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I originally posted this in the engine section, but since no one replied there, I figured the Caprice folks might be interested, since this applies to all 3 years, maybe more, I'm not sure....

I was going over the schematics in the back of my Haynes manual for '88-'94 Chevy pickups, I have an '88, and I noticed that the connector for the oil pressure sender was the same as the B-body. I then remembered that Chevy pickups for those years had a 60PSI guage in them. All of the LT1 Corvettes I have seen have an 80PSI guage in them, and the last one I rode in, the pressure sat at about 40PSI all of the time while driving. Based on the assumptions that GM guages are 12 volt guages, and that 40 PSI on a 80PSI guage would be around 6 volts, I figured 40PSI on a 60PSI sender would be at about 8 volts. I had installed the low reading 9C1 one in mine a while back, so I took the plunge, bought the pickup one for MadMav's car, which still had the oil pressure switch, and let fate take it's course. I took out the 68 ohm resistor, per instructions from the Impala home page, and went to put the sender in. Unfortunately, in order for it to fit, I had to get a 1/4" female to 1/8" male pipe thread adapter to put it in place of the stock switch. Anyhow, winding up this long post, his car with 166K miles, Idled cold at 3/4, and driving it as it warmed up it slowly dropped to the low side of the "normal" "U" shaped area on the guage. When idling warm, and in drive, it would drop to about 1/3 on the guage.(about 20 PSI) Better yet, it showed with far more detail, pressure changes with engine speed, than my 9C1 sender! If anyone is interested in this mod, I can round up the part # for the sender. MadMav is really happy with the mod, and we thought maybe some of you out there would be too!


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The sender part # is 12553175, and I got it for $25.73 at my dealer. I picked up the adapter at Advance auto for $1.49, or something like that. I also forgot to mention to put some type of sealing compound on the male end of the adapter before putting it in. After installing the sender, and removing the resistor in the dash, it's plug&play. Try not to get too annoyed by the tape that is used to wrap the wire harness in the dash...It's sticky as hell! All in all, the job shouldn't take more than an hour if it's your first time getting into the dash. Oh, and one more thing--They make a socket that fits the sender, I have one, but I think I read somewhere that an 1 ?/? deep well socket could get you by.


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Discussion Starter #4
Socket is either 1 1/16" or 1 1/8" (forget which), deep well, 6 point.

Used it on my car to remove (and replace) the stock sender when I "T-ed" in my Autometer aftermarket sender, worked fine.

Ed
 
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What about us 9C1 guys, do I just need to replace the sender and not worry about any resistors or anything, I'd like a more accurate gauge, and I'd like it to respond to RPM changes better than the 9C1 sender which is sometimes sluggish and/or jumpy.
 
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Yep, that's it... I forgot to mention 9C1's are exempt from having to pull their dash apart. Just take out the old sender, and replace w/one listed in my 1st post+adapter, and guage will then read from 0-60 psi, instead of 0-80. To give you an idea of how much better indications it gives of pressure, if you change pressure from 20 psi at idle to 45 psi while driving, the 9C1 sender pushes the guage from 1/4, up to just barely past 1/2 way up the guage. with this sender, it pushes the guage from 1/3, up to 3/4. If you're used to the 9C1 sender, like I am, this should be a very refreshing change.


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I love this mod! I constantly want/need to know what the engine is doing at all times. In idle, or at high speeds. The deflection with the 60PSI sender is so much more accurate, you have to get it. You can even compare oil viscosity after driving for extended periods of time, or the difference in oil pressure between say 55 MPH or 130 MPH. Found that out today, (My pressure drops down about 4PSI at high speeds). I'll just say that it is well worth the time and money. :eek:
 
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Besides the obvious "need a pressure guage" what would I need to do to install this on my 96 Imp?
 
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Hmmm..... Good question, Steve. I have spent very little time around '96's, so the only way I could tell you if it would work, or not, would to look at the oil pressure sender connector. If it has 3 wires, it should, you'd just have to track down the wiring in the dash. If not, then I would assume that some fabbing would have to be done. I will research this tonight, and see if I can get an answer for you by tomorrow, if not sooner.


