Injector Pump Issues

[96GMC6.5TDSubOwner]

Back in early 2003, I R/R the OPS & bad lift pump. GMC dealer R/R the original IP at 114K miles under warranty. Ran beautiful for awhile, but now at 117K I have the same old stalling issues either hot or cold, dying in city or highway driving even in the coldest weather! Also have had cold start issues with the new IP with white smoke, misses badly. R/R the glows with JK's (voltage/wires OK), still with no resolve. Modified all battery side terminals to top post marine type, good voltage/charging, all grounds scraped & received star-washers. Called GMC dealer, got 1/20 appointment (I really hate going back to the dealer). Not sure on codes, as it is a 96 & no Tech II scanner is available. Your insight & advice is much appreciated!

[BUZZ]

Check all connections. Stalling is likely the PMD. They will probably change your IP though. I am interested in the cold start issue. This is my problem since my only IP replacement. Now out of warrenty and I am determined not to let my local dealer touch until I fully understand why the start changed so much.
Keep us informed.

[Shad]

Does yours smoke heavily and miss at startup?

[BUZZ]

Mine does miss and smoke at start up. Once the smoke clears and is at fast idle still misses until engine starts to warm.
Buzz

[sbigos]

My '94 6.5TD issues seem to be similar. Hard smoky starting started immediately on warranty IP replacement and is getting steadily worse. I also have DTC 35. have replaced glows with quick heats, cleaned grounds, etc. I'm starting to think they didn't time it right. Also, I wonder if I could have an injector leaking down overnight - smoke at startup could be excess leakage into one or more cylinders, plus low fuel pressure from leakdown would cause hard starting (no low pressure fuel delivery until oil pressure is up), and my warm starts are perfect.

Stalling likely could be PMD or oil pressure relay from what I've learned here.

Steve

[BUZZ]

I wonder the same thing regarding injectors. Mine are original and 130,000 miles. I have a new OMD and cooler that fixed the shut down. I wanted to investigate the bad start and cold weather codes before i droped money on nozzles.
Buzz

[moondoggie]

Good Day!

sbigos:

[96GMC6.5TDSubOwner]

I neglected to mention that after the original IP was replaced at 114K, I started having cold start issues like hard starts, lots of white smoke with bad engine misses that have gotten progressively worse. Never had a cold problem until the IP was R/R. I changed over to JK's Quick Heats thinking the glows were the problem (white smoke), & although I found 2 glows open, there still was little improvement. I'm convinced its pump timing & now a bad PMD (stalling/no start), but only after 3K miles???

[sbigos]

Moondoggie - Thanks for the correction about the relay operating the pump at startup. I had read elsewhere here that this system does not operate the pump until oil pressure is built up. I'll have to check the relay system as I think, but am not sure, that my pump is not operating while cranking. Even given what you stated, I think it could be possible that a leaky injector could cause slow starts because it would take longer to build enough pressure to pop the injector.

To eliminate the pump question I think I'll try manually turning the pump on at the fuse connection at the firewall prior to cranking, and then also try those other pump tests that I think were yours in another posting.

The smoke is whitish but also has a blue tint, like you would see in a high mileage 350 Chevy with bad valve seals.

Steve

[sbigos]

Moondoggie - More info. Here is a post where others talk about mods to operate the pump while cranking.
http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=005600

I have seen other posts though saying these engines will start without the lift pump...

Steve link (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=005600)

[Barry Nave]

Sbigos
On my 95 befor start up I can put the truck in drive,turn key and the fuel pump will run.
This is also how I blead the fuel filter at change.
Your 94 may work this way also

[sbigos]

[QUOTE]Originally posted by sbigos:
[QB] Moondoggie - More info. Here is a post where others talk about mods to operate the pump while cranking.
http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=005600

I have seen other posts though saying these engines will start without the lift pump...

Steve

In my earlier post above, I should have written "during glow plug operation" rather than "while cranking"
Steve