XJ40 ( XJ81 ) 1986 - 1994

Goofy fuel guage reading

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  #1  
Old 06-29-2014, 12:05 PM
manwich66's Avatar
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Default Goofy fuel guage reading

Hi all,I took the Wife's car (champ) up to the shop yesterday to finish up a spray job.Stopped in and put in 30 bucks worth of premium fuel,found it would only hold 29.84$and not another drop.OK i said to self,good!

jumped in,fired her up and behold,guage reads MT,with fuel light on.Hmmmm.Proceded down the road,runs good,drives good,comfy...Damn fine car!
Got to the shop,work done,jumped back in and started rolling down the road.Guage now reads one quarter fuel.Ten minutes later ,five eights fuel.
A few km`s later,half fuel.
Then I realized the Wife is a 20 buck fuel buyer,and I have never seen the guage read full...
Does anyone have any Ideas on a quick test,I do not want to blow up the dash !
 
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Old 06-29-2014, 12:34 PM
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manwich66,

If you have a meter and access to Haynes Manuel, remove the leads to the fuel level sending unit and read the resistance (see Haynes for output readings for empty and full) and see what you get on the meter.

You're going to have to guesstimate on how much fuel is in the tank and backwards engineer what you think the resistance should be for the amount of fuel you think is in the tank.

You may want to read the resistance over the course of a few days until you feel confident of the amount in it, or simply fill it up completely and see what the reading is then.

Personally, I would fill it up and take a reading and compare it with the Haynes. With the tank full, the reading should be about 18 to 20 ohm's.

But, if you think you have less than half a tank (be sure, very sure!) you can remove the sending unit and take both full and empty readings with the unit out.

Disconnect the battery before you do a reading or remove the unit.

Good luck
 
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  #3  
Old 06-30-2014, 12:13 AM
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I've heard that a bottle of Techron or the Canadian Tire Formula1 fuel system cleaner (the red stuff) can often successfully free up a sticky sending unit - maybe worth a shot Jim?

Larry
 
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Old 06-30-2014, 12:40 PM
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Default Goofy juice

Yeah,i was thinkin about that,I have to be up around crappy tire today anyway,so I will pick some stuff up.It was raining pretty hard here yesterday,so put off testing things until today.Will let ya know how it goes...
Cheers,Jim.
 
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