Tankzilla sending unit

[DMC1983]

After much frustration with my fuel sender unit, I decided to dive into finding exactly where my problem resides. The module for the tankzilla on my car is the fault and I have no idea how to test it or fix it. Considering it's a sealed unit, is there any way I can bypass it? Is there anyone here that has knowledge of the circuit contained inside?

[DMCMW Dave]

After much frustration with my fuel sender unit, I decided to dive into finding exactly where my problem resides. The module for the tankzilla on my car is the fault and I have no idea how to test it or fix it. Considering it's a sealed unit, is there any way I can bypass it? Is there anyone here that has knowledge of the circuit contained inside?

If you bypass the unit, the gauge will read backwards and incorrectly. (I had a car come in like that once!) The box reverses the sense but keeps the low fuel light at the end.

I don't know of anyone but the now-gone maker who knows what's in there, so you may as well cut it open and start testing parts, looking for corrosion, burned traces etc.

[DMC1983]

Well, I broke into it. Didnt take much, but I did get to the top of the circuit. Problem is: I still dont know the layout of the circuit!

https://mail-attachment.googleusercontent.com/attachment/?ui=2&ik=5d7fcf13af&view=att&th=1368a8b8db1ce133&attid=0.1&disp=inline&realattid=1398553144096456704-1&safe=1&zw&saduie=AG9B_P-FyBtHG_6-9LvnZYdv998W&sadet=1333764333829&sads=2z2TghDrPN2zpcphiiUnd_qtS54&sadssc=1

[Elvis]

well - post pictures !!!

[Bitsyncmaster]

I opened my Tankzilla box and the circuit was sealed in epoxy. So yours is not?

[DMC1983]

My link must've died, I posted a pic last night. Ill get it when I get home tonight

[rbford]

After much frustration with my fuel sender unit, I decided to dive into finding exactly where my problem resides. The module for the tankzilla on my car is the fault and I have no idea how to test it or fix it. Considering it's a sealed unit, is there any way I can bypass it? Is there anyone here that has knowledge of the circuit contained inside?

I'm having the same exact problem with my Tankzilla...

[DMC1983]

http://i27.photobucket.com/albums/c174/Crockettsonny84/2012-04-06_21-56-52_329.jpg


My problem started when I had my binnacle off. I have had it off plenty of times since then probing and finding faults with no avail. I also tested the unit by shorting the wires to ground individually... also with no avail. The sending unit itself checked out, so it got narrowed down to the unit itself. I'd like to probe and test connections in this box, but I cut off the wrong side. Hopefully I can somehow pry out the circuit board

[Bitsyncmaster]

Yours is not potted. Look for bad solder joints but I would not think that unit heats up like the RPM relay does.

[Elvis]

Cool, thanks for the pic.

What exactly does your gauge show ? Couldn't find a real description of the problem.

Many caps in there, I wonder what they are good for.
Last time I took a Zilla device apart I got burned by many people as re-engineering is
not allowed... LOL

The black thing in the top left corner - is that a transistor ? Hard to tell from the pic.
That's the power stage that simulates the wire in the original unit - at least I expect it to be that. If it is - it may get hot - and hot stuff dies earlier than cool stuff.

But there must be another transistor that turns the low fuel bulb on. One of the little ones ? hm.

With better pics from both sides and a parts list I can redraw the schematic.

What does the IC say on it ?

[DMC1983]

Cool, thanks for the pic.

What exactly does your gauge show ? Couldn't find a real description of the problem.

Many caps in there, I wonder what they are good for.
Last time I took a Zilla device apart I got burned by many people as re-engineering is
not allowed... LOL

The black thing in the top left corner - is that a transistor ? Hard to tell from the pic.
That's the power stage that simulates the wire in the original unit - at least I expect it to be that. If it is - it may get hot - and hot stuff dies earlier than cool stuff.

But there must be another transistor that turns the low fuel bulb on. One of the little ones ? hm.

With better pics from both sides and a parts list I can redraw the schematic.

What does the IC say on it ?

Gauge reads empty all the time, with the low fuel light on. Once in a while the needle will run from zero to the 12 o'clock position and return to zero.

