Add fuel gauge to GM 4108

[richard5933]

After seeing the fuel gauge mounted inside the door by the fuel filler, I started thinking about how difficult this would/would not be to do.

Anyone know what it takes to add a fuel gauge to a 4108 that did not have one installed at the factory? Is this something that can be done without removing the tank? If so, any information on the necessary sending unit - which one and how to install?

Haven't really needed a fuel gauge yet, but I can see where it could be handy to have one. Certainly easier than using a dipstick to check fuel.

[chessie4905]

Your wiring diagrams should have one listed for that option. You will need a push button or momentary switch for it.

[richard5933]

Wiring I'm not worried about - it's the fuel sending unit I'm not sure about. I looked in both the parts book and the manual and see nothing about where the sending unit goes or what the parts are that would be required.

[chessie4905]

You tap into the one that is already in the tank. That is why you use a momentary switch. It disconnects the wire going to the dash unit while at the same time connecting to the gage at the tank.

[richard5933]

You tap into the one that is already in the tank. That is why you use a momentary switch. It disconnects the wire going to the dash unit while at the same time connecting to the gage at the tank.

Therein lies the problem...I don't have a fuel gauge at all. Not in the dash, not at the tank. I'd have to start from square 1 by installing the fuel sending unit.

When I saw the option of just mounting a gauge at the tank filler door it occurred to me that it might be possible to do the same. If it's possible to install a sending unit without pulling the tank I'm interested.

[Templar52]

I have an accurate fuel gage on my bus and i am happy to have one. So i am encouraging you to install one. The owner was just finish to install it whent i purchase the bus. I dont know if you have the space over the fuel tank to make a hole in your floor to have access to the tank. If yess that will be easy. If not,the tank will have to com out. Wich is a good think after all,you can clean it and inspect it while in the process.
Safe thing to have.

[chessie4905]

Not that hard to pull. I pulled mine to change to longer tank

[richard5933]

I have an accurate fuel gage on my bus and i am happy to have one. So i am encouraging you to install one. The owner was just finish to install it whent i purchase the bus. I dont know if you have the space over the fuel tank to make a hole in your floor to have access to the tank. If yess that will be easy. If not,the tank will have to com out. Wich is a good think after all,you can clean it and inspect it while in the process.
Safe thing to have.

Our actual mileage has ranged from 8.5 mpg on flat ground w/o the generator to as low as 6.5 mpg in the hills/mountains or with generator use while camping. Tanks holds 165 gallons. Figuring a safe useful capacity of 145 gallons, we have a range of between 942 and 1232 miles. Right now my 'fuel gauge' consists of a yellow sticky note on the dash where I write down the odometer reading 600 miles beyond the most recent fill up. Setting our fill up point at 600 miles gives at least a 342-mile buffer to find a station before we chance having problems. That said, it would be nice to have a fuel gauge.

I just went and took a close look at what's there. Just to the right of the fuel filler neck is a cast metal cover. Looks like it could be a place a sending unit could be mounted, but I haven't figured out exactly how to tell. There is a hatch in the floor directly above this area about 9"x9". Problem is that the area above it inside the bus is where the drawer base for the built-in couch sits, with a doubled plywood support running directly across the top of the hatch plate. It would require cutting away a piece of the plywood support to be able to get the hatch out. Maybe something I'll explore in the spring when it's warmer and things are easier to work with.

Not that hard to pull. I pulled mine to change to longer tank

Perhaps it wasn't that hard to pull for you. My shop at home consists of a gravel lot and I'd be doing this alone. My experience with things like this is that if it's not broke don't fix it - the tank is clean (just recently checked) and has no leaks or other issues. I'm very hesitant to pull it for something that is really a luxury item.

Where does the fuel sending unit mount on the tank? Some of these buses came from the factory with a gauge, so there must be a place for one to mount - anyone able to point me towards it? Even better, photo or scan of a manual page would be great.

Surprised that I can't find anything about this in the manual or parts book. Wouldn't be the first time I missed something, but damned if I can find it.

