Thirdgen89GTA

iTrader: (5)

This is something that i need to get fixed on my car, and its driving me nuts. I've been through 3 different senders and its just supposed to be a single wire setup for the stock gauge. So I'm not sure why it doesn't work. Its never worked, not with the stock TPI, and not with the LT1 swap.

The basic behaviour is that the factory oil pressure gauge in my 89 GTA pegs itself as soon as IGN is turned on. I don't even have to start the car. If I move the key to IGN On, the gauge will peg itself.

I've been through 2 senders, Autozoo NEVER has the right one. My sender is located just above the oil filter. Its driving me nuts. Does anyone know the correct P/N# for the oil pressure sender.

And does anyone have the wiring schematics for the oil pressure gauge on a 89 firebird?

I'm wondering if somehow the gauge is grounding out somewhere, the wiring harness in my car is a bit of a hack job thanks to previous owners. I've got about 99% of it sorted out and back to factory, except for this oil pressure gauge issue.

P.S, i'm moving to a serious heads/cam setup for the LT1 so while I was happy enough to let it be alone. But no longer. Don't want to risk the new build.

iroc-v

mine has that problem intermittently. I'm with you in thinking it's a possible short to ground. If the oil pressure sender is above the oil filter what is the one is located at the rear of the intake???

Thirdgen89GTA

iTrader: (5)

When factory my 89 had the combined sender/switch above the oil filter assembly. However, I don't know the wiring codes, and the TPI along with its harness is long gone.

However, the behavior now is the same as it was when factory.

I mean, its JUST a one wire setup. If I know the wire color, and its grounded correctly then the gauge must be bad. But since I haven't been able to verify the wiring, and getting the right P/N# seems to be a pain.

74Novaguy

unplug the sensor the gague should read zero. try unplugging and grounding out the lead wire and see if the gague moves. if not you may have a short to ground some where

Thirdgen89GTA

iTrader: (5)

I don't know if the sensor is even plugged in right now. Its been so long since I've really cared about this issue. Even if it is, unplugging the sensor is a little hard considering that its right next to the header tubes.

74Novaguy

ok my bad... i think i got it backwards unplugged (open circuit) is full oil pressure grounded is 0 oil pressure.

Thirdgen89GTA

iTrader: (5)

That does sound more right. My interior harness was hacked to hell, I got most of it working. Previous owner cut alot of grounds out for an alarm system. The main dash ground was cut so far back it was in the loom, not even a wire hanging. I didn't know a ground was supposed to be where it was until I saw an unmolested TPI car, and traced the ground wire back.

My car used to have the gauge read-outs die when the lights were turned on, unless the door was open. I hate grounds. The oil gauge has never worked right though. A schematic would be wonderful if anyone has access to one.

74Novaguy

I have full service manuals pm me your email and ill send you the wireing diagrams

Thirdgen89GTA

iTrader: (5)

Much thanks, PM sent.

camaronewbie

You mentioned a sender above oil filter, then you mentioned a single wire sender. I'm confused ...

The sender above the oil filter was either a 2 wire, or a 3 wire sender on your car (factory).

The single wire sender you would have only had IF the factory sender above the oil filter was a 2 wire sender. If it was a 3 wire sender, you would not have a single wire sender anywhere for oil.

IF the sender above the filter was a 2 wire sender, it is actually a switch, NOT a sender, it's for the fuel pump, and has nothing to do with the oil gauge. In the case where a 2 wire SWITCH was above the filter, then you would have had a 1 wire SENDER on the china wall driver side of the distributor.

Now - there are 2 different types of single wire senders - one for gauges, and one for idiot light. You have to make sure you get the one for the gauges.

OK - I have no idea how all the new LT1 stuff is wired up ... but what you need is a single wire oil pressure sender for gauges, mounted anywhere you like (either above oil filter or on china wall by distributor).

1 wire gauges: http://shop.advanceautoparts.com/web..._575824997____

1 wire idiot light: http://www.autozone.com/autozone/par...23380_0_0_5835

2 wire: http://www.autozone.com/autozone/par...420_15459_5835

3 wire: http://shop.advanceautoparts.com/web..._545544181____

Note: Different parts stores call them different things, although they are wrong - like AZ, calls all of them a switch but they are not. Basically, like I said, you need a single wire unit for a gauge.

The 1 wire sender sent info to gauge (or idiot light).
The 2 wire switch turn on fuel pump when it sensed oil pressure.
The 3 wire job replaced both above, and put it all in one unit with 3 wires.

Hope that helped. You might just have the wire bad, or grounding out somewhere as well.

9D1BURD

Wow...if only someone had wanted you to fix this years ago...and yes i realize it is more important now than it was earlier.

vtwinsroc

iTrader: (1)

can i get a copy of the wireing diagrams i have ground issue dont know how many are they thanks

evilemokid94

iTrader: (6)

did you figure out the problem with this? im having a similer problem, my gauge worked fine after i did an engine swap but i forgot to bolt down the wires and they got against the manifolds while going down the road causing my needle to bounce around like crazy, well it finally stopped and pegged itself like you said, iv replaced the switch 3 times and it always pegs itself, think maybe i need a new gauge?

sofakingdom

iTrader: (1)

That's backwards... unplug it, should read infinity; short the wire to ground, should read zero.

Compare to an idiot light switch: enough oil pressure, switch opens, wire basically floats; low pressure, switch closes shorting the wire to ground, light comes on.

Go disconnect the wire and short the connector to ground. If the gauge doesn't go to 0, you have a wiring or gauge problem. If it does go to 0, then the wiring and gauge are working, you have asensor problem.

emo, your wire is probably burned in half; investigate where it was touching the manifold and check to make sure the copper still goes all the way through. If not, cut it and crimp in a spice and wrap it real good with tape, and support it away from the manifold securely so it doesn't happen again.

evilemokid94

iTrader: (6)

thats the thing, the wires are fine, it never melted throw the loom, i pulled all the loom off and the wires are fine as can be

Thirdgen89GTA

iTrader: (5)

So you have a similar issue to me then. My wires are fine, at least they should be. I need to make sure they are going to the correct pin on the bulkhead. But I don't feel like diggin into it right now. I'll be doing a 4th gen dash swap later, so most of that will change anyways.

evilemokid94

iTrader: (6)

my wireing was never touched, besides the manifold touching them so im thinking i just ruined the gauge, because i really cant figure this out and i want my gauge to work again. this sucks and i need help

mrrman

watching this thread...I am having a starting problem and mu oil pressure sensor was replaced since my guage was reading 0, still didnt fix the problem.

sofakingdom

iTrader: (1)

So what happens when you touch the wire to ground? with a paper clip or something maybe? Does the gauge read 0?

Thirdgen89GTA

iTrader: (5)

Just looked back at this thread. Got busy, lost the urge to fix it.

Going to take out the C100 engine side of the connector tomorrow in the daylight and verify that there is even a wire in the E5 terminal on the C100. I looked for a tan wire coming out of the C100 connector on the engine side of the connector, found one not connected to anything. Grounded it, no change in the oil pressure. Found dark brown wire, no idea what thats going to.

Part of me wonders if all of the colors on the C100 connector from the swap are even the right colors.

Gonna pull the driver seat and lay down on the floor of the car and look under the dash to trace the wire. I hope its not broken somewhere in there.

I really only have this sudden urge to fix this because I'm driving the car again now that it has a 6spd and the old crappy A4 is outta there. And now that I'm driving it again the pegged oil pressure gauge is pissing me off.