Fuel Pump or Fuel Pressure Regulator?

[BlueSplash]

93 3.0L V6 - Vulcan 168K miles.

Cranks but will not start. KOEO - I can hear the fuel pump run for maybe 1 or 2 seconds and would stop. No pressure build up on the fuel rail.

Reading the Hynes manual, they seem to imply that the pressure regulator is bad. Am I on the right track or it is more of fuel pump beginning to go that is why there is no pressure on the fuel rail.

Motorcraft Fuel Filter was changed 2 years ago, I only put 5K miles on it.

If this is a fuel pump, how much should I expect to pay to get a shop do the work.

Thanks for your input.

 

[shane96ranger]

I've never seen a regulator go bad to where it didn't let enough fuel by.... not saying it's not possible though. I've only seen them allow too much and also let fuel seep past (and into the vacuum line) when the motor is shut off.

How are you testing for fuel pressure? A gauge, or are you pushing the schrader valve in with an instrument? When a pump goes bad, you can sometimes hear air coming out of the valve when the system is pressurized.

 

[Rearanger]

Is the regulator mounted on/near the fuel rail or is it incorporated in the fuel pump assembly inside the tank?

 

[BlueSplash]

1993 V6 3.0L - Pressure Regulator on the Fuel Rail

Checking for pressure at the schraeder valve with test gauge from loan a tool program.

I would like to reach in on top of the tank to wiggle the connectors and check for 12V to the pump but it is just too tight and cramped. The only way I see this is to drop the fuel tank, but I am not in a position to do this myself. How much should I pay for a shop to drop the tank, replace the fuel pump ?

I have searched for the pressure regulator p/n F4SE-9C968-AA, the mounting holes do not line up with regulators that you can easily get at local parts store. It is also more expensive.

I will try to do the pressure test again this weekend just to be sure.

 

[Rearanger]

1993 V6 3.0L - Pressure Regulator on the Fuel Rail

A pressure regulator in that configuration will be a normally closed valve with a spring and a vacuum modulator. It will bleed fuel back to tank to regulate pressure. You may know that already.

I doubt the valve is now jammed open and bleeding off all flow that you have no pressure. You can disconnect the vacuum line to see if fuel is in there. The rubber diaphragm can break and flow fuel into the intake, but you'd flood the engine, or at least produce poor running. You can try pinching the fuel return line to see if you get pressure - if it's a rubber line of course.

 

[BlueSplash]

Unfortunately, did not know that. Now it makes more sense. The vacuum line is dry.

So when I do another pressure test, here is what I will do.

1. Crank up a few more times to see if any pressure builds up at all.
2. Pull the vacuum line to check for traces of fuel on the vacuum port or line itself.
3. Remove the Pressure regulator and check for traces of fuel on the fuel ports. This might give me clues and hope that fuel pump is working as it should.

Thanks for the feedback.

 

[BlueSplash]

Fuel pressure regulator came in - installed, still no start and still "0" from pressure gauge.

Just for the heck of it, I pressed on the schraeder valve pin, fuel squirted out high like with pressure. When I also pulled the old fuel pressure regulator, the fuel source line is full and fuel leaked out of it, this is after the truck has sat idle for almost 9 days. By now, I can only speculate the loan a tool tester maybe bad or the adapter is not hitting the valve pin to read pressure of the fuel rail. The truck sat for a few more days after and I tried the schraeder valve again, fuel squirted high like before. This leads me to believe the truck is holding fuel pressure, I just don't know at what number. Fuel pump is sending fuel.

I will try to get a different fuel pressure gauge and in the meantime, since it is due for state inspection next month, I will be changing spark plugs, wires, distributor cap and rotor.

 

[Rearanger]

Looking back on your posts have you considered no spark rather than no fuel?

 

[BlueSplash]

Installed over the weekend - New wires, distributor cap and rotor, new AP764 platinum spark plugs gapped to 0.043. Still no start.

There is consistent spark as I crank using the old spark plug, just cannot tell if intensity is what it should be. Air filter is not bad. Just to check if air is an issue, removed air tube to throttle body, still no start. Both Throttle body and IAC valve are clean.

2 things I am about to do. Confirm there is fuel pressure using another tester. Check if there is any error codes even though the check engine light was off the last time it was driven and parked.

 

[Rearanger]

Open EGR valve will stall engine, would also cause fail to start. Open PCV valve or broken PCV hose - same thing.

Spark should be bright and blue.

 

[BlueSplash]

Got that $20 HF Fuel Pressure Tester. The initial reading after about 3 KOEO is 30psi. Haynes says 35-45 PSI. Tried to start it, like before, it seems like it wants to run but died 1-3 seconds later. It is one of those that maybe a little gas will get it going on a carbureted engine.

The fuel pressure also started dropping to about 20-25 psi. Tried to start it again, pressure just keep on dropping every crank until it settled to about 10 psi and still will not start.

Is it time to call it a fuel pump even though I can hear the pump running?

 

[Rearanger]

If you squirt gas down throttle body will it start better and run for short time?

 

[shane96ranger]

Got that $20 HF Fuel Pressure Tester. The initial reading after about 3 KOEO is 30psi. Haynes says 35-45 PSI. Tried to start it, like before, it seems like it wants to run but died 1-3 seconds later. It is one of those that maybe a little gas will get it going on a carbureted engine.

The fuel pressure also started dropping to about 20-25 psi. Tried to start it again, pressure just keep on dropping every crank until it settled to about 10 psi and still will not start.

Is it time to call it a fuel pump even though I can hear the pump running?

Was the vacuum unplugged. These base readings should be done with it unplugged.

Posting from the Galaxy.

 

[BlueSplash]

Rearanger - No, I have no starting fluid on hand, will be getting that next trip to auto parts store. I tried carb cleaner over the weekend, did not work for me, maybe not flammable enough because of cold weather in NJ.

Shane96ranger - Just basic KOEO pressurizing the fuel lines. Reads 30psi. When I tried to start, cranking the engine, pressure dropped 20-25 psi.
I tried several times to crank the engine, pressure just keeps on dropping.
The engine did not run at all. I don't recall from the haynes manual that the vacuum line needs to be removed to pressurize the fuel line. When it runs, that is when you can take the vacuum line to compare fuel pressure with or without vacuum to test pressure regulator.

Tried to tap on the bottom of the fuel tank several times last night, just as some people have done when the fuel pump started to go bad, no go.

 

[shane96ranger]

Oh, OK... I would say yes then, it could very well be your pump. Have you checked for air in the fuel line at the Schrader valve? That is a sure sign the pump is taking a dump.