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Electronic Fuel issue 1987 ford ranger v6

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Old Feb 2, 2021
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Willbrewer95's Avatar
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From: Marshall
Electronic Fuel issue 1987 ford ranger v6

Fuel issues some times ill have pressure some times it will not. Both pumps are new. All it will do is turn over. Relay is good. All connections are clean. Is there a common issue with these trucks that i need to check first?
 
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Old Feb 2, 2021
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RonD's Avatar
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There will be a fuel pressure regulator(FPR) on the engines fuel rail, it has the Return fuel line attached and a vacuum line
The FPR is set for 45psi pressure, the vacuum line changes that to 35psi with engine running(vacuum present)

You can remove the FPRs Return fuel line
Put a towel down under the FPR and turn the key on, if fuel comes out and pressure is under 45psi, then FPR is bad, its not holding pressure

The fuel pumps do have "back flow preventers", check valves that close when pump is off so fuel or pressure can't flow backwards into the gas tank

The FPR is the other end of the system, it holds the pressure at the injectors

The high pressure pump is capable of 70psi when its on full time, which is why there is a return line and an FPR, the vacuum line is used to keep fuel pressure between 30-40psi when engine is running
At idle vacuum is high and fuel demand is low, so FPR opens more and lets more fuel flow back to tank
When you open the throttle to accelerate vacuum drops and fuel demand goes up, so FPR closes a bit to keep pressure the same
 

Last edited by RonD; Feb 2, 2021 at 11:32 AM.
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