Update: PMD's arrived. Truck had sat for three days. I pulled plug from OEM PMD, mounted extension, pluged in new PMD (left existing ground in place) and tried to start, same issue. So I tried a 2nd new PMD (I'd bought two, along with the power transistors to repair OEM unit.) Still same issue. So wanted to isolate the new jumper cable, pulled it out, placed new PMD w/Heat sink in OEM plug ( I was able to pull enough slack on it to do easy enough.) Still same, turning over fine, no fuel. I loosened the bleeder valve on filter housing and air rushed out. Start more reading, thinking prime issue, pull fuel relay and jumper (not recalling exact numbers, but far front left, to far right rear (terminal 87? and one beside it is 87a seem to recall.) At this point, I've turned engine to start several times. At about time I'm about to wrap up to return home to read more it tries to start as I'm releasing ignition switch. The bleeder is still open, and the jumper is in place. So I turn ignition switch to start again (after GP light extinguishes) and it fires up. Running, but NO fuel is coming from the bleeder valve (think this is odd, but its running. Note I'll figure out of OEM PMD is bad after I get it home.) So load up, drive 15 miles back to house. Park it. Turn it off. Restart it no issues. Later I come out and do same. Now I've left the new PMD w/Heat sink in OEM plug, leaning with a plastic tie strap to the manifold. Everything is good. Next morning, same, fires up, I disconnect my '07 Duramax from trailer full of wood and connect to this '95 6.5L. All is great, truck pulls well, load springs are great, no sag, I'm really digging this 6.5L. (IMHO, Truck was super good deal as tight as it is, so worth the time to get it right.) I have to stop about 20 miles up road, to attend some civic duties I volunteer for, then about 2-3 hours later the ball buster occurs again. Exact same scenario. I'm backing the trailer up when it goes dead again. Essentially almost identical in events to first go round. I try jumping the relay again. Have a friend turn to start as I'm holding and listening for the inline fuel pump, aka the LP (ok, for my own peace of mind, I am referring to the pump that looks like a filter that is housed on frame rail under the driver's seat.) No joy, nothing from it. Try with relay in place as well. For gp I changed out the PMD again, same issue. I'm now reading in an online manual to determine what triggers what to actually turn on the fuel pump, as I want to see fuel coming out of that filter's primer valve. Ok, so if I haven't lost you yet, here's what I'm tentatively considering for next steps in trouble shooting:
1. Put 12Vdc to the LP's plug. I happen to have an external battery with me and jumper wires so this evolution should be easy enough. If it is good then it should pump even if key is off since I'll be supplying 12v directly to it. This should definitely tell me the lift pump is good. Yes/no?
2. On the '95 I understand the OPS is behind the fuel filter near the firewall. Everyone and their brother states to ensure to use an AC Delco (can someone tell me specs on why so critical? I have a relative that thinks only OEM Toyota parts for his Toys, but I don't follow same logic. I know/believe there are other mfr who mfr good parts and pieces.) Here is where I question how to TS, troubleshoot, this circuit. Will I have 12V at one of the terminals of the relay during the starting phase of starting the vehicle, aka while turning it over? I'm ok with replacing the component. But prefer to know its faulty vs replacing components to eventually find the lucky easter egg.
3. I did clean the ground terminal of the PMD and replaced it at its OEM location.
What gets hot, and causes intermittent problems? I've seen pix of the OPS where it's internal organs burn apart, typically this is a hard break, burnt contacts or metal don't typically cool off and make contact again. So I'm skeptical of it as the culprit.
I want to say I read where the injector pump can be overcompensating for a bad lift pump. On the '95 when should I definitively feel the lift pump working? At point of turning engine over, caused by the OPS sending signal to the relay which then energizes and supplies voltage to the LP?
Appreciate your time in reading and reviewing my thoughts and questions.
