Diagnosing dual tank balance module

[GM Guy]

looks fast!

How many guages does that make now? I just wish we had large pillars so we could fit more.


I am jealous of the 99-up psd with their 4 hole pillar pods..wish 88-98 at least had some other options such as steering column.

glad you got it taken care of, still curious what it could have been though? The dual tank setup is quite fun, we have contacts within the idaho DOT and they run NBS C&C chevys for the tiny dump trucks, and they say they are changing modules and related quite often.

 

[Matt Bachand]

looks fast!

How many guages does that make now? I just wish we had large pillars so we could fit more.


I am jealous of the 99-up psd with their 4 hole pillar pods..wish 88-98 at least had some other options such as steering column.

glad you got it taken care of, still curious what it could have been though? The dual tank setup is quite fun, we have contacts within the idaho DOT and they run NBS C&C chevys for the tiny dump trucks, and they say they are changing modules and related quite often.

Makes 4 gauges.............and 4 toggles, soon to be 6 toggles i think, one for manual powering of rear xfer pump, and one for Racor Fuel heater. Depends how expensive that balance module is.

Still doesn't work right. Started out at 3/8ths tank, and after a week or so of driving went up to 3/4................... lol I was making fuel! I was thinking at first it was just the rear tank xfering over, but too many miles went by, and it kept going upwards....

Added fuel into the tank with truck running, and watched it go down...........

When I unplug my balance module harness, the OHms change coming out of the senders, they go UP by about 30ohms.

The screwed up thing is, I ran out of fuel last week, but with the module unplugged BOTH MY SENDERS read 35. (not 0)...

I didn't get a chance to check them with the balance module plugged in when out of fuel.

That made sense to me and thought I was golden when plugging into the balance module it dropped ohms by 30.

FOr some reason I couldn't check my front tank sender earlier as it was grounded out according to Ohm meter, but the fuel gauge was reading 3/4.

WHen grounded the fuel gauge reads zero as it should.

I'm completely baffled here. Gonna price out a balance module.... ITs doing funky stuff.

I have gauge hooked up to front tank sender unplugged from balance module now. Just added 10 gallons of fuel, and I know it runs out at 35ohm, so thats about 1/3 of 90ohms (full on gauge), but adding 10 gallons brought me more to 5/8ths tank.

This blows. But the gauge sure looks nice.

Even worse rockauto doesn't seem to have that balance module.

 

[DieselCash]

Matt,

What brand is all your other gauges?

 

[Matt Bachand]

Matt,

What brand is all your other gauges?

I was all excited thinking someone had some insight............lol

Hmm, Fuel Pressure Stewart something, ISSPRO boost/pyro, and glowshift fuel gauge.

Stewart is by far the worst at night time. Glowshift by far the best all around for hooking up and looks. .

ISspro's are nice...


However, I'm stumped here. Without balance module, I burned about 60 miles and tank went up again. Somethings backwards somehow. I'll double check my wiring on the glowshift, but I can't imagine all the features working if I hooked it up backwards, nor can I imaging myself doing that.... Dont' see it possible.

Had walbro issue today, so no time to diagnose... see other thread.

When I have the power on, I can't read the ohms out of my fuel sender, it says 1.00. Key off, it reads what appears to be a normal ohms tank reading. I have to disconnect it from the glowshift and see what happens.

 

[Matt Bachand]

I do have the gauge grounded to the tie bar in cab, instead of engine ground as it says. I will try engine ground, but I would think a ground is a ground?

 

[GM Guy]

well, we are running a toggle in the 2000, luckily, dad is always buying junk at auctions, so he came up with a damaged modern tractor wiring harness, which had plenty of the the two prong plugs, so we cannibalized the harness, and the truck harness is unscathed, and we can go back to auto transfer if we want to, but this setup is problem free, so it is nice. (we used i believe a female to plug into the chassis harness to keep it clean, and ran a new wire to power the pump.)

 

[Matt Bachand]

well, we are running a toggle in the 2000, luckily, dad is always buying junk at auctions, so he came up with a damaged modern tractor wiring harness, which had plenty of the the two prong plugs, so we cannibalized the harness, and the truck harness is unscathed, and we can go back to auto transfer if we want to, but this setup is problem free, so it is nice. (we used i believe a female to plug into the chassis harness to keep it clean, and ran a new wire to power the pump.)

Please elaborate on what your toggle does? Switches in cab gauge between front and rear? Or manually activates the rear pump?

As much detail as possible on your solution because I'm flat out of ideas....

And thank you for digging up this thread to keep my dreams alive of a working fuel gauge.

 

[Matt Bachand]

My balance relay does xfer tank contents at the appropriate time, problem is I'm not getting decent tank readings off of either sendor.

