Fuel Gauge Twitches

**Frozen WS6** · 02-20-2009, 06:53 PM

I have a 98 GMC 2500 and last night the fuel gauge started twitching like a crack whore on spenard. ( Thats were the prostitues hang out.) What could be causing it. How to fix it?? Thanks in advance.

**Orcus79** · 02-21-2009, 06:08 AM

Probably just a broken wire near the unit, look for frayed and broken insulation.

**jp1967** · 02-21-2009, 09:43 AM

usually fuel level sensor in tank

**0rion** · 02-21-2009, 11:52 AM

I won't pretend to know what the problem is because I don't.

I can tell you what I think though and it might be wrong. The way those senders work is as the float rides up and down with the level of the gas it has an arm on it that rides up and down a resister and it changes the ohms. Most gm stuff and especially older gm stuff went 0-90ohms. 0 ohms being empty and 90 being full. The f-bodies work on 40-259ohms. If your needle is twitching faster than you would think it's physically possible for the arm to move I doubt it's the sender itself and most likely a wire or ground issue. That's my guess.

**Frozen WS6** · 02-21-2009, 12:26 PM

I was wondering about the gauge itself. I wasn't sure what gauges do when they are failing. I did a new fuel pump sender asm, geez, I guess that was around 4 years ago now. Which I know that that has bee alot of fuel tanks ran through it and it may be starting to fail again. But I was looking for any other possibilities. It isn't flucuating the fuel level yet, just twitching but it does move quite abit when I turn the key off and restart it. My bosses 2 99 tahoes did the exact same thing.
I havn't really looked in my gm service manuals yet, but I was hoping someone had ran into the problem before. Everything you guys are saying definately makes sense.

**jp1967** · 02-21-2009, 03:47 PM

you can check for diagnostic trouble codes and usually if it has codes for fuel level sensor performance failure it usuallu means the problem is wire problem or sensor in tank. I noticed that you said it was twitching, i have seen were they twitch real fast (i mean real fast almost make you go cross eyed) that is gauge problem. disconnect fuel sender at tank and see if gauge still twitches real fast. If it does you no its the gauge, or just swap clusters with your boss

**0rion** · 02-21-2009, 03:54 PM

another thing you can do diagnostic wise is to ohm out the wires coming out of the tank and see if the ohms are jumping around. They should be pretty steady. I don't have a schematic for that truck but the f-bodies are purple coming out of there if I recall correctly.

**jp1967** · 02-21-2009, 03:57 PM

same color for truck (purple)

**Frozen WS6** · 02-21-2009, 04:09 PM

Cool. I'll have to try that. Thanks. Can't I make the gauge do a sweep with my tech2. Or will that not tell me anything.

**jp1967** · 02-21-2009, 04:13 PM

im not sure but if you have tech 2 go into body functions and then to special functions and it will have the option to do a sweep test

**Goldcuffs** · 02-21-2009, 07:03 PM

Is it moving rapidly back and forth but in a tight area? (like 2 or 3 needle widths)
If so it's more than likely a gauge problem. I've replaced a half dozen or so clusters for the same problem and they have all been GM's. In the wiring diagram for the cluster there is an anti-slosh circuit. I don't know if something malfunctions in there or what. Good luck.

**Frozen WS6** · 02-21-2009, 07:23 PM

Originally Posted by jp1967

im not sure but if you have tech 2 go into body functions and then to special functions and it will have the option to do a sweep test

Ok. I pluged in my tech 2 and did not find any body function option. I only had 4 choices. So no luck there. Unless I missed something. I havn't figured out all the fine details on using it yet.

Originally Posted by Goldcuffs

Is it moving rapidly back and forth but in a tight area? (like 2 or 3 needle widths)
If so it's more than likely a gauge problem. I've replaced a half dozen or so clusters for the same problem and they have all been GM's. In the wiring diagram for the cluster there is an anti-slosh circuit. I don't know if something malfunctions in there or what. Good luck.

If the anti-slosh was bad then when I brake, accelerate, or turn the gauge should move. Theoretically.?
It mostly it just twiches spasticly all the time, in a really tight area. It will fluctuate a couple of needle widths when I start it and on a rare occasion. Man a new cluster is going to be expensive. But right now it's driving me up a wall.

**0rion** · 02-21-2009, 07:33 PM

Originally Posted by Frozen WS6

Ok. I pluged in my tech 2 and did not find any body function option. I only had 4 choices. So no luck there. Unless I missed something. I havn't figured out all the fine details on using it yet.

If the anti-slosh was bad then when I brake, accelerate, or turn the gauge should move. Theoretically.?
It mostly it just twiches spasticly all the time, in a really tight area. It will fluctuate a couple of needle widths when I start it and on a rare occasion. Man a new cluster is going to be expensive. But right now it's driving me up a wall.

put a piece of black tape over and just pull it off once a week to check when you need gas...problem solved. Your problem could be a whole lot worse....like not working at all.

I would just start trouble shooting it with the info here and see where that leads you. If it's the gauge start looking on ebay for a cluster and hope you get lucky.

**Frozen WS6** · 02-21-2009, 08:29 PM

Yeah.

This is all good info and starting points. As for the tape thing. That would work good since I gas this pig up once a week anyway, LOL. Sooner if it's 15 degrees or colder out. I found some really good tech 2 users manuals online a few minutes ago. So now I have better referance on extracting the info I want out of it. Thanks again. This def helps alot.