Help! 95 6.5L won't stay running!

[arveetek]

1995 6.5L in my Tahoe. Pretty much stock with around 200K miles. IP was replaced around 30K miles ago. New Stanadyne FSD on FSD cooler installed 2 years ago. Has Kennedy fuel pump harness.

The truck has been acting quirky for a couple of months now. A while back it acted like it ran out of fuel when I was below 1/4 tank. Several times it's acted funny when below 1/4 tank, as in it dies and is hard to restart. Sometimes when driving it acts like you shut the engine off for a split second, but the gauges don't change, so it hasn't lost power.

Tonight, after filling up the tank and changing my oil, I was pulling it out of the garage when it died with no warning. It didn't want to restart very easily, and acted like it ran out of fuel. If I held the fuel feed to the floor while cranking, I could sometimes get it start and run for a moment and then die.

After letting it set for a few minutes to cool the starter, it started right up like nothing happened. It then ran for about 1 minute and then died like you shut the key off. I tried restarting, but it wouldn't hit a lick. I let it set another 5 minutes, and then it started up again like nothing happened. Ran for about 1 minute and then died again, and it wouldn't restart. Waited another 5 minutes and it started right up, and so on.

So that's the current symptoms. With the engine close to normal operating temperature, the engine will start normally, idle and act normally, and then 1 minute later, suddenly dies as if the key was turned off. It will not restart for about 5 minutes. The engine turns over, but it won't fire. If I hold the foot feed down, it might start and run for a moment or two. But If walk away and let it sit for a few minutes, it will start normally again but only run for about 1 minute before it dies suddenly and won't restart.

I first suspected a fuel problem, but I have a good steady stream of fuel out of the fuel drain when the fuel pump is running, and when the engine IS running, it won't die if I open the fuel drain. I thought it weird that this problem happened after a fuel fillup, but it definitely appears to be an electronic issue.

Where do I start? My check engine light doesn't function so I can't pull any codes without a code reader. This doesn't sound like the normal FSD issues, and isn't like when my FSD failed the first time.....

Help!! :(

Casey

[ronniejoe]

Ignition switch?:confused:

[arveetek]

Ignition switch?:confused:

I wouldn't think so, since just the engine shuts off, but the gauges remain the same. And no amount of fiddling with the switch will get it to restart, only allowing a few minutes to pass, and then normal operation resumes for about one minute.

I've got the orignal PMD still mounted on the pump, so I might hook it back up and see what happens. I'm just afraid that if I go out in the shop right now, it'll probably start right up and run fine for a while. I'm scared to drive it, though.

Might be time to seriously think about the MFI swap....

Casey

[Robyn]

Have you ever changed the filter harness going to the IP.
This little fellow plugs into the very top suare plug on the IP and has a little black box thing in the center of the harness.

Actually you need to get the Mil light working.
The light is probably toast. The dash cluster can be yanked out in about 15 minutes and the bulb replaced.

Snap the dash bezel off ( whole thing with all the vents just pops off.
The dash cluster is held in with 4 screw or so and just lifts out of the bucket it sits in.
The bulb sockets are a 1/4 turn gizmo.

Get that done and then see what codes if any are present.

Better yet unhook the batteries. (Good idea before removing dash)

Then do a restart and let it do its thing and see what codes if any are set.

This whole process should not take more than a half hour to complete, with time for a coffee while you work. :D

Lets do this and proceed from there.

There is really no good sense in chasing a gremlin in the DARK

Let us know

Robyn

[chevy1988]

* Feepump placed under drivers seat near the frame(should give a good steady flow of fuel and 1-3psi preasure)
* The filter in the tank
* Leaks on the pipe from the tank to the IP on the engine
* Fuelfiter
* PMD
* Optosensor inside the diesel pump (http://www.mamut.net/royh/newsdet9.htm)

All of the above can give the same symptoms that you have and the order is the simplest an cheepest first and the hardest and costliest last.

The filter in the tank combined with a weak feedpump gives you problem when fuellevel is low as you discribes due to that it has a valve a bit up the fuelpipe in the tank tha opens when fiter is blocked, but you dont notice untill level is low. Eventually this wears down the IP due to poor cooling(fuel acts as coolant for the IP) and it eventually fails. so this is probably a good idéa to check first.

