Guys, I bought a good looking MEP-802a that seems to run very well, but the fuel gauge seems to be pegged out way past full and the temp gauge never moves off of being pegged out across the word 'water'. All wires seem to be hooked up and looking good on the gauges and the sensor and sender. Are there any common bugs that I should look for before I start replacing parts? Thanks in advance for your advice.
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802A Fuel and Coolant Temp Gauge Problems
- Thread starter CP92
- Start date
There's diag stuff in the tm if you feel like diving down that road. They aren't to tough to figure out. Temp guage you can see if it's warming up with a heat gun on the thermostat housing.
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The -24 TM has procedures for testing the related sensors and gauges to determine where the issues are.
I searched thru the only TM I've got (for an 803a, TM 9-2815-253-24) and couldn't find any troubleshooting for fuel and temp gauges. Is there a way to test the temp sensor, fuel level sender, and gauges? Am I missing a TM?
I wonder if I'm missing part of that file. I couldn't find those procedures. I'll keep looking.
I found several I didn't have just now in Guyfang's pinned post shown below. The one ending in 24-OLD seems to have a lot of stuff in it I need to search thru. Thanks for the tip.
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When ever you have a gauge problem, FIRST, check the wires. Make SURE, check it not just twice, but three times, check to see if the wires are hooked up at the right terminals. Over the years, I found most gauge problems were because someone hooked up the wires wrong. And don't check just the gage that's not working. Remember, the ground is interrelated between gauges.
The reason the -24 has "OLD" behind it is because there is a newer TM. But we can not post it in the forum, do to it being not allowed for the unwashed masses.
The reason the -24 has "OLD" behind it is because there is a newer TM. But we can not post it in the forum, do to it being not allowed for the unwashed masses.
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Here are where the items are tested in the -24 TM
Fuel Level Gauge Testing Para 2-39
Fuel Level Sender Testing Para 2-76
Temp Gauge Testing Para 2-40
Temp Sender Testing Para 2-92
Guyfang and Kloppk, thanks for the advice and direction. I will definitely check the wires again. It seemed like the fuel gauge was working for a little while and then just pegged out to the right one day. I'm not sure about the temp gauge. I don't remember seeing it registering since I bought the unit. And, thanks for finding the testing procedures in the TM for me, Kloppk. I found those sections and have them printed out now. I'll give this stuff a shot this weekend.
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When the fuel gauge works, and then goes wonky, pull the sending unit. The float may be stuck. Sometimes they get gummed up. Thats the first thing I check, when it works, and then wont.
Ok, I pulled the sending unit, cleaned it, and measured ohms at various float arm positions. All the way up (Full), it read ~27 ohms and all the way hanging down (below Empty) it read ~3,000 ohms. Holding the float about level with the bottom of the sender body bracket, it read roughly 100 ohms. I tested both gauges using the voltage potentiometer to give the required resistances and neither reacted at all...no needle movement. I also noticed that neither gauge needle quivers at all when I turn the master switch to Run/Prime like other gauges do. I also tested the temp sending unit to make sure it was above 300 ohms, while cool, and it was at 700 oms.
I'm thinking I need to replace the sending unit. I think the temp sender is probably ok. I'm also wondering if the gauges might be ok, but malfunctioning due to some electrical connection they have in common. Am I way off base with my thinking?
Ray70
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99% of the time it's a bad sender.
In your case the fuel sender is bad. This is very common on these machines.
The resistance should be 30 ohms full and 240 ohms. empty.
3000 ohms is why your gage is pegged.
Best bet is to replace it with a 5.5" long WEMA stainless steel marine sender with a SAE bolt pattern.
Drop in replacement for $50 or so.
In your case the fuel sender is bad. This is very common on these machines.
The resistance should be 30 ohms full and 240 ohms. empty.
3000 ohms is why your gage is pegged.
Best bet is to replace it with a 5.5" long WEMA stainless steel marine sender with a SAE bolt pattern.
Drop in replacement for $50 or so.
I just found another post where you left this comment:
"Oh, and one other thing to check... once you verify the gage wiring and ground are good, if you disconnect the "S" wire from the gage and measure resistance from the S wire to ground you should get somewhere between 30 and 240 ohms, depending on how much fuel is in the tank.
If everything checks out but the gage is still pinned, look closely at the gage. I know at least the Faria Beede gages can get stuck if they peg all the way up or down. The needle will usually hit the side of the housing and get stuck.
To fix it, loosen the nuts on the long mounting studs and tap the gage sideways against your palm, that should jar the needle loose.
tighten the nuts, reinstall and try it again. "
I followed those instructions and found that the needles on both gauges were stuck. I was able to take them out, free them up, and reinstall them. The temp gauge is working great now and the fuel gauge works at higher fuel levels but bottoms way out at lower levels...kind of expected after the ohms I measured earlier. I ordered a new KUS 5.5" sender that should arrive in a few days, so hopefully that should fix all the problems.
Thanks again guys for the help. I'll comment again with the final results.
THE RESULTS:
Guys, I found that guages were both mechanically impaired...the needles were stuck against the inside of the housings. Removing the gauges and tapping on them sharply from the sides freed the needles and allowed them to work again. The fuel level sending unit was shot and cleaning did not help. I replaced the sending unit with the one shown below and now everything is working as it should. Thanks for the help, fellas.
Guys, I found that guages were both mechanically impaired...the needles were stuck against the inside of the housings. Removing the gauges and tapping on them sharply from the sides freed the needles and allowed them to work again. The fuel level sending unit was shot and cleaning did not help. I replaced the sending unit with the one shown below and now everything is working as it should. Thanks for the help, fellas.