as possible. draining out of a small petcock this took a few hours.

While fueling I replace the steel line with rubber using fittings and hose from Leroy.

Now full, I fired up, took it out of the far east driveway onto the county dirt road, lightly give it some throttle, and it started to accelerate normally, and then it died. kick it in neutral and refire like nothing happened.
pull around far west driveway and circle back to shop, back in front of it, shut off, plug in code reader, read the first group of codes above, clear out, shut off, unplug, refire, rev to 2200 sustain for 30+ seconds, dies, check code, get the P0251 above.

Fast forward to this morning, I tighten the brass fitting on the FSU a little tighter, fire it up, sounds good, only the occasional hiccup. Let it warm up, and it gets worse.

Change out with a known good PMD ( heath kit with a flight systems) and no change. revert back to the currently installed remote to grille PMD. (PO work, not mine, looks like an import harness)

Undo the brass adapter fitting off the FSU, and connect the 2nd nipple and fitting I got from Leroy, connect the excess hose left over from the FSU to LP hose project, dip it into a diesel jug, fire it up, and it sounds the same.

I wanted to skip doing it, since it looks like such fun with the dual t-stats, but my next move is to go put clear line on the return out of the IP and see if the IP is making its own air.


So, what does everyone think it could be? wiring on the IP? IIRC the connector is zip tied to the Optic sensor, due to a broke off clip on the plug. I will pull upper intake, fiddle with wiring, and put the clear line on, and try again.

Any input greatly appreciated!
 
also, to recap on info, fresh vac pump, harmonic balancer, and pulley damper, it needs t-stats, as they are stuck open, and the PO somehow has the fan clutch locked solid (looks like took a punch and hammered the seal in on the shaft) so it is not warming up.

New AC Delco EP158 LP, and bypassed the steel line entirely.

Would a guy be able to do something with Key On Key off to get the pump to time itself, or will I need to take to GM and get a Tech II hooked on?

The reason I ask, is that I wonder if the pump is too retarded, as would the cold advance explain why it runs a little better cold?
 
OK, weather warmed up enough to go play.

I put a clear line on the IP and luckily no bubbles.

I unhooked the Optic sensor, and bingo, she runs smooth (after you floor it it get it to catch anyhow)

I also unhooked the ECM Coolant temp sensor, and it is rusty, but luckily still makes contact, goes to high idle and low idle when you unplug and plug back in.

I am still curious as to why it ran perfect that one time, but now is back to running like crap.

What do you think the chances are that the sensor is clouded over and running some fuel through it and getting her warm would help?

If replacement is in my future, I know its not kosher to replace it yourself without sending it off to a stanadyne shop for calibration, but honestly for a 500 dollar beater, could I actually do it?

If I could, how hard is it? does the top cover need to come off?

Any input appreciated!
Thanks
 
The Optic Sensor could be changed, it is below the top cover. The one thing you would need is a scanner that can read mm3 fuel output at idle so it could be set within a range of 6-11mm3. Anything less than 6mm3 will make for a touchy throttle.
 
Scribe a real accurate line you can put the new one to. It'll be close. I'd also run the scanner on it before too just to see where its at don't try to do a TDCO until your satisfied with where it's at as changing pump timing seems to affect the mm3 too.
 
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