The top left corner IS in fact a transistor with some sort of metal tab surrounding it. It has the patent number on it.

The IC's info is rubbed off. Now, THAT may be due to heat judging by the way it's rubbed off. However, I dont know until I get the board out of the box

[Bitsyncmaster]

Most likely the IC is an op-amp used to filter and maybe invert the analog signal from the sender.

Next time I'm into the tank area, I will check my Zilla unit again but I'm pretty sure it was potted. I wonder how many different versions of the Zilla unit were produced. I see yours has a #4 on the PCB.

[Elvis]

Any news here ?
More pics of the PCB ?

[DMage]

Gauge reads empty all the time, with the low fuel light on. Once in a while the needle will run from zero to the 12 o'clock position and return to zero.

Have one here as well that does the same thing. Do you have an LED in the binnacle? I looked over the old Zilla tech reference on DMCNews as well as a few posts on the DML, and the TankZilla pulls power through the low fuel light circuit. I was going to swap out the LED with a bulb to see if that fixes it.

[DMC1983]

Have one here as well that does the same thing. Do you have an LED in the binnacle? I looked over the old Zilla tech reference on DMCNews as well as a few posts on the DML, and the TankZilla pulls power through the low fuel light circuit. I was going to swap out the LED with a bulb to see if that fixes it.

Sorry about the long wait. Haven't had the car to do any follow ups for the past week.

Yes, I have LEDs in the binnacle all but the battery light of course. That does sound highly plausible, and i'll have to give it a try.

I also got the rest of the module box taken apart and ill get photos of it when I get home.

[dmc6960]

Excellent theory, I'm also curious to find out the result.

[DMC1983]

Sorry about the looong wait. But, I finally got time to post! As mentioned, I got the module box apart enough to see the back side of the circuit board. I'm not seeing any bad connections judging by the solder, so I'm going to have to start probing to find the problem. It would be interesting If I can get a good schematic written up so we know exactly how this thing flows.

As far as the LED goes, I'll have to rip my binnacle out when I get the new knee pad bracket in.

9842

[jawn101]

As far as the LED goes, I'll have to rip my binnacle out when I get the new knee pad bracket in.

9842

You can definitely reach the low fuel light from under the dashboard without removing the binnacle.

[DMC1983]

You can definitely reach the low fuel light from under the dashboard without removing the binnacle.

Well, I gave it a shot and now my low fuel lamp isnt working at all. Needle is pegged at 12 o'clock

[jawn101]

Well, I gave it a shot and now my low fuel lamp isnt working at all. Needle is pegged at 12 o'clock

Might not be 100% conclusive then, but it sounds like the lamp is definitely tied to the operation of the gauge. Did you replace the LED with a known good bulb?

[DMage]

http://www.dmcnews.com/Techsection/Tankzilla-HR.pdf

They have some 12 o'clock walkthroughs in there to check for a bad connection.

Hope to give the unit I have a test this week sometime.

[DMC1983]

Might not be 100% conclusive then, but it sounds like the lamp is definitely tied to the operation of the gauge. Did you replace the LED with a known good bulb?

The light went out yesterday during a drive, I figured it was more of a lead problem than a bulb. I replaced with a good connector and a brand new bulb. No gauge reading, no light. I tried shorting the ground and light lead with no avail.

[DMage]

Managed to get it working today. Bulb type 161 in place of the LED.

Put the bulb in, and jump the black and red wires that go into the sender (on the tankzilla harness). This should turn the light on your dash on. If it doesn't, then there must be a problem with your tankzilla.

Try also jumping the two wires where the red and the black plug into the car's harness. If that doesn't work, then its an issue with either your wiring or the bulb contacts in your binnacle.

[vin6635]

Is the fuel light in the dash turned on via the fuel sender?

My light works but that gauge does not. Was reviewing wires today and want to see if there's anything else I can test before giving up. I have a Tankzilla-like unit with a separate control box and a VDO fuel sender in the tank.

Rich

[DMCMW Dave]

Is the fuel light in the dash turned on via the fuel sender?

My light works but that gauge does not. Was reviewing wires today and want to see if there's anything else I can test before giving up. I have a Tankzilla-like unit with a separate control box and a VDO fuel sender in the tank.

