motoadve

I dont want to buy both if I dont have to.
We are haveing fuel pressure problems and the pressure from the pump is about 20 psi.
It could be just a worn out filter? Or the bad pump?
Or both?

How can I tell which one is bad?

ltc

If in doubt, it is always the pump.
Which, if you are replacing a fuel pump, you should change the fuel filter as well.

bigbuzuki

You have two fuel pumps.
You can try isolating each pump by pulling one fuel pump fuse at a time and see which one has the low pressure.
If both are low the filter is probably dirty or both pumps are bad.
I believe the filter can be cleaned once removed.

motoadve

We took both pumps out of the car and tested each one.
Out of the car both gave good fuel pressure so now dont know what might be going on.

Any ideas?

bigbuzuki

In that case, go for the filter clean.

mcbit

Fuel pump problems I had were intermittent so pressures would test normal.

Dennis C

I just had my primary fuel pump replaced. My dealer tested the pump at various RPMs and found it to be inconsistent in delivering good pressure across the range. It was also an intermittent problem.

mcbit

You were lucky the point being that just because it tests OK doesn't mean it is OK.

deilenberger

I'd be looking at the fuel pressure regulator and the fuel filter in this case. If both pumps produce good pressure removed from the tank, then you have to look at the components common to both pumps. Both pumps feed into the fuel filter, then one pipe exits and goes to the fuel pressure regulator (where one pipe leaves and connects to the fuel line to the injectors.)

The common points are the filter (which actually won't lower pressure IF the engine is off and the pump is run - if dirty it restricts FLOW - engine running which results in lower pressure due to inadequate flow.) The fuel pressure regulator can lower pressure even with the engine not running (and the pump running) since it bypasses fuel back into the tank.)

What I'd suggest as tests:

1. Test pressure and flow from both pumps. The factory manual gives specifications for both.
2. Test pressure with the pump running - engine running and engine not running.

The results from these tests should help narrow down what's going on..