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Discussion Starter #10
By the way MadMav, slow that damn thing down before it loses more than just 4 psi! :D :D :D

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Well now that my car is all smashed up, I guess I'll hold off on the mod, but it must be nicer than the 9C1 "is my oil pressure in the red" sender at idle when the engine is warm huh.

Well, after the insurance tells me whats happening, I'll have to do 1 of 2 things, swap senders in my completely rebuilt frame swapped 9C1, or pull a resistor out of the dash in my SS that I will aquire and then put the sender in.
 
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Yeah, I saw your post about your wreck. I'm very sorry to hear about your car, but glad you're ok. Best of luck dealing with the insurance folks, I hope everything works out for you.


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Here's what I determined from my limited shematic access to '96 Impalas:

The tan wire from the sender plug, to the instrument cluster is still there, only now it is wired to an idiot light. The light has +12v fed to it when the key is on, and if there is no pressure, the sender provides the ground, and the light comes on. My schematics do not show the resistor in the circuit for '96 Impalas, HOWEVER, if they left the resistor in there, it would NOT affect operation of the oil idiot light. So as far as the resistor being there, I can't say for sure. The wire, on the other hand, is. At this point you can do one of 2 things. 1. Unhook the tan wire from the Instrument cluster, and put in the new sender, and install a 60 psi guage for the sender in my post, OR an 80 psi guage to use with the 9C1 sender. Hook the tan wire to the the guage, along with a ground. the drawback is you wont have an "OIL" idiot light in the dash. OR 2."T" in an aftermerket sender+guage setup like AutocroSSer mentioned.


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Discussion Starter #14
Can't use aftermarket gauges with the GM senders. The aftermarket (i.e. Autometer) senders are calibrated differently. Trust me : been there, done that, crap didn't work


And THAT is why I had to do that PITA (but functional) "T" setup to get my Autometer OP sender in there.
 
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Discussion Starter #15
well, there ya go... Definitely Important info....

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Discussion Starter #16
OK guys, I'm reading through this as I'm having some fun installing a Z28 cluster in my 96 Impy.

I've installed the 9C1 sender (didn't know about the above one) and when I plug the cluster in the gauge pegs out. I've uplugged the sender and the gauge still pegs. I don't know how to read the connectors to take measurements and what I should see on the pins (12V+ - +DCV etc) to help me diagnose.

Any help would be appreciated.

Thx
Mike
 
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Discussion Starter #17
Mike : I've told this to Andy (a couple of times), guess the message didn't get thru....

At any rate, the Camaro (and 9C1) clusters expect to see a high resistance at high pressure, and lower resistance at lower pressure (BTW, Autometer is backwards from this). Both clusters use the same calibration sender.

If you look at the 9C1 OP sender wiring, it goes from the sending unit to the cluster directly.

In an SS (any year), as well as 94-96 NON-9C1 Caprice, it does NOT! It has biasing resistors to the cluster.

So in a nutshell, wire that ONE wire so it goes DIRECTLY to the gauge cluster input pin for the oil pressure gauge. If you don't want to crawl under the dash and change the wiring (not that hard when the dash is off, but you do need to know what you're looking for) then just simply run a new wire.

The 94-95 9C1 (and SS) senders have 2 extra wires to them (3 total), while the 96 sender is one wire. Ignore the other 2 wires, they are used ONLY for the Fuel Pump Relay Bypass on those cars (i.e. car will run the FP with the relay removed, although you have to crank the motor long enough to build oil pressure before the FP will turn on) that is NOT there on the 96 cars. These 2 other wires have ABSOLUTELY NOTHING to do with the gauge.
 
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Discussion Starter #18
Hey Mike,

I'm guessing you're guage is not getting the signal from sender. Other than that, I don't know much about the Z28 cluster change. I do know that if you unhook the sender on a B-body cluster, it pegs also. That's how I came to my conclusion.

Hope this helps.
 
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Discussion Starter #19
but if it changes the reading has anyone checked to see how accurete this makes the factory gauge ,i have the z cluster...
 
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