Another Stalling Possible PMD, Pump Issue?

[itsmysoul]

Hello there. I'm a new user here, so please excuse any posting faux pas.

I have read a few other posts concerning the stalling issue I am having. I just wanted to state my specific case and see if I could get any help narrowing down my problem even more.

My truck is is a 1995 Chevy Suburban 6.5 turbodiesel. It has been equipped with a 2 tank system so it can also runs on waste oil.

About a month ago I started stalling. No surging or hesitating, just a complete shut down. It would stall after running. Actually the first time it stalled, it started back up and allowed me to drive for a while. Then the next time I started it, It would warm up then It would stall, and sometimes let me move it a foot then stall again... I would also notice when I would try and start it that i wasn't hearing the lift pump (making its usual clicking noise) when I would try and start. So I assumed it was the lift pump.

I had it towed into a diesel mechanic and he had it for a long time (mostly due to being overbooked). He also didn't see to be too fimilar with the 6.5 diesels. He said it would start when cool, heat up, and run for about 3 mins and shut off... His suggestion was to replace the IP. Specifically he said, he thinks its the Fuel Shut-Off Solenoid and that someone suggested to him that the whole IP should be replaced instead of just the shut off. When he told me that new IP would cost 2500 I started doing some research myself. I read a little about the PMD failure issue and noticed that my PMD is already remotely installed. It's still under the hood, but not attached to the IP.

After it being at the shop for 2+ weeks, I suggested to him to check out the PMD and see if that could be the issue, but he called me a said that he started the truck and it was running for a couple of hours without shutting off. He was claiming maybe there was a bad batch of fuel that needed to make its way out.

So I went and got it. I dorve it for about a week, with no issues then one day I stalled, started it right back up and got it home without it stalling again. The next day I drove it for a little, then it stalled again. This time I had trouble keeping it running. I also noticed again that the lift pump wasn't making its usual clicking noise.

This time I let it cool and drove it to another mechanic. This mechanic said it may be a couple of weeks until he can look at it, but suggested that I start it, warm it up and when it stalls to but a bag of ice on the PMD and if it starts without stalling it could be the PMD. He said to try it with the Fuel Shut-Off Solenoid also.

The next day I came back with a bag of ice to try this trick. I started her up, let it warm up. I accelerated a bunch... and It wouldn't stall!

So this is where I am now. What to do? Is it the PMD, the lift pump? Do I nee to get the whole IP replaced (I hope not) or is it the Fuel Shut-Off Solenoid?

Any help diagnosing this issue would be a great help.

Thanks for your time.

Jon

[twaddle]

Hi Jon
First of all try and find someone local to you who is experianced with the electronic 6.5. There may be Dieselpage members who are located near you and can recommend an experianced mechanic or shop.

Is this problem something that has started to show itself after there was any work or repairs done to the truck or fuel system? How long has the bio fuel system been on and has there been any similar or other problems with how the engine ran on the biofuel?

Do you know if the injection pump is high mileage. If the engine usually fires up right away when still at normal running temperature then the fuel injection pump is probably OK.

Get a new PMD just in case. If your PMD is the older type you definately need a new PMD even if it is just for back up to be carried in the glove box at all times.
The PMD is usually where most people start to look at this type of fault as it probably the most common thing to cause it.

Can you hear the fuel lift pump buzzing as it pumps fuel. It is located under the cab on the LHS side chassis rail and can usually be heard when the ignition is turned on?

Good luck

Jim

[Ms54Coupe]

From what I know it seems like it would be your PMD...could possibly be the fuel shut off but I doubt it is the lift pump. I would think that the lift pump would fail and not work at all after that. The PMD has been reported to give multiple stall/re start issues but does not seem to always die compeltely right away...they seem to have a failure period.

the easy fix would be to test another PMD when the next stall occurs...if it does not start right back up then move to the shut off solenoid etc.

At least it is running now :D

[Robyn]

The stalling is likely the PMD
A lift pump failure will normally not cause an outright stall

If the PMD is still on the IP then get a Fresh DTECH Pmd and number 5 resistor
(goes in the plug cavity on the PMD)

Get a remote cooler, an extension cable and relocate the PMD

This should solve the issue.

PMD failure is a very common problem and your symptoms fit it perfectly.

OH Welcome to TDP

Missy

[itsmysoul]

Thanks for the quick responses. To answers some of these questions:

Twaddle... "Is this problem something that has started to show itself after there was any work or repairs done to the truck or fuel system? How long has the bio fuel system been on and has there been any similar or other problems with how the engine ran on the biofuel?"

No this problem seemed to pop up out of the blue and I have been mostly running regular diesel since it's been quite difficult for me to find grease in my neck of the woods.

"Do you know if the injection pump is high mileage. If the engine usually fires up right away when still at normal running temperature then the fuel injection pump is probably OK."

I'm not sure of the age of the IP. After it stalls I can sometimes get it to start right back but it will shut off almost immediately. After it cools, it starts up no problem.

"Can you hear the fuel lift pump buzzing as it pumps fuel."

I can hear it (clicking) when I start it cold... When the stalling happens, I don't hear it when I try and start.

"There may be Dieselpage members who are located near you and can recommend an experianced mechanic or shop."

Is there a way to search members and their locations? I live in a small town in the northeast of VT.

Robyn...

My PMD is not on the side of the pump it is remotely installed, but it is still under the hood.

