MC5a Fuel Gauge

Lin · April 23, 2014, 07:25:11 PM

I have been thinking of getting really fancy and putting a fuel gauge in my 5a. I spoke to a parts guy at MCI, who actually used to have his own MC9 conversion. Whereas the 8, and 9 had the factory opening for the fuel sensor on the top of the tank, the 5 has it on the side. It is very easy to get to and has the standard 5 bolt SAE plate.

MCI, of course, does not have the part anymore. but I figured it was worth asking. I have found a couple of sources for side mount sensors. One is electronic and has no float. The other has a float that I think rides a tube up and down rather than extending into the tank and pivoting. The former one comes in either to two wire or three wire configuration. The latter comes in only two wire. The difference, as I understand it, is that with the two wire type, the gauge is powered and sends a signal wire to the sensor, which also has a ground wire. The three wire type has the sensor powered, has a signal wire going to the gauge, and a ground.

I have two questions. First, is there any preference for one type over the other? Second, has anyone that may have added a gauge to a 5a have some alternate sources for the parts?

lvmci · April 23, 2014, 09:50:26 PM

Hi Lin, I got the factory updated mci gauge and sending unit from mci a few years ago. The 5A was updated to the 7, 8 then 9, and is 24 volts. The gauge fuel-dash is 7G-13-12, the sending unit-fuel gauge is 9G-6-1, Guillermo in Louisville identified the parts for me. This was 2012. They were $69 & $67. Heres the issue, it took 3 seperate trips for the mci mechanics in los alimitos, to get the sending unit working. The biggest problem was bending the float arm in several places to miss the screens internally mounted in the tank to reduce the sloshing effect of movement. It is a resistance based sending unit and they ended up changing the grounds a few times, altho I think it was the float arm sticking on the internal screens the whole time. They used the proper existing wires, which were still metal tab labeled from the factory, and the blank on the tank was the same size. The gauge fits very well in the 2 1/4 holes and looks very similar. I hope this helps, lvmci...

ol713 · April 24, 2014, 08:31:44 AM

Hi;
I have a MC-7 that I put a fuel gauge in some years ago.
I tried the float type and did not like it. Bounced around
all the time. The gauge I got from MCI, but the sending
unit I got from Centroid Mfg. Their sending unit is based on
capacitance. All large aircraft use the same type sending
unit. Only problem I had was setting the empty part of
the unit. (only way to set the empty part is to run out
of fuel) Try a google search for Centroid and see what
what you find.

Good luck, Merle.

Lin · April 24, 2014, 09:12:32 AM

Lvmci-- That's basically what the MCI parts guy said- that there would be a problem using the replacement part due to the tanks baffles. Since he himself had owned a 9, he knew more about the application than the average parts guy would have.

Merle-- Centroid is the supplier I mentioned that has both the 2 and 3 wire models. Which type did you use? I thought that if I ordered a 24" sender that it would read empty when the tank was down 24 inches. Is that incorrect?

Fredward · April 24, 2014, 07:29:42 PM

Lin,
When I bought my MC5 the gauge didn't work. I had the tank out of it for other reasons. And when I put the tank back in, I bought a sending unit from C&J bus here in town. Just installed it and connected it up to the dash (ran new conductors) and its been working great ever since.
Fred

Lin · April 24, 2014, 08:54:13 PM

Fred,

Is your sender powered or is the gauge powered (not including the light of course).

BTW, how do you like your Allison?

ol713 · April 27, 2014, 08:50:44 AM

Hi lin;
As I remember my sending unit used a two wire hook up.
one wire to the gauge and the other to a good ground.
Merle.

quote author=Lin link=topic=27308.msg300528#msg300528 date=1398355952]
Lvmci-- That's basically what the MCI parts guy said- that there would be a problem using the replacement part due to the tanks baffles. Since he himself had owned a 9, he knew more about the application than the average parts guy would have.

Merle-- Centroid is the supplier I mentioned that has both the 2 and 3 wire models. Which type did you use? I thought that if I ordered a 24" sender that it would read empty when the tank was down 24 inches. Is that incorrect?
[/quote]

Fredward · April 28, 2014, 04:00:17 AM

Lin,
It's been so long that I don't remember with certainty but I ran two conductors from the gauge. I think it runs on one and a ground.

I ordered the Allison conversion kit from Global on Friday. Picked up the dolly and plan to start removing the engine evenings this week.

Fred.

belfert · May 02, 2014, 08:14:02 PM

Quote from: Lin on April 24, 2014, 09:12:32 AM
Merle-- Centroid is the supplier I mentioned that has both the 2 and 3 wire models. Which type did you use? I thought that if I ordered a 24" sender that it would read empty when the tank was down 24 inches. Is that incorrect?

I'm not Merle, but I have a Centroid fuel sender. The two wire models only work with certain gauges. I have a three wire model. My bus had a fuel gauge, but the sender only had two wires so I had to run a third wire from the dash to the senders. The new model sensors (New since 2008) automatically calibrate empty and full levels. The old ones had manual screws to set empty and full.

Lin · May 02, 2014, 10:44:02 PM

Thanks, Brian- I think that difference is that the 3-wire one is voltage driven and the 2-wire one is resistance driven using a gauge the with a 240-33 ohm range. I might end up getting it from Centroid. There is another company that I was trying to buy it from, but they are making matching my bolt positions into a big deal and how that will be more expensive, so I am getting annoyed already. Centroid is a little quirky but do not seem be plagued with obstacles. They only accept calls for a short time four days a week, and their answering machine says, "It won't do you any good to leave a message."

I asked Luke about getting the original part. He said that he was going to check and see what it looked like in a 5a he had in the shop, which turned out to be Ed's bus. By the time I'm done, I will have spent a lot more time trying to buy the part than the time it will take to install it and the gauge.

belfert · May 03, 2014, 10:40:21 AM

Centroid's business practices are a little strange. They must be a small operation. There are open six hours a day now which I think is more than before. Tech support is email only or leave a message with the office and the tech guy calls back. The technical guy must either work part time, or he is the guy actually building the senders.

Good product that is very accurate. Mine is cut so empty should be when I have just over 20 gallons left. I know from experience that I cannot use the last 20 gallons.

Ed Hackenbruch · May 03, 2014, 10:52:10 AM

Hey Lin, if you want, i will pull that panel off and take a picture of the sender if i can see it, and email it to you. Might not be until tomorrow though, we need to make a run to the store for groceries.

Lin · May 03, 2014, 12:42:30 PM

Ed, don't bother. The only reason to look at yours was to see if it matched the one Luke had. I will just get it from one of the custom places Monday. Thanks

Ed Hackenbruch · May 03, 2014, 01:20:28 PM

Oh sure, now you tell me!

Just got done putting it back together. If you want the 2 pics send me your email address. Just so you know it is marked 12V on it and only has one wire.

lvmci · May 03, 2014, 02:18:06 PM

Hi Ed, put pics up here too! I want to compare it with mine, thanks, lvmci...