dual tank aftermarket fuel gauge help

[bakerboys]

Have a 1985 chevy k20 was a diesel now a roller 350 have to run electric fuel pump because has no manual fuel pump boss
I need a gauge mine dont work will a aftermarket gauge work for both tanks when you switch over the selector
Also what size are my two tanks are they 20 gallon each cant find answer

thanks alot guys

[hatzie]

Could be 16 or 20 gallon tanks. Long or short bed?

What's the gauge doing now? Usually it's wiring and not the gauge. But. A 90 ohm gauge will work with the GM senders.

Put the pump just after the valve and get it as low on the frame as possible.

[bakerboys]

Ok. Its a longbed was diesel 4x4
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[bakerboys]

Yeah I put a cheapo ele. Pump on it but at anything above 3500 its weak. So i orderd a holley pump today and have checked all wires at tanks and are.all good tried another gas gauge from junk yard and it does the same thing my other one does it stays way past the full mark. So i figure i will try aftermarket gauge and rewire it
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[frog210]

have you cleaned you ground conntact on gas sender?
i think if you clean the contact, the wire, sand some of the frame to get a good contact
that may fix it

[hartbraker]

if it's past full that doesn't necessarily mean the guage is wrong... sometimes you need to adjust you're float on the sending unit... this has been the case several times for me. Might want to pull em' out and try to adjust em'

[hatzie]

Your gauge is OK. Way past full means there's an open connection between the sender and the gauge.

Usually it's the tank ground, a broken sender wire or, the SPDT gauge switch inside the selector valve has failed. It's not impossible that the senders or sender to selector wires are both bad but it's unlikely. Ground the tank and see if it fixes the problem.

Get at least three MALE WeatherPak pins at NAPA?? or any GM dealership. If you don't have any... get some 12" alligator clip test leads.

1. Unplug the 6 pin weatherpak from the selector valve on the RH frame rail. Plug one of the MALE pins into the PINK wires' tower (avoid the temptation of clipping the test leads to the female tower pins directly you'll mangle em). Jumper the pin you just inserted to a good clean ground with a test lead. Turn the ignition ON. The gauge should drop to E. If it doesn't the problem is a break in the PINK wire between the selector and the gauge.

2. If the gauge dropped to E in the first test check the selector. Plug two more WeatherPak pins into the Pink striped wires. Jumper the PINK wire to one of the striped tank sender wires PINK/WHITE (LH) or PINK/BLACK (RH). If the gauge reads properly replace the selector.



The selector WeatherPak pins out as follows

PINK/BLK | PINK | PINK/WHT | LT GRN | DK GRN | EMPTY

[bakerboys]

ok HATZIE

I made new grounds checked all wires There is a wire that plugs into the red wire on drivers side tank like a round push together plug I think it goes to the sender
anyway the wire that goes to red wire goes up the framerail in some loom then comes out under engine bay and is NOT hooked up to anything also there are two green wires light and dark green that go up and into firewall i think to selector switch
the other wire may be pink or white cant tell but what does it go to thanks

[hatzie]

Originally Posted by bakerboys

ok HATZIE

I made new grounds checked all wires There is a wire that plugs into the red wire on drivers side tank like a round push together plug I think it goes to the sender
anyway the wire that goes to red wire goes up the framerail in some loom then comes out under engine bay and is NOT hooked up to anything also there are two green wires light and dark green that go up and into firewall i think to selector switch
the other wire may be pink or white cant tell but what does it go to thanks

Your correct about the green wires.

It sounds like you found the sender wire cut off in the engine compartment.

This may help

[bakerboys]

Ok i went and bought a aftermarket gauge for now hooked it up to the pink wire under hood and power wire and she works. But now my tank selector is not switching tanks it worked before but now it stays on driver side tank is there a secret to it
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[hatzie]

Where did you get power for the gauge?

If you unhook the gauge does the valve work again?

No Secret to the later tank switch system.
It's a polarity reversing switch hooked to a DC motor in the valve. Flipping the polarity reverses the DC motor. The valve has two isolated circuits. #1 is a DC motor running the valve on a screw with SPDT limit switch to prevent over-travel. #2 is an isolated SPDT switch that selects which tank sender is attached to the gauge.

Selecting the Left tank makes LT GRN + and DK GRN -
Selecting the Right tank makes DK GRN + and LT GRN -

Usually it's the cheap plastic switch that fails. Not the expensive valve.

You should find the other end of the pink sender wire at the assembled bulkhead plug under the brake booster.

[bakerboys]

when i was building the truck I installed a seperate aux..fuse panel and I am getting power from that ignition switch controlled

Where did you learn all this electrical You really seem to know your ****

Thank you for helping me out

[bakerboys]

no unhooking it makes no difference also it worked before and then I had a leak on pass.. tank so i dropped tank and fix the hole put tank back in and now it does not work I hooked the red wire back on the sender ran a new ground wire but now it does not switch over .That is the only thing I have done besides the fuel gauge but i ran seperate power and used the pink wire that was in the engine bay that was not hooked to anything it went to the senders

If i get it to work again should the fuel gauge change also to which ever tank I switch to

[hatzie]

Originally Posted by bakerboys

no unhooking it makes no difference also it worked before and then I had a leak on pass.. tank so i dropped tank and fix the hole put tank back in and now it does not work.

The valve is on the opposite side of the frame from the Right tank. There's 6 hoses and a long WeatherPack plugged onto it. Make sure the wiring didn't get pinched when you changed the tank. Check the green wires with a cheap digital multimeter for 12v with the ignition on. If there's no volts then the dash switch probably crapped out on you.

Originally Posted by bakerboys

I hooked the red wire back on the sender ran a new ground wire but now it does not switch over .That is the only thing I have done besides the fuel gauge but i ran seperate power and used the pink wire that was in the engine bay that was not hooked to anything it went to the senders

Find the pink wire from the bulkhead plug and attach it to the pink wire from the senders/selector-valve. Then the dash gauge will work. Bulkhead position in the plugs shown in the clip from the 83 schematic above.

Originally Posted by bakerboys

If i get it to work again should the fuel gauge change also to which ever tank I switch to

Yup. That's the function of the #2 SPDT switch inside the plastic Pollack valve housing. Two stripey sender wires going in (one from each tank) and one solid pink wire going out to the gauge... or in your case tailing off in the engine compartment where "that guy" cut it off.

[bakerboys]

ive got it working but now the gauge is working but when it gets to 1/4 tank it is actually empty
this is for both sides also tank is still leaking now from the top where the sending unit is I need two new tanks any one know a good place to buy from and why does it say 1/4 tank but is empty both sides do the same thing

[hatzie]

Originally Posted by bakerboys

ive got it working but now the gauge is working but when it gets to 1/4 tank it is actually empty
this is for both sides also tank is still leaking now from the top where the sending unit is I need two new tanks any one know a good place to buy from and why does it say 1/4 tank but is empty both sides do the same thing

That sounds like the calibration resistor on the back of the gauge can isn't making good contact with the studs.
or... The spring clips in the housing aren't making good contact with the studs from the back of the gauge can or the flexible printed circuit.