96 6.5TD will not start after replacing PMD

[mike928s5]

Hi this is my first post to this forum and I am desperate for someone to steer me in the right direction. I will try to give you as much info and backround as possible.
I have a 1996 suburban 6.5. I replaced the PMD six months ago and the truck run fine untill last week. While I was driving I felt it stall for a few seconds and then actually increase in RPM whithout me pressing on the acccelerator. The whole thing lasted 10 seconds and the truck died. As soon as I pulled over and opened the hood I could see smoke coming out of the PMD and it felt really hot.
NOW THE INTERESTING PART!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I thought OK fried PMD I will get another one and get driving again.... well I tried two units new out of the box and the truck will not start or even try to do so.
I am 100% sure that my PMD was fried BUT there is something else going on that is driving me crazy because I dont know what it is.
I checked the lift pump and it is working, I do not get any fuel though when I loosened the line to an injector. the solenoid makes a click when the ignition is turned on but I cannot say that good or bad just by that sound.
I find it hard to beilieve that the injection pump went bad in 10 seconds

Please help feel free to give your opinion even if just a guess it might help me see things from a different point of view
Thanks in advance Mike

[rabt]

I may be way wrong here but if your PMD fried that bad, that quick, could it have blown a fuse somewhere??

I'm sure someone that knows alot more than i do will chime in shortly, but this is just the Electrician in me coming out :confused:

[mike928s5]

Thanks for the reply
I did check the fuses and unless I am missing something they were OK
The thing is that I have 12v and 5v at the pmd connector

my guess so far is that the solenoid on top of the pump is not getting the signal required to open/close hense no high pressure output from the pump

[Bnave95]

Through all of this, you have no SES light?

[mike928s5]

I do but I got no power to the diagnostic port so i cannot read the codes
I need to fix that first but I dont know which pin is supposed to have 12v
I know is supposed to get power from the cigarette lighter circuit but I dont remember which pin

Today I checked the fuel shut off solenoid and it does not work even when I apply power to it. the thing that wories me though is that yesterday it was making a clicking sound when I provided 12v, maybe it was an intermited problem
I will get a new solenoid and go from there

The other thing that I did was to supply 12v to the pump solenoid the one driven by the PMD and although I used a piece of 16g wire the wire overheated within 5 seconds, the solenoid was working but if it is drawing too much current that will explain the severe overheating of the PMD

Anybody with any info please shoot this way
Thanks

[rjwest]

Just read post, how did you make out,?

[Hubert]

How is it going?

1. I read once that ignition on (Key on) 12v is supplied to fuel shut off solenoid from an ignition circuit. But PCM is the other part of the "switch" and makes the ground if it sees everthing is ok. ie bad FSD the PCM shuts down fuel shutoff solenoid. It has to click to work. I don't know if you can feel it if someone cycles the key on and off a few times its hard to get a full grip on it. But you might be able to get a few fingers on it.

2. Is the wiring harness ok? Shorted or open? Check all harnesses that plug into the IP too.

3. Have you put in a new calibration resistor? I have been reading some posts about the calibration resistor and still not clear on it. Some say w/o a resistor the truck won't start if the PCM tries to read the resistor value and does not see it. I have also read that the PCM/FSD will default to last stored value of calibration resistor. If your FSD smoked that bad it might have fried your resistor too.

4. Need to get codes. I don't mean to be a pesimist but sometimes rev up w/o throttle is bad news unless its just air making it run rough.

[mike928s5]

hanks for the replies guys
Here is where I stand as of today really not much progress but anyway

The shutoff solenoid is has not arrived yet
I cannot read the codes even though I bought an autoenginuity tool (scanner) with the enhanced GM package. The obd connector on my truck had no power on pin 16, cigarete lighter fuse was ok and since I had more important things to worry about I just spliced a wire and supplied 12v. I still cannot establish a connection with the obdII. Tkhe scanner works fine on other GM vehicles I will call autoenginuity and ask for support.

In an effort to explain the actual frying WITH SMOKE!!! of the pmd I was thinking of what the pmd supplies current to, well unless I am missing something the only thing will be the fuel solenoid on the pump (not the shut off). well I couldnt resist connecting 12V to test it. IT DRAWS SOME SERIOUS CURRENT OVERHEATING 16G WIRES. it clicked but not in a very "crisp sounding" way
So in the heat of the momment I had the bright idea to mess with the IP itself and I managed to unscrew the solenoid assebly. (now I now why is not a good idea nobody sells the damed things). Anyway it was actually stuck the plastic had melted and glued the moving part (dont now the proper name)
I managed to find a used one its on its way, the question is did I find the problem or did I caused it to overheat and get stuck by applying 12v to it?

