Stalling Problem Is it PMD ???

[Salt Shaker]

Hi Guy's, just joined the Diesel Page smile.gif any help would be much appreciated

First of all have read almost everything about this stalling problem. Came close today to shoving dynamite in the tailpipe and lighting it. :(

1995 Chev with 7 1/2' Fisher Snowplow.
Regular Cab Pickup 4X4
6.5 Litre Diesel
212,000 Km (Appx. 132,000 miles)

A little history.....
Started stalling about two weeks ago, last week alot more often. Changed the Fuel Filter (don't know if it had been changed before, bought it at 123,000 (appx. 76,000 miles)
Changed the Lift Pump (was not working as I can easily hear it in the cab now)

Got the lights (plow and truck) redone as there was a short or something that knocked out the indicators, the Hazard switch was not working properly, had to replace the whole turn signal assembly (great idea GM). First electrical guy did a brutal job, changed the signal assembly (coating was melted off the wires to the assembly), cut one of the plow light plugs (he knew I needed them), everything worked except the High Beams and said "I didn't touch them" and told me to get my mech to put the plug on (I was not impressed ).

Took it to a plow place, whole new harness, re did all the wiring (said there were no wires going to the hi beams), grounded it all right to the battery, the guy did a great job.
There was also 2 wires coming out from that large bundle behind the fuel filter, one was attached to the block, the other corroded off. Told it was a ground (black w/ white stripe), could not find where it broke off so grounded it too the same bolt on the block. Disconnected the batteries for a minute.

Now the Stalling...
-Drove home last night (20 minutes, half hour maybe) stalled once, restarted.
-Went plowing this morning, first job (running time maybe 1/2 hour), stalled, restarted.
-Drove to next job (20 minutes maybe) parked the truck, shovelling sidewalks, truck stalled. Finished shovelling, truck started up.
-Stalled 1 minute later, would not start, shovelled some more, started up (turned key longer than usual)

This is where I'm wondering if it's the PMD....
-Went to another job (10/15 minutes away) cleaned the driveway, parked the truck (bit of an incline, nose up) shovelled the sidewalks, truck stalled), would not restart.
Tried again, nothing. Put snow on the PMD, 3 more times, no start.
-Put truck in neutral, rolled down the driveway to an area more level, truck still would not start 3 times (more snow on PMD, nothing)
-Then, getting desperate, turned the key on (not to start), turned to off, turned back on to start, truck started.
-About 500 ft. down the road it stalled, took my foot off the pedal then back on once or twice, motor kicked back in (has done this before).
-Drove to the next job, turned truck off, started fine. Ran for maybe hour and a half, stalled once in a driveway and started back up (again turning the key a little longer than usual).

Sometimes it starts right back up, sometimes starts and stalls a minute later, sometimes have to give it a few minutes, sometimes runs longer and sometimes have to turn the key on longer.

Before the electrical was done had Codes 29, 35, 36 and shows them now, same order, 3 times each. (I may not have disconnected the battery long enough?)

Any ideas at all, this is just unreal :(

Thanks guys.

[ 01-31-2004, 01:54 PM: Message edited by: Salt Shaker ]

[Salt Shaker]

BTW...
Have a mechanic but he's not a Diesel mechanic and doesn't know alot about them.

Would take it to GM but talking to them you don't know if your getting a guy that knows what he's doing.

Examples.......
--Took the truck in to Foster's (GM Dealer) service guy wanted me to leave it with them all day to put it on the computer, when I asked why all day he said, well will have the guy's look at it. When I asked if there were Diesel Mechanics there he said "oh ya, we have guys that look at those"

--When I tested the lift pump and it wasn't working was told it is either that or the Oil Pressure Switch. Was told it was a little tricky to get out and I could not find it so I called just to see what it would cost for them to do it and was told "about $500". From what I had read the switch was maybe $50 and not that long a job to do.

--Called two GM dealers to find out how much a PMD for a diesel was and one guy had never heard of it, even when I told him it was a Pump Mounted Driver, he asked another guy and he hadn't either.

Reading on the web also about peoples experiences with tech's it unreal, the guy's that work on GM's seem lost.

