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I am surprised, I have heard nothing but good things from Merchant Auto
 

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Discussion Starter #63 (Edited)
I don't want to knock Merchant. They are good shop and good people. They said they replicated the issue, put the ball and spring back in, then the issue never came back after multiple tests. Kinda hard to believe since every time I tried it since I got it back it has dropped FRP. But I am not calling them liars. It costs me a lot money and schedule juggling to leave it with them for a whole week. I need my truck now so I it's not going back to them.

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so what kind of testing did they do? return rate? does the truck have any smoke, or a miss when it drops rail pressure? could indicate a sticking injector

ive never seen this on a duramax however I have had similar things happen on 5.2 Isuzu's
 

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Discussion Starter #65
so what kind of testing did they do? return rate? does the truck have any smoke, or a miss when it drops rail pressure? could indicate a sticking injector

ive never seen this on a duramax however I have had similar things happen on 5.2 Isuzu's
I didn't ask what they did. I assume they opened up the filter head, saw that the check ball and spring were missing, put them back, test drove it and observed no problem, then said it's done.

No smoke, no miss.
 

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Discussion Starter #66
I'm not celebrating yet, but it looks as if the lift pump cured the problem. It definitely drives a lot livelier than it did before. Spools up faster and accelerates harder. I tried twice yesterday and once today to get it to screw up, and it hasn't yet. Hopefully it stays that way.

The lift pump install was pretty simple, just took a while, about 6 hours total. The only thing not included in the kit is chafe protection for the hoses. I had a little bit of large wire loom in the garage, but need to pick up some more. My only complaint (and not really one) would be that you can't verify if the pump is actually running. I'm going to have somebody push the over-ride button with the truck off and see if I can hear / feel it running. It's that quiet.
 

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I'm not celebrating yet, but it looks as if the lift pump cured the problem. .
Did you go with one lift pump or two? I know Kennedy sells them both.
 

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Discussion Starter #68
Did you go with one lift pump or two? I know Kennedy sells them both.
Single. Easy to add on another to it to make it dual if I want to. But I never will. One more year and it's new truck time for this guy.
 

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I'm interested to see what happens in the following weeks. I'm glad that your truck is not messing up at the moment, but I hate to tell ya that I think a lift pump is a band aid for your real problem. The pump is keeping extra fuel pressure and not letting your truck fail as it was before.
 

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Discussion Starter #70
I'm interested to see what happens in the following weeks. I'm glad that your truck is not messing up at the moment, but I hate to tell ya that I think a lift pump is a band aid for your real problem. The pump is keeping extra fuel pressure and not letting your truck fail as it was before.
And the real problem is?

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Are you running a factory CP3?

If so how many miles ?
 

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I think the lift pump is also a partial band aid to a larger problem

I bet your CP3 is worn out

What about the injector tubes or cups? Injectors ever been removed from the truck?
 

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Discussion Starter #74
I think the lift pump is also a partial band aid to a larger problem

I bet your CP3 is worn out

What about the injector tubes or cups? Injectors ever been removed from the truck?
Injectors have never been touched.

If my CP3 is "worn out," how could I accelerate from a dead stop to 100 MPH @ 26,000+ PSI 10+ times in a row (before the lift pump) without a single problem? I know very little about the inner workings of a CP3, but it seems like if it was "worn out" I wouldn't be able to do that. And testing a CP3 is just a pressure test, right? Well, I pass that with flying colors.

I'll tell you what I'm not going to do. I'm not going to throw thousands of dollars at this trying to figure out what the "real" cause is when there's nothing wrong with what I've done to fix it. If something else fails, I'll address it. Until then, my truck is running stronger than it ever has.

I'm not going to do what a guy at work did and keep taking my truck back to the dealer every couple weeks and let them keep throwing parts at it until they finally put the right one on and the problem goes away. He was $3500 into and the problem still wasn't fixed. When they finally replaced all the rubber fuel lines, the problem went away. $4500 total repairs that a $400 lift pump would have fixed. And IMO, that's not really a band-aid. That's doing what GM should have done on these engines anyway.
 

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Yeah I understand, no sense throwing more money into the truck if you don't plan on keeping it

Hope things work out and the truck stays running strong
 

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That's doing what GM should have done on these engines anyway.
These trucks should have had a lift pump from day one. Add a little bit of power, a little age and it's almost a must.
 

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Look guys this is not rocket science. After three of these trucks all doing the same thing it became apparent to me that with high mileage you get wear. The problem is the fuel system sucks on the Dmax. First thing you need to do is install the Cat dual filter with a lift pump. The cat filter is a 2 micron filtration system. Stock filter is 7 microns. Under 26,000 psi its like running a wet sandblaster through your fuel system mainly your injectors. After the filter install put in a clean set of new injectors. Problem solved
 

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Stock filter is 4micron with a coalescing water separator built in. Cat filter is also a good filter but has no water separator so you need the dual kit to get that function. IMHO the stock duramax filter setup is better than many. The bigger issue is that fuel in the US sucks, bare minimum cetane rating (unless your in CA) and bare minimum lubricity which is why additives for lubrication work so well to extend the life of the parts.
 

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ironmangq:32672186 said:
Stock filter is 4micron with a coalescing water separator built in. Cat filter is also a good filter but has no water separator so you need the dual kit to get that function. IMHO the stock duramax filter setup is better than many

It might be better than some but it still doesn't meet Bosch's filtering and water stripping standards
 
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