Oil Pressure maxed...

[WeezyBlue]

I know this is a fairly common issue. But my specific symptoms seems a bit unique.

 

Did a cluster swap, calibrated tach, replaced coolant and pressure sending units.

 

Everything works except the oil pressure. It is maxed. All the time. It doesn't move, key in, or key out, acc, run, running, plugged in or not.

 

When it had the old on/off sending unit in it, it wasn't illuminated or anything.

 

Ideas? 

 

 

[Eagle]

Illumination has nothing to do with the sender.

 

What year is the "new" cluster out of? The early ("Type 1") clusters, which this appears to be, did not return the gauges to zero when the ignition was shut off -- they stayed wherever they were at that moment. Try turning the ignition off. Take the wire off the sending unit and connect it to a good ground using a jumper cable (or a helper). Then turn on the key and see what the gauge says. Repeat with the wire unplugged and not touching anything.

 

Report results.

[Minuit]

That's either an 84-86 "Type 1" cluster or an '87 Renix cluster, most likely '87 because of the odometer font. We need to know what year your truck is and the engine at the very least. I suggest putting this info in your signature.

 

I have an '87 cluster in my '89 specifically because I like the way it looks. When I got it, I had to replace the temperature and oil pressure gauges because they both read about 15 degrees of gauge travel too low. I used gauges out of an '87-'90 "3/4" cluster without a tachometer, and it's worked beautifully ever since. I know that the '84-'86 clusters had trouble with faulty gauges, and the '87 clusters might have had the same problem too.

 

If Eagle's test doesn't make the gauge do anything, double check that the plugs are pushed in all the way, and check the printed foil circuit on the back of the cluster for corrosion or damage. If those both check out, you might have to replace the gauge in the cluster. Not as big a deal as it sounds like, as long as you can find an OEM gauge of that style to replace it with.

[Ωhm]

Do Eagle's tests.

 

1 hour ago, WeezyBlue said:

When it had the old on/off sending unit in it, it wasn't illuminated or anything.

If this was your original setup (old cluster & oil pressure switch) then idiot light should have lit ON with KEY ON, Engine NOT running. Suspect open circuit between new oil pressure sender and gauge in new cluster.