Fuel and Oil Pressure gauges not working since body swap

[splehigh]

I'm having some trouble getting my fuel and oil pressure gauges to work after putting an 87 body on a 76 frame. I used the old 76 engine harness and plugged it into the 87 fuse panel on the firewall. All other gauges and lights are working. I tried other gauges with the same result so I'm pretty sure my gauges are fine. I have voltage at the gauge and I can get it to move to empty by grounding it at the gauge.

I tried grounding the brown sending unit terminal at the fuel tank sending unit but it did not move the gauge to empty like it should. I'm sure that wire is fine.

The brown wire goes into the firewall on the very bottom left terminal. The wire at the gauge cluster is pink at the top passenger side of the plug. I think the problem is in the fuse panel to the gauge cluster.

Any guidance would be appreciated. Perhaps someone knows of the differences in the gauge wiring between in 87 and 76. Thanks!

[splehigh]

The brown wire on the firewall plug meets up with a thin orange wire in the back of the fuse panel which then goes up towards the gauge cluster. I'm trying to trace that orange wire and see where it goes.

[splehigh]

Ok. I think I'm close to figuring this out. The brown wire going into the plug has no connector on the inside. So I think I need to remove the pink terminal and move it over to connect to the brown wire. I'm just not sure how to move the terminals. I've done it on a 71 but not an 87.

I'm thinking I'll probably have to do something similar for the oil pressure wires but I havent traced those yet. Fun fun!

[splehigh]

Has anyone ever moved the spade connectors before? I guess I could use the 87 engine harness but then I would have all the extra connectors for a TBI engine. This truck has a carb.

[splehigh]

Success! So after moving the terminals in the back of the fuse panel I was able to get the fuel gauge working. The pink wire from the gauge cluster is now connected to the brown sending unit wire. Moving the terminal wasnt bad but tracing the wires to make sure you have the right one is the hard part.

I had to move the tan oil pressure gauge terminal to connect the brown wire going to the sending unit also. There was a purple wire in its place but it was not connected to anything(I think). Wiring diagram seemed to say it went to the ign switch but it was connected to the oil sending unit before and the ign is working.

My oil pressure sending unit must be bad because after moving the terminals the gauge still went all the way past 60lbs. I then grounded the wire at the sending unit and the gauge went back to zero so I know the wiring is correct now. I'll try another sending unit sometime this week.

Woohoo! What a nightmare.

[hatzie]

The bulkhead plugs are Delphi Packard #56 & #59 terminals. They are easy to move as you've discovered.
The most difficult part of the operation is figuring out what goes where now.
If you haven't discovered them... I scanned and posted, in PDF, GM wiring diagrams from 73-91. They have detailed pinouts of the bulkhead plugs.

[splehigh]

Thanks hatzie. There is a lot of useful info in that thread. I wish I had found that while searching. I'm going to bookmark that for future use.

I think I have all the wiring corrected. I still havent had the time to try another oil pressure sending unit but hopefully I'll have time this weekend.

Thanks again