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98 K2500HD runs rough, possible IP?

Unfortunately I do not own a scanner.

Also, how will they behave when they fail?

It has been tripping codes concerning the OS, and I have tugged on the harness some with no change.

I did tug pretty hard once and got it to die, but I think I might have gotten the connector to pull out enough to break connection. (connector clip is broke, held in via zip tie)



How does one change the OS? does one take the top cover off and there is screws underneath, or is the snap ring all that holds it? I assume it drops out the bottom of the top cover?
 
So guys, I need your opinions.

I have been warned of potential runaways and other scary crap if a guy does not get the OS installed correctly, and am wondering if I would be better off swapping pumps instead.

So, if it was your truck, how would you proceed? change OS, or change IP?
 
If you don't is a scanner, is this the excuse to buy one? You have a big enough fleet going to justify one.

Get a pvc cap from Home Depot and pull the intake off the air filter housing so if you do get a run away from playing with ip, you can just cap it to kill engine.

Once you have the ability to play inside the ip, and not panic, you can save $ on these problems with all the trucks. Weren't you nervous a touch first time you learned to do anything new? No different. Whip that fear.
 
So everyone recommends give it a shot replacing the OS as long as I have a "snuffer plate" to slap on the intake in case of emergency? :)
 
Video is actually good so if you get lost on how it was, you can go back and look at how you took it apart.

Then when it works,my oh go from student to teacher.
 
well, figured I would fire this thread back up.

roughly June or July:
Drained the tank of red diesel this summer and filled it full of clear with a heavy dose of stanadyne lubricity formula with a new filter. drove around the yard a little, and then let it sit till recently.

"cured" the OS problem, it is now driveable, but it is still occasionally tripping codes and going into limp mode.

When floored, it will die, sometimes it will pick back up if you let completely off as its dying.

It will fishbite occasionally, has a no name small black wire cable relocation kit in the grille, I have a used intake mounted PMD that was still operating OK (occasional fishbite when warming up) that I just swapped to a Leroy kit that I plan on trying out as well.

I will go write down the codes and report back, but the one that was odd was a PCM fault.

Where is the PCM ground? I cleaned the two at the back of the engine, but still need to clean the one on the frame and the one on the firewall.
 
IMO this has air or vapor lock from a restriction written all over it. Fuel tank lining coming off plugging the screen will show up as silver runners in the fuel filter. What's the clear IP return line look like when it's stalling out? Remove the hood if you have too, but, when it's stalling out you should be able to stop and pop the hood to look for air. Shut it off when it's acting out and look also works.
 
old fuel filter was dark, but silver free.

I will check after dying on the road, but when I was chasing the OS issue I had clear line on, and could not see any air.

I will get a PSI guage on it sometime and tape it to the window and go for a spin.

Codes were:
P0183 IP related
P0251 IP related
P0606 dying ECM!?!?
P0236 only cheap news, hopefully a bad boost sensor.
 
I overlooked the ECM failure code. Ground is 1/2 of the picture for the ECM. Bad ignition switches, fuse contacts, ECM pin contacts, etc. supplying low voltage on the positive side is the other half. Although this is an old ECM and very well could have died of old age I suggest checking the voltage to the ECM by back-probing at the ECM connector.

Few ways to mess with a computer: Low voltage via high resistance on the positive or negative side, shorting sensor 5v references, and feeding it AC. The only AC source I know of offhand is an alternator going bad.

So back-probe to find the +12v memory wire and then you can eliminate that one as you track down the switched 12v power. Two +12v power sources and one ground. I have seen ECM's loose their marbles and refuse to store codes with the SES light on (ECM failure), store false codes (voltage issue), Refuse to go into diagnostic mode (low voltage) due to a bad splice on the positive side, and other weirdness.

With the voltmater on the ECM power and ground wires: fire it up and look at the voltage between the +12v and ECM ground - the entire point being to see what voltage the ECM is working with. (You ground your probe to the frame cab etc. you may miss the high resistance ground the ECM could have. I do not know what voltage the ECM fails at. Fail is where the processor attempts to make a "0" a "1" but the voltage is so low that the "1" gets read as a "0".

Some scanners can read ECM voltage aka the "easy" button.

Other than that swap the ECM for a known good.
 
something that I think I forgot to mention was that it had a bigger alternator swapped in, and it had failed in glorious fashion, had black staining around the plug. (shot fire out when it died? ) so is it possible there was a voltage spike that harmed the ECM?
 
some new info: pulled ALL of the underhood fuses and relays, and shined everything up, everything looked kinda "scummy" might have been white corrosion if the fuses are aluminum?

ECM-B fuse looks like its gotten hot, and its supposed to be a 20 amp, and its got a 30.

What all do you guys recommend to put on the fuse terminals? Dielectric or the electrical contact grease? (the brown stuff) I have both.
 
I put dielectric on the fuses and relays, and fired it up. Never tripped a CEL, but still had an occasional stumble.

Hooked up the used PMD on the new Leroy heatsink and harness and fired up again, and IDK if its the placebo effect, but I thought I noticed an improvement. still had the occasional hiccup.

I hooked up a fuel pressure guage and idling it runs 9 PSI, and at WOT it never fell below 2 PSI. It runs strong, it will break the rear tire loose and can get to 90 mph in about 3/4 of a mile, closer to half a mile if you do a boosted launch. (hardest I have ever drove a 6.5L, when its the auto truck it will not be treated like a baby. :) )

But, after getting it warmed up some, it is stumbling and hiccuping alot. surges when I get into the throttle, but smooths out some (not completely) when I go WOT.

But, the good news: its not tripping any codes anymore.

One more thing: will having stuck open t-stats be a factor for anything? maybe it wants to fine tune the timing but its running too cold to do so?
 
nope, gotta have one truck I truly have no attachment to so I can use it hard. :)

4 foot snow drift between here and town?

To the snow bogs in 4 high!!!!
 
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