94 K2500: DTC 18 & DTC 15, infrequent hard starts

[ishiboo]

I have a 1994 K2500 with the 6.5 and 5-speed, and occasionally run into hard starting (very infrequently) and stalling (EXTREMELY rare.)

SES light is almost always on, except above about 3000 RPM or when cruising at 70+ mph, the light goes off. Slowing down causes it to come back on. Codes read DTC 18 and DTC 15.

I know a lot of the issues here are IP, PMD and lift pump, however I'm curious if these particular symptoms point to something specific so I can start there. I think the cheapest start is I'm going to throw a small gauge on the lift pump and replace the fuel filter and verify flow to the IP.

PMD is original and still located on the pump.

Any thoughts? Thanks!

[Robyn]

The DTC 15 refers to the "Coolant temp sensor" (on top of crossover)

Likley has failed

The DTC 18 is "pump cam reference error"

This issue envolves components on the inside of the IP.

Check the connection at all the plugs on the IP to be certain they are clean and secure

Battery cable connections (grounds too) along with the small ground wires at the RH rear of the intake manifold.



Battery voltage of 13.5 to 14V is needed at the main supply to keep the electronics happy. Low voltage can cause all sorts of wierd stuff.

If nothing ominous turns up a real time scan with a tech tool is about the only solution to isolate whats going on.

Replace the coolant temp sensor as a good measure.

Could have internal pump issues.

How many miles on the IP ??

Let us know

Robyn