I have an 88' 4runner DLX and have done an SR5 cluster swap 7 months ago. It worked properly for the first month after the install then stopped working all the sudden. It bothered me for the first few days but I got over it, thinking that it was a bad oil sending unit (I bought it used from eBay).

So last week, my dad just sold his 87' SR5 4X4 Xtra Cab pickup and I had pulled the oil sending unit off his rig and transferred it to mine. (Upon removing the oil sending unit from his truck, I noticed that his had come with a rubber boot-like cover, which covers the oil sending unit and protects the wire.) Thinking nothing of it, I didn't think to place that cover on my rig.

Anyhow, the oil gauge came back to life with the swap and worked for a week, then died...my diagnoses? I washed my truck with a pressure washer and remembered spraying the truck in ALL areas that was dirty, including where the oil sending unit was and now it does not work.

So my guess is that the rubber boot cover was suppose to protect the wire and oil sending unit from water and other fluids. Has anyone come across this before or do I just have a bad connection? Thx in advance.

 

I hope this turns out to be just a rubber boot issue, my 89 DLX does the same thing after the SR5 cluster swap.

 

The water may have caused a short to happen, which I feel has disabled the oil sending unit....but the odd thing is that the original oil (light) sending unit was never affected when water was present in the same conditions? I dunno, may be someone else can chime in for answers.

 

I've never had a rubber boot on my '88 DLX 4runner. The PO did the SR5 cluster swap, but instead of using the original wiring in the engine bay, he routed new wires so as to avoid digging and finding the short in the wiring loom. Long story short, I have managed to get an aftermarket OP gauge working on the truck, but the wiring and connections are all exposed. I live in Seattle, and it's very wet here in the spring/fall/winter. I haven't had issues.

Check for shorts within the system, or perhaps your gauge?

 

Put the wire back on!!

Or clean the connection

Coat it good with dielectric grease you should be good to go till you wash it off again.

When sending units go bad most times they give reduced pressure readings