'86 vs '88 oil gauge

[vagabond80]

Hello folks

I've been reading about the ""options"" or sensors or senders with an idiot light for a gauge.

I just swapped a whole cluster from an 86 2.9 xlt into a late 87(88 model year) 2.9 XL.
The rest of the instrumentation seems to work normally, but when running the oil gauge is resting on L. When I turn the engine off but leave the key on, the gauge goes up to the top of the normal range. When I take the key out, it gradually falls back down to the L.

Does this behavior seem to align with having a proper sending unit, but a resistor(idiot light mod) on my gauge? Or is something else wrong, or do I just have no oil pressure? Good way to test this without taking the dash back apart? Not that it was too complicated
Engine seems to run fine, don't have much time on it since getting everything put together yet though

Thanks for insights

 

[Shran]

Well if your engine is not making noise it's got at least some oil pressure. I would rule that out.

As far as I have always been aware... either way, the oil pressure sender was always just a switch... you either have oil pressure and it shows "something" on the gauge or the light is off, or you don't have oil pressure and the gauge reads zero or the light is on.

I have zero faith in factory Ford gauges from the 80's. In your case it could be a difference in the truck's wiring, a bad gauge, who knows... I have aftermarket gauges in two of my first gen trucks because the factory ones suck so bad.

 

[vagabond80]

Hmm I was going off the info from the post here https://www.ranger-forums.com/gener...oltmeter-gauge-idiot-light-conversion-150694/
I'm not concerned about numbers that much, but perhaps I should just spend the $ on a new gauge

 

[SenorNoob]

Oil gauge? My 88 only has a light. I know there are 2 "sending units" listed for 88.

There's the small switch (for the light) and the big can sender (for the gauge).

IDK if there is a corresponding wiring change or not. Since both are a single wire, and you gauge moves now, I'd suspect not.

 

[vagabond80]

Oil gauge? My 88 only has a light. I know there are 2 "sending units" listed for 88.

There's the small switch (for the light) and the big can sender (for the gauge).

IDK if there is a corresponding wiring change or not. Since both are a single wire, and you gauge moves now, I'd suspect not.

The dash is from the 86 xlt, which seemed to plug in quite naturally. I don't recall anything unused or out of place when I did the swap. Perhaps I have a switch trying to signal a gauge... I won't be back to the truck for a couple weeks now, but it's a good research direction

 

[4x4prepper]

Running a gauge you need the big sender. Inside the truck, keep a plug, because the sender will likely leak sooner or later. What I do is convert the push on connector to a ringlet, then use a locking nylon-nut nut to lock it into place and place a boot over the connection. Packing with di-electrical grease does not hurt. It is worth noting on some models low oil pressure, will cause the CPU to shut off the engine, as when the connector falls off, which is why I ended up doing all my senders that way. Sludge packing up the connector tube can do the same thing.

 

[rusty ol ranger]

Well if your engine is not making noise it's got at least some oil pressure. I would rule that out.

As far as I have always been aware... either way, the oil pressure sender was always just a switch... you either have oil pressure and it shows "something" on the gauge or the light is off, or you don't have oil pressure and the gauge reads zero or the light is on.

I have zero faith in factory Ford gauges from the 80's. In your case it could be a difference in the truck's wiring, a bad gauge, who knows... I have aftermarket gauges in two of my first gen trucks because the factory ones suck so bad.

I always thought that too but then i read somewhere that mid 87 (iirc) and before the gauge actually did read pressure one way or another but after that they were dummy gauges. I know my early 87 moves around the normal band based on RPMs. So does my 77. But my 97 does not.

Im not saying youre wrong and what i read was right i really have no idea. But my older trucks seem to "function" more like s gauge should then my 97 does.

 

[Uncle Gump]

For what it's worth... My 86 EVTM depicts the system as having an oil pressure "sender" with a white/red wiring to the cluster gauge.

I don't have an 88 EVTM to verify if it was changed to an oil pressure "switch" ... but there was a change at some point.

I think I would just buy an oil pressure sender and install it and see what happens.

 

[SenorNoob]

^That seems like reasonable answer to me.

 

[RobbieD]

Here are the oil warning light and oil gauge pages from the 1988 EVTM.

Oil warning light; first wiring and then the troubleshooting description.

And here's the oil gauge wiring and circuit description. The page is labeled "Bronco II", but I think it's a typo; this is the only schematic for gauges in the '88 EVTM, and notice the fuel gauge mentions "or tank selector valve", which would be Ranger only, and not found in the B2.

I'm not sure when the oil gauge changed from a real gauge to a fake gauge. Later EVTMs show the resistor on the gauge, which turned it into the fake gauge. But, the '88 EVTM gauge description says that uses the "variable resistor" type sending unit (the larger can type).

It sounds like your newly added cluster oil gauge might work correctly with the right sending unit, especially if your original cluster had an oil warning light.

The rest of the instrumentation seems to work normally, but when running the oil gauge is resting on L. When I turn the engine off but leave the key on, the gauge goes up to the top of the normal range. When I take the key out, it gradually falls back down to the L.

An oil warning light sending unit closes, or grounds, when oil pressure is below 6 PSI. With key on (power to the gauge) and engine not running (no oil pressure, sending unit switch closed, full ground to the gauge) the gauge should peg "high".

Even with a functioning factory oil pressure warning light or oil pressure gauge, an additional aftermarket gauge is well worth the trouble and expense.