Fuel pressure

I have a 95 mitsubishi diamante 3.0 auto it will not start i checked the fuel pressure when i turn the key on i get no fuel pressure but when i crank the motor over i get 40 psi. should i get fuel pressure when i first turn the key on? Thanks

You should have fuel pressure with the key on. You need to check a repair manual to find the proper fuel pressure for your vehicle. I don’t think 40 psi is within your range however. You may have an ignition switch problem or wiring problem to the fuel pump. Since I am not that familiar with the Diamante so you will need the help of a good independent mechanic to get you going again.

I’m pretty sure I’ve got a wiring schematic for this car. Will check later and post back.

A strictly off the cuff wild guess could mean an ECM fault but I’ll try to verify that.

Are you sure you’re turning the key all the way to the “run” position? Its the position just before it will crank. When you do that all of the dash lights should light up and you should be able to hear the pump hum for a couple of seconds.

If you’re still following this you might check fuse No. 8 (20 amp) and fuse No. 11 (10 amp) for the first step. The odds of the problem being these fuses are zero IMO but you always weed that out first.

If the fuses are good then you need to go to the MFI relay and look for a white/red wire lead that goes to terminal A-8 on the ECM.
This lead is a temporary ground for the MFI relay which powers the fuel pump when the key is first turned to the RUN position. After a couple of seconds this ground electronically disappears but will reappear once the starter motor is engaged and an ignition pulse is provided to the ECM.

You can check for this ground with a VOM or by the use of a test lamp connected to a positive power source, not a ground. You use the lamp probe on the white/red wire lead and the lamp (or VOM) should light up or show continuity when the key is first turned on. If not, there’s a fault with the ECM.

This can be gotten around but there’s a downside to it.