Where are you getting your fuel gauge reading from? (purple wire that is at the balance module is factory)

 

[GM Guy]

we are letting the OEM setup handle the readings. basically, the thing should work fine, just a bit of mis-info prompted the toggle install. when we bought the thing, we tried to put fuel in, it kicked back, and Dad says tanks full, guage reads low, damn transfer mechanism is screwed up.. and i didn't give it a second thought...untill we were working on it. Knock knock, hmm this tank sounds dry.. odd. head out to idaho, and stop at the fueling station, whoa what do you know, she takes 18 gallons!

So it didn't need done, but the toggle was already there from a previous use, so why not!

 

[GM Guy]

basically, all the toggle does is energize the transfer pump. (just read the other post, needed to provide all info, and btw, you are welcome (in response to the thread dredging remark! )

 

[Matt Bachand]

Next time the rear tank is empty, can you test it for OHM's with the balance module unplugged?

looking at the harness, there is a PINK wire on one end, the rear tank is the one next to it, 2nd in.

I figure that tank will be empty first, if not already empty.

IF you could do that for me that would be awesome. While you are there with the sensor unplugged and checking PIN 2nd one in for rear tank. Check the 3rd pin in for OHMS. (Against ground). 3rd pin in is the Front tank. Lastly, tell me what your fuel gauge reads when you're doing this.

I know it sounds like a lot, but will only take 5 minutes tops. I have nothing to compare my readings to. There is NOTHING on the internet about this....

Thank you. If you don't have an OHM's tester, PM me your address and I'll get you one.

You are the only man standing that's brave enough to venture into this thread anymore LOL.


----------------------

It appears my glowshift gauge is still reading backwards somehow. I am almost empty (by mileage figures) and Gauge is creeping up to full......

When I filled the tank it went to 1/2, and gradually going from 1/2 tank readings to full tank readings when empty......

Baffled isn't even the word, but I'm learning patterns and habits.

I will not give up on this.

 

[GM Guy]

So all this testing is done at the harnesses at the balance module, or do i need to do this at the rear tank?

Don't expect results too quickly, i don't go home too often. I should really use this as an excuse to finally buy the video camera and computer that i have been wanting for a while. it would be kind of cool to take a video.

To tide you over till i get around to it, i personally would wire up a toggle, unless you don't want to hack and wack on the dash or wiring.

PS, with the auto, we have had great luck routing wiring in and out of the cab with a hole the PO bored right in the middle of the round plate where the clutch goes in a MT truck.

 

[Matt Bachand]

So all this testing is done at the harnesses at the balance module, or do i need to do this at the rear tank?

Don't expect results too quickly, i don't go home too often. I should really use this as an excuse to finally buy the video camera and computer that i have been wanting for a while. it would be kind of cool to take a video.

To tide you over till i get around to it, i personally would wire up a toggle, unless you don't want to hack and wack on the dash or wiring.

PS, with the auto, we have had great luck routing wiring in and out of the cab with a hole the PO bored right in the middle of the round plate where the clutch goes in a MT truck.

Thanks you sincerely.

All measurements at the balance module. Unplug it and test the 2 pins on the harness with all the wires. very easy, clean and simple. Easy to access too.

I'm in no rush. Mine reads 35.5 empty. Which doesn't make sense because everything I read about GM FSU's say they are 0-90ohms.

My thinking is the factory fsu for stock dual tanks do not have a normal 0/90 readout.

When I fill my tank up, gauge goes down to 1/2, and when its empty it goes to full.

GM also didn't use the same FSU's for dual tank vehicles. My thinking would be they would if they could have to save money. So perhaps they different.

What are the odds... Dual tank 6.5. So now I'm 1%, of 1%..........

GM GUY, My balance module does xfer fuel properly. It's my fuel gauges I'm trying to fix.

.............................................................................................


Ran out of fuel today, or was about too, it limp moded, when it does that I know I need FUEL NOW, or suffer.

I always keep 10 gallons or more in my xfer tank, so I just pulled over and pumped it in.

GS gauge was teetering on the FULL mark. So now I have a useable fuel gauge. Just reads backwards.

GS has a their own forum for tech support, I posted in there and we'll see what the results are.

............................................................


Here is my latest thinking, if the 2 wires coming out of FSU are reading and ground, what would happen if I grounded the reading, and tested the Ground for OHMS? Would I get the opposite?

cold wet ground is coming, so if i don't get this resolved I will in spring.

I'm sure the diesel gods have plenty of other things lined up for me to lay on my back in the wet slushy roads, getting dripped on.!!!!

 

[Hydrauk]

Dual Tank Module Follow up..Fuel Gauge Pegged!!

