Are VDO gas gauges made by Lucas?

[pinzinator]

I have never seen a VDO gas gauge accurately show the gas level in the tank. How can they be so consistently far off, unless they are made by Lucas, the Price of Darkness? I use a dowel rod to measure, it is always right! I'm sure every Pinz owner can relate.
With my 710M, 3/4 = Full, anything less than half could mean near empty.

[pcolette]

My new VDO is the same, 3/4 is Full. Even after replacing the sender and all new wiring too. When the gauge hits "E" I have about 5 gallons left according to my handy dowel.

On my other 710M with an original NOS VDO gauge the readings are amazingly accurate.

[GRCameron]

Unless you match the gauge to the sender the results will be all over the place. Looking at the VDO site, they list a number of senders with resistance values of 10-65 ohms, 10-184 ohms, 73-10 ohms (backwards), 240-33 ohms, 0-90 ohms & 3-180 ohms. They list a host of gauges specific to those resistance ranges, too.

Mine reads empty with about 5 gal. left in the tank. I think that's a good thing...

[rmel]

The bottom of the scale on the meter is not E(mpty) it is Reserve, which is
an additional 20 liters. By design the Sending unit sits above the bottom
of the tank, some versions of VDO sender also have a switch that closes
when you reach this point so you can tie this back to an idiot light. I have
that and it us VERY handy. I also have the VDO P/N and a source for
these senders across the pond if anyone is interested. The SAV version no
longer supports the warning terminal.

[rmel]

For those interested, I just looked up the P/N and distributor, real good guys.

Two terminal VDO sending unit (level and warning) is: VDO 224-817-008-002R
Distributor: Europaspares, Staffordshire UK.
Shaun Garner shaun@europaspares.com
http://www.europaspares.com
Phone 01283 815609

[Jimm391730]

Ron is exactly right; the stock fuel sender unit only measures the top ~12" of the tank; the bottom ~6" is the "reserve". The stock sender and gauge are fairly accurate and linear (half tank is about 6" down from the top, not a true half tank, but true if you ignore the reserve). However, the front of the tank is angled so more fuel is held in the top half than the bottom half (and the lower side is angled inwards as well, making the very bottom of the tank smaller in are than the top) so for a consistent fuel usage the upper portion of the capacity seems to deplete slower than the lower portion (the upper half holds more fuel than the lower half). But if you drive by the gauge you spend more time fueling up on long trips as you really only get to use about 12-13 gallons before the gauge says "R".

Some options that I have tried:

I have seen that there is a Mercedes sender that is virtually the full depth of the Pinz tank - the problem is that the mounting flange does not have holes that line up the same as the Pinz tank flange. I have reworked the Mercedes longer sender into the Pinz flange, but it is not a simple replacement (soldering and finagling is required). With this modification almost the full tank can be monitored.

I have also used "universal" swivel floats but because of the width of the tank, the float arm cannot be quite long enough to reach both the top and the bottom of the tank, and the float can hang up on the tank sides and baffles if care is not used in the sizing and placement.

Or have Andre make a custom tank, and design it to accept a good sender and matching gauge (as he did for me).

[rmel]

I like the R(eserve) feature, kind'a like an airplane which has the same notion but a reserve tank in their case --
Jerry can would be hard to use at 5,000' When I get to reserve a Bright RED LED goes off telling me I am on
reserve with 20 liters left. I then know I used 60 liters to get to this point and I now have 60 liters left
Reserve + 2 Jetty cans. Decision time! Do I turn back knowing I can get out, or proceed on and cross my fingers

[pinzinator]

I always reset the trip odometer whenever I fill up, since Lucas doesn't make speedometers. When it gets up to 300 KM or so I start looking for cheap gas. At 400 KM the spare gas can had better be full!

[TechMOGogy]

This is clearly the best solution - will work for Pinz too!
PM me if anyone want the plans

[stiffler4444]

I always reset the trip odometer whenever I fill up, since Lucas doesn't make speedometers. When it gets up to 300 KM or so I start looking for cheap gas. At 400 KM the spare gas can had better be full!

This is my method as well, usually at 350km's I'm filling her up.

[Hotzenplotz]

My Pinz suffered from this random level disease since I had it.
Now I took out the tubular sensor and the instrument and went to the local VDO representatrive to have them checked as a system.
Got the reply that checking and fixing is more expensive than a new set, so I went home with sensor 224-011-00-380G, instrument 301-040-002G and distance ring 14-067-014-5162

The weekend will tell...

[rmel]

Albert,

Might work. At 390mm long this unit will be longer than the stock version which is about 330mm.
Hopefully it won't bottom out. When this setup says Empty you will be Empty

Also I presume they sold you a match VDO meter, as this sender is 75 Ohms when empty the stock
version is in the ballpark of 85-90 Ohms. Will be a tad nonlinear due to the shape of the tank at the
bottom as Jim pointed out.

You might want to bench test your old meter and sender, both can't be bad. Might even find them
both good.

ron

[Jimm391730]

The list of VDO sender sizes is here: http://drabpol.pl/wp-content/uploads/VD ... enders.pdf. There are many, many different size options.
For those that are interested, inside the shielding tube is a "U" shaped piece of resistance wire that goes down one side, across the bottom, and up the other side. One end is grounded to the top flange, the other end connects to the sending terminal. The total resistance of this wire is the empty resistance of the sender. There is also a rod that runs down the center. On this rod slides the float which has two gentle "fingers" - one pair of fingers slides along the wire that runs down from the terminal, the other set of fingers slides down the other leg of the U wire. The fingers short out the legs of the U. When the float is at the top there is very little length of the U legs, so the resistance to ground is almost zero. As the float drops, more length of the legs of the U increases the resistance until the maximum resistance is reached when the float gets to the bottom.

One of the nice things about this sender style is that the shielding tube has only small (~1/8") openings for fuel to enter and exit, so the fuel level inside the shield tube can not change quickly. This dampens the response so the gauge only shows the average fuel level and not fuel sloshing around inside the tank. Pivoting float senders are very prone to this especially around 1/2 a tank when the float extends out sideways; sloshing of fuel moves it up and down easily.

[Hotzenplotz]

Feedback from the installation:

I swapped the gauge and the sender, and the reading still showed zero: Measured resistance of 64 Ohms at sender as well as at the connector to s-pin on meter.
Had 24 volts on + input against ground connector

I got desperate...and left.
Did some math to determine a 20 watt bullb should be a good test resistor, and unplugged the sender from the gauge.
gauge started crawling towards full

so i took a dipstick into the tank, and pulled it out dry !

All zero indication was correct, i filled up and got a "full"reading

Now I only have to figure out who drove the Pinz dry ......

The old compoents will be tested another day

[rmel]

Reminds me of a line in the movie Sling Blade "Ain't got no gas"