Rich

Yes, in the OE, DMCH replacement, and Zilla there is a contact in the sender for the light.

In the new integrated units the low fuel light is derived electronically in the logic box but is still fed from that area.

[vin6635]

Yes, in the OE, DMCH replacement, and Zilla there is a contact in the sender for the light.

Thanks, Dave, makes sense. So, what's the chance my fuel gague in the dash is shot vs. the whole sender unit being faulty? Do those fail much? Trying to pinpoint the root problem.

It may be cheaper just to upgrade to the whole new unit, just want to weigh my options.

[Silverbullet]

Ok... I just put the fuel pump/sender combo in... It is a REALLY nice unit, they give a plug for the Sender hole, you get rid on the Plastic Pot pick up in the tank... it is a 15 min install, after your tank is clean. Works great... ok you can only read fuel level with engine running... but that is a good thing as it tells you the Fuel pump is running... it has a damper, so the gauge does not bounce around... it is $399, but... it is really nice.. :hihi2:

[DMCMW Dave]

Thanks, Dave, makes sense. So, what's the chance my fuel gague in the dash is shot vs. the whole sender unit being faulty? Do those fail much? .

I've probabably replaced over 100 senders. And exactly one bad dash gauge. The senders fail all the time.

It's pretty easy to test the circuit. Unplug the sender and the gauge should point straight up. Ground the green/black wire and it should point straight down. Ground the light green wire and the light should go on. If that all works the gauge is good and the sender is bad.

[vin6635]

It's pretty easy to test the circuit. Unplug the sender and the gauge should point straight up. Ground the green/black wire and it should point straight down. Ground the light green wire and the light should go on. If that all works the gauge is good and the sender is bad.

Excellent - thanks, Dave! That's exactly what I was looking for.

I went out and played with the wire and was able to ground the light and make it come on. No action on my gague - it's seemingly stuck at 7p.

My gague worked a few years ago then went intermittent last year and this year is dead. My next thoughts are perhaps the wiring is loose to the gague, the gague is shot, or the sender and gague are both shot.

Is there a test to see if the output from the sender is working? I can get on my back and try to peer behind the dash. Or take it off...sigh.

Thanks for all the help.

[Bitsyncmaster]

I went out and played with the wire and was able to ground the light and make it come on. No action on my gague - it's seemingly stuck at 7p.

I had the same stuck at 7:00 with my Tankzilla. I think what fixed it was pulling the gauge and moving the needle. I think a bad connection caused the problem but then the gauge got stuck.

[David T]

I am having trouble with my Tankzilla. When the fuel tank gets down to about 1/2 the fuel gauge reads less than 1/4. I took the sender apart. It is a VDO part. When you remove the small nut on the bottom the tube comes off. You can see the 3 wires, 2 of which the float touches as it slides up and down. I took some sandpaper and shined up the 2 wires so the float can make good contact. I also had to clean the inside bottom blue plastic endcap, there was some dirt in there. I haven't had a chance to fill the car up and use up the gas to see if it is accurate again.
David Teitelbaum

[vin6635]

I had the same stuck at 7:00 with my Tankzilla. I think what fixed it was pulling the gauge and moving the needle. I think a bad connection caused the problem but then the gauge got stuck.

Winner! Took off the binnacle and pulled the gauge as you suggested. A little playing with it and voila it's now working again! I guess we'll see how long this last for....

Side benefit - I was able to remove that stupid fly that decided to die in my dash. Now to put everything back together...

[David T]

I drove the car and filled it up and now the fuel gauge seems to be working accurately again. I suspect anything in the fuel system that is not plastic or S/S is subject to corrosion because of the Ethanol they are putting in the gas now. In NJ it's usually 10%. Those fine wires in the sender appear to be steel.
David Teitelbaum

[EdR5150]

<bump>
I can confirm tankzilla needs an incandescent bulb to work properly. After replacing my binnacle bulbs with LEDs, my gas gauge needle was at empty, and the low fuel light was always illuminated.
So just like my battery light, my low fuel light will also remain incandescent. I'm not upset either, since I've only seen the low fuel light illuminated one other time during 7 years of ownership.