No Fuel Pressure

[Tin Medic]

I drove about 5 miles and then I lost power, no fuel flow. Let it cool down for 15 min or so and its good for another 5 or 6 miles then repeat. I added a new ground and no go. If I hook a 9 volt to the fuel pump it will run constantly but when using the key it doesnt always turn the pump on. I put a new fuel filter on right before the pump. Should I get fuel to the rail using the 9V battery to run the pump, because I'm not? Any ideas?

 

[Tin Medic]

YES, It has gas.

 

[Torxhead]

O.K. here are some guesses. I am assuming the f.i. unit you have is a Hesco or a Mopar. The 9 volts to the pump does not put out enough pressure to get to the fuel rail because the regulator can't work with 25% less pressure? So you are not getting juice to the pump, sometimes, the next thing up from the pump would be the relay. Are you getting any trouble codes?

 

[Tin Medic]

Haven't scanned it for problems. Where would the relay be? Can the relay cut in and out? This was a major issue last fall when I drove to SD. The issue is not consistent never know if it will cut out on me.


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[Tin Medic]

Can the relay work intermittently and cause the pump to overheat?

 

[Torxhead]

I would think with your description, a check engine light would come on, and would indicate if any codes are sent. Sometimes there is a problem, and no code will activate it, such as a ignition crank sensor, which is another possibility, if you have one. The fuel pump relay, like many electronic componets can go wacky when they warm up. That relay should be located upstream from the fuel pump. I once found a bad fuel pump plug that gave me problems, so I just eliminated that plug.

 

[Tin Medic]

The relay looks like it is mounted high center on the firewall.

 

[Tin Medic]

How can the ignition crank sensor cause this problem?

 

[csuengr]

If the crank position sensor goes, the engine shuts down and a trouble code is thrown.

If by 9V you mean a 9V battery, it doesn't have enough power to get fuel to the fuel rail. It can barely run the pump.

I would replace the fuel pump relay for starters.

 

[Tin Medic]

When the cps goes does it go for good or can it come and go until death?

 

[csuengr]

Most of the time, they just die. But when they go, the ECU sets a code.

 

[jdarg]

They will come and go too - esp. w/ temperature. I've read more than a few times that people with bad CPS sensors would often have the vehicle fire right up simply by unplugging them and then immediately plugging them back in. I used to know a guy w/ a comanche that did that all the time.