Hope this helps :)

[arveetek]

* Feepump placed under drivers seat near the frame(should give a good steady flow of fuel and 1-3psi preasure)
* The filter in the tank
* Leaks on the pipe from the tank to the IP on the engine
* Fuelfiter
* PMD
* Optosensor inside the diesel pump (http://www.mamut.net/royh/newsdet9.htm)

All of the above can give the same symptoms that you have and the order is the simplest an cheepest first and the hardest and costliest last.

The filter in the tank combined with a weak feedpump gives you problem when fuellevel is low as you discribes due to that it has a valve a bit up the fuelpipe in the tank tha opens when fiter is blocked, but you dont notice untill level is low. Eventually this wears down the IP due to poor cooling(fuel acts as coolant for the IP) and it eventually fails. so this is probably a good idéa to check first.

Hope this helps :)

Thanks!

I can definitely rule out a fuel related problem for the current no-start situation. It has a full tank of fuel, and the problem comes and goes very erratically. Last night I couldn't get it to stay running, but of course today it started right up like nothing was wrong. Fuel pump has been replaced recently, is running and pumping, and has the fuel pump harness from Kennedy to rule out the OPS.

I'm leaning towards another PMD issue. After thinking about the way it has behaved recently, it definitely acts like an electrical issue. One morning a while back, I started it up to let it warm up before heading off to work, and it died like you had turned the key off while I was inside eating breakfast. It started right up though, like nothing had happened. I'm very familiar at how the GM diesels behave when they are starved for fuel, and this particular problem does not fit those symptoms. It may be I have two issues: one affecting the problems occurring below 1/4 tank (like it's starving for fuel) and the current stalling/no restart situation.

I'm seriously leaning towards an MFI conversion. I don't see the point in spending any more money on an injection system that is universally considered to be weak at best. Even if it turns out to be a simple issue, I'm scared to drive my 6.5L anymore, because it might run fine for 5 minutes or 5 days or 5 months.... but I'm assured to be stranded one day soon if I don't do something....

I've never had these feelings with my 6.2L's! :) But I sure do like driving the Tahoe a lot more than the 6.2L powered trucks!

Casey

[arveetek]

Have you ever changed the filter harness going to the IP.
This little fellow plugs into the very top suare plug on the IP and has a little black box thing in the center of the harness.

Robyn

No, I haven't. I'm not sure I even want to mess with this DS4 system anymore. See my previous post.

Thanks,

Casey

[arveetek]

Naturally, it seems to be running fine again. I didn't have time to mess with it yesterday, but this afternoon it started right up like normal, and ran just fine for the hour I played with it. I didn't drive too far, as I'm afraid to get too far from the house.

I did notice that after about 30 to 45 minutes of idling and with the engine at operating temp, the back of the FSD cooler was so hot that I couldn't keep my hand on it. I have the cooler mounted in Kennedy's suggested spot, in front of the driver's side battery. The FSD faces the front and points into the air flow behind the headlight, with the back of the FSD cooler facing the battery. I touched the cooler to see if it was warm, and I had to yank my hand off, it was so hot! Is this normal? I don't recall touching the cooler before to see how hot it got.

I'm thinking my FSD might be dying (again). I was hoping to get more than 30K miles and 2.5 years out of it....

If it was just the FSD, it would be a whole cheaper to slap on a Dtech unit and be done with it, than to install a mechanical pump, tranny controller, and cruise control. But I hate spend money on a system that is weak at best. Going to MFI in my mind would be a permanent solution.

Hmmmm......what to do....what to do....

Casey

[a5150nut]

Geeese! I mounted my cooler backwards. I put the cooling fins forward into the wind. But I never felt mine so hot I couldn't touch it.

[Kennedy]

It's always a possibility that the PMD/FSD is going bad again. I've had my own Kennedy Cooler for a while now, just haven't had time to detail/document it. Actually someone in Martinsville IN was supposed to do an install photo shoot;) I think the original FSD cooler is a bit small.

