scope103

The fuel pump is an electric motor, so it will have a very low resistance; as in 1-2 ohms. Well below where your average ohmmeter (with hand-held probes) can read accurately. SO: a) if you read "infinite" resistance (or anything more than 10 ohms), you have an open in the circuit through the pump b) if you get zero resistance, but the pump doesn't run, you have a short. c) if the pump runs, it's NOT an electrical problem.

A pressure test, almost by definition, CANNOT give a false positive. If you have the right pressure it will run, no matter how you get there. Pressure tests are a little difficult, in that you need the gauge, the banjo fitting, and a set of replacement crush washers. If you have them, that's the gold standard. But if you want a quick preliminary test, replace the fuel return line (from the Fuel Pressure Regulator) with a hose into a gas can. With the pump on (engine off or on, but much safer with engine off), fuel should flow freely into the gas can. No flow means a very weak pump.

Just about the LAST thing you want to do to test a fuel pump is remove the tank. It's a big job, and what are you going to do when the tank is on the ground? The only thing that will give you is looking at the "sock" filter; you could have a good pump but a completely blocked in-tank filter. But your other (easier) tests will pinpoint that without removing the tank.

bomhour

There is a jumper test you can do from the diagnostic port in the engine that will turn the fuel pump on...if it is working. The test is spelled out in the FSM manual I believe. You could probably find it with a search on google. "3vze fuel pump test" or something.

bomhour

That was a long enough trip to beat my previous test drives. I know it's sad

Gevo

Scope? I have unknowingly already done that test. When replacing fuel injector I did a leak test just the way you suggested and the fuel flowed out of the pressure reg. Reason I am thinking a pressure test may gibe false positive is that tbe problem is intermittent. Driving around just now I found that most of the time its good but then it has total loss of power. I thought it may be fuel delivery.

Bomhour I am aware of that method.

Tha ks for the respons guys. I have more troubleshooting to do I guess.. before I drop the tank. I dont want to!

bomhour

Loss of power could come from a bad spark plug wire too. I had one melt on me because it came unattached during a repair. Just saying. Also, did you look inside your AFM to make sure your air flow switch operates smoothly. I don't know, I'm just throwing ideas out there. The tolerance on the air flow meter is high enough that corrosion can stop it from operating smoothly.

Gevo

bomhour, I have thoroughly cleaned the AFM, but in doing so it is highly possible I have damaged sensitive electronics. lol.. But, as far as the fuel pump is concerned, I am going to wait and see how the car feels after this new cat and muffler it's getting. It's at the shop right now.

Cost is going up on this build, lol.... but why am I still enjoying it all ?

I'm gonna go to my build thread to talk about a possible 'short' under the dash that may be causing the 'loss of power' ..