Fuel Prssure issue

[DTF]

My '90 Rnager 2.9 w/MAF is having trouble starting when cold. It turn over for 5-10 seconds before firing. If I cycle the ignition on/off 5 times it fires right up. I tested pressure reg and it seems to be working properly. only 1 thing, key on engine off pressure spikes to 40psi then falls back to zero. Is this supposed to happen or should it hold pressure? I've replaced the fuel filter and run injector cleaner. Any suggestions?

 

[alwaysFlOoReD]

I'm still learning these systems;
The 40 psi should stay for at least a few minutes. Possible problems could be a bad check valve in the intank fuel pump or leaking injectors or fuel pressure regulator.
Of course, I'm still running my 4.0L b-II with 32 psi and it also, like yours, has no pressure after initial KOEO, so I think it's not critical. At least for me. But mine fires up almost immediately.
Good luck,

Richard

 

[macx]

As part of researching a rough running 2.3 (93), I recently tested my fuel pressure.

My oem shop manual test procedure says the pressure should be 35 to 45 psi with the key on and engine off when you ground the fuel pump lead on the "short end" of the test plug. After turning the key off, it should not lose more than 2 psi in 3 minutes.

With engine running at idle, the pressure should be the same 35 to 45 psi. Then disconnect the vacuum line to the regulator, note the fuel pressure (will be higher), then gun the engine hard but let off of it immediately. The pressure should not drop more than 5 psi when you gun the engine.

If pressure drops quickly after the key & engine are shut off it can be either the regulator leaking pressure or the check valve in the pump. The book says to unhook the gas line on the downstream / tank side of the pressure regulator and plug the return line from the regulator (of course doesn't say how - just be careful not to spray gas all over!) and then turn the key on to build normal fuel pressure. If it holds after the key is shut off, then the check valve in the pump is good and the regulator must be bad.

It also says the voltage at the fuel pump connector should be within 1/2 volt of the battery voltage, but that would be more for testing inadequate pressure and flow.

 

[DTF]

Thanks for the help. For the time I would spend testing it...I might just replace both the reg and the pump. I know the pressure rises when I remove the vacuum line from the reg and my repair book said to kink the fuel return line, if pressure rises reg is bad. I did that and it raised about 2 psi then came back down. Seemed normal to me. I think I'll start by replacing the pump. Any more suggestions are welcome. Thanks