Thanks again for all the insight!

Jon

[itsmysoul]

Here's a little update on this situation.

She was running fine for a week. I couldn't get it to stall. I was told if she stalls and I put a bag of ice on the PMD, and it starts right back up without stalling it maybe be the PMD issue. So I have been driving around with a bag of ice. I haven't been making long trips.

I ride to work in the morning (all down hill, 2 miles) so it doesn't really heat up. My ride to my 2nd job after work is all up hill (about 3 miles). She heats up but doesnt stall. The truck then sits for 3 hours and on my way home from the second job it has stalled the last 2 days.

The first day it stalled once, I started it back up and drove home without stalling. The second day it stalled once and it was hard to get it to start and stay running... it would run for about 30 second and stall out. Each time it seemed harder to get it to turn over. I can hear the lift pump working. I finally got it running enough to zip up the rest of the hill and home. Right as I parked it, it stalled and was very difficult to start.

The morning after (today) it started up and ran for 15 mins with no issue. I shut it off and got a ride into work.

So the issue seems to be occurring after its been running for a little while. It starts up well cold. When it stalls, it doesn't sputter, hesitate, or jerk... it just shuts off which makes me believe its the PMD issue. Please note my PMD is already remotely installed.

http://farm4.static.flickr.com/3622/3351429753_6db25c3088_b.jpg

When I bought the truck 3 years ago the guy gave me an extra PMD and said he had one go bad and to keep this in the car. This is way before I even knew what the hell a PMD was and I cannot seem to locate it. However I did purchase a new (used) PMD to see if I replaced it, the problem would go away.

Does this still sound like a PMD issue? I think maybe. Could it be the fuel shut off solenoid? She runs like a champ when she DOES run, so I don't think its fuel issue.... I guess, I don't know.

Thanks for you time and help.

Jon

[DmaxMaverick]

You have your FSD mounted in the 2nd worst place possible. First being bolted to the exhaust manifold. Either leave it mounted to the pump, or get it out of the engine compartment in free flowing fresh air (with a heat sink). The location it is now will see higher temps than what the FSD is trying to shed. It will actually transfer heat into the FSD, rather than help it cool.

Either that, or don't go anywhere without bags of ice. If cooling your FSD with ice "helps" it, then it is, in fact, being overheated (not necessarily overheating itself). The "ice bag" trick (more commonly used is just water) does not diagnose an FSD problem. This "trick" is used to diagnose a worn out injection pump, FSD or not. If icing your FSD helps, it's dead and just doesn't know it yet. Damage is done.

[Robyn]

I will assume that you are not seeing and SES light showing.

Once in a while if the vehicle is moving at speed and the tranny is hooked up well (Higher road speed) the failure of the PMD can set a code (repsonse time) This is due to the fact that the engine stays turning and the computer does not get a return response from the failed PMD

Under most conditions the engine simply dies and stops turning and the computer does not have enough time with the engine rotating to calculate that there was a failure.

As Maverick mentioned, get the PMD out of the engine bay.

I have a mount similar to the one you have and it stays tucked neatly behind the back seat along with a wrench to allow me to quickly install it on a cold wet night without having to crawl under the truck and flip open the front splash pan under the radiator.

I like the spot down under as it is well protected and cool.\

The bad part is that in a hurry along the road its a PITA to get too, so I keep the spare so I can quickly mount it on the top hat and plug it in and get going.

For normal running the coolest place is the best.

Behind the grill is great too, except that its a PITA to get at quickly.

I have even seen the PMD mounted inside the cabin on a cooler with a little 12V computer fan blowing on the assembly.

A friend of mine here locally has two PMD's mounted on a cooler with a fan and they are easy to reach. In a pinch he can simply swap the plug and go.

Once a while back he and his wife were traveling along on the freeway and the thing died, his wife went into action and swapped the plug to the spare PMD and they never even had to stop.

Bill just turned the KEY OFF, shifted to Neutral and his Missus made the swap. Hit the starter Varoom and off they went again. Told me that they never dropped below 50 MPH

Not at all a bad idea. Having the PMD inside will protect it from the elements as well as the extreme heat.

Mounting a computer case fan is a snap too. These fans normally run on 12Volts and large high volume low noise fan will keep the PMD very cool.

I have seen the PMDs mounted such that the AC system will blow some cold air on the PMD when the System is on.

Been just about as many methods as there are folks out there dreaming them up.

Bottom line, keep the little black box COOOOOOOOOOOL :)

The other type of failure that can happen with a PMD is a "circuit burn through" and this results in a WIDE OPEN throttle with no control.

This is the rarest of failure conditions. I have seen two of these, once in a parking lot with some poor woman having her Burb doing brodies arounf the lot while she mashed the brake and screamed :eek:

I have had one happen to me and it was with the rig sitting still in the driveway.

I reached in a flipped the switch to srat the rig and WHAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA the thing went crazy until th engine reached past redline, then the computer shut it off.

This is why the shut off solenoid is on the IP.\
Normally when you turn the key off, the loss of power to the system will stop the engine.

The solenoid closes too, but this is not the primary shutoff.

Two conditions exist that can cause the Solenoid to come into full use, one is the failure of the PMD and the other is having the internal fuel solenoid stick and fail to respond to throttle/computer control.

Without the shut off solenoid, during a system failure, there would be absolutely no way to shut the engine down.


Good luck with the PMD