The first thing I did was use my test light at the fuel pump plug coming off the front harness to see if I was getting power and found nothing. I then went to check the most common culprit, the RPM relay. I ran a wire from my test light back to the negative terminal on the battery and then placed the pointer on the test light into the back of the RPM Relay plug where pin 87 of the RPM Relay fits into. After doing this I put the key into the on/second position and the test light went on for a second and then turned off, so the RPM relay was good. The second the test light turned on is when the RPM relay energizes to run the fuel pump for a moment to pressurize the system before starting the car.
The next thing to check is the inertia switch. I ran a line from the positive terminal of the battery to the test light and then pushed the point from the test light into the ground socket at the fuel pump plug and the light came on. I went back and pushed the plunger on the inertia switch up, no light, so the inertia switch is working as expected and the ground at the fuel pump plug is good.
So now what? To be honest I wasn't sure, so I called Dave at DMC Midwest to find out what else it might be, because there isn't much else inbetween the plug at the fuel pump and the RPM relay. Dave suggested checking the plug connecting the main harness to the front harness located up by the winshield washer resevoir. I opened up the windshield water resevoir box and checked the plug and found no power there. This plug is the only splice inbetween the RPM relay and the fuel pump plug so that left me with one possibility. There must be a problem some where in the main harness, probably a broken wire, and broken wires in the harness are notoriously difficult to find.
The first thing I did was remove the center console because the main harness runs underneath. I then jumpered the RPM Relay (put a wire from pin 30 to pin 87) so there should always be power going to the fuel pump. I unbundled the harness next to the drivers side seat and found the white/purple wire, and found power, so I was OK that far. I then unbundled the harness just before it goes through the firewall in the drivers side foot well and checked the white/purple wire there, and again found power.
Here is the problem: I now know that the problem lies in about 2.5 feet of harness that runs through the drivers side pontoon of the car and is inaccessible with out some real work. Perfect! The solution? I tied a string around the plugs on the end of the main harness up by the windshield washer resevoir so that I have a way to pull the main harness forward later on, because I am going to need to pull the harness into the car through the hole in the firewall in the drivers side foot well to inspect it. This is the point where this is becoming a real pain in the butt!
I did finally find my problem, one of the previous (rodent) occupants of the car decided to nibble on the harness and severed the white/purple wire. The picture on the right shows the damage to the harness. Amazingly, this was also the only wire damaged. Rodents just love to attack the fuel system! I am going to have to solder a new piece of wire in place to reconnect things, tape it back up, and then pull it back through the pontoon and re-connect everything. It will be as good as new when I am done, but this was no small task tracking this one down. When I started on this quest I was hoping it was going to be a simple matter of replacing the RPM relay or inertia switch, but it turned out to be something much more sinister. It also explains why the previous mechanic had run wires from the fuel pump into the engine bay and spliced into a wire there to get power. I yanked the "hack job" wires out now that the fuel pump will be able to run off the harness as it should.Once I fix this up, the car will have power at the fuel pump again, for the first time in many, many years. I am going into the office tomorrow due to another meeting I need to attend, so I probably will not get the wire fixed until Friday or Saturday. My next step will be to replace the fuel tank, hook up the fuel pump, and purge the lines of any old gas that might still be in there. I also still need to do some work on the fuel tank closing plate to clean up the area where the master cylinder leaked and damaged the epoxy. I'm taking this one day at a time, and today some good progress was made!
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