The fuel gauge in my 90 mgm hasn’t worked since I bought it. The po said he swapped out the pump assembly and it made no difference. I’m thinking it’s a wiring issue but I don’t know how to test it. Any idea? Thanks.
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unplug the sender and ohm check it. If that reads normal, its something forward of that point. Offhand I forget the exact range, something like 20 - 150 ohms I think?86 Lincoln Town Car (Galactica).
5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley
91 Lincoln Mark VII LSC grandpa spec white and cranberry
1984 Lincoln Continental TurboDiesel - rolls coal
Originally posted by phayzer5
I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers -
I checked it in all ranges and get .9 ohms on the 200 scale.Comment
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that doesn't sound right. Is the gauge pegged to full all the time ? I think these go low resistance at full and high resistance when empty.86 Lincoln Town Car (Galactica).
5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley
91 Lincoln Mark VII LSC grandpa spec white and cranberry
1984 Lincoln Continental TurboDiesel - rolls coal
Originally posted by phayzer5
I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousersComment
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No it’s always empty.Comment
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.9 on 200k ohms?
I think it should be under 100 or so?
Gadget is right- level low, resistance high, level high resistance low.
..Comment
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No it was set to 200. I initially set it to 20k and it would read 18k or so then drop until it displayed OL. So I tried it on lower and lower settings until I got to the lowest setting and that’s when it gave me a steady number.Comment
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Do these still use separate connections for the pump and level sender or is it one plug? You're dealing with newer stuff than I've had my hands in.
reason I ask, sometimes motors read wierd on ohm meters, the inductance screws them up. Just wondering if you're measuring the fuel pump and not the sender.86 Lincoln Town Car (Galactica).
5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley
91 Lincoln Mark VII LSC grandpa spec white and cranberry
1984 Lincoln Continental TurboDiesel - rolls coal
Originally posted by phayzer5
I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousersComment
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It’s all in one on my 90. I definitely could be messing the wrong thing. It’s hard to get under it and snake my hands around the axle to get to the pump. I tried a combination of the pins I felt and this is the only one that was a circuit. I’ll try to get under it again this week though. I remember there are two pins to jump that will make it read full to rule out the cluster. That’s how I narrowed it down to the float on my 87 but I’m sure the pins aren’t the same on this one. To be honest, I like the pre 90 panthers better.Comment
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My '91 CV/MGM EVTM claims 15 ohms empty - 160 ohms full. So always reading empty if it's seeing 0.9 ohms makes sense.
OL does not makes sense as this would peg the needle full.
What did you measure, terminals on the tank side? Terminals on the tank are what you want to see if the resistance is within range and makes sense for the current fuel level.
I'm not sure which terminals they would be for the sending unit, but it's the one with yellow with white stripe wire and the one with black wire. Since I don't see a pinout of that connector in the EVTM, I suppose there may be 2 black wires. If so, measure resistance on the tank pins from the yellow w/white stripe pin to each of the pins that the black wires go to. The correct one should show resistance (200 ohm setting should be fine) and the other black wire pin might show OL.
Approximately how much fuel is currently in the tank?
Measuring terminals on the harness side might behave like you described. As the Anti slosh module and needle do their thing the reading might change but that at least tells you that the wires are good if your measurements picked up on that.Vic
~ 1989 MGM LS Colony Park - Large Marge
~ 1998 MGM LS - new DD
~ 1991 MGM LS "The Scab"
~ 1991 MGM GS "The Ice Car"Comment
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On your '87, jumping the sending unit pins on the harness side would put the needle to full as a jumper wire is essentially 0 ohms and the pre '90 analog cluster panthers (excluding '88-'89 LTC) had low resistance = full.
For all '90+ panthers, jumping the yellow w/white and correct black will give you empty but unplugged should read full on the gauge.Vic
~ 1989 MGM LS Colony Park - Large Marge
~ 1998 MGM LS - new DD
~ 1991 MGM LS "The Scab"
~ 1991 MGM GS "The Ice Car"Comment
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Yeah the side of the tank. I think I measured the wrong terminals as I have a spare pump assembly and the wire for the float is the second from the top. I was measuring the resistance through the pump. I have a spare pump and hanger assembly that I tested to make sure I’m not an idiot. Well I am but this one tested within spec. It’s the top two terminals that are for the float. It’s wet and nasty outside or I’d get under it again. I have a feeling that it’s the wiring but I’ll reserve judgement until I test the pump in it properly. And there’s about half a tank. It’s hard to tell exactly because the odometer is broken too.
On a side note, I didn’t realize these pumps were so tiny. Don’t mind the mess lol.Comment
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Oh, that's super handy to have that spare assembly. Now you know for sure which terminal goes to the sending unit.
The blue wire in the pic and the 4th terminal has no wire since the sending unit must be grounded through the assembly body.
Since the spare tested fine, hook it up and move the float arm if the gauge (key on) does not respond accordingly then it could be wiring. Could also be the anti slosh module or the fuel gauge itself.
If the gauge in the cluster does not respond, I would yank the cluster then test at the cluster connector to see of the multimeter reads the expected values to confirm the wiring is good or not.
I can pull to the EVTM out again later to get the cluster connector pin out.Vic
~ 1989 MGM LS Colony Park - Large Marge
~ 1998 MGM LS - new DD
~ 1991 MGM LS "The Scab"
~ 1991 MGM GS "The Ice Car"Comment
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Solid advice thanks I’ll do just that once I have the time. I’m hoping this Wednesday I’ll be able to get under it again. It sucks when you live in an apartment and have no garage.Comment
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I wasn’t able to jump the wires but I unplugged the harness and turned the ignition on and it was still empty. Then I checked the right pins this time and it read 97 ohms. So I’m thinking it’s either a wiring issue or the cluster itself. I have to pull the cluster to put the new odometer gears in anyway. How can I test the cluster?Comment
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