Amazing that they spend so much money on the design of these things yet don't test to make surethe design is correct (like the PMD on the hottest part of the engine :(

[96GMC6.5TDSubOwner]

Salt Shaker:
Sounds like you have the same stalling situation as I do, only my IP is brand new (3K miles). Maybe tightening transistor mounting screws of PMD mounting screws might help, but if I'm going there I just may remove PMD & mount it externally from the pump with all the trouble it is to get there. Makes it easier to service & troubleshoot.

[MTTwister]

Salty - keep researching - I'm a newbie too, but :
failed lift pump reduces flow through IP, generating higher temps that 'harm' the PMD. Temp expansion of thh PMD "may" cause the transistors to expand and contract breaking internal solder joints - which can 'most times' be 'cured' by re-tightening the nuts that hold the transistors in place. Requres removing the PMD, pop the plastic cpas, tighten nuts finger tight + 45

[gmctd]

That stalling problem sounds more like wiring\grounding\voltage supply.
The 'cooling the IP' patch is for hot weather, where underhood heat soars. I think weather requiring snowplow useage would not allow high enough underhood temps to require cooling the IP.

Glow plug relay DTC29 and Inj pulse width error DTC35,36 codes are not related - each is fused separately.
Glow plug is GAGES fuse
FSD is F\SOL fuse

Together spells ground fault\wiring harness problems.

Going thru the wiring connectors, plugs, and grounds costs only time if you do it yourself.
Any further wiring melted by the 'fog lite installer' would best be eliminated before hot weather started.

Recurring DTC's will set the SES indicator. IF it does not light, the codes you are getting are uncleared history codes.

For the stalling Sub with Inj Pump replaced new Feb03, it's now Feb04 - please explain only 3000mi on the IP. Those details are important.

[ucdavis]

Salt,
Diconnecting batteries won't clear codes on my '95. I have to:
1) key off for 30 seconds, key on engine off
2) depress brake all the way & keep it depressed (like a 6.5 owner w/stalling, always down)
3) depress accel pedal all the way & keep it down for 30 seconds
4) release accel pedal, count to 5
5) release brake
6) key off
Then check codes to see they erased. If not, I repeat; always works by the second try.

If you clear the codes & then keep getting 35, 36 back you may be having injector pump trouble and not just FSD fritzing out. If you can drive quite a bit w/out a foul-up after clearing, it could be FSD. Gmtd's point about connections/grounds however is the logical place to start on a unit that has had wiring trouble anyway (like the issue of a wire being corroded off frinstance). As you clean up, brighten & tighten grounds, you may want to add a conductive anti-oxidizing coating like Kopr-Shield to assure that corroding metal won't just keep getting your goat.
Also, check out: http://www.thedieselpage.com/members/tt99-9.htm if you haven't, & follow the checklist. It's probably the best system for finding & curing your trouble.

[Salt Shaker]

Thanks guy's, I appreciate all the input.

I looked as much as I can (know) and my mechanic had a look also and the wires seem ok (never took off the plastic sleeves though) Only one that was broken may have been connected to the Turbo Cover (I don't really know)

It just feels like there is something sending a signal not to pump gas or not enough of a signal. Funny as you start it seems if you leave the key on longer sometimes it finally kick in (sucks up fuel)

But have never had a problem starting it when it sit's over night (watch, it won't start tomorrow)

Will look again at the wires and see if there is anything I can see. Will also look at that link ucdavis when I can access it, for some reason I can only access the forum, none of the Troubleshooting areas, sent the admin an e-mail.

Thanks again guy's, will look into the cooler this weekend just incase, need this fixed as soon as possible before I take my Turbo and starter motor out too.

[rjwest]

Just one small comment, As an ex northern
person, SSSSSnow plowing can overheat a truck real easy
Plow blocks a lot of air, also worse with big pile
oof snow in grill, makes it worse.


If I were ever to buy another 6.5 I
would do the list imediatly.

fuel pressure gauge, remote pmd , with spare,
Install power bypass switch for lift pump(pre96)
Inspect all wiring and GROUNDS, DO the Battery terminal fix, Just as a start

ANY MORE MUST DO'S.

.Small comment got big??????

[gmctd]

Makes sense, rj. Other than Korea, I've actually been in snow probably no more than ten times, and those were ground-cover only events, quickly melting.

Here, at only 30 - 40deg, power down, and even those 'mild' temps suck the heat right out of the engine. Fuel is at ambient, keeping the IP chilled, even with the filter heater.

