[Fozzy_Bear]

Hi all.

I am very comfortable with my knowledge of with gasoline engines, but I just bought my first diesel (a 96 Chevy 3500 ) and I am kinda lost. I know it will need some work, since I bought it for a pretty low price, and I've already identified a issue I need to address.

But before I go into details, I was wondering if anybody knows where a good FAQ is that is written for somebody comfortable working on gas engines showing primarily the differences between them.

As for my issue, at its heart it's a hard-start issue, but with a twist. the engine starts just fine and then runs totally smooth for about 45 seconds. then it coughs and dies unless you floor the pedal, and even then it will only manage 1200 or so RPMs for about 15 seconds. While the engine is struggling, it sounds pretty bad. Then, the Service-Engine-Soon lite comes on and it instantly smooths out and is fine until you turn off the engine. I've driven it for over 100 miles at a time without a single issue... once that initial what-not is done.

And just to check, I started the truck back up right after I got home (after 100 miles, it was certainly up to temp) and I had the exact same problem, but the coughing/struggling was not as intense... but still bad. Only for 15 seconds and only after it ran perfectly for 30-45 seconds after starting.


Any ideas or links to good sources would be appreciated.

thanks


.

[wilson1010]

I'd post that question up on the diesel tech section of FSC:

http://www.fullsizechevy.com/forums/index.php

[Indy]

http://www.62-65-dieselpage.com/

You have to join to view, but it's a really good forum for this engine. You made the same mistake I did with my first diesel, buying a 6.5l chevy.

I figured roughly same year diesels would make roughly the same power regardless of make. Dodge was running the 8v cummins, ford had the 'stroke, and I got a deal on the chevy. Further research though found that the 6.5 wasn't intended for 'diesel power' as the other makes. It produces roughly the same hp/tq as a chevy 350, but with a lot more weight and 50 extra cubes. Chevy's only intention in the engine was an alternate fuel to gasoline, and the engine was designed to produce 350 power. In other words, it's a ****ing dog of an engine. There are a few folks out there getting close to cummins power after a full rebuild, lowering compression, replacing the turbo, adding an intercooler... Basically it would be easier to swap in cummins. And who in their right mind releases a 3/4 and 1 ton diesel truck without an intercooler...

I sold it and picked up an f150 that towed my boat significantly better than the 3/4 ton diesel did.

90% of the time the engine has a problem, which is often, it's the PMD/FSD. This part is increadibly failure prone to start with, and the extra heat of mounting it to the fuel pump increases the failure rate quite a bit. There's a few heat sink options out there to get the pmd to a cooler location, but the part itself still fails often. And since it's an electrical part, no warranty once it's installed. I got lucky with mine and never had an issue but I learned the #1 rule in diesel trucks. Never buy a 6.2 or 6.5.

[Fozzy_Bear]

Originally Posted by Indy

...

90% of the time the engine has a problem, which is often, it's the PMD/FSD. This part is increadibly failure prone to start with, and the extra heat of mounting it to the fuel pump increases the failure rate quite a bit.
...

Ok... but what's a PMD/FSD ?

[Lud04X]

First off, check the fuel filter. If its all clogged up that could cause your diesel engine to starve for fuel.

[Indy]

Pump Mounted Driver / Fuel Solenoid something or other. It's been a while It controls the injection pump.

[Indy]

Ebay

http://cgi.ebay.com/ebaymotors/NEW-Improved-6-5L-General-Motors-Diesel-PMD-Black-Box_W0QQitemZ350100202677QQihZ022QQcategoryZ33555Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem


