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Discussion Starter #1
I have an Air leak somewhere,

I try to start her up and it takes 2, 20sec intervolves (good charge on batteries, with electric pump priming). Then struggles to keep going... I know its air that is causing the problem...after about 3min of air bubbles in the return line. It settles down and runs perfect with very little if any air bubbles in the return line.
I have gone through every thing twice and I have come up with this.

I have my electrical fuel pump next to the lift pump (electric is before the mechanical)...to far from the tank? Would putting it right next to the tank help? I can hear the electric pump struggling with air in the lines. After I turn her over once it is smooth and only fuel.
I have vacuum at the fuel cap, large whoosh when opened...should I drill a hole in the cap to let it out? Let it breath better
I have stock rectangle fuel filter (fram filter) fairly new 600miles but old filter... should I replace the filter?

I am thinking that putting the electric fuel pump close to the tank will help a lot.

Side note: I am planning a trip to Alaska :ro)this summer, any one have any information about Alaska or what I should do to my suburban be for going?
Any thing would be helpful.

Thanks!:grd:
 

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Drill a hole in your fuel cap and insert a rubber valve stem, make the hole the size it would be on a tire. Pressurize fuel tank to about 5 psi and look for leaks. A leak up stream of the lift pump will allow the fuel to drain back to the tank. If you can find a one way check valve, you can put it in right before your electric pump to prevent fuel from draining back to the tank.:grd:
 

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Will said valve stem be cumbersome after the leak is fixed? Also, are the tanks supposed to have a light pressure to them? or are they supposed to vent?
 

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My 84 seems to pull a slight vac on the tank, and it hisses when I open it to fill up....I guess thats the way the EPA likes it. If it were to build up pressure...that could get dangerous... However, I looked at my gas cap and drilling a hole for a strader valve would be a pain, cause the cap is almost an inch thick, hwat with the threads an all. Gotta be an easier way to do this little pressure test thing...
 

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Discussion Starter #5
update

Thanks for all the advice

I drilled a hole in the fuel cap and parked on a down hill instead of up-hill, moved my electrical fuel pump from front to on top of the tank. It works a lot better
I also tested the fuel lines, by putting a bicycle tube valve in a fuel line and the pressurizing it to look for leaks and none where found. Couldnt find a good cheap check valve
:grd:
 

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Which electric pump did you install?

You might have better luck bypassing your old mech pump than trying to push fuel through it.

I just fixed a customer's 6.2 blazer recently, he had a setup up similair to what you have. I bypassed his mech pump, and moved the electric to the pass side frame rail and it works like a champ now.
 

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Discussion Starter #7
installed

I Installed a universal from Napa 4-7psi pump.

i was thinking that bypassing would be a good idea. but i am priming with electric and then running off mech. just incase the mech goes out, i have the electric. but i see what your saying, its working alot better

Thanks
 

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In addition, a malfunctioning mechanical lift pump could cause your air leak in the first place.
 

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Drill a hole in your fuel cap and insert a rubber valve stem, make the hole the size it would be on a tire. Pressurize fuel tank to about 5 psi and look for leaks. A leak up stream of the lift pump will allow the fuel to drain back to the tank. If you can find a one way check valve, you can put it in right before your electric pump to prevent fuel from draining back to the tank.:grd:
I have to comment on that idea. That is a good easy way to find a fuel leak on your system.

I am not sure what the psi is on the return lines, I would think that it is less than the supply line psi.
Every tank that I noticed has a vacume on it at some point, new and old.

What have your fuel tank levels been at when you notice these problems? Maybe there is an issue with the pickup system in the tank.
Just a suggestion.
 
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