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Old 09-29-2008, 09:16 AM   #9
gintaras
Registered User
 
Join Date: Aug 2008
Location: Schererville, IN
Posts: 110
Re: Funky fuel system problems.. starving after 1/2 tank

Quote:
Originally Posted by Jtrux View Post
My first guess, vapor lock. A few things to do, one is put a phenolic spacer between the carb and intake, kinda expensive but works good (around 40 I think). Also insulate the fuel line somehow or route it where it doesn't get near anything really hot. Change fuel filter and don't let it rest on anything keep it suspended from the intake, valve covers etc. etc.
Changed the fuel filter, it is in the carb, I didn't see an inline filter outside of the carb.

Quote:
Originally Posted by 68C15 View Post
check the hoses between the tank and the pump. it may be collapsing internally. does it get better if you leave the cap off? (thinking it may have a non-vented cap)

the idle deal sounds like either water in gas or crap stuck in one of the idle circuits.
I thought the hoses were metal, but the ones that were rubber, that i could see, were in good shape. i will get under the truck today and look for more. It has a vaccuum vented gas gap, it is the original cap I believe, it has a nipple inside with a spring behind it.

I think you are correct about debris being inside the carb, but only disassembly will tell, I am hoping to pick up a rebuild kit for this quadrajet later in the week.

Quote:
Originally Posted by hotrodxy View Post
i agree with jtrux. also and this is a long shot but maybe your supply line and return are switched
The supply and return are correct, when I picked up the truck the tank was empty and it started right up.
Quote:
Originally Posted by dwcsr View Post
I'll go with crap gas. I'm having the same issue started last week. We are getting nasty gasoline here after the storm. Some of it smells like varnish, like last years lawn mower gas. Pings at 6* BTC on the timing
we made about 10 stops to top off for gas, yeah, maybe it was the first station with cap gas, but I would think that after 10 top-offs, it would be mixed enough and burned off


Quote:
Originally Posted by cdowns View Post
if you took the off gas cap would it run then?
I did try that wile driving and it made no difference.
Also, there is no pressure or vacuum when I remove the cap to fill the tank.
Quote:
Originally Posted by haysonj View Post
Mine was doing this on the rear tank and I think it had something to do with the pumps ability to pull the gas out of the tank. I added a electric pump in line ahead of the pressure pump and the problem went away. I don't think the FI pumps are meant to pull the fuel only push it under pressure. When you get below a half tank the siphon action is not strong enough to keep up with demand. I think this may be part of the reason new cars have them in the tank.
I was going to swap out the mechanical pump for an electric pump to see if that fixed it.
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