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1998 6.5 shuts off past 170° f

WarWagon said:
You have the PMD on a heat sink or on the pump? It will overheat and burn out without a heat sink.

The hole in the black wire loom in the left of your picture : are there rubbed through wires in it?

When the truck stalls after warm up: what are the dash lights doing? SES or STS lights come on?

Here is detailed troubleshooting of the PMD that dies in a codeless way. It's buried in the cal resister PDF. https://www.thetruckstop.us/forum/t...-5-db2-5-7l-info-online-from-stanadyne.26581/
Click to expand...
PMD is relocated behind the grille with a heatsink. No lights no codes
 
Have you checked the PMD extension harness? I had similar issue, heat made it worse, some of the pins were bot crimped. And the cheap wiring even was cracking.
 
Loganshaw_6 said:
I haven't pulled the loom off but I'll give it a shot. It's an extension kit I got off of Amazon so I have my doubts
Click to expand...

Leroydiesel.com for your next one.

Spare pmd is like a spare tire. If you are gonna own a ds4, that is the price of admission. Many keep the spare in glove box but what I suggest is have two PMDs mounted on heatsinks next to each other. put a dummy plug in one to keep the contacts clean and run the other one. When there is a problem just swap the wire over and your diagnostic is done, or you are back on the road in 5 seconds.
So if you are looking for an excuse to ditch the cheap one and you don't have a lifetime warranty pmd, get the complete kit and run on the new one keeping your old that's already mounted as the spare. When the one from Leroy dies, run on your old pmd and ship the toasty pmd back for replacement. Obviously run the quality cable that comes from Leroy.

If you don't want to sacrifice the amazon cable to use as dummy plug, the are available from ModMafia / bluehummer pretty cheap.

The REAL long term fix is loose the ds4 for the db2...:oldman:
 
Will L. said:
Leroydiesel.com for your next one.

Spare pmd is like a spare tire. If you are gonna own a ds4, that is the price of admission. Many keep the spare in glove box but what I suggest is have two PMDs mounted on heatsinks next to each other. put a dummy plug in one to keep the contacts clean and run the other one. When there is a problem just swap the wire over and your diagnostic is done, or you are back on the road in 5 seconds.
So if you are looking for an excuse to ditch the cheap one and you don't have a lifetime warranty pmd, get the complete kit and run on the new one keeping your old that's already mounted as the spare. When the one from Leroy dies, run on your old pmd and ship the toasty pmd back for replacement. Obviously run the quality cable that comes from Leroy.

If you don't want to sacrifice the amazon cable to use as dummy plug, the are available from ModMafia / bluehummer pretty cheap.

The REAL long term fix is loose the ds4 for the db2...:oldman:
Click to expand...
I was just researching a db2 swap... Is the db2 pump 100% mechanical so that if my truck does have an electrical problem that it will not effect it? I've gone over the truck and checked all recommended potential problems and have found nothing that looks out of the ordinary. I found another forum about somebody having a similar problem but there was never a resolution for it. I also attempted to unplug my coolant sensors and the truck still shut off. Fuel pressure looks ok, I even jumped the lift pump. Nothing...
 
Cant say 100% electrical proof. There is 12v power used in a few locations, but no computer nonsense for the engine. All the gauges don't talk to anything else. there is a 2 wire temp sensor for cold start controls that go to the db2. glow plug relay is different but not really needed.
Manual trans makes it easier, if auto get a stand alone controller.
Search for the book on here from Bobbie Martin.

You have to make sure your local gubmint will allow it though. I cant do it here because of smog laws, so for Hummer 95 is newest year and for pickups 93.
I wont own another 6.5 truck with a ds4.
 
Loganshaw_6 said:
PMD is relocated behind the grille with a heatsink. No lights no codes
Click to expand...

Not what I asked. When it STALLS what are the lights on the dash doing? Generally the SES light will come on. What I am asking is if the ECM still has power: thus the interest in the dash lights. At this age fusible links are suspect as well as ign switches.

Eliminate the PMD extension cable for now as Amazon China Crap is suspect and a known source of problems as mentioned. Just move the PMD with heatsink by the pump for testing. People simply don't know there is better USA made PMD cables for a non-stop problem area. Of all the things I killed on a 6.5 the USA PMD cable (used in AZ) wasn't one of them...

