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Discussion Starter #61
UPDATE: I replaced the lift pump today and bled the system. The truck fired right up. I noticed that now while its idling if I rev it (snap throttle) I get a nice little puff of black smoke. I didn't do that before I replaced the LP. I test drove it down the street and noticed that if I mat it and the truck downshifts it also let's out a little puff of black. Not sure if this is normal. Kinda looks cool tho :). I spoke with my old service director who is a huge diesel guy.( did I mention I was an automotive tech for 14yrs? Gas motors only tho) he said he also thinks I should drop the tank that the pickup filter is probably clogging. So guess that's my next step.
 

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Good to hear you got it going.

As for dropping the tank, you could do that if your so inclined but do it in a shop or a garage so nothing gets half assed this time of year.
 

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Discussion Starter #63
Is the black puff of smoke normal? Does that mean its fueling properly? Again I'm a diesel rookie. And it never did that before I replaced the LP.
 

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That lil puff of smoke happens when you get on the throttle hard and the engine is over fueled till the engine gets it's shiet together and takes off. It has never happened to your truck before probably because it was barely getting fuel before.
 

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Yes it is!!

I will push you to do one more thing, test your timing please by reading this thread after you ....

Click Here

If it's not right, possible too far advanced for example, reset it or mechanical damage can be done.
 

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Discussion Starter #67
OK I test drove it today. It did great for the first 1.5-2hrs of driving. I never shut it off when I went in anywhere either. On the way home going up a hill it bogged,revved high, and blew blue smoke. I never let out of it this time. The truck didn't die but it bucked badly for about 10 seconds then it smoothed back out. Once home I left it idling and opened the water valve. It had a very slow small trickle of fuel. I'm guessing my next step is to check inside the tank.

FYI on the test drive I drove normally with small periods of balls to the wall and no problems. 1.5-2hrs later it hiccuped..wtf!
 

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The little trickle out of the lift pump suggests to me the OPS is not working.

I read in an earlier post that you replaced the lift pump relay. If you replaced the factory lift pump relay, that relay only works during engine cranking.

To fix the problem with burning out the OPS, you have to do this mod. Click on the link here: http://www.dieselplace.com/forum/63-gm-diesel-engines/21-6-5l-diesel-engine/268296-ops-relay-mod-install-1992-1995-obdi-trucks.html. And you will need a new OPS to make the mod work.
 

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Have you verified that it has a diesel fuel cap and not one for a gasser?
 

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Discussion Starter #71
I looked at it. It looks aftermarket honestly. Doesn't say gas or diesel on it. Doesn't say GM or acdelco. Plain black cap that says remove slowly. I opened it and it had a ton of pressure behind it. Should it be green or say diesel on the cap? Never knew there was a difference.
 

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Diesel fuel caps vent. If you had a ton of pressure when opening it, then the cap is not venting.

Excess pressure will keep the lift pump from being able to move fuel.

In the short term you can run the truck with the cap loose so the tank can vent.

You can get a Stant Diesel Fuel cap, part # Stant 10830D. Autozone has them in stock around here. $8.49 + tax.
 

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Discussion Starter #73
Really? I thought it had to seal to create a vacuum inside the system otherwise it would put air in the system. Hmm I'll give that a try then. But wouldn't it have acted up sooner than the 2 hours it took today?
 

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Not necessarily. Depends on how long it took to create the vacuum.

Excess vacuum is something we all know about and watch for. Just didn't occur to me to ask you the question early on :banghead:

Loosen the cap and take it for a drive. Then check the fuel flow from the drain. If you get a steady flow after running the engine for awhile the vacuum issue could be the culprit.
 

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Slight vacuum is OK, loud "whoosh" vacuum is not. Extreme cases of excess vacuum have collapsed fuel tanks on these trucks.
 

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Discussion Starter #76
Lol when I checked the cap a few minutes ago it had a ton of pressure behind it when I unscrewed it. And I just went back there to loosin it and guess what... It had pressure behind it again and the truck hasn't been run all afternoon... Lol so maybe your right.

Kinda feel like I've gotten ahold of someone's basket case...:(
 

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Nope, you didn't ....cause my trucks is still sitting outside....

We'll get ya through this....:coffee:
 

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Discussion Starter #78
Slight vacuum is OK, loud "whoosh" vacuum is not. Extreme cases of excess vacuum have collapsed fuel tanks on these trucks.
Holy crap really? Well mine was a huge whoosh! The cap is definitely newer than the truck. I've got it loose now and I will pick up a new cap tonight or tomorrow. Thanks for that info, that could've been bad :O
 

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Discussion Starter #80
I was just reading an old thread on here about fuel caps. Does anyone know for sure which cap will actually vent off the pressure? After reading that thread it started to make sense. Someone said on gas engines it vent through the charcoal canister which is true. And diesels aren't hindered by emissions equipment so the cap needs to vent. So which one is a good cap to use?
 
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