Fuel pressure drops when electric fan turns on - Hot Rod Forum : Hotrodders Bulletin Board
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Old 09-03-2004, 11:11 PM
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Fuel pressure drops when electric fan turns on

Hello to everyone. I am in desperate need of some help. I have a 57 Chevy pickup with a very mild 350. It has an Edlebrock 1400 series carb, a polished Powerhouse intake, a mild cam and some headers with custom 2 1/4 dual exhaust and a stock fuel pump. It has a three row radiator with a 2150 cfm electric fan, no shroud and a 160 degree high flow thermostat and high flow water pump. It use to run just fine then all of a sudden it started running like it has vapor lock. It usually runs around 180 to 190 degrees.

I have installed a heat shield under the carb, a heat shield on my fuel line thats close to the header. I have installed a pressure regulator in the line as well as a summit liquid filled pressure gauge. I started it up today after installing the shields and regulator. The fuel pressure was holding steady around 6psi until my electric fan came on. As it started blowing the hot air around in the engine compartment the fuel pressure started going down until it reached zero.

Then it starts missing a little when I step on the gas pedal, however the motor doesn't die. Can someone please tell me what is going on? Could it be that I need a new radiator? I am also using water wetter and have also tried the other stuff 40 below or whatever it's called.

As I had mentioned before, it use to run just fine before with all the above listed components. Oh by the way the motor only has 454 miles on it and everything on it is/was brand new. I have tried some of the things you guys have mentioned on other posts regarding vapor lock. I am now stumped! So can SOMEONE PLEASE help me. Thanks to all in advance.

Oh by the way I live in Bakersfield CA......HOT!

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Old 09-04-2004, 12:14 AM
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Do you have an electric fuel pump?
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Old 09-04-2004, 01:00 PM
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I have a stock mechanical fuel pump.
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Old 09-04-2004, 01:12 PM
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vapor lock

The electric fuel pump will definitley fix the problem,but they are noisy...all of them. Mount the electric pump close to the tank. The electric pumps are way better pushers then pullers. You can even leave the mechanical pump on the engine. Ive seen a lot of people do this and it dosent seem to hurt anything. Keep the fuel pres. at 6 max. Any more then that and you will might have a leaking carb.
However, I would think that your vapor lock is caused by something else. If it started all at once?
1.Flush your cooling system
2. Install a new thermostat . A lot of debate between a 160 and 180 degree. Regardless which one you choose drill 4 holes 1/8 in. at the 12,3,6,and 9 o'clock positions on the thermostat. This helps purge air from the engine. My personal opinion is the 180 degree is better. The coolant stays in the engine longer to remove the heat.Thus, giving the coolant more time in the radiator,less cycle.
3. Change your fuel filter.
4.Lower your fuel press. 1/2 to 1 lb.
( check for a high float level or leaking needle valve seat. )

Yes, you should be using a shroud. I know looking at your engine compartment and large grill opening you would not think so., but it really helps.....alot

If all this fails...install the electric fuel pump.

Good luck
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