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Discussion Starter #1
..and won't stop. Trying to research for my dad. It's a 91 1.8L DOHC. He's telling me the fuel pump won't shut off. Replaced the fuel pump and a relay. Same problem. NO check engine light. Burning fuel up when he drives it. Someone suggested replacing the computer? Help is appreciated.
 

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denisond3 said:
Do you mean the fuel pump keeps running when the ignition is shut off?
See I was confused about that too. I'm in Japan so it's hard to communicate about it. All he told me was, the fuel pump continuously runs, w/ car on, causing it to burn more fuel than usual. Im no genius, but i figured it always ran when the car is on? Anyway, thats his story. Said he replaced the fuel pump itself, then they relay to it. Same problem occurring though.
Just talked to him. He said, the fuel pump is only supposed to 'pump' when extra gas is needed when accelerating. And when car is first turned on. He thinks it may be the computer. Any thoughts??
Oh and the fuel pump turns off, when ignition is off. They checked the fuel rail after turning car off and said it was filled with fuel. Thinking the engine is becoming flooded from the fuel pump constantly running.
 

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1) Fuel pump always runs when the car is running.
2)Fuel lines are a closed pressurized system, so fuel will stay in the lines and rail.
 

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The pump is working just as it should. The way the fuel system works is that the pump continuously runs, creating pressure in the fuel rail. That pressure is controlled by a regulator that sends excess fuel back to the fuel tank.

Casey
 

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So, what could be reasons it's suddenly consuming so much gas? They checked the fuel pressure regulator andthinkit's fine. Well, he's putting it in the shop monday, so it can at least be diagnosed correctly. Thanks for the help.
 

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If they put a fuel pressure gauge on the fuel rail (I just clamped a hose onto the outside of the schrader valve, after unscrewing the stem of the valve) they will be able to see if the regulator is working. It lets the pressure go up and down as you push on the gas. A stab on the gas pedal and the pressure should shoot upward, from maybe 30 psi to 36 or so. I think it sits at about 28 psi when idling.

You might want to do a search in the forums for something like 'poor gas mileage' or 'bad mpg', etc. It can have causes like a bad temperature sensor, a vacuum leak, an injector that is stuck, a bad oxygen sensor, and others. We had poor gas mileage (32 miles per gallon on the highway instead of 37 mpg) when the front brake calipers were not sliding across to compensate for pad wear. One side of the pads was wearing away fairly quickly, and the drag was causing poor mileage. Bad plugs will lower mpg also.
 

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denisond3 said:
If they put a fuel pressure gauge on the fuel rail (I just clamped a hose onto the outside of the schrader valve, after unscrewing the stem of the valve)
GT's don't have schrader valves.
 
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