The Stovebolt Site Forums The Parking Lot Panels 'N Burbs '55 2nd series gas gauge mystery

Hello fellow stovebolters! I am new to this website and it feels great not to be alone. I'm having problems getting my new gas sending unit to mark properly.

Before I decided to get my fuel gauge going I looked under the dash to try to figure out what wires hooked up to the back of the gas gauge (they were disconnected when I purchased the burb). I believe I did find them because when I connected them my needle did move slightly and thinking that maybe I had them backwards, I checked. I switched the wires and then the gas gauge needle jumped all the way to full, so I assumed all I needed was a new float. Much much later I removed the gas tank (I think it was the first time since '55) and the tank was full of rust residue and the sending unit looked rusty, pitted and the float was completely deteriorated except for a small ring held by the float arm. I ordered a new sending unit for a stepside since they don't make them for burbs and after a bit of bending and cutting I got it to fit and make the float arm swing the exact same way as the original. I took days washing out the tank until there were no more traces of rust particles coming out.

So now here's where I'm at: I put the gas tank back on the burb with the new sending unit installed, connected the wires and added some new gas. Now when I turn the ignition on, the needle goes slightly to the right, but still way before the first white dot. When I turn off the ign, the needle goes back all the way to the left. Thinking maybe I had the wires behind the gas gauge backwards, I switched them only to find the needle moving only a little bit further to the right than before, but still before the first white dot.

I have a reproduction wiring diagram for complete chassis for a 55.5 truck and according to the gas gauge symptom and probable cause section it say it could be one of the following:

Tank unit shorted: It's brand new and I hooked up the original one and it showing the same symptons as the new one so I dont think its that.

Wire from dash unit to tank shorted: I ran a direct wire bypassing the old one and it still has the same symptons so not that one either.

Float stuck in empty position: Well I think if that was the case it would have showed almost full after connecting the wires backwards like I mentioned in the beginning.

Bent hand on dash unit: Maybe but how did it bend if it use to go across to the full position before when I originally switched the wires backwards and not now.

And the last one is that the dash unit is improperly grounded on instrument panel: Shouldn't it be grounded with the gauge cluster already snug in the the dash or do I need to ground it with a wire?

I apologize for writing so much but I wanted to be thorough so I could get some good feed back or advice. This mystery is really driving me bananas and seems like this should have worked with no problems after reinstalling the tank with the new sending unit. I tried the old sending unit one more time earlier today but it's doing the exact same thing as the new unit. I would really appreciate any info on this matter.

Thanks -joe

I don't know the answer but could THIS be part of the problem?

This probably should be posted in the electrical section, you will possibly get better responses to your question.

Ground the tank sending unit directly to a clean chassis spot near sending unit. Do this by running a wire from one of the sender mounting screws to the frame (chassis) Make sure the screw is cleaned/wire brushed to shinny metal The gauge needs it's own ground wire straight to clean dash metal. Ground chassis to engine with good proper ground cable. Ground chassis to body. (remember there are RUBBER mounting pads between body and chassis) The engine is isolated from the chassis with RUBBER pads. of course you have the battery ground to engine, I'm sure. All of these old trucks need ALL of these grounds. If the truck is painted or rusted, the bolts will not carry the ground path, they are not meant to anyway. The no. 1 cause of malfunction of a gas gauge is the ground and that means the entire ground system.
You did NOT say if you tested the gauge/sender in the tank BEFORE installing into vehicle. You should have tested it all with a temporary ground and hot hook up. You need to know that it all works by isolating the sender and gauge by running test wires that are not part of the harness. Then you will know it's a wiring or ground problem and NOT the gauge or sender. Also, are you sure that your modified sender is not binding inside the tank? I have done what you did for my suburban, modified a truck sender (cut the pick up tube shorter and coil the float wire to make it shorter). Since you bought a 55-59 truck sender it would be the correct ohmage. Ground! ground! ground! Clean metal to metal!!!!!!! all around the truck!!!!!!!!!
ALSO when you "reversed" the wires during your test you could have burned out the gauge. Do not hook up a gauge unless you know for sure which is ground terminal and which is hot.

gmoniz, im new and didn't know there's an electrical section. i just put it under suburban because i felt maybe alot of other suburban owners have had similar experiences. bartamos, thanks for the info. i think ultimately it is the grounding like you said. i did not test the sending unit before installing it back in the burb because it was new. i did run direct wires from sending unit and acc/ign switch to the gas gauge and it still did the same thing-that is the needle goes to the right before the first white dot then back to the far left when ign is turned off. i did test the old sending unit out of the vehicle with direct wires as well and same things as before-it goes to the right just before the first white dot and to the far left when ign is turned off. so both old and new sending units are doing the exact same thing even with direct wires. according to the wiring diagram for this year truck, the gas gauge has 2 wires-one from the sending unit and one from the acc/ign switch. im thinking the gas gauge is not shorted or i don't think it would move at all-i could be wrong. i think you are right about the grounding. i have not really paid attention to this. i will wire brush the chassis where the sending unit ground attaches and i do have a good ground on one of the sending unit screws like you mentioned. it does have a good ground from battery to engine, but i have to check to see if there is a ground between the body and chassis. and most importantly i will put a ground from the dash gauge cluster unit to the body or probably even better to the chassis. im assuming that i can attach this last ground mentioned to one of the gauge cluster unit screws in the back like for the speedo, right? then to the body or chassis. as far as the float arm binding in the tank, i dont think so because i compared it to the original float arm side by side out of the vehicle and they both are in the same position and orientation, they travel up and down swinging the exact same way and distance. even the floats are tilted the exact same way when at full and empty positions. one good thing from all this is that i am now an expert at removal and reinstallation of a '55 chevy burb gas tank as i have done this 3 times already. thanks again for the help. -joe
p.s. i was looking at your '57 dq panel the other night...it's cool to see history like that.

Three things: when you did your direct wiring test you would have needed to have a ground from sender to gnd and from case of meter to gnd. The case of the meter needs a good gnd also. Not the two terminals but the case. Like you said one term is hot and one is sender. Second thing: Always check the system before installing a new component so you know all is well and that the new component did indeed fix it, right now you don't know that for sure. Third: IF, IF, IF you did the testing correctly with grounds, then the component that is common to both tested systems is the gauge. Which means that the gauge is BAD! Two different senders with same test wiring and same gauge means gauge is BAD! It also probably means your original sender was OK. Keep the sender, it can be used to test other gauges, such as the temp gauge. The rheostat sends a variable resistamce signal to any gauge that uses a variable resistance signal, I.E. temp gauge.
P.S. If your tests were not "pure" and did not have proper hookups and grounding, then retest all or you will go crazy and start shooting things with a shotgun. You must start with known good components before installing in truck. And just because they are new does not mean the Chinese guy built it right. thanks for your words on the DQ.