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Author
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Topic: Gauge-related fuel flow problem?
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Fastback68
Gearhead Posts: 4169
From: Sucat, Paranaque, Philippines
Registered: Jul 99
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posted 11-09-2005 09:33 PM
   
This has my mechanic, my electrician and me scratching our heads.
The car runs fine until it stops - duh! At which point the fuel gauge reads empty regardless of how much gas is in the tank.
A check reveals that the pump seems not to be working, so we change that. And also change the filter on the carb 'cos there's some crud in there.
Off I go again, with the fuel gauge (and tank) on full.
A couple of hundred miles later (with the tank refilled of course) the same thing happens. The car just dies, the gauge goes to zero.
I watch my wife's face growing longer in the midday sun, and decide to give the damn thing another shot. I turn the key, the gauge shoots up to full again and off we go!
The tank was cleaned and the fuel lines changed a couple of years ago, so it could just be a crud problem. But why on earth would the fuel flow problem show up on the fuel gauge?
Perplexed,
Simon
[This message has been edited by Fastback68 (edited 11-09-2005).]
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kcode
Gearhead Posts: 3318
From: alvaton,ky,usa Suburb of Bowling Green, M&M #79, MCA #29208
Registered: Jun 99
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posted 11-09-2005 10:59 PM
Simon, it sounds like a short somewhere in the dash wiring. Somehow voltage is shut off to the gas gage and the ignition at the same time. Are any other instrument showing the same response, temp gage, radio, anything? Mike
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Fastback68
Gearhead Posts: 4169
From: Sucat, Paranaque, Philippines
Registered: Jul 99
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posted 11-10-2005 02:45 AM
Thanks!!! It's so damned obvious in hindsight! All the symptoms point to just what you said!
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buening
Gearhead Posts: 247
From: Decatur, IL
Registered: Mar 2005
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posted 11-10-2005 09:46 AM
This may also seem trivial, but check the alternator wire on the positive side post of the starter solenoid. If that doesn't get a good connection, the car won't start, none of the gauges will work, and even the dome lights won't come off. I too agree that it is a short in the power wire feeding the underdash harness. No power to the ignition doesn't necessarily mean the gauges won't work and vice versa. But no power to the underdash harness and nothing will work.Also, this is another bugger than had plagued me for months. My car would run fine and the next day the ignition and all gauges would be dead. I had relocated the battery and solenoid to the trunk, so i figured it was something i did with that. I made darn sure the solenoid body was touching bare metal, as that is how it is grounded. I also made sure my battery ground wire was attached to bare metal. It still plagued me until i double checked my ground strap to the engine. Sure enough, there was a good ground to the block but the connection to the frame still had paint on it. That is the only ground for the starter and if it is a weak ground nothing it will only work when it wants to. Just another thing to check. ------------------
1970 Grabber Blue Mach 1 H-code
1970 Fastback
2003 Torch Red Mustang [This message has been edited by buening (edited 11-10-2005).]
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Fastback68
Gearhead Posts: 4169
From: Sucat, Paranaque, Philippines
Registered: Jul 99
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posted 11-10-2005 06:22 PM
Thanks for the ongoing tips all. My electrician wasn't quite as euphoric over Mike's suggestion as me, not 'cos he disagreed but 'cos he was trying to think where a short - or loose connection - might be.
Anyhoo, we're all back in the city now and the car's 300 miles away, so I'll keep you posted.
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kcode
Gearhead Posts: 3318
From: alvaton,ky,usa Suburb of Bowling Green, M&M #79, MCA #29208
Registered: Jun 99
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posted 11-10-2005 10:46 PM
Simon,
When you think about it, there is no connection mechanically or electrically that ties your fuel gage reading to the operation of your fuel pump, unless you are driving a late model with an electric fuel pump. What controls both the motor running and the gage reading? Battery, alternator, Ingition Switch. My quess would be the switch. I had the back portion of a Ign switch deteriorate in the contact area and do funny things also. Good luck, tell your electrician that I'm sorry.Mike
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