2001 SF won't start unless I start it with fuel pump relay out and then replace it.

[bradashton]

4 Cylinder engine. Every morning it has started just fine and some days it will even in the afternoon and night. But sometimes the starter will just crank and I have to remove the fuel pump relay under the hood, start it and let it die then replace the relay and it will start fine 9\10 times. The 1\10 times I have to replace the relay in the 2 seconds it runs and then it'll run fine.

I tried replacing the FP relay with the AC and there was no change. Also I tried cycling the key into the on position for 5-10 seconds a few times and that didn't work as well. The oil pressure light will sometimes blink and the temperature gauge will move a little but it's always running at the correct temperatures as far as I can tell and the oil level looked fine. Was thinking of trying a thicker oil. Any suggestions on things to try would be great, thanks.

 

[melsg5]

1. How long since you changed the fuel filter?
2. Can you do a fuel pressure test including how long pressure stays after key is off?

 

[EaOutlaw]

It sounds like you have a oil pressure sending unit that is malfunctioning, the one that will shut off the fuel pump circuit when it doesn't report proper pressure.

So either you have a real oil pressure problem which could be effected by the wrong weight oil for the climate your in. or it is simply a bad sending unit or faulty connection to it.

Start with the obvious, and do a oil and filter change putting in the correct oil for the ambient temperature range your car is experiencing.

Install a manual oil pressure test gauge and run the engine at idle and off idle slightly to see if the oil pressure is safe to operate the engine.

Post your results, you could do the oil pressure test before changing the oil but if your suspecting you have the wrong oil in the engine why risk running it for another second with known wrong oil in the engine.

 

[EaOutlaw]

the ECM works differently at cranking speed then it does at running speed. I found only once where a ECM under cranking condition would intermittently not send the signal needed to run the fuel pump under cranking condition.

I found that this cars problem to be a bad ECM that had a bad solder connections in it.

To avoid confusion and wasted time any money, after I made sure I had the correct oil in the engine, Thicker is not better with the close tolerance engines of today. using the correct oil for ambient temperature is critical.

an example of this is, Some modern Volkswagen engines found in the new beetle will not even prime the oil pump and lose all oil pressure if the engine doesn't have the right oil in it after a oil change. yet they do not have a oil pressure protect circuit.

you may need to use a factory manual and the diagnostic flow chart to get to the bottom of this problem. because many things could be causing your issue.