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just bought a 94 GT and the gas gauge doesn’t work.
It always reads just over the “full” line, when I turn the key to the “ON” position it dips down just below the “full” line and then climbs back above.
I disconnected the fuel pump/sending unit harness and turned the key on and it does the same thing.
I’ve read about the anti-slosh module, but everything I’ve read about that says the guage will say empty all the time and not move.
now, with unplugging the harness and it doing the same thing, that says to me that either A: the sending unit/float isn’t the issue, or B: the sending unit IS the problem and has infinite resistance so unplugging the harness wouldn’t make a difference.
anyone have any input on this? and does anyone know what wires from the harness plug in the trunk go to the sending unit itself? my repair manual doesn’t say anything about the wire color or known good resistance values for the sending unit.
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Hello 🙂
Resistance emty around 20 Ohm, and full around 150 Ohm.
Wire color from sending unit til gauge are yellow/white. Black are ground. Brown/Pink (or dark green/yellow) are fuel pump power.If the gauge is reading full with the fuel pump module connnector disconnected then the cause will likely be that the gauge lead going to the fuel tank sending unit is grounded somewhere (chaffed wire or whatever) or the gauge itself is flaky. The less resistance in a gas or temp gauge circuit the higher the needle will read.
With the pump module and the cluster disconnected the wire lead from the gauge to the sending unit could be probed to see if it shows to be grounded. With an ohmmeter there should be no reading at all on that wire with both ends unplugged.
thanks for the replies and info, this manual I have is borderline useless lol. I traced the wiring around and found that both wires were cut and stuffed back inside the wire loom/ribbed protector. it was intentionally cut because I could see the marks from a set of side cutters, no idea why someone would want to do that but I hooked them back up and the gauge reads fine. thanks again
I have no idea why someone would do that with the wire harness but congrats on getting it sorted out so quickly.
As to manuals and wiring schematics I find most of them (especially Chiltons and Haynes) to be garbage due to inaccuracies or lack of detail. You might consider getting a Helm manual for your Mustang if you would like to have a good, accurate manual around. You can get these in just the electrical and vacuum only and the way it’s laid out is very clear and easy to follow.
I’ve bought several of them for my Fords off of eBay for 10-15 bucks each and they are lifesavers. I’m not sure but I think new Helm manuals are in the 30-40 dollars range but even that is not bad for what they are.
yeah, this manual is garbage.. the more I look at it, the more I regret getting it lol. it says to remove the front bumper I have to drill rivets out on either side..nope. also says that 94-95 GT’s have a throttle valve/kickdown cable on the automatics.. I’ve had multiple auto 94-95 GT’s and have yet to see anything like that on them. I believe the kickdown is controlled by the vehicle speed and throttle position sensors.
I’m going to have to look into a helms manual, especially for this winter because I’m going to need pretty accurate wiring diagrams an how everything interacts in these cars because I intend to swap a carbureted 351w into it. eliminate all the sensors and I’d be fine, these computers just make things more aggravating to diagnose and single out.
Yes, they’ve just about complicated cars to death electrically. Those Helm manuals are worth their weight in gold and sure make things easier to understand.
My memory is a bit hazy but I think the last Helm I bought for my Lincoln was off of eBay and gave 14 bucks for it in like new condition.I’ve done carb swap engines into injected cars but not on a Mustang like yours. The engine itself shouldn’t be a problem although you will need to swap the fuel pump to a low pressure pump or add a resistor to cut the voltage down to the injected pump which would then lower the pressure to an applicable number for a carburetor.
The part not clear to me would be the transmission controls as I’ve never had a reason to get into that area yet. It might require an aftermarket controller.
I’ve done a couple efi to carb swaps on mustangs, but they’ve been all out track cars that never see street time.
my goal is an 11 second car that can be daily driven. the engine itself isn’t bad to swap in, the fuel system needs gutted and started from scratch, I’ll probably run all new lines for brakes and fuel both to serve the purpose of the car and maintenance, its a 20 year old car with 200xxx miles.
transmission shouldn’t be an issue because I’ll either get a 5 speed or a c4 auto with a manual valvebody because I’ve never had any luck with AODE’s built or not.
the reason I’m looking at wiring is because of the PATS (or is it VATS on these?) causing the locks and interior issues that some people have had, and I want to use the factory gauges to give it a stock appearance without the hood being open.
a fuel cell is probably going to be my route for the fuel because I have to cut the trunk pan out and do some rust repair anyhow. I rarely put anything aside from tools in my trunk so i’ll probably just weld a flat panel in once I take care of the rust and cut the old out and bolt a fuel cell to it, it’ll give me enough room to relocate my battery and have space for a nitrous bottle down the road perhaps.no sensors except something to drive the speedo, and sending units for oil, water, and fuel. WAY less headaches to deal with.
Sounds great to me. An 11 second car on the street is going to fool a lot of people and I could see some guys with big bucks Shelbys and Vettes complaining to the dealer after their new ride gets smoked……
I’m currently modding an engine again for this toy. Bored SBF, cam, reworked heads, dual 4 barrels, AOD, and a Pontiac Trans Am hood scoop.
http://i250.photobucket.com/albums/gg268/bluesnut/merk1.jpg
This thing has been on the dyno and the torque curve is amazing. It hits max torque at about 1700 RPM and stays flat up to 5500. Nail the pedal at any speed and it never stops pulling and pulling and pulling……
right on man. what kind of heads are you using? I’m looking around at different heads for this winter, I haven’t decided yet if I’m going to go with a 351w, or stay with a 302 and just have it bored to a 306 or 331. been thinking gt40 heads with some port and valve work if I stay with a 302 block.
no it wasn’t lol.
whats weird is I checked the car out and drove it a couple weeks before I took ownership and the gas gauge was working fine then. so sometime in that timeframe someone got the brilliant idea to cut the wires.. lolThe heads are the stock 5.0 E7TE heads with mild porting and oversized valves. The block is bored. 040 so that makes it a 308.
I’ve got a Lincoln Mark VIII engine that I’d like to do something with when the right opportunity presents itself. Those are the all aluminum 4.6 Teksid blocks with DOHC heads and very similar to the Mustang Cobra engines.
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