Author Topic: low pressure in fuel filter  (Read 1691 times)

john jay 69Z

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low pressure in fuel filter
« on: September 11, 2022, 09:33:09 AM »
Hi All,
I could use some help with diagnosing an issue with my car if anyone has experienced similar problem and how you ended up fixing it.
My Z28 when I start it the fuel filter is full when the car warms up it empties and stalls, I have changed the fuel filter I have also checked to see if the hose from the tank is cracked or leaking and blown air through lines in case of blockage.
I have disconnected the the fuel line from the fuel pump and cranked it with good amount of fuel collected in a container. I have also changed the Fuel pump still the same issue. I have just remover the fuel pump again to check the lenght of the push rod it is 53/4 inch long, any help would be appreciate.
Thanks in advance
John

uscrichter

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Re: low pressure in fuel filter
« Reply #1 on: September 11, 2022, 11:23:52 AM »
John, I have had the same issue before with my 425 hp vette only to find water in the fuel, I would siphon some fuel from the bottom of your tank into a glass jar and see if there is water separating. Are you using fuel with ethanol in it? If so you may be getting vapor lock and try to find some non- ethanol fuel. I know it sounds too simple, but hear about the same problem a lot in the collector car community a lot in the summer with higher levels of ethanol in premium fuels.

john jay 69Z

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Re: low pressure in fuel filter
« Reply #2 on: September 11, 2022, 12:02:31 PM »
Hi uscrichter,
Thank you for your help and info, I only use 98 High octane unleaded fuel but the water that you mentioned in the tank I have not thought of. I have heard in the past that if you were to pour Methylated spirits in the fuel tank it evaporates any water or condensation that might be present in the tank.
John

uscrichter

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Re: low pressure in fuel filter
« Reply #3 on: September 11, 2022, 03:25:19 PM »
Your welcome John, Iím have not tried that additive, so not sure how it works, however when it happened to me I had just filled my tank with the same fuel you are using at a small gas station on the way back from a car show, I checked the fuel filter, pump and pressure just like you have an even rebuilt my Holly carb before taking a step back out frustration and called a buddy who runs a restoration shop and is a certified GM mechanic who found the problem, sometimes those pumps donít get a lot of customers and the tanks get condescension, I would siphon some fuel from your tank and drain it if needed. Good Luck! Curt

David K

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Re: low pressure in fuel filter
« Reply #4 on: September 11, 2022, 03:57:05 PM »
We need a bit more information on this.
How long does it run and then stall?
Does it start back up easily?
Does it start right away?
Water isnít the issue because itís heavier than gas and it wouldnít run if the tank had water inside butó-
how much driving have you done since the last fill up?
Do you use any fuel stabilizer or treatment?
How often have you driven it this week, month, year?
Carburetor?
Octane has zero to do with water in gasolineó- trust me on this one.
What youíre describing seems more like an ignition problem to me.
What distributor/coil system do you have?
Upload some pictures, as there are pretty sharp minds and eyes on this forum.

john jay 69Z

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Re: low pressure in fuel filter
« Reply #5 on: September 12, 2022, 01:06:17 AM »
Thank you Kurt.

And thank you David.K
David my car starts and runs and when it warms up it runs rough I noticed this when I would pull up to the lights while waiting the revs would drop and would need to pump the accelerator or it would stall. Upon closer inspection once the fuel filter and fuel pump where replaced I notice the clear plastic fuel filter would be full when the engine was cold and when you fired it up and let it run till you get heat to the engine the fuel filter starts to drop under half full and slowly drying up and revs would drop and stall. My engine has around 1200 miles and on it, it was rebuilt in 2017 back to factory specs.
Thanks again to all for your input.
John

68camaroz28

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Re: low pressure in fuel filter
« Reply #6 on: September 12, 2022, 01:12:51 PM »
Thank you Kurt.

And thank you David.K
David my car starts and runs and when it warms up it runs rough I noticed this when I would pull up to the lights while waiting the revs would drop and would need to pump the accelerator or it would stall. Upon closer inspection once the fuel filter and fuel pump where replaced I notice the clear plastic fuel filter would be full when the engine was cold and when you fired it up and let it run till you get heat to the engine the fuel filter starts to drop under half full and slowly drying up and revs would drop and stall. My engine has around 1200 miles and on it, it was rebuilt in 2017 back to factory specs.
Thanks again to all for your input.
John
Was engine rebuilt with flat tappet cam?
Chick
68 Z/28 NOR 01B Orig motor/trans/rear
69 Z/28 NOR 07A Orig Block & GM Cross-ram/carbs
69 L34 Rest. Nova Father/Son Car
69 L78 Surv Nova Purch 4/69 31K miles
67 L89 Corv Tribute
68 Corv 427/400 Orig motor
07 Corv Z06
R 68Z build- http://www.camaros.net/forums/showthread.php?t=182584

john jay 69Z

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Re: low pressure in fuel filter
« Reply #7 on: September 13, 2022, 12:52:40 PM »
Hi 68camaroz28
Yes I am using a crane flat tappet cam with the same grind as the 30/30
John

 

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