Diesel Doctor

[Uncle Al]

John C., Thanks for responding to my plea for help. Unfortunately, I still need it.
First, let me answer your questions; When I first had the problem,I cleaned the ground terminals at the right rear corner of the block.(there were 3 ring terminals with 4 wires attached); then I cleaned the three connectors at the firewall. It didn't seem to make a difference. Then I proceeded as I mentioned in my previous threads.
As far as the computer is concerned, I checked the numbers on the unit and the last four digits on the replacement matched mine. The odd thing is the PROM chip had a number on it that started with BP and on the bottom of the chip the word BLUE was spelled in raised letters. I've changed GM chips before but never saw one like that. My FI pump is not the original . It was changed sometime before I got the truck. I believe the original pump was a 5067 and this one I believe I remember as a 5288.

Now for the good part! I went out this morning to start the truck and it wouldn't start.(I had not tried to start since my last post) I had a harness extension going from the OE PMD connector to my remotely mounted PMD and I read that these can sometimes be a problem. I disconnected the extension, pulled the orginal connector up the PMD and plugged it in. The truck started right up. I drove it for a while and experienced the same problems as before. I drove for a longer time and the Check Engine Light came on and the RPM increased during idle when I came to a stop. I drove the truck home and shut it off. I waited a few minutes and tried to start it. No Go! I checked for codes and had the same three codes I had in the beginning DTC 18, 35 ,and54. I tried the truck again after it cooled but no go. While I was at I checked the connector at the PMD as per the GM test Procedure. I got the right values at the lettered terminals but the coding on my connector was differentt than what was in the book. The connector shown in the book was labeled from top to bottom as A D C B and mine was A B C D E F . Has this connector been changed or are the depictions in the book for reference only.

If you still believe that my problem is a contact or wiring problem, will I have to take the manifold off and check the harness from the firewall to the pump, or is there an easier way. Any help would be greatly appreciated. It doesn't seem to matter what I do, the truck starts when it wants to. An intermitent short could do that but couldn't a finicky component do the same? Please help!

[JohnC]

ADCB refers to the harness end of the cable. AEDCBF is the PMD end. B and F go to the fuel solenoid. The ground wire must attach to the injection pump, NOT the PMD heat sink.

Note that they match up PMD - Harness as A-A, E-D, D-C and C-B then B-red and E-black