Codes can take 30 seconds or longer to set thus the reason these primitive ECM's are useless esp. for PMD failures. You stall quicker than 30 seconds and then the tests / program quits running... 30 seconds is to eliminate intermittent noise or connection problems from setting a nuisance code.
 
Two things, do you have tools to do a pin drag test? The terminals on the extension harness might be making poor contact. As they heat up it may turn into a open circuit long enough to cause the engine to stall.

Also do you have a lab scope? Scoping the power, ground, signal, and control wires at the PMD might be a good way to catch what's going on. The great thing about a lab scope is you can see the issue on a graph. Takes away any guess work. I've fixed many unfixable vehicles that way.
 
WarWagon said:
Not what I asked. When it STALLS what are the lights on the dash doing? Generally the SES light will come on. What I am asking is if the ECM still has power: thus the interest in the dash lights. At this age fusible links are suspect as well as ign switches.

Eliminate the PMD extension cable for now as Amazon China Crap is suspect and a known source of problems as mentioned. Just move the PMD with heatsink by the pump for testing. People simply don't know there is better USA made PMD cables for a non-stop problem area. Of all the things I killed on a 6.5 the USA PMD cable (used in AZ) wasn't one of them...

Codes can take 30 seconds or longer to set thus the reason these primitive ECM's are useless esp. for PMD failures. You stall quicker than 30 seconds and then the tests / program quits running... 30 seconds is to eliminate intermittent noise or connection problems from setting a nuisance code.
Click to expand...

Truck shut off this morning after warming up although it seemed like it died sooner than normal. Unfortunately I did not have the scanner connected to the truck so I don't know what the actual temperature was per the ECM. The check gauges light came on and then the battery light (Brake light has been on since I bought the truck) The truck started to idle lower and as soon as I moved the pedal and let off it shut off. I was able to get it to start again but required me to give it throttle while cranking. At that point it would not idle and shut off as soon as I released the pedal. Over the past few days I cleaned multiple connectors with electronic cleaner and a wire brush also checked the grounds and found nothing unusual. In order to set the timing it has to be above 170 degrees. It wants to shut off above 170 degrees so I'm forced to keep my foot on the throttle to get it to idle at about 1000 RPM while watching the scanner my act timing will fluctuate around 3.5. it will drop down to 3 and go to 3.9 is it possible I have the timing set wrong maybe it's retarded? I did remove the extension harness the other day and the truck acted the same with the pmd plugged into the pump.
 

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I hate to say it... but it sounds to me like you may have another bad injection pump. Get it warm to the point where it stalls and is hard to start. Then pour a gallon or two of ice water over top of the pump. If it starts better then you have a bad pump. If it's still the same... DB2 swap time.
 
Can you post video to youtube and put a link here of it?

Description really sounds like fuel starvation, but hearing/seeing it can help sometimes.

Do the cold water test, but in my opinion- NEVER change an ip without doing fuel pressure test and being 100% no air in fuel or other fuel contamination.

What was result from clear fuel line? Can you show it in video also?
Your description sounds exactly like the video I posted with the 6.2 db2. Air in line was the only problem.

also before ip swap is use a fuel can with new fuel in it feeding directly to the ip to ensure any fuel supply issues aren’t the problem.
 
Rockabillyrat said:
I hate to say it... but it sounds to me like you may have another bad injection pump. Get it warm to the point where it stalls and is hard to start.
Click to expand...

x2. The new IP is supposed to be rebuild. I think you still get a bad IP.
I thought you have source of a good rebuild IP locally?
 
That right there is the scary part of anything rebuilt. Rebuild alternator or starter fails soon after installing. Suddenly the remorse of not having paid more for brand new...
 
Most pump builders reused the H&R assembly because it can be around $750 for a new one. That's almost more than most rebuilt pumps cost. So it's not uncommon to have a "rebuilt" pump that has over 100k miles on the H&R already. With the age of these engines the pump builders are running out of good cores. If you want a good quality pump buy a new one from stanadyne. Otherwise get used to going through 3 or more pumps till you get a good one.
 
How much fuel is in the tank? Try a 5 gal can of diesel. Old fuel gauges (senders) don't always work. X1000 on clear return line looking for air.
 
Making sure that there is lots of fuel in tank should help.
There were a lot of members have this type of issue only to find out that it was caused by low fuel level.
 
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