Temp and oil psi gauge spikes???

[gundigest]

I just got a 1980 CJ7 with the stock 6 cylinder. The temp and oil pressure gauge look good when you start it up, but after about 5 minutes idleing in the driveway the temp and oil psi guage will go to the max. Could this be the sending unit or the gauges? There is coolent in the radiator. Are these linked or seperate problems?

Thanks
Tom

 

[CJ007]

Maybe the temp guage is plugged into the wrong sensor. Try swapping the connection that is on the back, drivers side of the head near the firewall with the one that is on the top rear of the intake manifold.

I am sure others could tell you how to track down, but that is the best I got and have done it myself so I know the temp was bouncing and went up when I had them mixed up.

Good luck.

 

[gundigest]

Well they are not backwards. I got a new filter, oil and oil sending unit. Plan on doing that tomorrow. We will see if that takes care of it.

 

[jasonmark1993]

Since they are both spiking I would suspect that its a wiring problem.

you'll have a power wire, ground wire, and the sender wire to each gauge.

Pretty sure that grounding the sender wires is what spikes them.

You can test the gauges by removing the sender wire and grounding it. Key has to be on. This should peg the gauges.

Seems weird if both senders, gauges, or combo of either failed at the same time.

Id look to see if the sender wires are taped together and touching ground somewhere.

 

[GatorBate]

I had the same problem the first time I pulled my dash apart. Turned out I had the wires mixed up. Maybe this diagram will help.

 

[gundigest]

Thanks for the info. I changed the oil, filter and sending unit last night. It will be about 30-35 psi and then it will go to 75 psi. It would come back down and jump agian. I am going to run a new wire from the guage to the sending unit and see if that helps. I cleaned the connections on the temp sending unit and ran it a little. The last two times I had it running the temp gauge read fine and didn't spike. The way the gauge is bouncing now it looks like a bad wire. If there was a line plugged somewere wouldn't the PSI be high all the time even on start up and not bounce back down to 35 psi?

Thanks.

 

[jasonmark1993]

Every engine I have seen has the sender right next to the oil pump so even if you had some restriction in the block (unlikely) you should still see oil pressure right off the pump.

I could see it moving around like that if you had a plugged pickup or something where the pump couldn't pick up oil.

75 is awful high though; I don't think anything but a very high performance pump would do that. If a supply problem were happening, I'd expect to see it be at 35-40 on the high side and drop towards 0 when it was starving.

I think you are on the right track that the sender wire is chaffed and touching ground somewhere.