[john8662]

Hmm, sounds like you got some electrical gremelins going on here..

About the solenoid, it should respond to 12v and not get hot, afterall it's taking current the entire time the engine is running. I've got an old one with a bent plunger that I'd test tomorrow night at the shop to verify this...

Check all your fuses, you have two fuse panels on that truck. One is inside the cab on the side of the dash, open the door and remove the panel on the side of the dash, that's a large portion of them.

Second, there is a panel in the engine compartment next the abs controller and on the driver's side. Open this panel and inspect the fuses within, there are several engine related fuses in this location. Even one labeled f sol, for fuel solenoid (well the shutoff one)

The problem with not getting power to the OBD-II connector seems fuse related or pcm related. I'll get a chance to refer to some manuals not with me currently that might shed some light on that situation.

Also, do you have a known good PMD? You may also need a PMD harness that connects to the back of the fuel solenoid on the back of the pump (inside the mess of injection lines).

J

[JohnC]

When you melted the FSD you likely damaged some wiring or maybe blew a fusable link somewhere. No power to the ALDL is telling.

The uncommanded increase in RPM was probably caused by the FSD going full on (shorted) and the stall was the PCM droping the shutoff solenoid as a failsafe.

[andro70]

I have a 1996 2500 with 212000 miles. I recently replaced my FSD because that is what I've always done when I've had similar problems and found out that my fuel injector pump was shot. I replaced my fuel injector pump and that fixed the problem.

[mike928s5]

thanks
well fuses are OK dont know where a fusible link might be though
The diagnostics connector did not have power long before this problem and the truck run fine for six months with that problem

I think I might be wrong on my initial post about the increase in RPM whwn it failed. coming to think of it it I believe it just felt like an increase because as i wascruising right above idle it decelerated and then accelerated for a few seconds but the acceleration was back to the speed I was initially driving at.

As for the solenoid although not an expert on diesels my feeling is that its not normal for a transistor driven devise to draw that much current

I have a "known to be good PMD" well not 100% sure though because I am making the assumption that two brand new PMDs to be bad is not very likely the case but there is that possibility. I am not buing a third one though unless I can find out for sure.
I have a new harness and I will also check the old one for resistance/continuity.
I dont remember if I had mentioned this but I do have 12v and 5v at the Pmd connector with the key on.
thanks to everyone that is taking the time to pitch in their ideas

[john8662]

Here is a little more information I found on your dead ALDL connector.

1. CHECK condition of AUX PWR Fuse. If Fuse is open, LOCATE and REPAIR source of overload. REPLACE Fuse.
2. CHECK Grounds G103, G104, and G200 are clean and light.
3. CHECK for 12 volts at terminal 16 (CKT 840) of the DATA LINK CONNECTOR. REPAIR if necessary.
4. CHECK terminal 4, CKT 150 and terminal 5, CKT 451 for continuity to ground. REPAIR if necessary.

Besides this, I'd pull the PCM out of the glove box and check the connectors on it, make sure they're all tight, or unplug and re-connect ensuring a good connection.

I'll bet your PMD is good that you have as a replacement.

I guess the next step will be to get that new shut-off solenoid installed. I still haven't gotte to my bum solenoid to check it's operation, will later.

J

[mike928s5]

John Thanks for taking the time to do this
I dont know where Grounds G103, G104, and G200 are!
everything else checks OK
I still dont have the solenoid
even if I did It wont do any good until I get the fuel solenoid
If you read my other post " need a fuel solenoid...... " you will see where I am at right now

[rjwest]

email me (privat) I can probably kelp tou with the solenoid,

Fuel Shut Off Solnoids don't fail to often, when they do they
usually fail 'open' high resistence,

You can take it off easily, and test it with a battery

check the pins in the PMD and solinoid connections...

[mike928s5]

Hello guys
I really need to fix the OBDII connection issue. I have 12v on pin 16 and ground on pins 4 and 5. I tried both my autoenginuity scan tool and a snap on one. I cannot communicate with the vehicle. the condition was preexisting its not something that came about after burning the PMD.
thanks

[mike928s5]

Does anybody know if the purple wire from pin 2 on the connector runs straight to the pcm?
If yes do you know which pin?
I would like to try running a jumper wire connecting the two and see if that fixes the communication issue.
VPW is the protocol used on GMs and is a transitioning protocol moving to fast for a voltmeter to pick up (i do not have acces to a scope right now) thats why I would like to try the jumper wire
thanks