I would not think 'cooling' the IP to be a curative for stalling\erratic restart in the dead of winter. The melting snow over the connectors around the IP could even be adding to the problem.
But I am always open to factual evidence.

External Cooler\FSD may be a good choice in any event, and could ease the mind if the stalling went away.

The chronology of events would indicate that stallng began after the fog lite\electrical failures.

DTC35 could be bubbles in fuel, DTC36 could be bad fuel\dirty fuel\jelled fuel. Could indicate faulty filter heater.

Addressing the wiring harness\connections\grounding\batteryposts\ign switch, etc, would be my first course of events.

Professional fog lite installations inter-source with the hi beams, where fog is on with park and low beam, but off with hi beam. Light switch, dimmer switch\relay, fuse panel could have been damaged. Those are in-cab harness.
Fusible links at main power buss, both load and source, would be suspect.

[Salt Shaker]

Hi Guy's.

gmctd, that's the exact feeling I was thinking, canot see anything wrong with the wires, always get gas a brand name stations and put in additive (anti jelling, injector cleaner). Ordered a PMD/Remote kit just in case, only other thing was it was a bit wet just before the Lift Pump but it could have been from changing it I don't see any sign of a leak really.

Am taking it to my mech shop tomorrow just do the Peacock thing and go over everything again.


Originally posted by rjwest:
Just one small comment, As an ex northern
person, SSSSSnow plowing can overheat a truck real easyCouldn't you have taken the cold and snow with you ;)



Originally posted by gmctd:

DTC35 could be bubbles in fuel, DTC36 could be bad fuel\dirty fuel\jelled fuel. Could indicate faulty filter heater.
Professional fog lite installations inter-source with the hi beams, where fog is on with park and low beam, but off with hi beam. Light switch, dimmer switch\relay, fuse panel could have been damaged. Those are in-cab harness.
Actually the wires weren't even connected on the high beams, the first guy must have removed them (have no idea why) as I know they worked, and the plow is hydraulic so it was just the light wiring at the front (don't know if that made a difference).
Didn't even know there was a filter heater :(

Thanks again guy's, honestly don't know where I'd be if it wasn't for the internet, met a ton of people who have been very helpful in trying to figure out something that the guys who make the vehicle can't, have certainly learned alot.

Your time is much appreciated.

[ 02-01-2004, 08:28 AM: Message edited by: Salt Shaker ]

[turbovair]

Trace the wiring harness from the ignition switch down the bottom of the column to the plastic connectors where it interfaces the main harness.Check carefully. Thats where I found a broken green 12 or 14 gauge wire(cant remember which)right at the connector(unsolderable). My truck was experiencing wicked stalling right in the middle of traffic.I was in the middle of changing switch/harness assy when I found the broken wire.I had diagnosed the problem by playing with the key while the engine was running, and the engine died.Based on info I found on this site, I solved the problem.

[Salt Shaker]

Thanks Turbovair, Tried the shaking ignition thing last time and it didn't stall but you never know, will have a look at that tomorrow.

Thanks

[gmctd]

The oem fuel filter has internal heater, intended to warm fuel to above jelling temps. Not sure how it fares at cold ambients in keeping fuel any warmer than that, but aerated fuel or jelled fuel can cause stalling\starting problems, with Inj Pulse Width errors short 35\36 long.

Again, spare FSD\Cooler can be the prover.

[scotts]

Salt Shaker, I was having the same problems that you are having. I am in Calgary so the temp should be the same. Anyways, sometimes the engine runs fine, other times it stalls every 5 min. I put a new PMD on the biggest heat sink that I could get and it has been fine since then. It hasn't stalled since I put the new PMD in, which has only been one week. BUT the temp has ranged from -35*C to +5*C. One day I went skiing and it was -30 in town and -5 at the hill, so I don't think my problems were directly heat related (but over time that might have caused the old one to fail).

[canada cold]

I experienced exactly the same problem with my 94 diesel. If your injector pump has been replaced lately under the warrenty that gm gave there is a shunt betwwen the driver and the optical sensor that has a resistor that causes the problem. I removed the shunt and connected the driver directly to the optical sensor and my van has not stalled since. Also be very careful where you buy your fuel and only buy it where they sell large quanities.