[luvrbus]

Fuel gauges are nice to have,I was driving across Or one night when the clamp broke on my cross pipe (Eagle with 2 tanks ) I filled up in Boise when I reached Jordan Valley Or about 70 miles I notice I used a 1/4 of tank of fuel.I told my wife damn this 8V92 has never used this much fuel before,we stopped at truck stop In Jordan Valley I had fuel pouring.I would have never knew I had a problem without a gauge,no smell and I had plenty of power lol the Jeep was covered and dripping fuel 

[chessie4905]

It mounts on top of tank it has 5 offset holes the sender sets on a 5/8" raised circle in from passenger side of coach. To remove tank, you need to disconnect filler neck, 8 -1/4" bolts. Disconnect fuel line. The tank is attached to 6or 7 small cross members that have straps attached that go up around tank. To remove tank you remove 12 or 14  3/8th inch x 1 or 1 1/4 bolts that attach these crossmembers to channels that tank rest on. The heads of these bolts point to the ground under coach. Once you remove the bolts, you can slide tank out driver side of coach by opening HVAC door. You don't have to mess with the straps, as it is sort of module designed. I believe it is a 90 ohm gauge. Standard 5 hole mount, single pin.
Oh, don't attempt this with fuel in tank. There is a 3/4 inch?? Brass hex drain plug on bottom of tank on pass side.

[dtcerrato]

We added a fuel gauge to our 4104 right after bringing it back home to FL from CA. In TX my wife asked "when was the last time we fueled up?'' About 20 min. after that question we ran out on I-10 middle of TX. We ran the 5 gal Gerry can back & forth to a gas station with the Jeep toad 25 miles down the interstate 3 times. We never got it to start. Knowing well where the station was we hooked up the toad to the bus & pushed it with the Jeep (had a high performance V8) to the station. We had 2way communication - that helped a lot. As we exited the off ramp a TX Hwy Patrolman came in behind the Jeep with his pretty blue lights on. Looking in my side views I can see the officer exit his cruiser walk around the back side of his car & up the passenger side eyeballing the wife in the Jeep & heading to the bus front door.
Keep reading, this gets good! The year was 1982. I has a full head of hair down to my waist and a beard that covered the chest. As the officer approached the door I swung it open from the dash & almost knock him over - when he saw me sitting there, his hand went down to his holster & unclipped his fire arm while simultaneously telling me that he had to site me for illegal towing a person in the toad. My response was I'm not towing her officer she's pushing me, "we're out of gas". To shorten up this memory - when the cop knew what was going on - cool engine on the bus & hot engine on the Jeep he turned into our best friend & escorted us into that gas station (not the police station!) waited for us to fill & asked us if there was anything else he could do for us. I mentioned to him a real long parking lot would help because I may need to push start the bus after I kill the batteries trying to get it primed again. He escorted us to a large mall parking lot. Once we got it started it didn't run as good as id did for days after that while still finding air trapped in the system. So Richard putting in a fuel gauge shouldn't be a real problem & we think its a good idea. 

[Lin]

I suppose it's different with the GM, but our MC5a also did not come with a factory fuel gauge.  However, the wiring was there as well as a round plate where the sending unit would go.  This was easily accessible by removing the side panel by the tank since the hole was on the side of the tank.  If yours is on the top of your tank and you know where the access port is, it would seem that cutting an access to the port through the plywood using an oscillating saw would be simple.

[RJ]

Richard -

It seems that the only busnuts who run out of fuel are those with a fuel gauge!   

I advocate and adhere to a strict "500 mile" rule, and I use the "A" trip meter of our Garmin gps to keep track, resetting it every time we fuel the rig.  Even with your additional fuel capacity, I'd still stick to the "rule."

Do you have the stock dashboard in your 4108?  Is there a blank space for a fuel gauge?  Been awhile since I've seen that dash panel, so I don't remember.  If you don't have a spot, where will you install it? 

Don't forget - you'll need a 24vdc sender and gauge for the project, should you proceed.

There's my 2¢ worth for you to ponder.

FWIW & HTH. . .

[luvrbus]

Fuel gauges work from resistance the voltage is usually for the lighting on the gauge ,some of the buses have a Moller or Rochhester at the tank that requires no electrical 

[chessie4905]

The GM sending unit is 90 ohms, a standard resistance they used to have on all their fuel sending units, cars, trucks,busses,coaches. Nowadays all different.