Hope you can help reduce the number of problem sources...

Recently purchased 1994 Blazer 171K well cared for and serviced regularly. New PMD and heatsink relocated atop engine cover @168K. No problems until recent trip. Service Engine Soon light illuminated intermittently, but still running smoothly -accelerating and idling -normal temp and oil pressure. Made it home, shut it off and wouldn't restart. Let things cool down (next morning) and tried again. Almost started, then just turns over. Seems like a common problem with multiple possible causes, but the SES looks like a different twist. Unfortunately, from what I'm reading, the SES is not that specific an identifier as to the cause, but seems to be very coincidental with the no start. A little direction would be greatly appreciated.

First read all the FAQ, then pull your codes via the paper clip routine. See if that helps you figure out whats happening. I had the Orginal Beta Cooler that mounted on the Intake and had a modual failure in 30,000 miles. Some folks have had good luck with an intake mount but in MNSHO I think the PMD/FSD needs to be located off the engine in a cool location for max reliablity.

Thanks for the quick reply. FAQs helped. Tried to start this afternoon and no start. I moved connector and wires at PMD and it started and restarted flawlessly. Problem solved or coincidence? Still not much to restore my confidence.

Tried to pull codes with paper clip as per Turbine Doc; I must be missing something in the procedure and don't want to experiment with electronics. Jumper to connect which terminals?

Go to kennedydiesel.com tech tips for the 6.5 for pictures of how to get codes. OBD-I is real easy.

Sounds like you've got a wiring problem in your extension harness possibly....

Pulling the codes is a definite must though.

Thanks again...

DTC35 and DTC36 - Injection Pulse width error (response time short and long)
Fired up and drove a couple miles with no unusual symptoms. SES illuminated at steady speed and acceleration - SES went out during coasting/decelerating.
Shut engine off and reread codes : same 35 & 36. Reset codes. Warm engine restart failed. Outside temp 65F.

This afternoon, it started after a few tries and ran smoothly initially. Drove around and SES illuminated again under slight or hard acceleration. SES immediately and consistently went off when lifted accelerator and went on under acceleration. Accelerated to 3000rpm a few times then it started to stumble, losing power gradually and steadily until it shut down. No restart. While waiting for a tow, I reread the codes. DTC36 and now, DTC85 Undefined Ratio Error.

Once again any direction would be greatly appreciated. Meanwhile, looking for nice used service manual so I don't bug y'all so much.

Thanks!

35 and 36 together is bad news, fuel solenoid in the pump is worn out. Its pump time.

Sounds like you've got a wiring problem in your extension harness possibly....

Pulling the codes is a definite must though.

After pulling latest codes (36 & 85) since the latest no start, thought I'd take another look at the relocated PMD/heat sink setup. I tightened the bolts a bit and had a successful start. While running, I moved the cable around, and then I moved the heat sink resulting in an instant shutdown. I'm no electrician, but I wonder if anodized aluminum is conductive; assuming that it's not, I buffed or filed every point of metal-to-metal contact. Reinstalled PMD/heat sink and went for a ride. Smooth running and no SES. Rechecked PCM - no malfunction codes!

Thanks for the help and support. Just like the early FI Datsun Z cars, the connections are critical. But the PMD is even more demanding as the driver for the solenoid. That's why the problem manifested itself more under acceleration. Makes you feel like you forgot to connect the coil wire on a gasser.

reZtoration

Check your ground wire on the IP, should be a ring lug attached to the pump that goes into the PMD cable, The PMD should not have to be grounded .

Someone with MORE expetise plese, verify....

Check your ground wire on the IP, should be a ring lug attached to the pump that goes into the PMD cable, The PMD should not have to be grounded .

Someone with MORE expetise plese, verify....
The previous owner had the ground wire attached to the heat sink; in doing that, the heat sink needed to be solidly in contact with its mount. Since my heat sink had come loose, corrupting the ground, I was getting codes and problems relating to the IP not getting enough drive from the PMD. That little ring lug must have a solid ground otherwise you'll get codes and symptoms that point to a failing IP/PMD relationship.
Since assuring a good ground, I have had no more SES or codes. Thanks again for the suggestions; it's amazing how much you learn about these beasties when investigating one problem.