fuel gage question
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fuel gage question
what is the proper amount of ohms, for the fuel gage in a 1988 sd diesel? mine is reading 300 ohms, the older trucks were about 70 full and 130 empty best I recall. anyway my gage is pegged way past full, and neither tank is full, any suggestions? besides obvious to pull the senders for a clean up or costly replace.
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From: Brandon MS
I would check my wires around the tank to make sure they are still well insulated and not full of corrosion it almost sounds like the wire is exposed and touching something to have that much resistance.
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new gage same problem
Ok all wiring is good and little to no resistance in wires going in to and out of fuel sifter valve or harness to gage with good grounds, no corrosion, tried new fuel gage, even tried different gage cluster but still pegs past full. even with out the yel. wht. wire connected The other gage panel did this too but tach acted funny bouncing and reversing, it appears the previous owner was monkeying with the wiring but found no "problems" cut and splice as for as this goes. Every thing else works fine so may be the being flooded but every thing is reading good but gage still pegged. I'm at point of getting two new vdo's for the ohms rang of the senders and A pillar pod and saying F"it", any other suggestions?
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Posting Guru
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From: Baltimore
Turn the ignition ON and select the Front Tank.
Disconnect the electrical plug at the tank selector valve under the vehicle.
At the disconnected electrical plug take a piece of wire and short the Dark Blue/Yellow wire to ground,
The gas gauge should show empty. If it does that indicates the problem is the Front
tank sender.
Disconnect the electrical plug at the tank selector valve under the vehicle.
At the disconnected electrical plug take a piece of wire and short the Dark Blue/Yellow wire to ground,
The gas gauge should show empty. If it does that indicates the problem is the Front
tank sender.
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From: Columbus, Ohio
If there is any splicing in the wiring, that will add resistance. Butt connectors (head out of the gutters, folks!) are horrid in terms of adding resistance to a circuit. Twisting a wire together is even worse.
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yep butt connectors are bad
the wireing is solid and has correct readings including the sending units, all the way to the gage printed circuit connect. but it still pegs even with this unplugged but as have found the fuel pressure warning light gets power feed from fuel gage power, and the idiot light is staying on for that just says engine with red lens so possible short causing this? or maybe printed circuit? I really hate electrical trouble shooting especially on my stuff when I'm not getting paid by the hour, LOL!
Posting Guru
Joined: Jan 2002
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From: Baltimore
the wiring is solid and has correct readings including the sending units, all the way to the gage printed circuit connect. but it still pegs even with this unplugged but as have found the fuel pressure warning light gets power feed from fuel gage power, and the idiot light is staying on for that just says engine with red lens so possible short causing this? or maybe printed circuit?
You said the tank resistance reading from the sender was 300 ohms. The fuel gauge will read Full with any value over 145 ohms. 300 ohms is to high so the sender is bad.
With the sender wiring harness disconnected the fuel gauge will read Full because the circuit will be open and the resistance will be infinite.
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wiring good definately
Grounds read -1.5 to -1.3 and sender feeds read .3 and .4 ohms resistance from gage plug to tank connector(unplugged from tank, completely different plugged in 300ohms plugged in). I jump my test light from any ground and to the sender terminal and I suddenly get a little over 1/4 front and little under 1/2 rear seems about right without pulling the senders out but senders read ok checking the terminals, what gives? By the way are the senders the same for diesel or not and where to get if not? Or should I just get the universal vdo senders in the right ohms range and pop some holes in the tanks? My meter is an old fluke 73, if that helps last calibration was 2006.
Posting Guru
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From: Baltimore
lmctruck.com shows the 19 gallon side tank sender for $150.00.
No mention of a sender for the rear tank which should be around 17 gallons.
http://www.lmctruck.com/pdfcatalogs/pdf/fd/FD17.pdf
No mention of a sender for the rear tank which should be around 17 gallons.
http://www.lmctruck.com/pdfcatalogs/pdf/fd/FD17.pdf
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thanks
I will have to check their catalog out they were mostly a GM supplier, when I first started driving. Thanks for the help, If I had known the truck had been flooded, would not have bought for what I gave for it, 12' flatbed dump or not vehicles that get flooded always have electrical malfunctions buyer beware.