bigjimmy wrote:

Found online... GM Technical Service Bulletin #77-63-06Ab states that: "stalling, hard starting, and hesitation are symptoms of a failing PMD (Pump Mounted Driver) module." These symptoms usually (but not always) set a code 35 or 36 in the 1994 - 1995 models, or a code 1216 in the 1996 - up models. www.scheiddiesel.com/d...t/1056.php - people relocate them with a wiring harness to a cooler location and... Tests have shown that even a low fuel level in the tank or a non operating electric fuel-lift pump will cause the FSD to work harder and generate more heat Add a high ambient temperature (or a dry, thin fuel), such as that found in the Southwestern US during the summer, and you begin to see why these heat induced FSD failures occur more frequently in those areas of the country. Depending on the problem the truck may go into 'limp home' mode. When the timing signal is 'missing' the system will advance the timing to the max, hence the engine will get very noisy. The trans doesn't up shift and you can drive about 30 MPH. Your engine will be running at higher RPM's due to this. www.dieselbombers.com/...weaks.html

Did lift pump testing, it works (thread here: www.dieselplace.com/fo...?t=39350). Truck also has a remote mounted FSD, same brand as this:

www.mwfi.com/cooler/fsd_cooler.htm

Engine isn't throwing any codes at all. Truck doesn't stall, and is easy to start after one cycle of the glow plugs.

I know this is going step by step, but I'm just posting as I eliminate things... Wastegate operates as it should. Vacuum is to actuator, and it keeps it in position. If you move the slide manually, the turbo slows down and exhaust gases come out by the turbo.

So what's next?

More google....

Dirty injectors will lean out the air/fuel mixture, causing a loss of power, rough idle and sometimes white smoke in the exhaust. Leaky injectors will richen the air/fuel mixture and cause black smoke.

There are a couple of ways to find a bad injector on a diesel engine. One is to use a digital pyrometer to check the operating temperature of each cylinder. A temperature reading that's lower than the rest would indicate a weak cylinder. If compression is okay, the problem is restricted fuel delivery. Another quick check is to use an ohmmeter that reads tenths of ohms to measure the resistance of the glow plugs while the engine is running. The resistance of the plug goes up with temperature, so if one or two cylinders read low, you've found the problem. For example, if a glow plug normally reads 1.8 to 3.4 ohms on a hot, running engine, a reading of 1.2 to 1.3 ohms on a glow plug would tell you that cylinder isn't producing any heat.

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and on bears note it could be worth messing with the 4wd shifter and then driving to verify that it is not in low range, if it is anything like my truck the stock "selector" was a broken plastic tab, the only use of the trim piece was to teach me the pattern, and the linkage on my brothers was all screwed up, it was in 4H for a long time with no front shaft so we did not notice/end rant/ your truck should have a (EDIT 4l80e, i was thinking 700r4) 32 spline np241

bigjimmy wrote:

More google....

That's where I've been living, but the extra help searching is greatly appreciated... Thanks guys for helping out!

bigjimmy wrote:

Dirty injectors will lean out the air/fuel mixture, causing a loss of power, rough idle and sometimes white smoke in the exhaust. Leaky injectors will richen the air/fuel mixture and cause black smoke. There are a couple of ways to find a bad injector on a diesel engine. One is to use a digital pyrometer to check the operating temperature of each cylinder. A temperature reading that's lower than the rest would indicate a weak cylinder. If compression is okay, the problem is restricted fuel delivery. Another quick check is to use an ohmmeter that reads tenths of ohms to measure the resistance of the glow plugs while the engine is running. The resistance of the plug goes up with temperature, so if one or two cylinders read low, you've found the problem. For example, if a glow plug normally reads 1.8 to 3.4 ohms on a hot, running engine, a reading of 1.2 to 1.3 ohms on a glow plug would tell you that cylinder isn't producing any heat.

