1995 Chevy 2500 6.5L
 

Iam having problems with my 95 chevy 6.5L, 2 wheeldrive:
Hard start, takes longer to change gears from 1st to 2nd, check engine light on, if idel step on gas padel and truck starts to surg once RPM hit 2.
I have changed the following so far:
Changed in-line pump,
changed fuel filter,
changed ECM.
i get engine codes:
DTC 18 - Pump Cam Reference Pulse Error
DTC 35 - Injection Pulse Width Error (Response Time Short)

PLease help, this is my work truck and now sitting at home and eating my $$..:argh:

Where are you located?

Sounds like a PMD issue. What do you have for a PMD? Do you have a spare, known to be good PMD to try. New does not necessarily mean good. There have been a few "new bad" PMD's out there.

Have you checked your glow plugs.


I get my PMD's from pmdcable.com

Do some searching & reading

x2 or see if you got any leaks in the fuel line

Thanks Guys,
Replaced the Stanadyne PMD with a cooling unit about 3mnths ago.

checked fuel line - all seem ok, no leaks.

Glow plug`s yet to be checked.

Did you transfer over/check the resistor when you changed the pump driver? Although, I would also expect a code 56 if the resistor was missing...

18 and 35 are codes that are consistent with a PMD going south.

Grounds are worthwhile checking for corrosion and tightness.

Is your remote mount PMD harness still grounded to the IP? It should be.

Also try to remove your optical sensor and reinstall it. Corrosion often sneaks it's way in to the connectors and remove/install gets you good contact again. The optic sensor can be part of the "reference error" as the PCM compares the Optical sensor pulse to the crank sensor pulse. If the PCM "sees" something it isn't expecting you get a reference error. It knows something is wrong, just not what.

Air in the lines can also cause a code 18. The optical sensor can't "see" through aerated fuel well, it needs straight fuel. This could be something as simple (and hard to find) as a rust pinhole in a line somewhere.

Low fuel pressure/flow can also cause this. You've replaced the filter and lift pump, but did you check the output? Have you checked the "sock" on the pickup tube in the tank?

Along the same lines with the optical sensor, what fuel are you running? IE: straight diesel, dyed fuel, WVO, WMO, etc. Once again, if the fuel isn't relatively clean and clear, the sensor can have trouble "seeing" through it.

Just for some background, the optical sensor is in the IP. It's the "black thing" on top LH side of the IP with the electrical plug in it. It "looks" through the fuel and there is a disc that spins with the IP rotation in front of the sensor. The disc has slots cut in it and these slots are what the optical sensor "sees" as it looks through the fuel. The PCM uses this input to tailor timing of the injection event. The disc is spinning pretty fast and the slots are a very precise measurement, that's why anything that "impairs" the optical sensor (IE: dye, air bubbles, etc) is a problem.

well, that's quite a few things to start with. I'll stop there for now....

A new PMD is not the same as a known to be good PMD. There have been cases of Bad PMD's brand new out of the box. IS there anybody close that you can borrow a known good PMD from?

Al the suggestions so far are good. Keep us posted

Important correction after I re read it.....

haha that wouldnt of been good

I have a 1995 chevy 6.5l 2500 and truck is blowing out black smoke and power lost when excelerating. What could be the problem?