oil pressure gauge shakes

[lerndoutofnesscity]

Anyone know why my 93 transport's oil pressure guage seems to jump all over the place when the van warms up and is idling? It seems to go right back to normal when it's in drive and giving it gas but will shake again when I coast.

[LMP]

Originally Posted by lerndoutofnesscity

Anyone know why my 93 transport's oil pressure guage seems to jump all over the place when the van warms up and is idling? It seems to go right back to normal when it's in drive and giving it gas but will shake again when I coast.

Is it a 3.1 or a 3800? On the 3.1, the pressure gauge is just a fake: it just jumps to a predetermined position as soon there is adequate pressure: the sensor is just an on/off switch. So may be the switch or a contact is erratic.

On the 3800, there is a real pressure transducer and the indication is proportionnal to actual pressure but there again, a poor contact could give the same result.

In any case, it seems that torquing the engine changes the position of a wire and procures a better contact, or that at higher rpm, more pressure triggers the switch to a positive contact(3.1)...

Tell us what wou find.

[sds2372]

It must be just something that they do because mine does the same thing.

[LMP]

3.1 or 3800? I guess 3.1!

[telepunk]

My 3.8 does that too it hangs out around the orange zone when I am at a stop, but when I am driving its in the middle....

[Gebo]

WHere is this sensor connector? I figure I might try to wiggle it a little.

LMP,

Have mercy on me and don't give me a schematic (wink). Talk to me like I'm a 14 yr old.... You won't offend me. oops..3.8

[richtazz]

These engines are notorious for having bad oil pressure sensors. They are located on the back of the block near the oil filter, and are inexpensive and relatively easy to replace. They will normally act up at idle because that's when oil pressure is the lowest.

[Stuart1003]

I am having problems with a oil pressure gauge that reads only as high pressure. Is it just a bad oil pressure sender? It is a 3.8L engine. Where is it located and is it easy to access? Thank You...

Stuart1003

[Stuart1003]

Sorry folks,

I just scrolled down and saw Rich's notes on location...Thanks

[LMP]

Originally Posted by Stuart1003

I am having problems with a oil pressure gauge that reads only as high pressure. Is it just a bad oil pressure sender? It is a 3.8L engine. Where is it located and is it easy to access? Thank You...

Stuart1003

THe oil pressure sender electrical resistance is about 1 ohm with no pressure (indication low) and about 90 ohms at 80 psi (high). So if you test the gauge with an ohmmeter with no pressure, you should read nearly 0 ohm, which amounts to a equivalent short to ground.

CONsider the possibility that the contact to the oils pressure sender is faulty . Simply, if you take the wire at the sender and connect it to ground with a jumper, the gauge should indicate low and then this says your oil pressure sender is wrong. If it continues to indicate high, then the wire is broken somewhere .

[Stuart1003]

Thank you very much for taking the time to offer your advice. From your description, I am assuming that the oil sender has only one wire versus two wire plug attaching at the sender point. If it is only one wire, that this is simply just shorting it to ground, thereby reading low or zero 'pressure' on the dash gauge. Simple enough and thank you. But, what if it is two wires? Is one just a return line back to the gauge and the other wire is the sender wire coming from the gauge? Am I making any sense?

Regards,

Stuart1003

[LMP]

THe diagram I have (1993 3.8) just shows one wire comes from the gauge to the sender and "the other" wire (not clearly shown as a wire, I thought it was the sender body) goes to ground. So the "other wire" goes to ground and just jumping the 2 wires one to the other should send the indicator to LOW.

[LMP]

BUT...as I look for more details, it seems the "connector" that serves the oil pressure gauge also serves the fuel pump switch...honest, I did not look at it on the car, just in the book. ANd the connector should look like : www.avigex.ca/xport/connector.jpg
I'm not too sure it this helps more than it hurts... and according to the schematic, contact A would be the one that goes to the oil pressure gauge.

[Gebo]

LMP,

YOu are the man... I'm in the hurricane rain at present. I'll check it out after it clears up.

[lerndoutofnesscity]

Thanks guys for all of the ideas.....sorry I took so long to check back