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Fuel sending unit problem? 95 6.5 diesel Tahoe We just installed a new sending unit i

J

jrsavoie

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Fuel sending unit problem? 95 6.5 diesel Tahoe
We just installed a new sending unit in the Tahoe. Added 5 gallons of fuel. Hit the key and the gauge goes down hard - way below empty.

I spent extra money on an AC Delco sending unit. It was made in fricking china.

Did I get a bad sending unit? Any ideas?

Thanks
 
There was no ground wire to the frame from the sending unit like on our other vehicles and no ground wire on the new sending unit.

It's a 2 wire plug.

The backwards wire possibility crossed my mind also. Any ideas on how to check things out without dropping the tank? What could possibly happen if I reversed the polarity? Anything bad?

Can I test the connector for continuity to ground on one of the wires?

I'm assuming it must be line in and line out with only 2 wires. I originally thought one hot and one ground. But I'm guessing it must be hot in and the other wire goes to the gauge.

If there is supposed to be a ground wire from the sending unit, how would one go about installing one without dropping the tank again?

I can run an alligator clip from ground to the tank and see if that makes a difference
 
Wire polarity wont matter here. You can use the temp test clip to ground to see if its a bad ground. Try from tank to frame and again from frame to neg post of bat.

Do you still have the old sending unit? If yes is it in good shape other than sending unit (no rust) DieselSlug was wanting a unit to add my MRFSU to. His is all rusted up.
 
Sorry the sending unit is shot. The tubes were bad and I cut them with a pair of side cutters, then I cut the wires off right up close. Kind of sorry I cut the wires off now. I wanted to hook it back up and see what happened when I adjusted the float on that one.

I hooked a ground to the new tank and no change. I disconnected the plug and the gauge went to full.

Any further suggestions would be appreciated. I need to diagnose if I got a bad sending unit so I can send it back if necessary.

Does anybodies else's vehicle ever bury hard to the empty side?
 
I hd a similar issue with mine....I found my problem at the lift pump. My sending unit is grounded with the lift pump. HOWEVER my truck is a cab & chassis though but its a thought.
 
The gauge pegs to below empty with 5 gallons of fuel. It goes to about 1/2 tank when full. With the sending unit unplugged the gauge shows full.

Running an extra ground wire to the tank did nothing
 
Maybe get another unit and try this: (what I allway do) Plug new unit into connector outside the tank. Just hold it there with your hands, have friend turn the key to run, then slowly raise and lower the float to confirm its opererating the gauge.
If you make alittle extension cable from the wire you cut off the original you could do the test by yourself.
I'll allways do this test before going through the trouble of dropping the tank...blah blah...
 
I always test starters and alternators. I don't know why I didn't test this sending unit before installing. Bad move on my part


Burning oil said:
Maybe get another unit and try this: (what I allway do) Plug new unit into connector outside the tank. Just hold it there with your hands, have friend turn the key to run, then slowly raise and lower the float to confirm its opererating the gauge.
If you make alittle extension cable from the wire you cut off the original you could do the test by yourself.
I'll allways do this test before going through the trouble of dropping the tank...blah blah...
Click to expand...
 
Do you have an ohm meter to check the resistance on it? If so what is the resistance of the sender? Sounds to me like you got an early style sender and put it in a late model truck as it will make your guage show half when full if you hook up an early sender to a late model truck.
 
I'll try that - probably tomorrow.

THEFERMANATOR said:
Do you have an ohm meter to check the resistance on it? If so what is the resistance of the sender? Sounds to me like you got an early style sender and put it in a late model truck as it will make your guage show half when full if you hook up an early sender to a late model truck.
Click to expand...
 
I did not check to see what the gauge read before starting messing with it today- I should have

The last time we checked it read about 1/2 tank.

I tested resistance on the sending unit -46.2 ohms - which I'm guessing would be about 1/2 tank. The tank should be near full unless I'm getting really poor fuel milage. It's only gone about 8 miles after being filled.

I tested voltage to the sending unit - 8 volts

After these tests the gauge read empty - it may have been reading empty before we started - No way of knowing as we didn't check the gauge before we started this morning.

I ran a ground from the battery to the ground on the sending unit. I made jumper plug with the ground accessible to add the ground from the battery. I cleaned and copper-coated the ground connection.
 
The FSU should be 0 ohm at empty and 90 ohms full.
There should'int be any voltage at the FSU.
 
Thats right, you will have voltage from the gauge side. Had it in my head you were on the FSU side.
 
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Price: $77.56 & this item ships for FREE with Super Saver Shipping
 
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