If you'd like to try a Dtech unit let me know and we'll get you one. I'm curious to see how long they live. I know they claim to have tested, but their tests were not rigorous enough to fail any Stanadyne units either. At this point I see the only key advantage being price.

[ronniejoe]

Actually someone in Martinsville IN was supposed to do an install photo shoot;)

Sorry! It'll be done before the month is out.

[arveetek]

If you'd like to try a Dtech unit let me know and we'll get you one. I'm curious to see how long they live. I know they claim to have tested, but their tests were not rigorous enough to fail any Stanadyne units either. At this point I see the only key advantage being price.

Okay, that sounds good.

Casey

[Kennedy]

Unfortunately we won't really know anything (barring premature failure) for what was it, 3 years for the last one?

I've seen a fair number of repeat failures in somewhat short time periods when intake mounted coolers are used, but far less when off the engine altogether, and I'm hopeful that my KD Cooler remotely mounted will allow any PMD to last a long long time.

[chevy1988]

Naturally, it seems to be running fine again. I didn't have time to mess with it yesterday, but this afternoon it started right up like normal, and ran just fine for the hour I played with it. I didn't drive too far, as I'm afraid to get too far from the house.

I did notice that after about 30 to 45 minutes of idling and with the engine at operating temp, the back of the FSD cooler was so hot that I couldn't keep my hand on it. I have the cooler mounted in Kennedy's suggested spot, in front of the driver's side battery. The FSD faces the front and points into the air flow behind the headlight, with the back of the FSD cooler facing the battery. I touched the cooler to see if it was warm, and I had to yank my hand off, it was so hot! Is this normal? I don't recall touching the cooler before to see how hot it got.

I'm thinking my FSD might be dying (again). I was hoping to get more than 30K miles and 2.5 years out of it....

If it was just the FSD, it would be a whole cheaper to slap on a Dtech unit and be done with it, than to install a mechanical pump, tranny controller, and cruise control. But I hate spend money on a system that is weak at best. Going to MFI in my mind would be a permanent solution.

Hmmmm......what to do....what to do....

Casey

I have an idéa that an extra fan mounted on the PMD-Cooler might help (Ideling or be stuck in traffic dont give much circulation around the cooler) , even though you might have to replace the PMD itself.

A 12V-Fan should'nt cost that much I think, the type found in computer chassies but is weather proof should be easy to find to a resonable prize!

By the way, I bought 2 used PMD's on ebay for about $60 each, took 2 to have one as a spare. rund fine on the first one now :)

[arveetek]

Naturally, the engine has been running fine since this situation arose. I do now have a Dtech FSD in my hands, but I think I'll wait to install it until the engine shuts down again. That way, I can plug in the new FSD and see what happens. I'd like to know for sure that the FSD is the problem. I don't want to install the new FSD and never know if that was the problem or not....

Casey

[arveetek]

This morning I stopped by my parents' house to pick up an item, and I left the engine running in the driveway. I came back out and it had died and would not restart. I popped the hood, unplugged the old FSD, and plugged in the new Dtech unit. It started right up and ran just fine. I then unplugged the Dtech and plugged in the old FSD. It started right up, ran for about 10 seconds, and then died and would not restart. I plugged in the new FSD and it started and ran just fine.

Whew! I'm glad to know for certain that the FSD was definitely the problem. I'm also glad it stalled in the driveway and not on the highway.

Apparently the FSD can cause a stalling/no restart situation as well as the usual stalling/restart symptoms.

This last FSD was purchased new in October '05 and was installed on a new FSD Cooler. It lasted 2.5 years and about 30K miles. Is this a typical lifespan for a Stanadyne FSD on a remote-mounted cooler?

We'll see how the Dtech FSD holds up.....

Casey

[Robyn]

There is no particular time line on these things.
I had a 95 Burb that lost its first PMD at 20K and the dealer did a warranty IP on it. Then again at 50 K and again at 65K.

This was back before I found the page and really understood these things. I offed that truck and got a gasser for a while.

In recent years I have seen all sorts of things happen with the PMD's

From the sporadic stall/restart to an all out stop and no start until cold and everything between.

You got all the goodie from the little creature.
The reports on the new Dtech units are very good SO FAR :)

I am running one on the DaHoooooley.

We shall see

Robyn