Hello. I'm an owner of an 89 F250 5.0L V8. Is it possible that a faulty oil pressure sender can prevent the EEC-IV PCM from letting the car start? Let me give a brief synopsis of my situation. The last time I drove it I noticed some strange errratic behavior of the pressure gage hovering around the low side and bottoming out while idling and then stabilizing later while both driving and idling again. The oil level is ok, the truck runs strong and I doubt the oil pump is bad. Anyway, I let the truck sit for a week and then upon starting, it would turn over but wouldnt start. I did a quick ignition check and discovered no spark at the coil secondary. The primary had full 12+VDC at the run position, but was very weak while in the start position. After a week of more extensive troubleshooting focusing on the notoriously troublesome TFI module, I checked the PIP signal which was ok, but I noticed that the SHOUT circuit from the PCM to the TFI had a very low effectively zero AC voltage (while cranking). So I unhooked the shunt "jumper" on that line and rechecked for spark - this time I got it. The system apparently defaults to a 10 degree distributor advance when it detects the SHOUT circuit open. However the engine still wouldnt start. To make a long story short, before going into a fuel system check, Im now wondering if it is the low oil pressure voltage at the oil pressure sender that is causing the EEC-IV to disable the fuel system and subsequently the SHOUT system, preventing the engine from starting? Any insight would be greatly appreciated.
<!-- / message -->

 

The computer does not monitor the oil pressure. But it does monitor the signals from the distributor. If it doesn't see any, it won't activate the fuel pump relay. See if you have any wires shorting out going to the distributor. One of them may be shielded, and I read somewhere that the shield can get frayed on the end, and ground out some of the signal wires.

You may also want to pull some codes. Here's how to do it.


http://dalidesign.com/hbook/eectest.html

 

Thanks Franklin2. I forgot the mention that I already had pulled an error code - 22. Which is the MAP sensor being out of range. Is the presence of this code ok when the engine isnt running? I did check the fuel pump relay, and Im getting a full voltate at the secondary (red wire). I will keep looking...

 

I replied to your post in the other forum already.

 

thanks.. hope the cross posting doesnt bug anyone.