LB7 - Engine starts then dies - Reusing low pressure fuel hose clamps

turbo_bu

Member
Mar 27, 2007
193
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18
Central IL
Just finished replacing the original LB7 injectors on my 2004 LB7 with 110,000 miles on it, with S&S SAC 00 injectors. Other than the usual pains of getting to the injectors, everything else seemed to go back together without too many issues. FWIW - I went ahead and pulled all the injector cups and re-sealed them since I really didn't want to have to go back and do this job again. The other "while I was in there" jobs were to rebuild the factory fuel filter head and swap out all the low pressure rubber fuel lines. For both these jobs, I used kits from Merchant and reused the factory constant tension hose clamps.

After getting it put back together, I primed the fuel system with the factory manual primer (truck fuel system is stock without a lift pump). While pumping, I noticed fuel leaking at the first rubber hose connection from the outlet of the fuel filter. I replaced the constant tension clamp with a regular hose clamp and that seemed to fix it. The engine seems to run ok, and so far I have driven it a couple hundred miles. No obvious leaks, and no fuel in the oil. The one issue I am having is that if I let the truck sit for a few days, and try to start it, the engine will start, then die. I then have to use the manual primer (it will be soft) to get the air out of the fuel line and then the engine will start like normal.

After the first few times it did this, I thought that there might be an issue with the stock factory constant tension hose clamps. So I went back in and replaced all of them with regular hose clamps. Unfortunately, it now takes longer (no longer a day or two, but now if you let it sit for like a week) but it will start then die. And then you are back to priming the fuel system before it will start and run like normal.

Anyone else have issues with re-using the factory constant tension hose clamps? Any issues with the Merchant rubber hose kit? I have since noticed that the Dirty Hooker hose kit comes with new "heavy duty" constant tension hose clamps. Not sure if these are the real issue, or if I am chasing something else.
 

JoshH

Daggum farm truck
Staff member
Vendor/Sponsor
Feb 14, 2007
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Texas!!!
Did you replace all the banjo bolt seals in the system when you had it apart?
 

2004LB7

Well-known member
Dec 15, 2010
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Never had issues with reusing those clamps. Issues were more from old rubber hoses more than the clamps. Try a clear hose going into the CP3 to see if you have air bubbles
 

bimmer95

Member
Mar 16, 2019
82
7
8
Morgantown Pennsylvania
I've had problems with the copper banjo gaskets on ficm already. That is pre filter so wont leak fuel unless you have a lift pump. Most gasket kits dont supply all the banjo gaskets so they get reused a lot. As far as factory style clamps, they may leak a bit at first with new hose, but often after a day or two once the hose seats in they're good.
 

turbo_bu

Member
Mar 27, 2007
193
6
18
Central IL
Ok, the saga continues .... I had replaced the clamps with hose clamps and that seemed to help for a day or two. Now we are back to it will bleed down overnight. I started looking at the cold start valve (shrader valve next to the alternator) and think I saw a bubble or two. This makes me think that this could be my issue (or at least one of my issues). I did push it when I was originally bleeding out the fuel system after replacing the injectors. But I haven't touched it since (and never did for the past 20 years!). Are these things touchy and prone to leaking?

Rock auto shows one for $25 (12637722)

Also noticed the Merchant sells an o-ring? At least it looks like it might go with this valve. Are these rebuildable?
 

2004LB7

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Dec 15, 2010
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Cold start valve? Never heard it called that. It's just a port for testing the CP3 vacuum or suction. You can bypass it if you think it's leaking
 

turbo_bu

Member
Mar 27, 2007
193
6
18
Central IL
Cold start valve? Never heard it called that. It's just a port for testing the CP3 vacuum or suction. You can bypass it if you think it's leaking
How best to bypass it? Are you removing the whole valve and then capping the fitting? Or is there a plug for the ID of the valve?

Wonder what the thread size is for this valve, metric I would think.
 
Last edited:

darkness

Well-known member
Jul 15, 2009
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vegas
How best to bypass it? Are you removing the whole valve and then capping the fitting? Or is there a plug for the ID of the valve?

Wonder what the thread size is for this valve, metric I would think.
I capped the valve on my Kodiak. I can’t remember what I used but not going to lie, I think I used a dime.
 

2004LB7

Well-known member
Dec 15, 2010
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I don't remember what I used but I think I found a bolt or something with the right threads. But you can always run the hose from the filter straight to the CP3. Or if you want, from the FICM to the CP3
 

darkness

Well-known member
Jul 15, 2009
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vegas
As in just put it over the top of the valve and use the plastic cap to trap it?
Correction, I used a bolt head. Had to take it off to remember lol. Take the valve off and set the bolt head on and screw valve back on.
 

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