Fuel gauge issue

Ctg1971 · Mar 28, 2018

So I've recently gotten a 91 ranger 2.3 5 speed and when I got it the fuel gauge didn't work or the temp gauge so a new sender fixed the temp gauge so I figured the same would go for the fuel gauge so I bought a new fuel pump sender and all installed it same issue dealt with it for about a month and today I pulled the bed and found the arm was stuck on the new pump so I warrantied the pump installed the new one and saw with the pump out it was full to the top of the tank on my way home the gauge would bounce between a half and quarter tank but when I shut the truck off I turned the key back on but didn't start the motor and the gauge reads right on full where should I start as far as checking for wiring or gauge problems? Thanks in advance and sorry for the long post just wanted to make sure that problem was as easy as possible for people to understand

RonD · Mar 28, 2018

Welcome to TRS

Anti-slosh module on the back of the instrument cluster

Fairly common issue.

When you go around corners the float in the tank will go up and down quite a bit, so to prevent the gauge from doing the same the anti-slosh module was used, it basically slows down quick changes in the gauge

Google: ford anti slosh module bypass

Or get a new "used" one from wrecking yard if avalable

Ctg1971 · Mar 29, 2018

So the anti slosh module would cause the gauge to go that crazy even though the tank was full to the brim? I wouldn't think the float could be moving that much with the tank full but that is a good place for me to start thank you for your reply

RonD · Mar 29, 2018

The anti slosh module is the connection from sender to gauge, if it is intermittent then so is the gauge, your description of what the gauge did would point to anti slosh module.

One more thing, although a long shot, Ford changed the type of senders and gauges used in 1989.
If you put a 1988(or earlier) sender in a 1989(or later) Ford vehicle then it will read opposite, full when empty and empty when full

If you got a 1991 sender/pump then that will not be the problem.

Fuel gauges use a Pulsed 5volts, from a small power supply behind the instrument cluster
There is a yellow wire that runs from the gauge(anti slosh module) to the sender, and the sender is also Grounded.
As the float in the tank goes up or down it changes the OHMs(resistance) to Ground
16 ohms will show Empty, 160 ohms Full

Good read here: http://www.fordification.com/tech/fuel-sending-units.htm

Fuel gauge issue

Ctg1971

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RonD

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Ctg1971

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RonD

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