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View Full Version : Fuel Sending Unit- A look Inside


Ron
08-16-2011, 04:39 AM
3779
Blackie
08-16-2011, 07:13 AM
Very good, thanks for poting this, always wanted to know what the innards of these consisted of, not as messy as i thought.

Is there a way to test the low fuel light? Mine doesn't come on when the fuel gets real low, and i did try replacing the globe, must be something a bit further down the line?
Canon20DFan
08-16-2011, 12:10 PM
The Delorean fuel gauge is notoriously inaccurate...is it the guage or the sending unit? Is there a modern replacement?
sean
08-16-2011, 12:13 PM
The Delorean fuel gauge is notoriously inaccurate...is it the guage or the sending unit?

Sending unit


Is there a modern replacement?

I suppose this guy (http://www.delorean.com/store/p-6566-fuel-tank-sending-unit.aspx) would be considered a modern replacement but there have been some fitment issues with a few of them, probably an early version thing.
DavidProehl
08-16-2011, 12:30 PM
I suppose this guy (http://www.delorean.com/store/p-6566-fuel-tank-sending-unit.aspx) would be considered a modern replacement but there have been some fitment issues with a few of them, probably an early version thing.

I am currently running the new one Sean linked to but thinking about sending my OEM unit to Hervey to be rebuilt. The replacement unit reads at 3/4 for me on a full tank and turns on my low fuel light at a 1/4 tank.
stevedmc
08-16-2011, 12:39 PM
Is there a modern replacement? Just get a DMCH unit for $99. It isn't perfect but it gives a prett good suggestion of how much fuel you have left. If you learn to interpret your fuel gauge and keep track of your mileage per tank you will always have a good idea of how much fuel you have left.
TTait
08-16-2011, 12:46 PM
I am currently running the new one Sean linked to but thinking about sending my OEM unit to Hervey to be rebuilt. The replacement unit reads at 3/4 for me on a full tank and turns on my low fuel light at a 1/4 tank.

+1

I have a Houston unit in one car, and the oem in the other - I had the Houston unit replaced under warranty because it wasn't accurate - neither was the replacement. I'll give them props for having them made - unfortunately the production units aren't perfect. They own them and have paid for them, so that's what they have.

Try to get your oem unit fixed first...
Cory W
08-16-2011, 01:24 PM
I saw an attempt at fixing some of the issues with the "new" fuel baffle before. It dealt with putting a small metal screw in the open hole at the bottom, sort of like how the screw is in the second hole at the bottom. Did it to a car I've been working on recently, and will be back at this weekend. Pics to follow when I'm around the car again.
Ron
08-16-2011, 02:31 PM
Is there a way to test the low fuel light? Mine doesn't come on when the fuel gets real low, and i did try replacing the globe, must be something a bit further down the line?Ground the Light Green-Orange (LGO) wire at the sending unit (ignition switch on). If this turns the light on, then that half of the circuit is good.(Make sure the LGO wire to sending unit connection is good.)
dmc6960
08-16-2011, 03:26 PM
The original TankZilla units used this Saab fuel level sender...
http://www.redlinemotive.com/store/replacement/wizard.asp?year=1985&make=SA&model=900-T-002&category=All&part=Fuel+Level+Sending+Unit
3795

Since it reads in reverse from our senders, its not directly compatible with the stock gauge. TankZilla was a logic box that went between this sender and the gauge to correct those readings. TankZilla may not be available anymore, but this sender still has life for DeLoreans. I plan to make the new electronic instrument cluster fully compatible with this Saab unit, along will all DeLorean units available. A user-selectable jumper will switch between types.

Fuel level will be averaged over 30-60 seconds. No quick swings, no "clicks". Just averaged exact level.

Not available yet, but putting it out there as another option.
sean
08-16-2011, 03:37 PM
The original TankZilla units used this Saab fuel level sender...
http://www.redlinemotive.com/store/replacement/wizard.asp?year=1985&make=SA&model=900-T-002&category=All&part=Fuel+Level+Sending+Unit
3795

Since it reads in reverse from our senders, its not directly compatible with the stock gauge. TankZilla was a logic box that went between this sender and the gauge to correct those readings. TankZilla may not be available anymore, but this sender still has life for DeLoreans. I plan to make the new electronic instrument cluster fully compatible with this Saab unit, along will all DeLorean units available. A user-selectable jumper will switch between types.

Fuel level will be averaged over 30-60 seconds. No quick swings, no "clicks". Just averaged exact level.

Not available yet, but putting it out there as another option.


THANK YOU FOR THIS!!! I've had a used tankzilla on the shelf for a while, sender and ecu, but have never done anything with it yet b/c I wasnt sure the status of the sender
stevedmc
08-17-2011, 02:03 PM
THANK YOU FOR THIS!!! I've had a used tankzilla on the shelf for a while, sender and ecu, but have never done anything with it yet b/c I wasnt sure the status of the sender

My TankZilla quit working about 18 months ago. Hopefully I didn't throw the thing away. If my DMCH unit ever fails it would be nice to couple the logic box with a new sender for less than $40 at my favorite auto parts store.

