So I just traded my son's IROC for a Fiero from a forum member. Its a really nice car I he was up front with me on these issues. Problem is that none of the guges are working. The fuel gauge pegs out when you key it on. By the way this is an 87 with a 3.4 conversion. Second I see it has the three wire oil pressure sending unit. When you go to start the car the oil pressure bumps up just a tad and then when the car starts it shows nothing. The battery charge gauge reads nothing also. Now a previous ower before the fella I bought the car from installed an aftermarket oil gauge and water temp gauge in the center console (Looks like crap) however they are functional. He tee'd off the oil line to install this mechanical gauge and he removed the stock sending unit for the water temp as well to install the aftermarket one. Not really sure what the oil pressure is right now because the line to the gauge got a pinhole in it so it was capped off temporarily until the hose could be replaced (When car is running it is not making any abnormal noises). My other issue is that the original owner also tied into the 2 speed fan and installed switches one for low and one for high speed. I do not want my son to have to keep an eye on the temp gauge that much so he is turning the fans on at the correct time. So I want to get this hooked back up properly as well. I think the switch is fine if you have a temperature issue or are driving in stop and go traffic but for normal driving around I can't see using them. Lastly once the car comes up to temperature is is really hard starting is this a timing issue? It also seems as though it is getting no gas once this happens. I am not sure how much gas is actually in the car however so it could be out of gas for all I know. I did pour some gas form the gas can in it last night maybe 3/4 of a gallon and when I started it this morning it ran rough for a while and then kind of smoothed out. I ran the car for maybe 10 or 15 minutes and then it just up and died and wouldn't start again. When I try to start it turns over really slow like the battery is about dead but when I put my charger on it my charger said it was still at 77% charge so I don't think its a battery issue but again the charging gauge is not operating either so I am not even sure the alternator is putting out. Is there a common ground that could be making all these gauge issues? Oh I almost forgot too the tach does nothing either. It does not move while cranking or after start up. I'm a little baffled. The fella I got the car from told me last year when he drove the car none of these problems were there. He also told me that when he was working on the temp issue that it was having prior to me buying it that he noticed once that when he turned the lights on some of the gauges started to work. Again is this something in the grounding?? Sorry this may be a confusing saga the way I have it written. On a side note I did replace the gauge cluster this morning to see if that fixed the Tach and gas gauge problem but it is still the same. Here are a couple of pics of the car in question. While I traded a running car for this one I don't feel like it was a bad trade at all. There are a ton of receipts for this car from work done to it including a new long block in 2007 and rebuilt transmission in 2008. Tons of other small mods already done including a cheaper Macco paint job. I am happy with the car I just have to get these bugs worked out before I turn my son loose with it. Thanks in advance for any help.

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Getting closer every day!
https://www.fiero.nl/forum/Forum1/HTML/080998.html

Donnie

As for the car running for a little bit of time and then cutting off without fuel pressure. I can say that is a ground issue.
That is just what mine was doing about 2 weeks ago. It left me stranded once and then it cut off in the driveway again.

Symptoms: with a mechanical fuel pressure gauge I could see that when it was running it was running at around 40psi, then it would cut power to everything in the fuel system and drizzle down to about 18psi. It would turn over but not have enough to start.

I replaced the fuel pump, the ICM and then the ECM. On my last nerve with this car I decided to throw a extra negative battery cable on from the negative terminal to the intake. The car started up perfectly and has been running so much better all around.

These are old cars and need the grounds cleaned all over, where ever. BUT until you get to that a extra ground line will never hurt.
This might solve all your issues. Who knows. It will at least solve the fuel related issue.

I have an extra ground strap from where I put an an extra on mine. I will throw that on and see if it helps. I still think there is something common with all of these aguges though that is making them all inoperable. Even the tach does nothing.

Well the common thing between the oil pressure gauge and the temp gauge is neither are hooked up to a sender anymore.

While there is a chance there is a 'common cause" it's a lot easier to troubleshoot them one at a time.

There are two heads on your son's Fiero. There are two holes where a temp gauge sending unit can be screwed in. You will have to take off the lifting hook if you want to use the second one.

Well the oil sending unit is still hooked up. The PO tee'd in below the sender to use the aftermarket so the original is still plugged in. I understand why the temp does not work since there is no sender on the block currently. On the oil gauge it just moves up a little while cranking and then goes to "0" once the car is started. Is this a sign that the sender is possibly bad? Is there a way to check the sender?

[This message has been edited by donnie072003 (edited 08-06-2011).]

The tan (center) wire of the plug is the only one used by the gauge.

With the wire disconnected from the sending unit you should get a beyond full scale reading.

With the tan wire grounded you should get a zero oil pressure reading.

If you care to, you can by a resistor at radio shack as close to 90 ohms as you can. A 90 ohm resistor to ground should give you a full scale reading on the gauge.

Resistors are $0.99 at Radioshack. The wattage of the resistor doesn't matter.

You can also read the resistance of the center pin of the sender to ground. Again you should read somewhere around zero ohms with no oil pressure, and you can estimate the reading of between 0 and 90 ohms to be between no and full scale on your oil pressure gauge.

[This message has been edited by phonedawgz (edited 08-06-2011).]

Update: Got all the gauges working except the water temp (waiting on sender from parts store). Guess I had a brain fart because I didn't check the fuses first. Yep gauge fuse was blown. I found out why though. The wires for the oil pressure sending unit were just twisted together and they had gotten into each other. Pulled it all apart and put some good soldered splices and heat shrink in place. Good to go now. Tomorrow hoping to tackle the fan issues and why they don't run on their own without the switches that were installed. I think I will install the new temp sensor in the normal spot but I may leave the mechanical gauge hooked up for a while just for reference to make sure the stock gauge is close to acurate. I still have to install the thermostat back in it too. PO took it out while burping the system. I did go ahead and install the additional ground strap just in case!