[formula_73]

I have a 73 formula 400 with a weird problem. The fuel, temp, and oil guages weren't working untill I noticed that the fuse for the guages was burned out. Easy fix right? Wrong... I replaced it only to find out that only the temp guage was working right. The oil was all the way to the right and the fuel needle was way past full no matter how much gas or how much oil pressure I had. Then I found out something interesting, it seemes that when ever I peel out pretty good, almost to full WOT that the fuse burns out and those three guages just float around and do nothing. Where as before when I turned the key the guages would jump to their extreme right (oil and gas) and the temp guage would read correct. I'v already replaces two fuses and an oil pressure switch wich did nothing. What else could be wrong? Should I try getting a new fuel floater? The oil switch did nothin, and I think a new floater will do the same. SHould I think about a new wireing harness? I think therte migh be a short to ground somewhere but why would it only blow the fuse a WOT?
Anyway if anyone has some advice it would greatly be appreciated.

[formula_73]

I have a 73 formula 400 with a weird problem. The fuel, temp, and oil guages weren't working untill I noticed that the fuse for the guages was burned out. Easy fix right? Wrong... I replaced it only to find out that only the temp guage was working right. The oil was all the way to the right and the fuel needle was way past full no matter how much gas or how much oil pressure I had. Then I found out something interesting, it seemes that when ever I peel out pretty good, almost to full WOT that the fuse burns out and those three guages just float around and do nothing. Where as before when I turned the key the guages would jump to their extreme right (oil and gas) and the temp guage would read correct. I'v already replaces two fuses and an oil pressure switch wich did nothing. What else could be wrong? Should I try getting a new fuel floater? The oil switch did nothin, and I think a new floater will do the same. SHould I think about a new wireing harness? I think therte migh be a short to ground somewhere but why would it only blow the fuse a WOT?
Anyway if anyone has some advice it would greatly be appreciated.

[NW S/D]

I think your right, sounds like a ground problem , try cleaning all the seprate grounds you can find that might be related,use emery cloth or even steel wool.

[formula_73]

I was thinking about just going ahead and get a new wiring harness but I've it'll be my first time doing something like that. But for nwo I guess I'll go wire hunting and check all the paths for grounding, thanks!

[soupman]

Its definetly the ground. If you have no ground the fuel gage and oil pressure will read full. The is a 90 ohm resistor on the fuel tank sending unit that gives the range from empty to full. When flooring the car, you are twisting the motor, thereby probably tightening the ground strap on the firewall and making a better connection.

[formula_73]

I don't even think I have a ground strap on the engine block to the firewall. Around where would it be located? And why would that not affect the temp guage if they're all on the same circuit? (at least at the fuse level)Sp it's a posibility that I have a bad groung and a short somewhere?

[Lloyd-TX]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by formula_73:
I don't even think I have a ground strap on the engine block to the firewall. Around where would it be located? And why would that not affect the temp guage if they're all on the same circuit? (at least at the fuse level)Sp it's a posibility that I have a bad groung and a short somewhere? <HR></BLOCKQUOTE>

Here's a pic of the OEM engine-to-firewall ground strap on my '72 Formula. The strap I'm speaking of is the braided copper one, and the other end attaches to one of the unused bolt holes at the rear of the passenger side cylinder head. I'd lay money that the '73 Firebird would be exactly the same.

Hope this helps.

[Squidward]

Might it be related to the kickdown switch (assuming TH400 tranny)? That circuit works off the gas pedal at WOT. Just a thought, maybe a short circuit related to it.

[formula_73]

I think it originally had a 400 but right now it has a 350 with a kick down bracket. Would it make a difference if it was a 350 or 400?

[formula_73]

BTW thatkns for the pic post Lloyd!

[Gordy Doyle]

Formula 73 did you get your problem solved? I'm quite sure you don't need a whole wiring harness
Gordy

[formula_73]

Actually I'm going to work on it today. I needed to get a multimeter to check the wires so I'm borrowing one. But I don't know where to start. I don't know which wires are supposed to be grounded and which aren't. I'm also not sure as to where to check the fuel floater wiring. Would I have to get under the car?

[x-bird2]

fuel sending unit ground is on the ring around the the opening on the top of the tank for the sending unit, it grounds to the inside rear of the unit body rear panel. a lot of times, this ground gets snapped when people drop the tank without disconnecting it. the positive wire for the unit goes through the trunk/rear panel with a grommet and should be visible next to the tank filler neck with the license plate pulled down, from there it goes to the top of the sending unit plate on the tank. iirc, the pos. wire comes out of the lighting harness at the left rear taillight area.

[NW S/D]

73 if you need it i have a 73 shop manual wireing diagram I could try to send via email or if nesscary snail? JF

[formula_73]

Sound's good S/D. I'd appreciate that a lot! How do I give you my email? And thanks for the info on the fule wires X. I'll look into that today.

[NW S/D]

73 call me @ 360-882-9077 & I,ll arraege how to send it,Jeff.

[NW S/D]

73 try sending me your email To [email protected], JF

[formula_73]

Thanks! Hope you get my email.

[formula_73]

I can see where the wire is behind the lisense plate but where does it connect to the tank?

[formula_73]

Thanks for the diagram! Really appreciate it. It's really easy to read. Now all I have to do is find the bad one.