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6.5 wont stay running. No ideas anymore.

SuperSport01

SuperSport01

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Winston Salem, NC
I have a 1995 vin f 6.5td, modifications in my signature. The codes I have are 19 21 22 23 25 26 27 29 34 35 36 63 64 65 84 88. The truck will start run and drive normally. But one time in 100 the truck will start normally, run for less than 10 seconds, and then turn off. It will start right back up but will run for less than 10 seconds and shut off again. I can do this until the batteries are dead.
I have cleaned grounds multiple times. New fuel filter. Checked lift pump flow. Replaced crank sensor. Replaced optical filter harness. Installed Heath pmd relocation. New stanadyne injection pump. New throttle pedal. Gutted the fuel shutoff solenoid because I thought it was giving me issues. The injectors are relatively new, under 15,000 miles, and don't seem to be giving me any problems when the truck is running. I'm beginning to think the ecm is the problem but that's a 1 in a million chance.
 
You cleaned all the grounds? the frame to firewall beneath the turbo and the 2-3 on trans dip stick?

When you clear the codes do they all come back?
 
Check all the wires on ECM connectors also make sure the pin side looks good and makes solid contact with the pins. Check the pins on ECM too.
Maybe to a wiggle test before.
 
a buddy of mine had the same problem with his 96 but it wasn't throwing any codes, theres a fuel filter inside of the tank that got clogged on his. if this helps at all
 
check for intermit on C1 orange wire ECM .......it's the first wire in the block pack{ecm} closest wire pack to the firewall....runs between your junction block on firewall through firewall to ECM ......it's your main ecm power wire...usually on your third post on the junction block when looking from fender orange wire
 
What is fuel pressure just before ip when you have the problem? If you don't have one yet, make sure you use one that reads into vacuum, this will tell you of blockage vs loss of pressure from Lp.

On the electrical side, have you swapped in your spare pmd?

Run a temp wire to monitor power into ECM to check for bad ignition switch problem.

On edit: forget fuel problem for now. Definitely electrical. O2 codes? Yeah! Your losing power or ground to the ECM/engine somewhere.
 
The fact that you have so many codes popping seems to indicate a bad ground or a whole power buss is out. Fuse??? The same ground feeds and references all sensors in that path. In that regard pick the lowest code and address that and likely the other higher codes will disappear being they are on the same ground. Thats my thinking anyway!! Not sure which pin to trace from on the ECM cause i don't have the manual in front of me.
 
Check that the ECM fuse has a good connection. I have seen the blades on cheap fuses be thinner and not make good contact with the female end inside the box. It's no doubt a power/ground issue.

Sent from my ADR6350 using Tapatalk 2
 
Hey guys sorry for the late reply. For fuel pressure at idle I have 8psi and the pump is powered by the Kennedy harness. ECM fuse looked good but I replaced it anyway. The grounds have been cleaned multiple upon multiple times. The PMD should be good as its a newer style Stanadyne on the Heath heatsink mounted to the skidplate, and is less than a year old. The ignition switch hasn't been replaced but when the truck dies it restarts and runs the exact same (under 10 seconds) amount of time, though sometimes it spins over for a few moments before refiring. A switch doesn't seem like it would be that repeatable. The codes can be cleared but will return in less than 1 day of driving. FWIW the truck has always started and ran normally the day after it does this repeated dying and restarting. I know this problem is 1000% electrical but cannot determine from where.
 
Maybe the computer is fried. Never seen a bad ECM but I do know it happens and with that many codes and a solid ground makes me suspicious. Do you have a spare ECM to swap in to check? Maybe a buddy would let you borrow his if not.
 
Never assume the PMD is good. Try a known good one. Unplug the pmd extension cable and try the new pmd into the factory harness. It's tight to get to but can be done.

Sent from my ADR6350 using Tapatalk 2
 
Assuming you have an auto a couple of PDF's wiring...Good place to look is where the wires enter firewall,they break there
 

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You have three types of power. Good power, brownouts, and blackouts aka no power.

Good power - you wouldn't be posting this problem.

No power - it's dead till you find and fix it. Cakewalk.

Brownouts: These are the interesting intermittent ones. When a computer aka your ECM gets bad power it does very weird things. As you know computers deal with 1's and 0's. 1 being "on" and 0 being "off". Now when your computer has bad power and is trying to change a 0 to a 1 it may not have enough voltage to change the 0 to a 1. It is a voltage reading in memory where anything above a fixed voltage is a 1. If it can't get the voltage up it stays a 0. So all of a sudden your computer is dealing with bad data and may not be able to command things like injection solenoids "on" with a "1". Weird data also will set ghost codes pointing at everything but low system voltage.

Bad connections cause brownouts. Bad GM ignition switches cause brownouts. When the electrical load changes because the engine stalled the bad connections can cool down and start working properly again.

Shorts in any affected system can bring down the ECM bus voltage esp the regulated 5v rails and cause many systems to fail and code.

I would start with the positive battery cables making sure they are tight and not internally corroded, check voltage at the ecm pins, both the key on power AND the memory power wires. Then check the ground for a voltage reading from the ECM to a good ground location. You can use a scanner and read the ECM voltage.

ECM's do fail with cracked solder joints. With good voltage readings you can do a wiggle test. Passing that replace the ECM. Remember it's nearly 20 years old. It is still possible a sensor or wire is shorting out and taking several systems with it.

Clean grounds and or connections mean nothing when the wire going to it is green with corrosion. Check the wires.
 
wiggle. The engine harness was replaced in 98 due to broken wires at the firewall. I had forgotten about that, and the issues were similar. Im also going to add ground cables from the ground stud on the back of the engine to the front of the intake manifold where the battery grounds are, and another ground cable from the engine block to the frame.
 
Check the PMD? also the extension cable? and also check the original IP Harness?

There are a lot of people having issues with the IP harness, aging factor.
 
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