Fuel problems

DALE JOHNSON2

MEMBER
1985 MERCURY MARQUIS
5.0L
V8
2WD
AUTOMATIC
185,000 MILES

The vehicle starts but will not stay running. Have changed, fuel pump, fuel filter, pump relay, ignition switch, catalytic converter, distributor, oil level is fine. The motor does not use any oil. Only have 9.2 volt to fuel pump in the on position. I am scratching my head.

7 Replies

MHPAUTOS

MECHANIC
31,937 POSTS

Do you have fuel pressure when the engine stops? Are you able to test for this?

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Tuesday, October 17th, 2017 AT 11:30 PM

DALE JOHNSON2

MEMBER
5 POSTS

No on the fuel pump pressure. Only have pressure in the start position. The engine use to run until it warmed up and then stop, now it stops as soon as you release the key.

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Friday, October 20th, 2017 AT 2:15 PM

DALE JOHNSON2

MEMBER
5 POSTS

I've had to get 12v from a different source as the 9.2v from the relay was not sufficient to run the fuel pump. In the run position on the ignition switch. Works fine now, why the low voltage I don't Know, It does not appear to be a wiring problem. Any suggestions? Thankyou.

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Saturday, October 21st, 2017 AT 7:42 AM

KEN L

MASTER CERTIFIED MECHANIC
43,070 POSTS

We need to find where the voltage drop is happening. Here is a guide and fuel pump wiring diagram so you can do some testing.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please let us know what happens.

Cheers, Ken

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