Hello All I am new here. I have been watching this post in the past few days.
I learned ALOT form reading Matt Bachands posts. Thanks Matt!!! It helped out alot. But I still have a "Pegged" fuel gauge when truck is on/running.This truck is a: 1996-97 GMC K3500, Mason dump, 6.5 Turbo, Dual tanks, 4WD, Automatic. Here is what I did so far:

1. I removed and cleaned every Ground connection I could find in the Engine compartment.(Engine,Firewall,etc) I used a angle grinder with a scotchbrite pad. They all shine better than new and are tight.

2. Did the same as above with Battery connections.

3. Cleaned and Re-grounded connection near the front fuel tank. (It comes out of the wire harness with the fuel sender connection)

4. I checked the Oil Pressure switch and Relay. Seems to be operating. 10-20 PSI at Idle HOT. 30-40 PSI at Idle COLD.

5. Checked and cleaned Relays and other connectors on firewall. I did find one real bad connection, which I repaired. Hoped it may "Fix" everything type of find!!!!!!:nonod:

6. Checked Charging system. Got 14.4 Volts when running. One of the batteries seems to be going bad though.

NEXT:......Fuel Module located in frame rail under Driver seat:

1. Removed Module and inspected it. Took apart as well. Seemed clean and dry.

2. Term "A" Pink: Has 12 Volts with key on run.

3. Term "B" LgtBlue: 52.8 Ohm reading. Tank is about half full +/- (Rear)

4. Term "C" DrkBlue: 89.1 Ohm reading. Tank is damn near full, I filled it. (Frnt)

5. Term "D" LgtGreen: With engine running I grounded this wire, The relay did indeed "click" and the Rear pump ran fine.

6. Term "E" BlkWhite: Checked for Ground using meter and test light. It tested Good.

7. Term "F" Purple: With key on, I Grounded this wire, gauge went from "pegged" to the Full mark not Empty mark. When I took off the ground, the gauge went back to "pegged"

So it seems to me that the Fuel module IS working. Both fuel pumps checked good. All other tests that I performed passed.

I then removed the Gauge cluster. Inspected the Circuit board, and the molex connecter. No damage or breaks. I traced the Fuel gauge connection to the molex connector (Gnd, pwr,and signal). I then tested for continuity between the connector and the purple wire at the control module. It tested Good. I tested the Grounds at the Molex...they tested Good. Shows no breaks in the wires.

I cleaned the connector with Electrical cleaner and blew it out with compressed air. Re-installed the Cluster.

So after performing all above work in detail..Iam very meticulis!! I still have the "pegged" Fuel gauge. It actually Vibrates a bit when it's pegged.
So here you have it....Iam Stumped.....and getting irritated.

I suppose the Gauge must be at fault..or Maybe a Battery is going bad?

Anything I looked over? Any Input? Any more tests? Anything at all in relation to this problem?

I want to keep this truck interior all Stock. No aftermarket Gauges.

Would a Fuel Gauge from a GAS powered truck work? I saw 4-5, 95-98 Gmc/Chevy trucks at the bone yard last Saturday. The interiors where all MINT. They are Cash for Clunkers. What size are those Torx screws that hold the gauge on...seem real small.

Thanks in advance for your time!! Please anyone out there with input greatly accepted. Cheers!!

David D.

 

[GM Guy]

Hello All I am new here. I have been watching this post in the past few days.
I learned ALOT form reading Mark Bachands posts. Thanks Mark!! It helped out alot. But I still have a "Pegged" fuel gauge when truck is on/running.This truck is a: 1996-97 GMC K3500, Mason dump, 6.5 Turbo, Dual tanks, 4WD, Automatic. Here is what I did so far:

1. I removed and cleaned every Ground connection I could find in the Engine compartment.(Engine,Firewall,etc) I used a angle grinder with a scotchbrite pad. They all shine better than new and are tight.

2. Did the same as above with Battery connections.

3. Cleaned and Re-grounded connection near the front fuel tank. (It comes out of the wire harness with the fuel sender connection)

4. I checked the Oil Pressure switch and Relay. Seems to be operating. 10-20 PSI at Idle HOT. 30-40 PSI at Idle COLD.

5. Checked and cleaned Relays and other connectors on firewall. I did find one real bad connection, which I repaired. Hoped it may "Fix" everything type of find!!!!!!:nonod:

6. Checked Charging system. Got 14.4 Volts when running. One of the batteries seems to be going bad though.

NEXT:......Fuel Module located in frame rail under Driver seat:

1. Removed Module and inspected it. Took apart as well. Seemed clean and dry.

2. Term "A" Pink: Has 12 Volts with key on run.

3. Term "B" LgtBlue: 52.8 Ohm reading. Tank is about half full +/- (Rear)

4. Term "C" DrkBlue: 89.1 Ohm reading. Tank is damn near full, I filled it. (Frnt)

5. Term "D" LgtGreen: With engine running I grounded this wire, The relay did indeed "click" and the Rear pump ran fine.

6. Term "E" BlkWhite: Checked for Ground using meter and test light. It tested Good.

7. Term "F" Purple: With key on, I Grounded this wire, gauge went from "pegged" to the Full mark not Empty mark. When I took off the ground, the gauge went back to "pegged"

So it seems to me that the Fuel module IS working. Both fuel pumps checked good. All other tests that I performed passed.

