Chevy & GMC Vans

I figured it would be a ground problem. Neither bother me enough to do anything about it.

LiftedAWDAstro wrote:That's not necessarily true Don. I switched out the fuel pump/sender unit with a new Delco unit and my gauge twitched just the same. I have not hear of anyone fixing this problem yet.

I don' think this is true either as I've replaced two already, still twitching.

my 99 has all the forementioned problems even with its new pump/unit, and i can actually see water spots on my neddle. i rely more on the overhead computer than the needles reading, as my original sending unit died years before the actual pump failed and some how the overhead computer was still always accurate.

Just an update.. I put an osciliscope on the signal line to the cluster, and while it has a spike it in it, it doesnt look like that is what is causing the twitch.. Not what I expected as this same cluster was fine with the 97's wiring and control module.

It was mentioned that the gauges were liquid dampened. I didnt think that was correct, but I tried something anyways. I took the gauge itself out, and poured some oil inside of it. With a completely full tank, the twitching is gone. I didnt expect it to fix it, but so far so good. I'll know for sure once I've burned some gas up.

I'm not sure if this will really fix it yet, but I thought I'd post an update for you guys. Once I've driven the van a bit I'll let you know if it keeps steady or not.

Scott

My 2001 does it also - in this cold blast we've been having when I leave the van to idol it actually goes all the way down and turns on the low gas light - normally (when not -25C) it only twitches. I myself have NO idea why it does this - but I don't really care.... if it's an easy fix let me know - I'll cross that off the list

I enjoy the twitch. Tells me the van is running, I'm in it and going somewhere. When it doesn't twitch it scares me. All the way full (don't see that much) no twitch, when it stops twitching you have about 20 miles to get some dang gas.

My 96 Safari had the twitching fuel level gauge needle. It wasn't really a big deal for me, but Cherie was driving the van for a week while I worked on her Explorer and she said the twitching needle drove her nuts. She's goofy about everything working perfectly. So, today while I was standing around in the shop doing nothing I decided to investigate the "TWITCHING NEEDLE MYSTERY". I have a spare instrument cluster so it didn't require anything more than switching the gauge. Now there is no twitch. What I did notice is that the good gauge needle has some resistance when you move it. The old gauge needle would spin freely. Also there is no liquid in this gauge. I think replacing the gauge is the proper fix.

A 1997 Safari passenger van I sometimes borrow has this problem as well. The gauge vibrates. When I first saw it I immediately thought the coil must be picking up some electrical noise from somewhere. There could be a grounding problem somewhere or a bad filter capacitor in the computer or harness. I deal with a lot of electronic crap at work that goes bananas when electronic noise is present. Looks like the same type of thing to me.

Though I must say I think we are comparing three different problems here:

1: Bad tank baffles.
2: Bad gauge, the movement can get gummed up.
3: An electrical noise issue.

The gauge I've seen did not swing around at random, it just vibrated back and forth about 0.5mm and read correctly otherwise.

Would like to thank the person who started this thread.
Didn't have a problem until I posted and now mine goes from full to empty when it is in park. Advisor says I need a new part in the tank and will wait until it breaks.

Don, I realize that this is an old thread, but my wife's 2001 Bonneville had the same problem you described. The fix for it was to replace the fuel gauge sender in the tank. Actually, just the wiper in the sender was replaced--the original wiper wasn't made the best and the contact fingers would wear off and cause erratic readings on the gauge.
But the symptoms in her Bonneville never included a gauge twitch, so I don't know if a wiper replacement would help out there.

I'm just going to stick my two cents worth in on this - partly because it's started to happen on my van and partly because there seems to be a lot of mis-information about how the Astro fuel gauge works.

Not sure about all years but according to the GM Techline, on my '98 it doesn't read directly from the sender and it isn't a single input.

The gauge has TWO coils - one for full and one for empty - and the actual reading is a product of the DIFFERENCE between the two. The applied voltages are 'synthesised' by the vehicle computer system. The theory is that in this way, the reading isn't affected by battery voltage because the difference between the two applied forces will remain the same regardless of voltage.

Makes sense when you think about it long enough but most other makes manage without!

The gauge is NOT fluid damped so don't go squirting anything in there. Any vibration (and though the movement is small, the force is considerable if you touch the needle!) has to be created by a conflict/irregularity between the two applied fields.

Mine also goes bananas for a second when you first switch on (spins around like crazy but only once-ish!). I also know I have a fault somewhere on the dash wiring as only four of my idiot lights actually work (seat belt, indicators and high beam). I need to dig deeper to find out what the other eight have in common.

More later......!