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New to Duramax c5500 -- lost prime and will not fire.

19K views 19 replies 8 participants last post by  shrttrackr  
#1 ·
So, We purchased a C5500 6.6 Duramax powered RV about a year ago (73k miles). We had the fluids changed and new filters put on as soon as we bought it.

It's been running great up until we went to start to prep for a trip. The engine would crank and crank with no start (always started on the first attempt before).

Since its stuck in my driveway, i decided to get up to speed on my Youtube Diesel certification... :eek:

I found that the fuel filter was loose and tightened it back up and tried to prime the system. I tried several times and still no fire.

My questions:


1. if I prime the hand pump/button until it gets somewhat hard, should it stay like this? if i walk away and come back 5 min later, it is soft again (i didn't try to start it in the 5 min). I am thinking the seals are bad in the hand pump/button because it does feel somewhat spongy. Or maybe a cracked hose ? I have found no evidence of leaking fuel anywhere.

2. I bought a new bracket and filter assembly this past week and am working on installing; however, there is this pesky bracket in the way -- all the Youtube certification classes i have viewed show 2 bolts holding the bracket on but my truck has this big and bulky bracket blocking the other bolt. Is this an LLY? VIN says yes. Is this an update or was this bracket on only certain years? does the entire bracket need to come off? i think so.. i cannot see the second bolt that holds the fuel filter head on.

Image



Thanks
 
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#2 ·
...

2. I bought a new bracket and filter assembly this past week and am working on installing; however, there is this pesky bracket in the way -

Image
Well, I tried to post an image of the bracket, but it's not showing up.
 
#7 ·
:welcome2: to DP.
Have you tried to replace the filter. If old filter was loose. It would have been sucking air with dirt around filter seals/orings. This will cause filter not to completely seal properly.
Unlike many vehicles the Duramax is sucking fuel from the engine back to fuel tank. Most likely place for a leak is fuel filter. If you can pump primer until it is almost hard that is not good enough. Should pump until pump is hard. Did you open the bleeder screw and continue pumping until only fuel comes out? Close bleeder screw then continue to pump until pump is hard.
No experience with replacing complete assembly. Mine was mounted to firewall. Picture you posted looks like it is mounted on engine. Mine was a 2004.5. LLY's were made until mid 2007. Then they changes to LMM. Your 2007 is probably a LLY with LBZ electronics.
 
#8 ·
Thanks. i did open the bleeder. I replaced with a brass version bleeder just in case the plastic bleeder was cracked / leaking but it did not help.

My truck is a 2004.5, i believe. i'll check the build date.
 
#9 · (Edited)
Are there any lights on the dash while trying to start?
 
#15 ·
This worked (I think). I pumped up the fuel filter then used the schrader valve to bleed -- I really could not determine if any air was in the system as a bunch of fuel came out. I did this twice and then it fired up after about 3-4 seconds of cranking.

Now, the next question -- with 72k miles and the original lift pump, is it worth getting a new lift pump installed? if so, any suggestion on which one to buy? GM dealer part or aftermarket?

thanks
 
#13 ·
I have a 2006.5 LBZ and cured the same problem by installing an Air Dog II fuel lift system. Got rid of the original fuel filter mount entirely. No problems with fuel since (20K miles ago).
 
#16 ·
There is no oem lift pump on the Kodiaks, you have to purchase an aftermarket pump and install it.
 
#18 ·
The Cp3 pump has to draw fuel all the way from the tanks to the front of the engine, adding a lift pump will extend the life of the CP3 pump and reduce the incidence of low fuel pressure codes. It is a good investment.
 
#19 ·
The Kennedy lift pump, IMHO, is the best choice for a stock truck. It passes fuel even when off.