Technical inspection of the fuel gauge on the M1009 / Chevrolet Blazer K5 Diesel. - solved

[Elektroman99]

Dear Steel Soldier Community,

to my regret I could not find a clear explanation in the TM and this thread (link) how to check the fuel gauge on the ex military M1009. I would like to exclude one possibility, running the 100 liter tank empty.

Is there anywhere I can measure / test if the gauge is still "functional". I know when I filled up 40 liters at the time, it was off 2/3 full. At the moment it seems to move a bit "barely noticeable", but I also fill up every time I stop and it's usually not over 10 liters.

Maybe someone can link a tutorial, a page of the TM or something else. Maybe there is already such an answer and I just have not found it.


Sincerely
Bernd

 

[Barrman]

The fuel gauge is basically an Ohm meter and the fuel gauge sending unit and float in the tank is a variable resistor. A full tank should give you 90 ohms. Empty is 0 Ohms.

I have switched senders and I have switched GM gauges. No matter the combination the gauge tends to hang around past full on my M1009’s until I have driven around 100 miles. 3/4 tank indicated usually equates when I fill up again to about half tank. That is just the nature of the GM components.

Ford is actually the other way around for the same year vehicles. They drop like a rock to 1/4 tank and then seem to never move until you run dry.
Ford used a different Ohm range as well.

I now believe most of the fault is with the GM gauge. I put Dakota Digital gauges in my Cowdog Suburban project. GM sender and when I indicate 1/2 tank. I usually end up filling within 2 gallons of half tank.

 

[Elektroman99]

Hello and thank you for the explanation.
Thus, with the operating voltage 12 v and the direct bridging of the two test leads should be a movement of the tank indicator, or do I see that wrong, since with a normal cable 1-2 ohms of resistance value are achieved.
Does one possibly know which contacts it is exactly in the speedometer or dashboard?

Sincerely
Bernd

 

[jdowney]

Ford is actually the other way around for the same year vehicles. They drop like a rock to 1/4 tank and then seem to never move until you run dry.
Ford used a different Ohm range as well.

OT to the thread, but I can't resist relating a story - I was driving my boss's 1980's Ford in Mexico around 1995, first time I'd driven it. Gauge was very slowly dropping, so slowly that I didn't worry about topping up at one of my usual (trusted) stations on the route. At just above 1/4, it started dropping fast, spooked me so much that I pulled into the first station I came to (now running on E) and filled up with premium as we always did. As often happened at untrusted stations, premium was regular (leaded back then) and burned up the catalytic converter

My dad's 79 Ford did behave more like you relate though.

 

[Elektroman99]

The - let's call it - "hesitant" display I can confirm. The weekend before last I had consumed about 11 liters, the display had moved 1/10 or 1/8. Thus, it is functional, how exactly at ¼ full tank I can not say yet....
5 liter spare canister I have with me.

Is there anything to consider when driving the diesel 6.2 L "dry" due to incorrectly read fuel gauge?

 

[Barrman]

If you run it dry. Add fuel. 5 liters might not be enough if you are an an incline.

It will take about 2-3 minutes of cranking on the starter to get it primed again. I count to 20 while cranking, stop, let it rest for around a minute, repeat, repeat, etc…. 2 good batteries will be able to handle a single priming cycle and shouldn’t be hurt. However, if you run it dry again without at least 30 minutes of charging time. You will not have enough battery to do it again.

 

[CenterMass762]

When my truck shows 1/4 tank and the needle starts bouncing around a little bit, I know that I'm about ready to run out of fuel. I learned that the hard way, but thankfully I was lucky enough to learn it in my driveway instead of at a stop light.