Fuel Pressure Issue - Chevelle Tech
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post #1 of 11 (permalink) Old May 20th, 16, 12:34 AM Thread Starter
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Steve
 
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Fuel Pressure Issue

ok long story here. I'm running an electric Edelbrock fuel pump and Holley regulator. What happens is after driving for say a 1/2 hour on the highway and I slow down to turn off I'll loose fuel pressure, drops from 6 psi to 3 or so and then starts bouncing around and will eventually go back to 6 psi for a bit and will then drop down again. I've got full voltage at the pump relay, tried another relay and no difference, tried another known good Edelbrock pump of the same type and same deal, also tried another known good regulator and same deal. Pump seems to flow ok at the outlet and after the regulator, doesn't seem to be a restriction in the tank but I did notice that it seems start doing this after I slow down from highway speed to make a hard right hand turn off the highway. Has a new pick up in the tank as well. Voltage on my gauge is 14.5 all the time. Never had it happen on short trips. What else should I be looking for? This is a 406 with Tunnel Ram and Eddy Carbs and no fuel return. Thanks for any help.

65 Beaumont Sport Delux,406,AFR 195 Competition Eliminators, Edelbrock Tunnel Ram, Voodoo 60113 Hyd Roller,
540 hp,525 Tq, Faceplated TKO 600.

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post #2 of 11 (permalink) Old May 20th, 16, 12:47 AM
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Dave 383 now
 
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Re: Fuel Pressure Issue

Mine did weird stuff like that if I ran it below 1/2 tank of gas.

Dave
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post #3 of 11 (permalink) Old May 20th, 16, 12:51 AM
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Re: Fuel Pressure Issue

Which Electric fuel pump? Could be a lack of return line, but I know people who have dead head regulator and they work fine. I have ran a few different style pumps and in the end a return line to the tank and simplifying the setup made it more reliable.

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post #4 of 11 (permalink) Old May 20th, 16, 2:00 AM
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Re: Fuel Pressure Issue

I doubt this is the problem but you have verified that there are no venting issues right?

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post #5 of 11 (permalink) Old May 20th, 16, 2:55 AM
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Re: Fuel Pressure Issue

Quote:
Originally Posted by fridgeguy View Post
ok long story here. I'm running an electric Edelbrock fuel pump and Holley regulator. What happens is after driving for say a 1/2 hour on the highway and I slow down to turn off I'll loose fuel pressure, drops from 6 psi to 3 or so and then starts bouncing around and will eventually go back to 6 psi for a bit and will then drop down again. I've got full voltage at the pump relay, tried another relay and no difference, tried another known good Edelbrock pump of the same type and same deal, also tried another known good regulator and same deal. Pump seems to flow ok at the outlet and after the regulator, doesn't seem to be a restriction in the tank but I did notice that it seems start doing this after I slow down from highway speed to make a hard right hand turn off the highway. Has a new pick up in the tank as well. Voltage on my gauge is 14.5 all the time. Never had it happen on short trips. What else should I be looking for? This is a 406 with Tunnel Ram and Eddy Carbs and no fuel return. Thanks for any help.
How much fuel in the tank ? The fuel will slosh around and have points of no fuel at the tank pick up and the pump gets a big gulp of air before the fuel returns.
The air won't come out until it gets to the carb and will disrupt the fuel gauge until it all passes by and is replaced with fuel.
I bet if you stand on it real hard as if you were racing it will do the same thing right after launch or just after a hard shift.
There maybe another issue, but the above scenario is very common with lower fuel amounts and no baffling in the tank.
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post #6 of 11 (permalink) Old May 20th, 16, 10:31 AM Thread Starter
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Re: Fuel Pressure Issue

Quote:
Originally Posted by Dave427 View Post
Mine did weird stuff like that if I ran it below 1/2 tank of gas.

Dave
Quote:
Originally Posted by tucson67ss View Post
How much fuel in the tank ? The fuel will slosh around and have points of no fuel at the tank pick up and the pump gets a big gulp of air before the fuel returns.
The air won't come out until it gets to the carb and will disrupt the fuel gauge until it all passes by and is replaced with fuel.
I bet if you stand on it real hard as if you were racing it will do the same thing right after launch or just after a hard shift.
There maybe another issue, but the above scenario is very common with lower fuel amounts and no baffling in the tank.
Might be on to something here. My fuel gauge doesn't work but I'll try with a full tank and see what happens. I'm thinking, based on the km on the tank that I'm on the top side of half a tank.