I then removed the Gauge cluster. Inspected the Circuit board, and the molex connecter. No damage or breaks. I traced the Fuel gauge connection to the molex connector (Gnd, pwr,and signal). I then tested for continuity between the connector and the purple wire at the control module. It tested Good. I tested the Grounds at the Molex...they tested Good. Shows no breaks in the wires.

I cleaned the connector with Electrical cleaner and blew it out with compressed air. Re-installed the Cluster.

So after performing all above work in detail..Iam very meticulis!! I still have the "pegged" Fuel gauge. It actually Vibrates a bit when it's pegged.
So here you have it....Iam Stumped.....and getting irritated.

I suppose the Gauge must be at fault..or Maybe a Battery is going bad?

Anything I looked over? Any Input? Any more tests? Anything at all in relation to this problem?

I want to keep this truck interior all Stock. No aftermarket Gauges.

Would a Fuel Gauge from a GAS powered truck work? I saw 4-5, 95-98 Gmc/Chevy trucks at the bone yard last Saturday. The interiors where all MINT. They are Cash for Clunkers. What size are those Torx screws that hold the gauge on...seem real small.

Thanks in advance for your time!! Please anyone out there with input greatly accepted. Cheers!!

David D.

His name is Matt! ):h

Anyways, welcome to the site, and the input is greatly welcomed! Also, glad that we have another dual-tanker!

 

[Hydrauk]

His name is Matt! ):h

Anyways, welcome to the site, and the input is greatly welcomed! Also, glad that we have another dual-tanker!

Thank you I looked over that, So I fixed it. I appreciate the welcome!

Cheers!

Dave

 

[Hydrauk]

Dual tank issue..Fuel Gauge

Hello...I have a bit of update and some input. Yesterday I went to the local Auto junk yard. I took a Gauge cluster out of a 1997 Chevy suburbon, this vehicle was a "cash for clunker" trade in. The vehicle is in excellent condition, although the engine was destroyed.

Ok...so it' a Gasser, BUT the Gauge cluster in front and back is completely Identical!! It has all the provisions to install the Glow plug lamp and what ever other options you may have. Only thing is that has "Unleaded Fuel only" printed above Fuel Gauge. No big deal, that can be fixed.

I will attemp to put this entire cluster in the truck sometime today. I will post results.

Also...I was thinking last night, I figure the Rear tank sender has nothing to do with the Gauge at all! The Rear tank sender is merely installed for the Fuel module to "Read" level and keep the transfer of Fuel steady. Does that sound plausable?

Cheers!

 

[GM Guy]

so you are wondering if the rear sending unit is just an instrument of measurement for the module to decide what its plan of action is?

I personally think that the module recieves a level signal from each tank, and as far as the guage goes, somehow averages the ohm reading and sends that new reading to the guage.

I also think that when a preset ohm reading is reached on the front (low), it energizes the pump circuit to transfer from the back, and that also means that i believe that when the rear tank reaches a preset ohm reading (empty) it will cut juice to the pump circuit to keep from wearing out the pump.

 

[Hydrauk]

so you are wondering if the rear sending unit is just an instrument of measurement for the module to decide what its plan of action is?

I personally think that the module recieves a level signal from each tank, and as far as the guage goes, somehow averages the ohm reading and sends that new reading to the guage.

I also think that when a preset ohm reading is reached on the front (low), it energizes the pump circuit to transfer from the back, and that also means that i believe that when the rear tank reaches a preset ohm reading (empty) it will cut juice to the pump circuit to keep from wearing out the pump.

GM Guy.....That sounds exactly on the spot! Good post!!

Good News!! I think I have resolved my Fuel gauge issue!! And It solved other minor Gauge issues as well! Seeing both tanks are close to Full, I need to run it lower that Half Tank, to get actual results.

Indeed that the Gauge cluster CAN be taken apart, and It's quiet easy!
And Yes each gauge can be changed out by itself. I learned ALOT form messing with the Gauge cluster. There is a few things one can look for once the cluster is disassembled!!!!!!

Today I have a crapload of work to do. I will be back here in the next day or so to fill you guys in. I will try to post pictures as well.

Cheers!

 

[GM Guy]

Sweet. Glad you got it resolved. We have a vibrating needle on the 98, but everything else works flawlessly, so I believe it is in the cluster.