Fuel gauge still not working, What am I missing? Options

[john77]

With the ignition on the needle on the gauge lifts to E but goes no further despite the tank being full.

I pulled the sender, wired up a new ground and hooked up a new wire from the gauge to the sender and tested the sender manually by turning it upside down and then back. The needle goes from empty to full and back to empty. Just to double check I test the resistance, 0.2 ohms right side up, 89.9 ohms upside down (the range is 0-90 ohms).

So I put the sender back in the tank with the new wiring, switch on the ignition and... the needle rises to E and goes no further.

So I think maybe, somehow, the floats not lifting. So I pull the sender, fill a bucket of water, dip it in, and the needle on the gauge rises and tells me I have half a tank - or less or more depending how much I submerge it. In other words, the damn thing is working.

So I put it back in the tank and nothing, the gauge rises to E and stays!!!

What the hell am I missing here? It works in a bucket of water but move it a foot and put it in my gas tank and nothing.

John

[914itis]

The gauge is only receiving 12 volts, nothing from the sende. Check the wire.

[john77]

The gauge is only receiving 12 volts, nothing from the sende. Check the wire.

Yep, checked that. It's receiving 11.8 and putting out 5.9v to the sender with the ignition switched to ACC, which is correct according to the manufacturer.

[stugray]

Are there two wires coming off of the sender unit (G and GND?).
Or does the sender unit ground through the tank?

[john77]

Are there two wires coming off of the sender unit (G and GND?).
Or does the sender unit ground through the tank?

The sender has two wires coming off it, one that grounds it (I've rewired it to the ground under the dash by the fuse panel) and the other goes to a terminal on the gauge - these are aftermarket, not standard 914.

Just learned the dialectric constant of water is way higher than gas, so my water test was pointless.. who knew (IMG:style_emoticons/default/smile.gif)

I know the sender has a good ground and the gauge to sender wire is good as I just rewired both, and I know the gauge is getting 11.8V with the ignition switched to ACC, so I guess, seeing as it's the only thing I haven't rewired, next thing is to rewire the ground to the gauge...

[904svo]

Guess a WAG but I supect the grond is missing off the gas gauge (brown wire) to
the gauge case.

[john77]

Guess a WAG but I supect the grond is missing off the gas gauge (brown wire) to
the gauge case.

Sorry, do you mean from the gas gauge ground terminal to the gas gauge case? So an internal wire?

I've run a new wire from the gauge ground to a ground under the dash. A new wire to give power to the gauge. A new wire from the gauge to the sender. And a new ground from the sender to a ground. So all new wires. And the damn thing still won't rise above E with 4/5ths of a tank of gas!

[timothy_nd28]

aftermarket sender? Perhaps the rubber gasket is isolating the sender from chassis ground? Post a pic of this sender.

[john77]

aftermarket sender? Perhaps the rubber gasket is isolating the sender from chassis ground? Post a pic of this sender.

Yeah, the sender and gauge are both from Fuel Safe, so they're definitely compatiable.

Here's a pic of the sender. If it's relevant, when I spoke to a guy at Fuel Safe he said the aluminum shaft of the sender is grounded. (Ignore the fact both wires are white, it's all I have to test with right now. Left terminal goes to gauge, right to ground.)

As I said earlier in the thread, if I remove the sender and invert/right it the gauge works fine, it just stops as soon as I put it back in the tank.

[timothy_nd28]

Great, one more pic of the back end of the gauge.

[john77]

Great, one more pic of the back end of the gauge.

Back of the gauge:



As far as the DAMN NEEDLE WILL GO WITH THE IGNITION SWITCHED ON (sorry, deep breath):



And the 'instructions' the Fuel Safe guy sent me:



John

[timothy_nd28]

Okay, is this how you have it wired up?

[john77]

Okay, is this how you have it wired up?

Yeah, that's how it's wired. I'm getting 11.6V with the ignition switched to ACC.

[timothy_nd28]

Remove the sender wire off the gauge. With the ignition switch set to on, try jumping the ground terminal (back of gauge) to the sender terminal. This should simulate 0 ohms.

[john77]

Remove the sender wire off the gauge. With the ignition switch set to on, try jumping the ground terminal (back of gauge) to the sender terminal. This should simulate 0 ohms.

Do you mean the sender terminal on the back of the gauge or on the sender?

[timothy_nd28]

Gauge

[zambezi]

sounds like the sender is not grounding properly once mounted in the tank.

[john77]

Gauge

Okay, just got home and tried this out, hopefully I'm connecting it right. When I switched the ignition on nothing happened, the needle didn't move at all. But when I then replaced the ground and the sender wire and switched on the ignition the needle flipped all the way over to the other side and stayed there.

[john77]

sounds like the sender is not grounding properly once mounted in the tank.

I wondered if it had something to do with the metal shaft of the sender possibly touching the edge of the hole it sits in in the tank, so I asked a guy from the company and he said "The outside aluminum shell or shaft of our standard senders is grounded so touching the side will not hurt anything as long as the ground wire is on the correct lug or terminal.'

So unless it's a problem internally with the sender I'm not sure what it could possibly be. Doesn't the fact it read 0-90 ohms when removed and inverted show the internals of the sender are fine though?

[904svo]

Thats not a Porsche gas sender (Porsche has 3 connections). Most after market
senders read 90 ohms (empty) 0 ohms (full). Porsche senders are 90 ohms empty
0 ohms full. Try removing the sender from the tank and turn it upside down and
see what happens.