Fuel Level Sender

[VicCrownVic]

97 ohms should be over half tank, I agree, it sounds like the sending unit is not the problem.

For the cluster, it could be the antislosh module (lower right of the cluster) or the gauge itself is removable and replaceable. I have a spare '91 MGM cluster somewhere. I'll see if there is a way to test it out of the vehicle.

[87GrandMarq]

That would be great, thanks.

[VicCrownVic]

So, since the sending unit is believed to be good, I would next hook the connector back up at the tank and move to the gray connector on the back of the cluster. Pins 1 + 2 to be exact. The pins are labeled on the connector so wire color is not so important since the spare connector I have (no idea what year the connector is, '90-'94 MGM) and my EVTM do not agree on the color of pin 1. '91 EVTM says Gray w/Red stripe, actual connector has Black w/White stripe. Pin 2 should be Yellow w/White stripe.

The same resistance (or very close to it) should be measured across those 2 pins. If it reads OL, then you do indeed have a wiring problem OR clean the crap out of the connector at the tank to be sure it's making a good connection.

If the same or very close resistance as your prior sending unit measurement is measured across pins 1 + 2 on the gray connector, something in the cluster probably isn't right. Antislosh module or the gauge itself, OR do a visual inspection to make sure there are not broken traces or any obvious damage.

If someone has been in the cluster before, the copper traces can pull away from the plastic backing in a way that the pins of the gray connector no longer make contact. You can also try reseating the fuel gauge and the antislosh module (clean the connections to be sure) to ensure there is not oxidation causing them not to make a connection to the board/back of the cluster.

To test the cluster itself, the only thing I can think of is to pull the cluster out but leave the electrical connections on. Be careful doing this though. If the backside of the cluster touches something metal, like the gear shifter, it can cause a short and blow a fuse such as the fuse for the speedometer. Yeah, that was fun. If you can hook up some jumper wires from the 1 + 2 pins of the gray connector to the correct 2 pins of your spare fuel pump/sending unit assembly, you can move that float and see if the cluster responds. But this would only be necessary if the resistance measured on the disconnected gray connector pins 1 + 2 seem correct while the in tank/currently installed sending unit is connected.

Pics for reference.

[friskyfrankie]

So, since the sending unit is believed to be good, I would next hook the connector back up at the tank and move to the gray connector on the back of the cluster. Pins 1 + 2 to be exact. The pins are labeled on the connector so wire color is not so important since the spare connector I have (no idea what year the connector is, '90-'94 MGM) and my EVTM do not agree on the color of pin 1. '91 EVTM says Gray w/Red stripe, actual connector has Black w/White stripe. Pin 2 should be Yellow w/White stripe.

The same resistance (or very close to it) should be measured across those 2 pins. If it reads OL, then you do indeed have a wiring problem OR clean the crap out of the connector at the tank to be sure it's making a good connection.

If the same or very close resistance as your prior sending unit measurement is measured across pins 1 + 2 on the gray connector, something in the cluster probably isn't right. Antislosh module or the gauge itself, OR do a visual inspection to make sure there are not broken traces or any obvious damage.

If someone has been in the cluster before, the copper traces can pull away from the plastic backing in a way that the pins of the gray connector no longer make contact. You can also try reseating the fuel gauge and the antislosh module (clean the connections to be sure) to ensure there is not oxidation causing them not to make a connection to the board/back of the cluster.

To test the cluster itself, the only thing I can think of is to pull the cluster out but leave the electrical connections on. Be careful doing this though. If the backside of the cluster touches something metal, like the gear shifter, it can cause a short and blow a fuse such as the fuse for the speedometer. Yeah, that was fun. If you can hook up some jumper wires from the 1 + 2 pins of the gray connector to the correct 2 pins of your spare fuel pump/sending unit assembly, you can move that float and see if the cluster responds. But this would only be necessary if the resistance measured on the disconnected gray connector pins 1 + 2 seem correct while the in tank/currently installed sending unit is connected.

Pics for reference.

Going to assume your references are for an analog dash? Not sure the digital one has an anti-slosh module? Perhaps someone can verify that.

[87GrandMarq]

I’ll poke around more tomorrow when it’s light out. I have most of the dash torn down right now.

[87GrandMarq]

How do you take the headlight knob off? I can’t snake my hand up the dash like I could with my 87.

[VicCrownVic]

There is a little prong on the backside/base of the of the knob. The knob comes off the shaft. Turn the knob and youll see a notch, that's where you push the prong toward the driver seat if I remember right.

'91 Heater core write up, Driver side step 2 is removing the headlight switch.
http://www.grandmarq.net/vb/forum/te...36#post1064636

Also, Driver side step 9 of that guide might be of use to remove the cluster, but you might have figured that step out already.

Yes, analog. I'm not sure digital was an option for '90-'91 CV/MGM.

[friskyfrankie]

Yeah, I don't think digital dash was available in the early 90's. Might of started in '92 but definitely in '93, as an option. Just don't remember if the anti-slosh module existed in a digital dash like it did in the analog one. I have to check the EVTM on that one or if someone knows - great!

[87GrandMarq]

I was finally able to pull the dash apart today. What a PAIN IN THE ASS. Anyway, I back probed pins 1 and 2 and got 128 ohms (I filled it up), which means the wiring is ok. I pulled the anti slosh module and sanded the crap off the pins and reseated it but no cigar. I’m thinking it’s the anti slosh module. I’ll bypass it and test again. In the meantime, I’m replacing the odometer gears and am cleaning it up. There are pieces of those gears everywhere. What can I lube the new ones with?

[Tiggie]

I think I used something like dielectric or other silicone-based grease. Some of the gears say no lube needed, so you might want to check to be sure with the manufacturer.

[gadget73]

if they had anything I'd guess an extremely light wipe of lithium grease but silicone will do just fine. Don't need or want much, just enough to get a light coat on the worm screw. That will distribute around as needed.

[VicCrownVic]

The gears that I got did say not to use lube. Something to do with the material composition of the gears that I got, but this was about a decade ago so my memory might be a bit fuzzy.

Also, good to hear that the wiring seems to check out.

I will not be home for another week, but if you need an antislosh module let me know unless someone else has one they can get to you sooner.

[friskyfrankie]

Still trying to figure out if the digital dashboards have the same module as the analog ones?

[87GrandMarq]

Yeah man I’d take your anti slosh module, that would be great. There doesn’t seem to be too many out there at least specifically for our cars. Many of them across most models look the same but I’m sure they’re not. And good to know on the grease. I’m waiting on another set of gears to come in so the cluster is sitting on a table until I at least get those installed.