140 miles into a 600 mile round trip my 88 4cyl fiero dies in the rocky mountans. No phone signal, electricity, running water, nada. No fuel pump with a blown fuse and strange voltage readings on both ends of the fuse. The oil pressure guage is on/off/all over the place. The spare 10amp fuse blows in 5 seconds. A stupid man once said "If you want to find a short, put in a larger fuse and the short will show it's self!" A 20amp fuse causes smoke in the engine compartment so I pull out the fuse and watch as the smoke coming from under the intake turns into a ball of fire. Visions of my car burning to death on the side of the hi-way race through my mind. 1/2 litre of diet pepsi later the fire is under control (is there anything diet pepsi can't do?). I find a melted plug assemply on the end of the internally shorted oil pressure sensor. I cut all 3 wires to the sensor and tie them out of the way. I now have no oil press guage but with the 10amp fuse from the radio, the fuel pump fires up and away I go.
The questions: Has anyone heard of these sensors causing engine fires in our cars? Are they known to be a commonly faulty part? Does anyone else now carry a fire extinguisher in their passenger compartment?

scary moment thats for sure!
i would try to find a new sensor quickly. out of all the gauges. i would think the oil pressure would be one of the more important ones to have.

Earlier this year I had a one year old sensor go bad by starting to leak oil where it is crimped together. It happened on a trip to Florida from my home in Michigan, so I was over 1000 miles from home. I got a lot of help from the Fiero people in Florida, especially Frank aka the Dragon. So with their help I found out what was leaking and then I had a fun time trying to get a new sensor over the weekend, which really didn't happen. I had to plug off the hole and drive it home like that. Once home I replaced it and then about 2 months ago it just quit working so I had to replace it again. I am getting pretty good at crawling under the car to do that.

However, I luckily did not have any fires or blown fuses. Glad it wasn't worse for you and you were able to make it home OK.

Great story! I know exactly the sickening feeling that came over you as you saw the car catch fire. I had an aluminum oil cooler crack on my V8 Ferrari 308 kit about ten years ago and spew oil onto the hot exhaust manifold. Orange flames and heavy black smoke were pouring out of the decklid grill. Three empty fire extinguishers later, I had given up hope and had actually started wondering what I would do with the insurance money! Blasphemous, I know. Just then the fire dep arrived.

quote Originally posted by Reallybig: The spare 10amp fuse blows in 5 seconds. A stupid man once said "If you want to find a short, put in a larger fuse and the short will show it's self!" A 20amp fuse causes smoke in the engine compartment so I pull out the fuse and watch as the smoke coming from under the intake turns into a ball of fire. The questions: Has anyone heard of these sensors causing engine fires in our cars? Are they known to be a commonly faulty part? Does anyone else now carry a fire extinguisher in their passenger compartment?

Nope.. Normally the fuse blows first. LOL (Sorry!)

Friend's car in High School had a flaky switch that would blow fuses.. (switch was full of soda) Replaced fuse with a piece of wire, car burned up that night..

Was it the older-style pressure sensor (large can) or the newer / '88 style? I've had a few of the older ones go bad, but the newer ones seem much better. Just need to attach the newer style plug, but it sounds like you need a new plug now anyway..

I switched to a mechanical guage because my old switch was going haywire and now, No problems whatsoever and..... get ready.... wait for it..... I get correct oil pressure readings! TA-DA!!! easiest fix ever!! Glad your car didnt burn down though! I had an 85 gt a long time ago and they previous owner had put a remote starter switch on the back and one day I turned a corner and all of a sudden,. the car dies and smoke fills the inside. I jumped out and opened the trink and the wiring for the switch somehow caught fire, I hadnt cleaned my car out so there was a coke which helped me put mine out! (i dont like diet sodas!)

We suggest you read this:

http://fierosails.com/OilSensor.html

Paul McKibben
Norcross, GA

ok, now that being said, what happens when you just unplug the oil pressure sensor? Thats all I did and have has zero issues witht he fuel pump.

quote Originally posted by NEVERDONE: ok, now that being said, what happens when you just unplug the oil pressure sensor? Thats all I did and have has zero issues witht he fuel pump.

You just don't have the secondary fuel pump (backup) conection and the gauge signal. You can get by without it but if you are running a high performance fuel pump a secondary current path is helpful to keep up with the higher current requirement.
As for Fiero engine fires; they may get more common as we are driving older vehicles that use 80's era hoses, wiring, and connectors,Best to carry a couple of fire extinguishers ABC rated for automotive use

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, ZZP Intercooler, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by joshh44: scary moment thats for sure! i would try to find a new sensor quickly. out of all the gauges. i would think the oil pressure would be one of the more important ones to have.

I will be installing my 4.9L engine stand ornament soon, so not fixing the 2.5 is goning to make pulling the engine feel that much sweeter!

Oops. Posted wrong window.

[This message has been edited by Reallybig (edited 05-05-2012).]

Another "trick" that the oil pressure sender will do, is shorting closed and leaving the fuel pump running after the key is off.
Very effective at turning your battery into a doorstop. I have had to replace 2 or 3 senders for just this reason. One just a year old.
I moved my fuel pump feed from an unswitched to a switched wire, behind the fuse box.
Now, when I turn off the key, the fuel pump feed is "cold" too.

quote From " TARGET=_blank>http://fierosails.com/OilSensor.html[/b] Apparently these contacts are not rated for the full pump load. This can cause the contacts to overheat and damage the pressure-sensing portion of the sensor. We believe GM erred in this application. The sensor as described by AC Delco (the sensor manufacurer) is for "oil pressure w/light". It appears the contacts within the switch were intended for an "idiot light" on the dash, not as current-carrying components for the fuel pump. Therefore, running fuel pump power through the sensor seems to be a design error, but that's the way it is (unless you change it).

1. Who is "We?"

2. Which sender? old (87 and back) or new (88 and newer) or both?
2a. Parts catalogs, including ACdelco and 22P etc, are great for errors and other problems. (Good example. Fiero Stant Rad Cap was wrong for 20+ years...) Trusting description in a parts catalog? Not good enough for forensic/design work.

3. GM Design is to take normal full load of FP BUT things can overloaded the rating for the contacts and even cause the contact to burn out... Blowing an OP sender and/or relay can be a Symptom not a Root Cause and treating as a cause can and likely will bite you. Iffy power and/or ground will cause FP to draw more Amps than the switch/relay/both can handle.
Yes, a rusty etc OP sender can overheat/burn too... but still likely has multiple problems.
More? See my cave, electric motor in general electrical section.

4. If OP sender does get full power then Relay, ECM, or wiring to FP relay is bad.

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(Jurassic Park)

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