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Topic: Fuel pressure issuses

in Forum: C3 Fuel, Emission Control, and Exhaust Systems

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Fuel pressure issuses

Posted: 2/9/15 1:59pm Message 1 of 14
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DaveM
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Flanders, NJ - USA
Joined: 1/27/2004
Posts: 2553
Vette(s): 1982 Black, ZZ4, Hooker Side Pipes, 3.55 Rear, Rebuilt & upgraded 700R4, All new suspension, brakes, & new Charcoal interior.

I have an electric pump (in the tank) and I have a carb which needs about 6.5 psi. I installed a regulator but the most pressure I'm getting is 5.5 psi. the regulator adjusting screw is in as far as it will go. Any thoughts on what to look for or any other options.

This is an '82 with a ZZ4 engine with a Holley 770, (no mechanical pump)

Thanks,

Dave




 

Lifetime Member #116
Dave's '82

   

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Re: Fuel pressure issuses

Posted: 2/9/15 2:34pm Message 2 of 14
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Sarge81
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WEST SENECA, NY - USA
Joined: 12/3/2001
Posts: 2379
Vette(s): 1981 Blue Ice Met. w/pearl ghost flames TKO500 5speed. LS1 Swap 3.45 Dana 44.
Is there any way to get a pressure reading with no regulator in line? Maybe the pump isn't putting out to it's fullest potential.

Does the car still run?




GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44
'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975




Click here to see more pics of my Vette on CarDomain.


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Re: Fuel pressure issuses

Posted: 2/9/15 5:56pm Message 3 of 14
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DaveM
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Flanders, NJ - USA
Joined: 1/27/2004
Posts: 2553
Vette(s): 1982 Black, ZZ4, Hooker Side Pipes, 3.55 Rear, Rebuilt & upgraded 700R4, All new suspension, brakes, & new Charcoal interior.

The car runs. I'd have to disassemble the regulator and get a  fitting to go from the AN-8 to a 1/8NPT to mount a gage. Would be a pain in the a__. I don't see that pump going from 55psi(stock) down to 5psi. When I can get to the underside I'm going to change out the filter, maybe that will help?

Dave




 

Lifetime Member #116
Dave's '82

   

Re: Fuel pressure issuses

Posted: 2/9/15 6:03pm Message 4 of 14
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crossfire1982
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Cramerton, NC - USA
Joined: 8/22/2006
Posts: 1094
Vette(s): black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion
Dave, I know you did your engine upgrade quite some time back, did you change the pump at the same time?  The pump itself may indeed be your problem or if not replaced when you did the engine upgrade, the short hose section between the pump and output hard lines going to the engine.  If you still have the frame  rail mounted fuel filter, it may be worth a swap if its been a while since it was changed.

Update:You must have posted while I was typing.  From your reference to 55 psi you must have installed a C4 pump previously, probably when you were still running crossfire.  Id check the filter.

|UPDATED|2/9/2015 6:03:08 PM (AZT)|/UPDATED|



Re: Fuel pressure issuses

Posted: 2/9/15 9:50pm Message 5 of 14
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DaveM
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Flanders, NJ - USA
Joined: 1/27/2004
Posts: 2553
Vette(s): 1982 Black, ZZ4, Hooker Side Pipes, 3.55 Rear, Rebuilt & upgraded 700R4, All new suspension, brakes, & new Charcoal interior.

Hey Chip how are you? Yes I have the '85 pump in there. I have to wait for a little warmth, since I have to move the car outside to get under it to change the filter.

Thanks,

Dave




 

Lifetime Member #116
Dave's '82

   

Re: Fuel pressure issuses

Posted: 2/10/15 11:34am Message 6 of 14
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Adams' Apple
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Change the filter first, certainly. Thumbs Up
I would try to find a way to test the fuel pressure before the reg. at the same time, if possible. As was mentioned, the rubber-like hose on the fuel pump can split/crack, and cause a severe loss of pressure and volume, as could a collapsed "sock" filter on the end of the pick-up tube on the sender unit.
Also, a loose/corroded connection can lower the working voltage available at the pump, and slow it down.
Hope a filter takes care of it, tho. Big smile

One way to kinda-sorta test for a cracked rubber hose on the pump unit is to fill the tank full. When full, the hose will be covered, so the crack/split would be moot. If the pressure at your gauge goes up with a full tank, then that points to the rubber hose being bad.


|UPDATED|2/10/2015 11:34:23 AM (AZT)|/UPDATED|



Joel Adams
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Re: Fuel pressure issuses

Posted: 2/10/15 3:40pm Message 7 of 14
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crossfire1982
Former Member
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Cramerton, NC - USA
Joined: 8/22/2006
Posts: 1094
Vette(s): black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion
Thanks for asking Dave.  Im doing well, just dont bet by the forum as often as I used to.  Still have my 82 and she is running fine.   Hope all my old friends here are doing well.  Ill try to poke my head in a little more often.


Re: Fuel pressure issuses

Posted: 2/10/15 6:59pm Message 8 of 14
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DaveM
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Flanders, NJ - USA
Joined: 1/27/2004
Posts: 2553
Vette(s): 1982 Black, ZZ4, Hooker Side Pipes, 3.55 Rear, Rebuilt & upgraded 700R4, All new suspension, brakes, & new Charcoal interior.

Well it looks like I'll have to wait awhile for the weather to get better so I can change the fuel filter. I could put a gage on the rubber hose at the filter when I take off the old one. Can't get out to fill the tank because of snow & salt. I'll keep you up to date.

Thanks guys!




 

Lifetime Member #116
Dave's '82

   

Re: Fuel pressure issuses

Posted: 4/14/15 4:16pm Message 9 of 14
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DaveM
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Flanders, NJ - USA
Joined: 1/27/2004
Posts: 2553
Vette(s): 1982 Black, ZZ4, Hooker Side Pipes, 3.55 Rear, Rebuilt & upgraded 700R4, All new suspension, brakes, & new Charcoal interior.
So I changed the fuel filter and set up the carb and all is well, timing is perfect, 15lbs. of vac, mixture right, and idle is set. Thumbs Up We are good to go!!!!!!!!
Dave



 

Lifetime Member #116
Dave's '82

   

Re: Fuel pressure issuses

Posted: 4/14/15 7:21pm Message 10 of 14
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Adams' Apple
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

in Forum: C3 Fuel, Emission Control, and Exhaust Systems


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