The fuel gauge on my John Deere gave up. It comes as part of the entire
instrument panel. There's a reason they paint John Deere green, you need
lots of it to buy a part.
Anyway, I ordered a fuel gauge from Bumper Bumper. Its 10 to 73 ohm empty.
The Johnny sending unit is 4 to 97.5 ohm empty. I need to improve on the
range compatibility a bit if I can. I'm most concerned about the empty side,
if you've ever reprimed a diesel in the field, you know why.
any suggestions on a resistor combo or other?
If the JD sender goes to 97 ohms at empty, your 10-73 gauge will show empty
while there's still ample "reserve" in the tank. It just won't come off
"full" as soon.
Don't sweat it. You won't run out of fuel. (and yes, I have primed one, and
it's no fun without compressed air and a few tools. I built a tank cap with
a Schrader valve in it to help pressurize the tank (1-3psi).
Ive had some good success with using trim pots to fine tune these setups
rather than resistors. they are cheap and small and easily fit behind the
dash or anywhere else. rather than having a big knob, they have a small
screw that you turn to adjust. Even if you do get a gauge that meets your
requirments you can probably tune it a bit better with a trim pot.
The original range was 93.5 ohms (97.5 - 4). The new one will have a
range of 90 ohms. Add somewhere between 4 and 8 ohms in series with the
0-90 sender and you should be in good shape. I have never checked the
current in such a system, but you will need to in order to pick a
resistor with enough wattage capability. We can't estimate the circuit
current from the data we have because we don't know what the rest of the
series resistance is.
If you don't want to or don't know how to measure the current (at worst
case), then you can try this:
It's hard to imagine that the fuel gage would take more than 1 ampere,
worst case, so:
if 12 volt system, 12 X 1 = 12 watts
if 6 volt system, 6 X 1 = 6 watts. Get a 10 or 20 watt 4 or 5 ohm
Karl Townsend wrote:
First guess Google hit - "fuel sender resistance VDO" leads to:
And from there (and a few more places including
came up with this chart: *****
0 Ohms empty - 30 Ohms full is Early GM - Cars and most trucks
pre-1965, some trucks through 1968
0 Ohms empty, 90 Ohms full is post-1965 General Motors standard.
73 Ohms empty, 10 Ohms full (opposite) is 86 and earlier Ford,
Chrysler, and VW Beetle Type 1.
10 Ohms empty, 70 Ohms full is Ford F-series trucks Pre-1987 with
15 Ohms empty, 160 Ohms full is Ford F-series trucks Post-1987 with
16 Ohms empty, 158 Ohms full is 87 and later Ford cars.
260 Ohms empty, 33 Ohms full (opposite) is Stewart-Warner
10 Ohms empty, 180 Ohms full is VDO
If you can't find a sender that matches your existing John Deere
gauge get a sender that fits the tank, and then get a gauge that
matches the sender.
Here's an interesting one - a Universal Electronic fuel gauge that
works with any range sender...
Frankly, given the PITA value of diesel priming (the main reason I
despise changing my fuel filter, which is the only time I have needed to
do it other than when I replaced the leaky petcock) I don't give a darn
about the fuel gauge. Mine, as it happens, is dead with all the other
electricals except the starter. It's way down the to-do list to fix
them. I can work as much of a day as I can stand without emptying the 16
gallon tank. I fill the darn thing up every night. If I only burned a
half a gallon, I put in half a gallon.
If I had a smaller tank or a thirstier tractor, I'd fill it at
lunchtime. There's just no point in running the thing around near the
bottom, so precise fuel gauge readings are a pointless exercise. Oh
look, I have 1/32 tank left - oops, I went on a hill and sucked air -
now I have to prime the thing - so glad I didn't waste a minute putting
fuel in when it got down below 1/4 tank...
If you are working far from whatever your usual fuel source is (such
that driving the tractor back to it would be inefficient), get a few
diesel jerrycans and bring them with you, full, to the tractor in the
morning. When you shut down, fill it up, and take the empty or partially
full cans back the main fuel supply for the next day. If you stop for
lunch, put in what fits at lunchtime.
Do you guys have priming pumps on your diesels? Priming my Onan DJE
diesel, as well as Cummins L423D diesels is next to trivial. Either
the hand priming pump, or just cranking a little does it just fine.
No hand pump. Have to crank, but also have to loosen injectors while
cranking until no bubbles come out. It's the latter I hate messing about
with. For some reason the way the pump works it won't simply pump and
vent to the overflow line any bubbles, it needs the injectors loosened
up to get them out.
What model JD is it? Most JD have a wire with a cork. All you need to
do is bend the wire to calibrate empty. I can maybe give you some
pointers on bleeding it. I've done it many times in the last 40 yrs.
Karl Townsend wrote:
Bend the wire was gonna be my suggestion...
FWIW, put 2 new fuel bladders in the Cessna-182 about a year ago... ya have
to bend the senders a bit to get them out, so ya gotta re-bend em when you
FAA regulations state that the ONLY time an aircraft fuel gauge must read
correctly is when it's empty... and empty is define by the manufacturer as
to a certian ammount of 'un-useable' fuel in the tanks... soo.. ya dump in
how ever much gas is 'empty' and bend the wire so the gauge reads 'E'...
Oh and if you guys are pissed about the price of auto gas, be glad you
aren't buying 100LL...