65 Beaumont Sport Delux,406,AFR 195 Competition Eliminators, Edelbrock Tunnel Ram, Voodoo 60113 Hyd Roller,
540 hp,525 Tq, Faceplated TKO 600.

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post #7 of 11 (permalink) Old May 20th, 16, 10:32 AM Thread Starter
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Re: Fuel Pressure Issue

Quote:
Originally Posted by Cam View Post
I doubt this is the problem but you have verified that there are no venting issues right?
Yup, venting is good

65 Beaumont Sport Delux,406,AFR 195 Competition Eliminators, Edelbrock Tunnel Ram, Voodoo 60113 Hyd Roller,
540 hp,525 Tq, Faceplated TKO 600.

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post #8 of 11 (permalink) Old May 20th, 16, 10:35 AM Thread Starter
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Re: Fuel Pressure Issue

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Originally Posted by Rob G View Post
Which Electric fuel pump? Could be a lack of return line, but I know people who have dead head regulator and they work fine. I have ran a few different style pumps and in the end a return line to the tank and simplifying the setup made it more reliable.
Edelbrock 12 psi pump. Not sure on the part number. I did try another pump of the same and no diff. I was thinking maybe return line but I've been running it for a while like this with out issues. This just started within the past two week. Bombing around town it's fine but after a highway run of about 30-40 min. Ambient temps have been in the high 70's to low 80's. Maybe I need a fuel cell.

65 Beaumont Sport Delux,406,AFR 195 Competition Eliminators, Edelbrock Tunnel Ram, Voodoo 60113 Hyd Roller,
540 hp,525 Tq, Faceplated TKO 600.

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post #9 of 11 (permalink) Old May 20th, 16, 11:45 AM
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I've dealt with MagnaFlow 275 and 500, that wasnt street friendly at all and kept over heating. That was no return line w magnaflows. Then I switched to mallory 140 pump w return line and it fixed everything. Currently I'm running aermotive in tank pump w return line and drives fine on street. Check for symptoms other than psi such as hot over heating pump, low fuel, high pressure in tank (ie huge vent when popping gas cap). Ive always keep tank at least half full and notice gage moves when it's less than half full when cornering or what not.

Could be pump wearing out? Is it rated for continuous duty? Etc. Fuel cell won't solve everything if it's still the pump. Is it a factory tank wit added sump?
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post #10 of 11 (permalink) Old May 21st, 16, 12:38 AM Thread Starter
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Re: Fuel Pressure Issue

Quote:
Originally Posted by Rob G View Post
I've dealt with MagnaFlow 275 and 500, that wasnt street friendly at all and kept over heating. That was no return line w magnaflows. Then I switched to mallory 140 pump w return line and it fixed everything. Currently I'm running aermotive in tank pump w return line and drives fine on street. Check for symptoms other than psi such as hot over heating pump, low fuel, high pressure in tank (ie huge vent when popping gas cap). Ive always keep tank at least half full and notice gage moves when it's less than half full when cornering or what not.

Could be pump wearing out? Is it rated for continuous duty? Etc. Fuel cell won't solve everything if it's still the pump. Is it a factory tank wit added sump?
No vent pop when removing gas cap to vent is ok. I'm think I might have a crack in the pick up in the tank and might be sucking air. Also thinking of swapping to a mechanical pump to see if it still does it.

65 Beaumont Sport Delux,406,AFR 195 Competition Eliminators, Edelbrock Tunnel Ram, Voodoo 60113 Hyd Roller,
540 hp,525 Tq, Faceplated TKO 600.

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post #11 of 11 (permalink) Old Jul 17th, 16, 6:58 PM Thread Starter
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Steve
 
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Re: Fuel Pressure Issue

This thread is a little old but I thought I'd post the fix. I dropped the tank and pulled the sending unit out and removed the sock and all is good.

65 Beaumont Sport Delux,406,AFR 195 Competition Eliminators, Edelbrock Tunnel Ram, Voodoo 60113 Hyd Roller,
540 hp,525 Tq, Faceplated TKO 600.

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