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Help Please

Well you never replied to the questions of your previous post about this same issue a month ago.

When you crank does it crank smoothly or does it seem like it fires but doesnt turn over? Is there any smoke when you crank?

When you unplug the crank sensor does the cranking change, it should just be smooth cranking, no firing? Your truck will not start with a bad or unplugged crank sensor, might just be a 94-95 thing, I dont know, since Ive seen people say it should start without it, but it certainly will not.

Could be your crank sensor. Could be air in the fuel lines. Try cranking with the fuel cap off of it, have you replaced that? Also try starting with the bleed valve on the filter cracked.

If you havent been driving it then its probably not the ULSD yet, but you MUST add something to #2 ULSD or you will kill your IP. Need lubrication.

Why did you change the batteries? Were they dead from sitting? Have you jumped the truck recently? Shouldnt jump your truck with vehicles that are on, you can do it with two cars that are off. And dont use start assist battery chargers either. And why are your glo-plugs on for only 4 seconds? Is that right in the morning, first thing, or after a couple cycles of it?

With codes 17 and 18 its not your PMD, I got the same codes and PMD made no difference. I ended up replacing the IP and Crank Sensor, not sure which fixed it since they were done at same time, but my crank sensor crumbled when trying to remove it.
 
When you unplug the crank sensor does the cranking change, it should just be smooth cranking, no firing? Your truck will not start with a bad or unplugged crank sensor, might just be a 94-95 thing, I dont know, since Ive seen people say it should start without it, but it certainly will not.

Verbatim from GM manual: and what I've seen for DTC 19 (FYI for newbies out there 2 rpm sigs; scan rpm is from crank/ dash is from alternator)


"Scan tool shows rpm, rpm will be displayed with a fault in this circuit (scan) if signal is lost while running, the fuel injection system will shift to a time base fuel injection mode based on pump cam signal, and engine will continue to run.

The engine can be restarted and will run in backup fuel mode as long as fault is present."


So crank sensor is a valid possibility, but it should still start with bad crank sensor, code 17 & 18 are optic codes sensor which could result in complete no start if both cam and optic are bad, generally you get one or other not both, except for some reason when PMD or optic goes bad you get odd ball combinations of codes.

IIRC 94-95 also has RFI filter in PMD harness that bad can cause oddball starting issues.

RJ is code 19 one of the codes you are seeing ??? if so:

Crank sensor can be verified by unplug sensor with key on engine off Pin C to gnd should be 5V, if not suspect open in ckt 416 or bad PCM, if 5v is present then probe harbess terminal B with test lite/meter connected to B+ lite on/12 present, if no check connections or PCM or ckt 416 (grey wire)

If you have lite/volt then reconnect sensor, disconnect engine shut off solenoid, at PCM probe to PD 13 pin (pink 24 pin connector) to gnd crank engine are 4v present, if no bad CPS, open CKT 643 (yellow wire), bad connections, if yes faulty PCM connection or faulty PCM (rare uncommon condition)
 
odd as quote above was from a 94 service manual, I take it rpm on scan tool matches the rpm from alt? As I have no desire to promulgate mis-information, can another of you 94/05 6.5ers help with science experiment and try to start with CPS unplugged, not 1st time I've found inaccuracies in tech manual.
 
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RPM does not match, I get lower RPM from scanner than from the dash guage. As a function of speed, the difference increases to like 250RPM difference at 70MPH.
 
I'm going to replace the alternator soon, I'll see if it makes a difference. I got a higher output one, like 140amps. It doesnt bother me a whole lot, just means I have more to go than the guage says, but explains why Im reading same RPMs as a guy with 4.10s compared to my 3.42s! I was so confused by that before, thinking maybe previous owner changed out rear end.
 
Measure them both... the belt-pulley contact surface measurement. Mine were different and I forgot to check and swap them ... grrr. I gave the old alt to the guy as a core. Now I read almost 400 rpm high.

Some days, I'm SO stoopid...
 
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