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97.5 H1 Hummer 6.5TD need help

So what is the point of unplugging it? Doesn't that only prove that the CKP is either working or not?

I have a diesel compression tester otw. What should I see cold dry?

I can do the wiring testing from the service manual and let you know. I also have a new PCM otw.
 
If it runs good on the CPS it's most likely a wiring/connection issue on the OS side of things. A bad pcm is possible just not very common
 
mk1spyder said:
Which connector is the OPS? Top middle on the IP right 6 pin?

And no I dont have a diesel compression tester. But I can get one.

This is a brand new stanadyne pump benchtested prior to being sent to me from Leroy I seriously doubt the OPS is bad.

I am going to buy a spare PCM for the truck, they are only $250 new.
Click to expand...
Is it popping codes?
 
No, not anymore unless I unplug something.

Below is a clip of it running cold start without the CKP plugged in. If I unplug the OPS it will not run, crank crank crank almost hit and then nothing. But with the CKP unplugged it takes a while cranking but it will fire up and run not much smoke and rev fine.
 
I have an oscilloscope, I'm starting to wonder if my tone ring is messed up or if the cam is really off a tooth. I did change out the crank pulley and harmonic balancer could I have damaged the crank sensor tone ring?
 
If you read up I already said, AC Delco, and it isnt doing any better than the other brand that is in there.

How do I test the ckp circuit/PCM/hook up the oscilloscope I assume just signal wire and ground. The Hummer service manual sucks.
 
I read to many threads to remember details. As far as testing things I know you should be able to ohm out the wiring but beyond that your getting out of my level of experience
 
If it won't start with the OPS unplugged it may not be seeing the crank sensor. You got skills to probe those wires with a scope at ECM connection. It's just a pulse. The ECM and sensors ground on the engine by the trans dipstick for pickups, idk on Hummers - ground scope to engine after you test wires to ECM. Guessing as I don't know if CPS is 2 wires direct to ECM or 1 and ground.

In depth info on DS4 troubleshooting is a PDF on cal resistors buried in here. Frankly few understand trons it gets into.

https://www.thetruckstop.us/forum/t...-5-db2-5-7l-info-online-from-stanadyne.26581/
 
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His cpsis exact same as pickups use. Only db2 hmmwvs have the 2 wires.
Only funky wiring thing with hummers and hmmwvs is the entire frame is bolt together so there is no frame or body grounds.

@mk1spyder did you remove and clean all engine grounds?
Remove and clean fuses, and ecm connection.
And yes verify signal from cps connector all the way back. Wish I could tell you what it should be.
 
Ok so if it is 3 wires that is 5v feed, signal, and ground right? I'll check my fuses but yes grounds are perfect, I even added about 5 extra grounds to a grounding strip and tied them all together. Brand new battery terminals batteries etc the PCM/ECM connectors are in great shape but I'll double check the CPS terminals.

I'll hook an oscilloscope to it at the ECM connector and see what I see after testing the wires for continuity.

So I don't have to wait on shipping I have a diesel compression tester and new PCM otw.

What should I see PSI wise on a cold dry compression test? Also am I doing this through the glow plug hole or the injector hole? Do you kill the IP somehow prior to cranking?
 
You should pull all the glowplugs just like pulling the sparkplugs on a gasser. Hopefully the tester you bought has the correct adapter. To shut off fuel simply unplug the fuel shut off selenoid (round vertical cylinder on the IP). IIRC anything less than 400 is bad
 
Yes you want 400, and you should not have more than 10%. Variation between cylinders.

To access all 8 plugs remove dog house and after undone fuel solenoid, crank the engine a couple seconds to ensure you clear any oil or fuel before installing gauge.

Only do dry compression test. The normal wet test oil squirt done for gassers will turn that oil into fuel and it will fire the cylinder possibly b exploding the gauge in your hand.
 
Charlotte NC is not that far lol. I re-read the service manual and I think the problem is just that I am an idiot. The TDCO shows 2.46 so who knows how advanced it really is, I thought I was supposed to go toward the passenger side but that is advancing it more per the service manual. I was supposed to go towards the drivers side, which explains why it got worse by putting it towards the passenger side. Also I have done the TDCO learn like 10 times without driving the truck, and the KOKO like 8 times without driving it, from what I read the PCM will give up if you do it too many times without learning the rest of the driveability deal.
 
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