http://cgi.ebay.com/ebaymotors/GM-6-5-Turbo-Diesel-FSD-Heat-Sync-Kit-w-PMD_W0QQitemZ150294816415QQihZ005QQcategoryZ33553Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem
"The PMD (pump mounted driver) is that small black box mounted on the side of your injection pump. It is a signal amplifier that powers the fuel solenoid. It contains 2-500 watt transistors which create a lot of heat. The factory mistakenly mounted this PMD module on the side of an already hot injection pump and in the engine valley below the intake manifold where temperatures skyrocket. As everyone knows, electronics do not like heat and they will fail prematurely. Symptoms of failure are stalling, hard starting, surging, poor fuel mileage, erratic idle and finally no-start. When they go it usually will not give any codes with the SES (Service Engine Soon) light. This American Made Cooler kit, relocates the PMD to a cooler area of the engine compartment, above the intake, on a massive oversized heat sink. A proven design. Our design has some distinct advantages over all the competition's. Please write for a list of our advantages over the competitions. This kit includes everything INCLUDING a new Stanadyne latest version PMD to complete the installation. I also include a new #9 calibration resistor. (other resistors available upon request at no extra charge) The PMD and resistor will come pre-mounted to the cooler using industrial heat sink compound instead of a pad. (proven better heat transfer then any pad made) Included in this kit up for auction is 1) cooler as pictured, grade 8 mounting hardware (required to obtain proper torque for heat transfer), and industrial heat sink compound used in mounting PMD to cooler. Also a brand new warranted Stanadyne PMD, and #9 Stanadyne calibration resistor, and complete step-by-step instructions. The original harness will plug right into module without modification and absolutely NO strain on wires. Only basic hand tools required. No drilling or cable splicing. Approximately a 10-20 minute installation. A truely simple Plug-and-play installation.
Questions or tech support please write.
Buy from the 6.5 diesel experts. An ASE certified diesel tech can assist with all 6.5 TD problems. Glad to help!
***WORD OF CAUTION*** Heat Transfer Technology is a science. The sizing of a heat sink requires calculations for the heat sink load of 2-500 watt transistors in an underhood environment exceeding 150DF. The mass of the heat sink, cooling fin design and cooling fin surface area are CRITICAL to PMD life. Although my "Heat-Sync" runs significantly cooler then most of the competitors, (write me and I'll tell you why) most others will still somewhat do the job. However, I see one out there with little to no "home made fins" that can't possibly dissipate the heat of 2-500 watt transistors. Temperature will fry your PMD again in short order. Look to buy the best functioning one, not the prettiest one. Extensive research and engineering have gone into my design. No guesswork involved! Thank you!
Attn Canadians: We ship International only by UPS and include a NAFTA certificate to exclude from duty. There may be other fees imposed by your Government upon delivery such as GST tax and Brokerage fees that are out of our control."

[Fozzy_Bear]

Originally Posted by Indy

Ebay

http://cgi.ebay.com/ebaymotors/NEW-Improved-6-5L-General-Motors-Diesel-PMD-Black-Box_W0QQitemZ350100202677QQihZ022QQcategoryZ33555Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem


http://cgi.ebay.com/ebaymotors/GM-6-5-Turbo-Diesel-FSD-Heat-Sync-Kit-w-PMD_W0QQitemZ150294816415QQihZ005QQcategoryZ33553Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem
"The PMD (pump mounted driver) is that small black box mounted on the side of your injection pump. It is a signal amplifier that powers the fuel solenoid. It contains 2-500 watt transistors which create a lot of heat. The factory mistakenly mounted this PMD module on the side of an already hot injection pump and in the engine valley below the intake manifold where temperatures skyrocket. As everyone knows, electronics do not like heat and they will fail prematurely. Symptoms of failure are stalling, hard starting, surging, poor fuel mileage, erratic idle and finally no-start. When they go it usually will not give any codes with the SES (Service Engine Soon) light. This American Made Cooler kit, relocates the PMD to a cooler area of the engine compartment, above the intake, on a massive oversized heat sink. A proven design. Our design has some distinct advantages over all the competition's. Please write for a list of our advantages over the competitions. This kit includes everything INCLUDING a new Stanadyne latest version PMD to complete the installation. I also include a new #9 calibration resistor. (other resistors available upon request at no extra charge) The PMD and resistor will come pre-mounted to the cooler using industrial heat sink compound instead of a pad. (proven better heat transfer then any pad made) Included in this kit up for auction is 1) cooler as pictured, grade 8 mounting hardware (required to obtain proper torque for heat transfer), and industrial heat sink compound used in mounting PMD to cooler. Also a brand new warranted Stanadyne PMD, and #9 Stanadyne calibration resistor, and complete step-by-step instructions. The original harness will plug right into module without modification and absolutely NO strain on wires. Only basic hand tools required. No drilling or cable splicing. Approximately a 10-20 minute installation. A truely simple Plug-and-play installation.
Questions or tech support please write.
Buy from the 6.5 diesel experts. An ASE certified diesel tech can assist with all 6.5 TD problems. Glad to help!
***WORD OF CAUTION*** Heat Transfer Technology is a science. The sizing of a heat sink requires calculations for the heat sink load of 2-500 watt transistors in an underhood environment exceeding 150DF. The mass of the heat sink, cooling fin design and cooling fin surface area are CRITICAL to PMD life. Although my "Heat-Sync" runs significantly cooler then most of the competitors, (write me and I'll tell you why) most others will still somewhat do the job. However, I see one out there with little to no "home made fins" that can't possibly dissipate the heat of 2-500 watt transistors. Temperature will fry your PMD again in short order. Look to buy the best functioning one, not the prettiest one. Extensive research and engineering have gone into my design. No guesswork involved! Thank you!
Attn Canadians: We ship International only by UPS and include a NAFTA certificate to exclude from duty. There may be other fees imposed by your Government upon delivery such as GST tax and Brokerage fees that are out of our control."