Thanks for the info.
DMCH James
08-26-2011, 11:36 AM
The latest version of the DMC replacement fuel sender (marked with the letter "A" in the top housing) contains 12 reed switches and one reed switch for the low fuel light that are activated by the float. I had posted photos on the old DMCTalk (RIP). The fluctuations in fuel readings are caused by the fuel flowing quickly in and out of the sender tube. This can be compensated for by plugging the either of the two large holes on the bottom with a tight fitting screw. In some cases, we've filled BOTH and then drilled in 3/32 or smaller hole in the same general vicinity.

We've found that many of the units that when installed do not read "full" or not reading full for very long are simply a result of a combination of either the tank not being *completely* filled (which we don't like to recommend to prevent the boot popping off the top of the tank). Removing the sender from the tank, but leaving it connected and flipping it 180 degrees will show that it will read "full", but the shape of the tank, position of the sender, and the required location of the reed switches don't give the float enough travel to stay at the top switch for very long.

James
Ron
08-26-2011, 12:28 PM
We've found that many of the units that when installed do not read "full" or not reading full for very long are simply a result of a combination of either the tank not being *completely* filled (which we don't like to recommend to prevent the boot popping off the top of the tank).
Might I suggest a resistor between the signal wire and ground? ..or is it off so far that it will lie (too much) on the empty end?
sean
08-26-2011, 12:39 PM
The latest version of the DMC replacement fuel sender (marked with the letter "A" in the top housing)...

Has the height of the latest unit been shortened since the first run? Do owners of this new unit need to do anything for proper fitment? i.e. Loosen fuel tank closing plate bolts.
Farrar
10-27-2011, 04:20 PM
Since Houston has released its new pump/sender all-in-one module, I was wondering if development on the Saab tank sender was going to proceed. For those of us not planning on using the new module, a separate tank level gauge sender will still be necessary.

Quick question: when you say "the sender reads in reverse" from ours, do you mean that its polarity is reversed? If memory serves, that can be easily cured with a single SPDT relay. Or is it something else?

My sending unit (Zilla) seems to be fine, but it never hurts to plan shead...

Thanks,
Farrar
dmc6960
10-27-2011, 06:28 PM
I dont think anyone was proceeding on an independent project for the Saab sender. I was (and still am) planning to have it as a user-selectable setting for my electronic instrument cluster since it would be a very minor addition to the programming.
Bitsyncmaster
10-27-2011, 07:13 PM
The original TankZilla units used this Saab fuel level sender...
http://www.redlinemotive.com/store/replacement/wizard.asp?year=1985&make=SA&model=900-T-002&category=All&part=Fuel+Level+Sending+Unit
3795

Since it reads in reverse from our senders, its not directly compatible with the stock gauge. TankZilla was a logic box that went between this sender and the gauge to correct those readings. TankZilla may not be available anymore, but this sender still has life for DeLoreans. I plan to make the new electronic instrument cluster fully compatible with this Saab unit, along will all DeLorean units available. A user-selectable jumper will switch between types.

Fuel level will be averaged over 30-60 seconds. No quick swings, no "clicks". Just averaged exact level.

Not available yet, but putting it out there as another option.

I have the Zilla unit and I'm happy with the way it works. I did have a few connection issues but those are solved. You will still see a little gauge movement when braking or acceleration but I expect that. Reversing the signal to work with our gauge would just take an op-amp and some resistors. Or better yet a micro could do everything an cure that minor movement.
Ron
10-27-2011, 10:31 PM
Reversing the signal to work with our gauge would just take an op-amp and some resistors. Or better yet a micro could do everything an cure that minor movement.
:slap: THAT'S what I just couldn't remember to ask Sean about at the meet!...

I was looking at a LM107 OpAmp (with a 12V regulator, if needed) and then a 1NA117 Difference Mode Amplifier (Data Sheet (http://www.ti.com/product/ina117) Vo=V3-V2 ).
I wanted to measure the units resistance through its range if he still had it.
...Sean?
Bitsyncmaster
10-28-2011, 05:10 AM
:slap: THAT'S what I just couldn't remember to ask Sean about at the meet!...

I was looking at a LM107 OpAmp (with a 12V regulator, if needed) and then a 1NA117 Difference Mode Amplifier (Data Sheet (http://www.ti.com/product/ina117) Vo=V3-V2 ).
I wanted to measure the units resistance through its range if he still had it.
...Sean?

Lots of opamps can run up to 30 volts but you need to see how much current the gauge takes (check resistance). My TankZilla electronis is potted so I could not see what they used. May also need a transistor to get higher current.