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Fuel Pressure Drop?
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Split 1
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PostPosted: Fri Aug 21, 2009 1:53 am    Post subject: Fuel Pressure Drop? Reply with quote

I am running an electric pump, have a holley guage and when I start the engine which has twin 40mm Dells with 38 venturies/chokes, the Holley guage reads 4 lbs pressure, after about 5 mins it reads nothing, the carbies still work, ( we are waiting on some jets but it runs) why would the presure drop, I switch the motor off, it still stays at less than 1 lb pressure.
Have changed the pump, have cleaned everything???
Come back to the engine in a hour os the next morning, first switch the ignition on the guage reads 4lbs, start engine same again??

Any ideas???

Dave
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sturgeongeneral
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PostPosted: Fri Aug 21, 2009 12:39 pm    Post subject: Reply with quote

Have you cleaned the screen in the bottom of the gas tank? Sounds like you have restricted flow.
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Split 1
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PostPosted: Fri Aug 21, 2009 3:11 pm    Post subject: Reply with quote

Yes, even replaced the guaze sock in the tank and fitted a new in-line filter??

Dave
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Guack007
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PostPosted: Fri Aug 21, 2009 3:45 pm    Post subject: Reply with quote

You checked the floats?
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Split 1
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PostPosted: Sat Aug 22, 2009 3:40 pm    Post subject: Reply with quote

No havent checked the floats, ,,,how would that alter the pressure??

Thanks
Dave
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A.J.Sims
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PostPosted: Sat Aug 22, 2009 5:16 pm    Post subject: Reply with quote

vapor lock?
Take the cap off and retest!
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Split 1
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PostPosted: Sat Aug 22, 2009 6:38 pm    Post subject: Reply with quote

Tried removing the cap, no change ????

Dave
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SGKent Premium Member
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PostPosted: Sat Aug 22, 2009 7:14 pm    Post subject: Reply with quote

it could be just a bad sender.
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Split 1
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PostPosted: Sun Aug 23, 2009 4:45 am    Post subject: Reply with quote

Tried new carbies, no change.
Tried squeezeing the pipe needle goes up??

Dave
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Split 1
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PostPosted: Sat Aug 29, 2009 1:21 am    Post subject: Reply with quote

If you come out to a cold engine, switch ignition on and pump, I get 4psi, then drive for 10 mins get 1psi but it still drives.
Guage working fine when you squeeze the fuel pipe ,the needle moves???

Dave
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JustBarry1972
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PostPosted: Sat Aug 29, 2009 10:09 am    Post subject: running out of fuel Reply with quote

Hi, i found this thread looking for a fix for my fuel prob... i drive about half a mile and run out of fuel - ie coughs and splutters, i jump out and with engine off give the throttles a blip (dual dells) and no fuel squirts from any barrell.
I wait a while for the fuel filters to fill before and after the pump to fill up (5 mins? ) then blip the throttles and see fuel from all.
ive rebuilt the carbs twice without finding any dirt. Ive replaced the fuel pump as it trickles into the empty filter pre mechanical pump.
ive left my car with the front jacked so the tank is above my carbs (cars raked when diving)
will the filters ever stay full once filled? or do they allways turn to vapour?
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teamasr
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PostPosted: Tue Jan 26, 2016 9:22 pm    Post subject: Re: Fuel Pressure Drop? Reply with quote

Split 1, did you find a solution to the problem? My motor seems to be doing the same exact thing. Running duel webers, holley regulator, liquid filled gauge and electric pump. After a minute of idling, pressure drops to zero or near zero with engine running, but exhaust starting to make popping sound.
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Split 1
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PostPosted: Wed Jan 27, 2016 3:12 am    Post subject: Re: Fuel Pressure Drop? Reply with quote

Sorry never did fix it and it carried on driving?
Since sold it so not sure what it was
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modok
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PostPosted: Wed Jan 27, 2016 3:19 am    Post subject: Re: Fuel Pressure Drop? Reply with quote

The first thing I think if I hear "pressure falling" and "liquid filled gauge" in the same sentence
is
The gauge is leaking internally.
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