Won't Start

[bobt]

My son has a '98 6.5 dually/4L80. Replaced the PMD a while back. Truck drove fine the other day. Tried to start yesterday. Wouldn't initially. Played with the PMD connection under the bumper (extended wiring harness and heat sump) and started. Further playing and shut down, wouldn't restart, moved the PMD to IP, still wouldn't start, tried new different PMD, wouldn't start. Getting fuel to/ past the fuel filter which is not too old, IP soleniod is clicking, lift pump is working, grounds appear to be good, batteries are good. Tried starting with the fuel cap both on and off. There was slight vacuum when cap was opened. There are no codes.

Haven't checked yet for air in return lines. MY current thought is that it is most likely an electrical problem, but trying to look at everything. I did a search to answer two specific questions I have and couldn't find straight definite answers, so:

Questions:
If the PMD is not working properly but everything else is, will(can) you still get fuel to the injectors (check by cracking a line open)?
In a '98, will a faulty OPS prevent the vehicle from starting?

Bob

[suburbanK-2500HD]

Try to open a injector line at one of the injectors, wont hurt.

The PMD controls the fuel solenoids at the pump, as a know.
The ops controls the lift pump. When there is enough oil pressure it starts.
But i think you should be able to start the lift pump if you open the bleader at the fuel filter, and with ignition on it will start to pump... !

Normally it can run for a few seconds every time you turn on ignition, if the truck have not been used for a while.

[racer55]

With a faulty pmd that works intermittantly you will get fuel at the injectors when it decides to work and none when it doesn't.
Where is the ground located on the IP PMD harness?

[rameye]

Its my experience that when the PMD goes south so does fuel at the injectors. However many other components can cause this condition such as the shut off solenoid.

[racer55]

Its my experience that when the PMD goes south so does fuel at the injectors. However many other components can cause this condition such as the shut off solenoid.
Agreed but later stanadyne PMD's can be intermittant failures as well as no start hot failures.

[rameye]

4 sure...the failure may or may not be a permanent condition...in the case of a PMD...

However if the PMD has been failing regularly...it will one day give up the ghost and not come back..

[suburbanK-2500HD]

Funny thoose PMD´s, i once moved the PMD to the front behind the headlight at the left side.
But i moved it back at the intake.
I experienced lower idle rpm. and not the same behavior of the engine.
I have had it at the intake for 1-1/2 year now, and it works fine.
I check the torque at the PMD regularly....

The PMD is the only engine/fuel component that has failed on my truck
"Knock on wood". Hope it stays like this, i love these rattlers..