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fuel psi gauge jumping up and down
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otis305
New User
Jul 20, 2014, 11:16 AM
Post #1 of 6
(3360 views)
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fuel psi gauge jumping up and down
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hi i got a 84 chevy c10 305ci with a turbo 350 trans. and i installed a fuel psi gauge do to fuel will not stay in fuel line too long. it will drain down and hard to start after i drove it stopped for 20 minutes and when trying to start back up i got to pump the gas and stell hard to start so i installed a fuel psi gauge on fuel line and the gauge jumps up and down at idle and when i give it gas.do ya'll know why the fuel psi gauge jumps up and down thank you ya'll
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 20, 2014, 11:39 AM
Post #2 of 6
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Re: fuel psi gauge jumping up and down
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Assuming this is a TBI engine, because the fuel pressure regulator operates off engine vacuum and varies the pressure while the engine is running.
If the rest pressure is not holding when the engine shuts off, you will have to determine where it's leaking to, whether it be back into the tank through the pressure line, leaking at the throttle body or bypassing the regulator and leaking through the return line.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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otis305
New User
Jul 20, 2014, 12:40 PM
Post #3 of 6
(3351 views)
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Re: fuel psi gauge jumping up and down
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hey there thanks for the reply, and im sorry i forgot to say its got a edlebrock 1406 carb and i put a inline fuel psi gauge on it (its a uesd one) when engine running the guage jumps form 0 to 9 and when i give it gas it jumps up and down faster and higher.and when i turn off it goes straight to 0 psi and after 15 minutes the fuel filter ( inline glass) i can see gas going back down into fuel line and it has no leaks no where. thanks for replying. let me know if you need more info
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 20, 2014, 12:46 PM
Post #4 of 6
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Re: fuel psi gauge jumping up and down
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OK, a whole different set of rules for a carbed system. You've got some kind of fuel supply issue there. I would probably test the volume. Now, I
'm assuming this has a regular mechanical pump too.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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otis305
New User
Jul 21, 2014, 11:22 AM
Post #5 of 6
(3314 views)
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Re: fuel psi gauge jumping up and down
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Yup its a stock fuel pump
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Tom Greenleaf
Ultimate Carjunky
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Jul 21, 2014, 12:55 PM
Post #6 of 6
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Re: fuel psi gauge jumping up and down
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Guess is pressure from stock mechanical is ~4-6 PSI and limited by the pressure of a spring inside it and really can't put out more but could get dirt inside and push some back to tank.
If like the other carbed GM (Chev) "V" engines uses a pushrod that of course falls down to install a new one or even take existing one out that doesn't come apart to check so new would be the only choice. OE any filter more than screen/sock at fuel pick up in gas tank would be at carb. If that one deleted you would still want one between fuel pump and carb.
What range of "jumping around" pressure are you seeing? If normal range then low it about must have a problem locking fuel in pump and sends some back to tank.
TMK the OE fuel pump will not fit in if not correct or if the pushrod lifter looking thing is in the way for installation. Some chance of the thing plain not pumping enough with worn arm on pump if erratic or if not working well or capable worn camshaft but less likely and would probably make noise,
T
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