Syncro Fuel gauge inaccuracy (how to ground the sending unit)

[Sodo]

These pics are for Syncro.
2WD doesn’t have this “rusty pin” problem.
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My fuel gauge is intermittent, sometimes showing 3/4 full when I know the tank won't take another drop.

It could be a faulty fuel level sending unit, but it's a well-known problem that the connector gets rusty - because it's a steel pin.

Its steel because it's spot-welded to the sender plate.
But steel is not a proper material for an electrical connector.

It would be real difficult to clean these pins, especially "on-car".

But you can nullify the rusty pin (and its OEM ground wire) by adding another ground from a tank-bolt.
Then you only have ONE questionable connection remaining, but it's not the rusty one.

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The Syncro fuel tank sending unit is behind the shock tower in the left side wheel well.
You have to unbolt the charcoal canister mount.
It's not easy to work in there, but the task is fairly simple.
-----provided you DON'T break off a rusty m6 fuel tank sender stud.
......better be frikiin' careful, be sure you know what you're doing with rusty m6 bolts.

Be real careful unscrewing this 10mm nut.
I threaded an M6x1.00 thread die on first to clean the threads out before attempting to unscrew the nut. I screwed it on (by hand) on then flipped it over to cut right up to the nut.

it would be wise to soak a rusty nut with penetrating oil for a few days before starting the job.
When you unscrew the nut, go back and forth a few degrees at a time, giving the penetrating oil time to soften the rust.
Don't twist the stud off or you have a bigger problem.
Plus you won't have a stud for your ground wire.

Under the nut is a large diameter washer, and under that washer was clean, shiny metal for a good ground connection.
The ground wire ring is directly against the sender flange.

Here's the ground wire attached to one of the screws that hold the charcoal canister to the shock tower.

You may be wondering if this solved my fuel level problem.......
Sorry, I don't know, because my tank is about empty right now.
I'll know more next time I fill up. Funny I'm not really looking forward to filling it.
But this corroded pin in the connector is a well-known Syncro problem.

Here is a better pic (different van).
This van is unlikely to have a fuel pump grounding problem for many years, with a brand new sending unit.
The connector is attached with dielectric grease inside to prevent corrosion.
The ground is added here 'cuz it provides a nice pic for this thread. 👍🏽
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[DuncanS]

'91 2WD DD on salty roads. My gas gauge has gotten really squirrely. First it didn't work at all because of poor wiring on my part, and then when that was fixed, in still didn't go. Put in a new/used one and it sort worked, but took 10 miles to get to a steady needle position, which didn't seem to mean anything. Have checked the ground feeder from the gauge, but get an open circuit reading on the VOM. So now the gas gauge is the same as my '57 23 window was--the odometer. Will be putting in new stainless coolant lines shortly and will go all through the system including a new sender. It's 31 years old fer crying' sake! I'll add to this topic when I do it, but will ground some other place than the spot welded male connection where I can get to it and keep it clean.

Duncan

[atomatom]

the fuel needle on my van will change by half a tank if i go from uphill to downhill. eg, downhill it is 1/2 full, uphill looks empty. i don't trust it a bit.

when flat, it seems reasonably accurate. or perhaps least wrong on average. hur hur.

i am overdue a fuel tank reseal/replacement, but i wonder if the crap accuracy is due to it being a relatively flat shallow tank, so you can't really fix that.
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84 Vanagon Westy, 1.9L, California raised but defected to Canada.

[riceye]

A while ago I lost my temp gauge in my analog dash clock face. I pulled the panel apart to ensure all the connectors and the foil were secure (they were). Prior to this my gas gauge would never go to full even though the tank was, in fact, full. While I was checking connections I also loosened and retightened the brass nuts securing the foil to the back of the clock/gauge assembly.

My temp gauge still doesn't work, but SURPRISE! My fuel gauge now reads full when the tank is full.

Something else to check. Your mileage may vary. Yuk yuk.
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'87 Westy Weekender - daily driver on salt-free roads

There's gonna be some changes made.

“I find that things usually go well right up until the moment they don't.” - Ahwahnee

"Quality isn't method. It's the goal toward which the method is aimed." - Socrates, later quoted by R.M. Pirsig

[Mckinleyvillian]

thanks for posting this. I went to fill up a couple days ago, thinking I was near empty, and it only took 9 gallons til over flow!
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so many roads i know
all i want is one to take me home

85 Vanagon GL 1.9 stick

[ALIKA T3]

Very clever ground fix

Side note: pretty please call nuts by their thread size and not their hexagonal size, you're so much better than that (10mm nut is generally M6, 13mm nut is M8 but Japanese cars often have 12mm for M8, M10 is 17mm but now VW has cheaper hardware with 16mm hex, while the Japanese have 14mm hex etc....)
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Silicone Steering Boots and 930 Cv boots for sale in the classifieds.
Syncro transmission upgrade parts in the Classifieds.
Subaru EJ22+UN1 5 speed transmission
http://www.thesamba.com/vw/forum/viewtopic.php?t=416343
Syncro http://www.thesamba.com/vw/forum/viewtopic.php?t=4...num+gadget

[kamzcab86]

[Sodo]

[Pchill2]

I fought through the 3/4 tank when full issue recently and finally fixed it.

1. P.O. had already replaced sender with non OE sender
2. I replaced sender again and still received 3/4 tank reading
3. Jumping sender pins resulted in full tank reading
4. New aftermarket sender ground tab was broken from plate. I had to weld it back but still did not result in proper reading.
5. Removed sender from tank and manually cycled float arm. I was able to get a good empty and full reading on the gauge.
6. Determined the float was not contacting or anywhere near bottom of tank when empty by removing filler neck and looking into the tank. I have pictures of this in my build thread.
7. Added several degrees of bend to the float arm and now tank reads full when full and empty when empty.

Once I fixed this nagging issue and thought I was home free, the Syncro gods bestowed upon me the gift of several other unrelated component failures. But at least my fuel gauge works now...
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87 Syncro Westy
Honda K24 swap

[Californio]

Not sure about the circuitry here and I don't have my Bentley in front of me, but isn't there another place this could be grounded that's easier to access?

[ALIKA T3]

[Steve Arndt]

Great tip.

Did it fix your gauge reading?

s
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Steve
Steve's 87 Syncro project

[Sodo]

[ALIKA T3]

[Sodo]

[4Gears4Tires]

Huh, now I wonder if my new fuel level sender issue is just a grounding problem.

I will add a new ground and see. I doubt it. But I can be hopeful.
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'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[Sodo]

[SyncroHead]

[0to60in6min]

I did the same for the coolant temp. gauge. (Slow to respond and not showing real temp). The ground is on the base of the sensor and it's not enough. I added a wire ground wire from the sensor to the chassis and it's working great.

[cmayna]

Great thread. My fuel gauge shows 3/4 full when filled up. Have been wanting to rip into this issue but had no idea of where to begin. Will check the grounding points of the sending unit. Will reply back soon. Thanks.
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'90 Westy / automatic.
If I'm not working on the camper or my '50 Chebbie truck, I'm either fishing with the wife or smoking Salmon.


Craig