First Post ..Help

[peter nap]

I have a 95 Chevy 2500 with a 6.5 Turbo Diesel.

I have had very few problems until the last two months.

It always started and ran fine.

2 months ago, I was crossing a mountain and it seemed to have no power. It heated up (Not badly, just hotter than normal) and really didn't have any power. When I got home I replaced the fuel filter and air filter.

That cured the power problem but started another issue.

It would start fine and run all day until I stopped. Then when I restarted it, it would run for about 30 seconds and cut off . It took a couple of minutes of cranking to get it started again and it would run fine until I stopped. Then it would repeat the whole starting thing again.

If I let it sit overnight....no problems...until I stopped again.

I thought I may have gotten a bad seal on the fuel filter, so I replaced it. That seemed to cure it until today.

Today I used the truck. Drove about 30 miles. Stopped foor an hour, got back in and went another 10 miles. No problems.

At the second stop, I was in the store fot 30 minutes, started the truck and let it idle for a minute. It stopped, just cut off.

I was able to restart it after a couple of trys so it is not as bad as it was.

I drove the 40 miles back, stopped for dinner and restarted. This time I didn't let it idle but drove right off. It stuttered for a few seconds then no problems.

I dtarted looking on the net for possible problems and the lift pump kept coming up.
From what I read, I should be able to open the Tvalve next to the gooseneck and get a stream of fuel ....while it is idleing.

I tried that and nothing came out...BUT....the engine didn't stumble or cut off either.

Any ideas?

Sorry for the long winded post.

[Robyn]

First off

Welcome to TDP :D:):D

The issue sounds like a typical PMD problem (little black box on LH side of the Injection pump)

You should do a remote mount out of the engine bay.
There are many outifts that sell a extension cable kit and a finned cooler/mount

The PMD thats on the pump now has a resistor inside the plug socket in the PMD.
You likely wont get that to come out as tight as the space is down in there.

You can unplug the wiring ok though. Use a number 5 resistor with a new DTECH PMD on the remote mount kit.

Leave the OLD PMD on the pump as it is likely NG anyway.

Heat wreaks havoc with the two heavy transistors in the PMD and this is what causes the issues.

I am assuming that there has not been any codes set ??? (SES light on)

Another possibility could be a bad oil pressure switch that not working??

The lift pump (LH frame rail) could be giving up when it gets hot

Keep us posted

best
Robyn

[peter nap]

Thanks Robyn!

It does seem to fit the symptoms!

I'm puzzled as to why I don't get any fuel flow when the T valve is opened and the engine running. According to the troubleshooting charts, I should get flow if the engine is running but the engine should starve and quit in 30 seconds if the lift pump isn't working.

I do have pressure if I open the bleeder valve on the filter. I have pressure if the engine is running or not. Would an intermittent problem with the PMD still allow pressure?

The PMD kits aren't inexpensive. Is there a way to test it?

Thanks for the quick reply!

[6.5 Detroit Diesel]

Welcome to TDP.

To help members here help diagnose any problems, fill out your signature. :D

[rameye]

I had a DOA lift pump for about 500 miles making me crazy with weird symptoms ..trying to figure out what it was till Morepower got me straight and set me to the path of enlightenment!

Your injection pump can draw fuel from the tank if its in good shape...this however kills the pump prematurely.

Why it didnt stall when you cracked open the valve is curious, but nothing to really ponder...strange s#it sometimes happens.

Enjoy

[jerry598]

You said it heated up. This won't address the stalling problem, but check the space between the air conditioning cooler/(condensor) and the radiator by removing the cover on top. I bought my 95 with 94K miles and found about 1/2 the space between the radiator and the AC cooler was jammed with plant debris - seeds, leaves and other crud. At first I thought it was a mouse nest, but no, there is something about this cavity that collects dirt and debris, especially if the truck was used in farm country.

[Robyn]

The heating issue is likley either a plugged radiator (area in front of with crap)

The no fuel issue when running is a faulty Oil pressure switch and or a faulty lift pump.

\The oil pressure switch opperates the Lift pump once the engine has oil pressure.

Switch is benind the intake manifold and right under and behind the glow controller.
LH rear of the engine.

The switch on these is a common problem with accumulated miles.

As was mentioned the area between the condenser and the radiator will fill with crap. Clean it out with air and then wash it with a stream of water.
Fludh the radiator fins as well as the condenser.
Its amazing how much dirt and junk finds it way in there.

Be sure your fan clutch is not leaking around the bimetal spring assembly in the center of the unit facing the radiator.

A small amount of oil can collect a lot of dirt and cause the spring to not work properly.

This spring moves when hot and adjusts the internal valving to allow the clutch to engage.

Good luck

Robyn

[peter nap]

Thanks Guys!

The lift pump tests OK when putting it in drive and turning the switch.

That means the relay is OK. I'm not sure about the OPS yet. I may just install a relay wired to key on, and bypass the darn thing. Then there won't be any question.

[JohnC]

...I may just install a relay wired to key on, and bypass the darn thing. Then there won't be any question.


Not a bad idea for testing, but electric fuel pumps must shut off automatically if the engine stalls to prevent pumping fuel on to a potential fire.

[peter nap]

Thanks John...but that's debatable. First, the OPS doesn't shut it down immediately, but it is safer than no shutoff.

Then you have to decide which side of the fence your on. There seem to be two schools of thought.

The first thinks the small chance of fire is worth the increase in reliability.

The second thinks that safety at all cost is needed.

I fit solidly in category 1 but I am also the only one that drives the truck.

[DmaxMaverick]

Not a bad idea for testing, but electric fuel pumps must shut off automatically if the engine stalls to prevent pumping fuel on to a potential fire.

......Not to mention it's illegal, and irresponsible, except for testing purposes. If someone could realistically guarantee me that they will always have a solo crash, and don't mind pumping fuel onto their vehicle (among other things), then so be it. Probably no big deal if the truck never leaves the ranch. But, almost EVERY serious collision involves fuel spillage. More is not a good thing. And, the fuel shutoff working in 5-10 seconds is somewhat better than, say, waiting for the tank to empty.

Please define inconvenience. Next of kin notification is inconvenient.

[Robyn]

The need for a safety fuel shut off is definately important.
The method that was employed by GM to handle this task was to say the least a little sketchy.

The design is not bad but the parts used are not of the best quality.

I would just scew in a new OPS from your fav NAPA store and have it over with.

The incidence of failures on these is very low.
Most failures occur after many many miles.

The later systems (96 on) have a slightly different setup that does not use the contacts in the OPS to handle the full load of the lift pump

Robyn

[JohnC]

Yeah, sorry, not debatable. Required by law, although I was trying to be a little more diplomatic.

The issue seems to be that the pump presents enough of an inductive load that switching it off causes erosion of the contacts. An additional relay cures the problem permanently.

[peter nap]

Yeah, sorry, not debatable. Required by law, although I was trying to be a little more diplomatic.

The issue seems to be that the pump presents enough of an inductive load that switching it off causes erosion of the contacts. An additional relay cures the problem permanently.

Your right John. It isn't a subject that should be debated, certainly not here. This is a site for facts and answers, not moral or even legal debates. Sorry I brought it up!

[MTTwister]

This is triggered by the OPS, but takes the load off the OPS points. Faily easy install. Search the board for the mod. If you can't find it, I might still have the write up I ued when I did mine. ( Need to learn not to save so much "stuff").

Contact me at TomsTruck @ cox . net ( remove spaces) if you need help. <My diesel page subscription should be running out soon>