B2 low fuel pressure

Catterman · May 22, 2014

Thank for your help, I finally found my fuel injection pressure testing spot.

Now I hooked up the gauge and it was a steady 15, with a peak of 20 on occasion. While cranking the engine to start it was zero for a while before finally getting going (7 seconds maybe?)

So, I have replaced the fuel injection pressure regulator already. Does that mean it is my pump that is bad? Or is there anything else I should look at before doing the pump? I do have an access panel cut in the back already so it is easy to get to.

RonD · May 22, 2014

If pressure gauge is accurate then yes the fuel pump would need to be replaced if FPR is working.

35-45psi is what you would expect on your '90 B2

This system has 2 valves to hold pressure, the FPR(fuel pressure regulator) and the fuel pump's check valve(back flow preventer).
The FPR valve is opened by engine vacuum, so with engine off this valve should be closed.
The computer runs the fuel pump for only 2 seconds when key is turned on, it doesn't come on again until RPMs are above 500, i.e. engine is started.
You can cycle the key on, count to 3, then turn key off and back on, repeat this a few times to see if fuel pressure comes up and then holds at 40psi.
If pressure starts dropping or never gets above 20psi then one of the valves is open or leaking.

There is also a chance that the metal or rubber pipe in the fuel tank has a hole/leak, so pressure/fuel is leaking out of the system but in the tank.

adsm08 · May 22, 2014

A failed fuel pressure regulator rarely causes low pressure. They are generally designed to produce high pressure when they fail.

Catterman · May 23, 2014

Thank you for the info. I will try and did into it more this weekend. I wonder if I do have a leak somewhere maybe... My fuel tank has been patched before, and my pump replaced already too. I will try the turn the key and wait/repeat trick. But I don't think it will hold pressure at all - also, the fuel pump is very whinny...

RonD · May 23, 2014

Non-Ford fuel pumps are much cheaper but......................some have gone out in a few days to a few months, so could be fuel pump issue if it is a 3rd party brand.

One fellow, here I think, was on his 3rd or 4th pump, lol, they have a 1 year warranty so replacement was free but from his own admission he was getting tired of pulling the bed or dropping the tank to put in another "free pump".

adsm08 · May 23, 2014

Whining pump usually means air in the lines. You may have a leak, or a drain-back issue.

Catterman · Jun 2, 2014

Okay, had a chance to check it out real quick this weekend, I couldn't see anything wrong with the fuel line or tank (but I do know the tank has been patched in the past).

I did the turn key 3 times trick and fuel pressure would go to 12psi, and never get any higher.

I went to rockauto to see what is available to buy and I have no idea what I need to look at. Do you think the pump is bad and I should get the new valve back there too? Anything else I should be looking at?

Thanks guys!!!!

RonD · Jun 2, 2014

If possible remove the return line from Fuel Pressure Regulator(FPR).
Cold engine

Cycle key on and off
NO fuel should come out of the FPR, if it does then replace it
If no fuel comes out it would be time to drop the tank

Catterman · Oct 7, 2014

Just to put closure here... My issue was the fuel pump. New one in and runs great.

RonD · Oct 7, 2014

thanks for the update

24 years ain't bad for a fuel pump.

B2 low fuel pressure

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