Exactly, that's why the grey wire needs to be isolated from the fuel pump relay when it exits the OPSU.




Perfect, the only problem is getting at it with it installed.

Bottom line is if the orange wire has voltage at the OPSU, either the OPSU is bad, oil pressure is in fact low, or the grey wire from the OPSU to where it splices to the grey wire from the fuel pump relay is open.

 

As an alternative, you could test continuity on the grey wire from the OPSU connector to the fuel pump relay connector. At the same time, you could test for +12V to the orange wire. Process of elimination would either show a fault with the orange and/or grey wire. If both check out, the OPSU switch is not closing either due to a fault or due to low pressure as you have stated cap.

 

That's it Kyle! That's the easiest way to test it! With the ignition OFF, unplug the OPSU and check resistance on the grey wire at the OPSU harness connector to the red "pump prime wire" near the fuel pump relay: must be less than 5 ohms. The orange wire at the OPSU harness connector must show battery voltage at all times. If those two tests are ok, it's a bad OPSU, (or low oil pressure).

** For these tests, the fuel pump relay must be plugged in and the ignition OFF. In the OFF position, the fuel pump relay connects the grey and the red pump prime wires together. When the fuel pump relay is activated, the pump prime wire dead ends in the relay. **

 

Great to see some real troubleshooting going on. I missed all the fun while I was blowing snow. Its more satisfying to figure the problem out instead of guessing correctly!

 

The main objective in do-it-yourself repairs is to save money, guessing rarely saves money. That's why proper diagnosis is so important.

 

Update... Ok guys, first off, I just want to thank all of you to take the time and help me out here. I attempted to access the OPSU, but to do that I need to remove the distributor cap, and of course, the top of the torx bolt is stripped from who ever changed it last so I am going to attempt to drill it out or sumtin tomorrow. As far as testing the truck while it is running, that cant happen because it rly wnt stay running.. It actually will stay running only when they oil pressure is up, so everything is still pointing to the switch. As far as the testing goes, I own one of those multimeter/engine testing tools from Actron but I rly dont know how to use it that well... When I am testing the connector, Do I put the postive probe into the plug and the black probe to ground? Or another part of the wire..... uggg this has turned into such a fiasco!

 

The engine should be off while testing. Post #23 explains how to test it. To test resistance, set the meter to the ohms scale. Unplug the OPSU, touch one probe to the grey wire in the OPSU harness connector and the other test probe to the red pump prime wire near the fuel pump relay. Resistance must be less than 5 ohms.

To check voltage on the orange wire at the OPSU harness connector, set the meter to the DC volt scale. Touch one test probe to the orange wire and the other test probe to chassis ground or battery negative. Must show battery voltage.

Be careful not to strip the threads in the distributor housing when installing the cap. The OEM housing is plastic, Dorman makes a replacement distributor with an aluminum housing, much better quality but costs about $100

 

Dont drill yet! If the screw heads are stripped, I bet the guy didnt strip them trying to put it on! Are you absolutely certian you are using the right sized TORX head to take them out? I bet that distributor cap is older than dirt if the heads are stripped. I would try to "Gently" break the cap apart so i could get vice grips on the heads to turn them out. I dont know how you would get a drill behind the dist. Good luck! I leave in a few to go out of town. I will check to see if you had luck later!

 

Ok guys, so I was finally able to get that distributor cap off without breaking anything. I then performed all the tests yall told me to do and everything was still pointing at the OPSU, so I replaced it. What a pain in the *** that was, the "oil presure switch socket" that I bought from AZ fit around the socket, but I didnt have enough clearence behind it to fit a ratchet. So I ended up having to REMOVE THE DISTRIBUTOR to get a wrench around the switch. I then removed it and installed a new one. However, at some point after I removed the distributor I remembered I had to mark its position, and I forgot to do that. So now my malfunction is that the truck WONT START, because of the distributor being in the wrong position, please tell me how to fix this someone...

 

EDI Engine Timing