98 Chevy box van with 6.5L
 

I have a 98 chevy with the 6.5 and having fuel gauge issues. The initial problem was an erratic gauge so one of my guys replaced the sending unit. That didnt cure the problem. They then thought faulty gauge so we had it tested and calibrated. That was not a good idea because it was ruined and replaced. We then replaced the anti theft module which we later found out it would have ecured the erratic gauge. Now our fuel guage is reading beyond full, like at three o'clock full. Not sure what is left. The tank is in fact full but not that full. We unpugged the sender and the guage did not move. Any ideas? we spent nearly 600.00 on this thing. Bright side, not erratic anymore. Thanks in advance for any ideas or suggestions.

Ground wire on the tank.

I'll check that again but I asked the guys about it already. Thanks for the suggestion.

sometimes the tank selector switch can cause this too.

I checked and cleaned all grounds and they are good. This truck has a single tank. My next step is to drain fuel and check the new sender. Maybe the float is hung up.

I would do an ohm check on the existing wire to confirm you have a good contact, or run a jumper ground to a known good place.. It is easier than draining the tank.

Well as luck would have it, the company that sold us a rebuilt cluster gave us one for an unleaded vehicle in stead of diesel. Now we have to wait a week for the correct one. Maybe that is our problem.

Ok, correct cluster is now installed and the same issue is at hand. This is not a simple system as previous gauges. The fuel sender runs through a buffer module and also the Pass module before it reaches the gauge. All indications was a faulty guage however that was replaced along with the buffer module and sending unit. This vehicle only came in with an erratic gauge and not it is ready 3 o'clock full. We checked all the grounds and wiring.

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Finally, problem fixed. I worked backwards from what our technicians did and found out that the buffer module that was replaced, was bad as well. Replaced it again and system works great. Now, I doubt I will get my money back since we bought the first one in June. Chapter closed!

What the heck is the buffer module?