Aux fuel tank with non-Isuzu Sending unit help needed.

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Aux fuel tank with non-Isuzu Sending unit help needed.

Postby jc_in_az » Mon May 03, 2021 7:34 pm

I'm hoping to install a 1973 Datsun pickup fuel tank (around 13 gallon) under my 96 Trooper.
By adding a resistor, I have the Datsun sending unit range at 21 - 114 ohms (F to E). From what I gathered from this site, the OEM Trooper sending unit range is 17- 120 ohms (F to E). So the range is fairly close to Isuzu.

So I thought I'd crawl under my 1999 Trooper since it's easier to access right now than my 96 Trooper to test the Datsun sending unit where the harness attaches to the tank.
Key on, the fuel level is at half tank.
No matter how I tested the Datsun sending unit with the Trooper wire harness, the needle would stay at E.

So then I read that some of the other Isuzu's sending units run through the ECM (PCM?) which converts the resistance to a different number for the gauge.
Oh, and when I tested the 1999 Trooper's sending unit at the tank port I got 125 ohms for a half tank.

So I have 2 questions...
1. I tested on the 99 Trooper because it was easiest to access and crawl under. The 96 it'll eventually go in... not as easy to get under right now. Are the two years going to yield the same results?
2. Did I miss a step in trying to attach wires to the 2 Datsun sending unit tabs and connecting to the 99's sending unit harness?
Any ideas?
THanks
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Re: Aux fuel tank with non-Isuzu Sending unit help needed.

Postby Jake.Werecat » Tue May 04, 2021 7:38 am

I'm not really into >98' Troopers, so can't say anything about those, but 92-97 fuel gauge is hooked up directly to the sender, and it runs just on resistance.
Isuzu Trooper 3.1D 1997
Toyota 4-Runner 3.0V6 1991
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