Thanks.

I've brought it into my local shop today to get them to do a diag... Hopefully it will be something obvious to them. (and cheap.... but that might be too much to ask )


.

[Indy]

Get it figured out?

[Fozzy_Bear]

They pulled a bucket full of codes from the computer... So many that they suspect that there is a problem in the wiring harness. Since the only problem is a hard start (once up to temp, the thing really does run sweet) they are thinking some of those codes are somehow bogus. They are going to pull the intake off and give the wires, sensors and everything a good going-over.

As with everything you can never have good, fast, AND cheap... The shop I took it to has a reputation for being good and reasonably priced... so FAST is not a real expectation. - which is fine since this is just a part-time tow rig and I haven't even bought a trailer yet to tow with. (it would just be sitting in my driveway anyway).

Once they get everything figured out, I'll be able to determine (depending on the cost of repairs) when I can buy my trailer. Once that happens, the plates come off my JEEP and THEN the fun starts!


I'll be sure to post here when I learn more.

[soulman67]

6.2/6.5 diesel's where build for fuel mileage. You can get a reprogramed ecu, and install a mechanical wastgate, that could get the power up to around 300hp. My old 96 K3500 had a 80hp reflash and I ran 12lbs of boost, it ran great. Intercoolers weren't used in diesel's till the late 90's. In 96 a cummins had stock like 145hp and a powerstrock had 215hp. The 6.5 had 195hp excpect for a some models got 215hp, which was the same as the miltary use.

you will want to keep a spare fsd with you cause they do go out sometimes fast. stalling and dieing is a sign it is going out. Your hard starting could be caused by air getting into the fuel system.

I think you'll be happy with that chevy they are very well built and ride better then a ford or dodge.

[Indy]

The 6.2 had 130hp, the 6.5 started with 190 and topped 200 by the end of its run. Drive a dodge and a ford the same day as the 6.5l is a night/day difference.

Increasing the boost on a 6.5 with the stock turbo and no IC only increases your combustion temps. The turbos are notorious for low flow and high heat, neither of which is good for an engine. The stock wastegate pops at 4 or 5 psi from memory (again its been a while). Experimenting with a manual gate found a little increase in power up through a couple more psi, but the EGT gauge had to be watched very closely even at that pressure, topping 1200 was pretty easy just cruisng the interstate. More or less pinning the gate gave ok boost, but EGT went through the roof even with really large exhaust and wide open air intake, and no noticeable increase in power.

The hard-core 6.5 guys are getting somewhere around 300hp, but that's from a complete rebuild incl. low compression pistons, larger turbo, large IC, upgraded fuel system, propane injection etc etc etc. They were posting 4-10k in cost and had to use the later engine blocks as the early blocks were failure prone all by themselves.

They're an ok engine for what they are, an alternative fuel truck. If they had left them in the 1/2 ton trucks where they belonged they would be decent. But in the 3/4 and up, they just don't compare.

Speaking of 1/2 ton diesels... I'm looking forward to them

[Old4X]

http://www.dieselplace.com/forum/index.php?


This is the place on the web for GM diesels. They will want you to fill out the troubleshooting page before you ask for assistance on the problem, also fill out your equipment profile whan you sign up.

[Fozzy_Bear]

Just as an update...

The injection pump had to be replaced, and one sensor (cam position IIRC).

Also, there was a small leak in the fuel system. It wasn't big enough to pour fuel everywhere, but it was big enough to let air INTO the system if you let the engine sit for a while (even just overnight). that would leave the pump pulling air to start and they believe THAT was what the root cause of the pump failure was.


Either way. Now it starts great and runs super smooth.

I'd rather have fuel mileage than a few extra horses, so I'll probably leave it pretty much alone (a trailer with an XJ on it is the primary load this thing will be carrying... possibly with a slip-in camper. So I'm nowhere near needing more capacity than I have.

Thanks for all the help guys. It helped to have a basic background when I was talking to the mechanic.