I guess that's where I'm going to start tomorrow. If anything, I would say the truck has white smoke. I don't smell coolant, and the level in the reserve coolant tank is good, so I think I can rule that out.

bigjimmy wrote:

and on bears note it could be worth messing with the 4wd shifter and then driving to verify that it is not in low range, if it is anything like my truck the stock "selector" was a broken plastic tab, the only use of the trim piece was to teach me the pattern, and the linkage on my brothers was all screwed up, it was in 4H for a long time with no front shaft so we did not notice/end rant/ your truck should have a 27 spline np241

I just ran it a bit, and it is in 2WH. I didn't really think that would be related because the truck doesn't want to rev up much in neutral, park, or in gear.


Tomorrow will be testing glow plugs, get temp readings on cylinders, and then going from there... fun stuff.

Hmm. That video of it barely turning at idle would have me a little weirded out, but maybe that's just how the turbos on the 6.5's are. Seems to be good once its been revved. I'd be really interested to see once of the turbo (and hear what it sounds like) while its under load.

What happens if you yank the vacuum hose off the wastegate actuator so it is fully shut? I'm guessing yours works like mine, in which case you have an actuator connected via a rod to the actual wastegate housing. As you apply / remove vacuum to the actuator, is the wastegate itself sticking?

78jeepstang wrote:

Hmm. That video of it barely turning at idle would have me a little weirded out, but maybe that's just how the turbos on the 6.5's are. Seems to be good once its been revved. I'd be really interested to see once of the turbo (and hear what it sounds like) while its under load.

That might be hard to do. If I had to guess, I would say that I'm not getting over 1000 rpms out of it before it stops going up.

78jeepstang wrote:

What happens if you yank the vacuum hose off the wastegate actuator so it is fully shut? I'm guessing yours works like mine, in which case you have an actuator connected via a rod to the actual wastegate housing. As you apply / remove vacuum to the actuator, is the wastegate itself sticking?

The vacuum holds the wastegate closed. When the actuator is not connected to the vacuum, the rod (just like yours) moves freely back and forth. When the vacuum is removed though, it doesn't "self-open", it just sorta sits closed and stays where you leave it. When the vacuum is applied, it wants to stay closed all the time. I can't get it to rev high enough to open up...

I don't know if it makes any difference, but the CDR valve is blowing out a lot of air... This valve is the same as the PCV valve in gas engines, and it looks like this (top right, gold):

www.ssdieselsupply.com...Valve.html

Does this signal something? It says that failure is represented by oil on the turbo, and there was some, so maybe this is a problem spot, or maybe it is just another unrelated thing.

Huh, weird. The K03 defaults to 'full closed' on the wastegate when there's no vacuum applied. Its held shut by spring tension and opened by vacuum -- controlled by a solenoid. If you pull the line from the solenoid off it makes for some real fun times until it goes in to limp mode from the overboosting

nah, that sounds just like a pcv valve, the only thing it will cause, if not functioning properly is excessive blow-by and ring wear, hence oil consumption, but I would not think it would cause your current situation. EDIT- is it plumbed properly, I just read that some people put them on upside down, it said they have a "this side up" label on them???


have you posted this to any diesel/chevy sites? ck5 has a small diesel section, i skimmed it over and it is great for 6.2 tech but not much on the 6.5, it seems a sort of bastard child

EDIT:
Good troubleshooting website, for 6.5L hummers
flashoffroad.com/Diese...eshoot.htm

Try dieselplace.com...they have a legit 6.5 and 6.2 section. I would not even bother worrying about the turbo right now. The problem your having has nothing to do with it, its in the fuel system or electronics. Like Tim said, if you have a pyro, shoot each manifold runner once its warmed up and see if you have any dead (cold) cylinders. If you do, chances are the injectors are bad for those cylinders. Those are cheap. I wouldnt worry about the PMD much right now because it seems like you have this problem ALL the time, even when it is cold, and you have a nice FSD setup.