fuel gauge/cluster wiring woes

[fidelity101]

I have been doing some routine maintenance to my 85 suburban and all was well and went for a test drive and noticed that my fuel gauge stopped working, it pegs beyond E on key on, but that's when I turn my lights on...

My first thought is grounds might be an open somewhere because the voltmeter in the dash stopped working too. However the factory fuel gauge has never really worked all that well and I already have aftermarket tach, water temp and oil pressure so I opted to go with aftermarket fuel level gauge as well.

The issue that I am having is that this truck was originally a 6.2 diesel then the PO swapped it to a TBI 5.7 and I'm not exactly sure what wiring is actually in there. (or if the diesel tank is still in there) I have since swapped it to carb to simplify the mess. I found this schematic but it doesn't look like my instrument panel connector.

1985 dieseler:

1987 TBI:

I was figuring I could tap into the sending unit wire at the connector for the cluster but mine is an 18 pin connector with 1 pin un-used. The ones I found for gasser or diesel were 17 pin (with 1 un used) or 32 pin. The TBI one looks like my connector but the connector is labeled 1-18 so Im not sure which pin is 30.

I have not resorted to dropping the tank yet because it will be an ordeal and I also have to remove the skid plate and cutting a hole in my floor sounds fun but dumb.

Am I on the wrong connector? Anyone have a photo of where they tapped in?

 

[dyeager535]

I don't have the time to get all into it, but I saw "tap" and I don't like that.

AFAIK gas/diesel wiring for fuel gauge is no different (except water in fuel or something indicator, but that's not the gauge sender) check my link for the proper (as in GM) electrical manuals. Should be the same for just about forever.

 

[fidelity101]

Yeah both senders are 0-90 ohms, which is lucky for me. Vehicle was only a single gas tank so that saves some complexity.

I believe I found my schematic:

This is the 18 pin that has 1 pin not used going to gauge cluster. It looks to be the double pink wire on the end of the connector for fuel gauge. I was just going de-pin that and wire it to the aftermarket gauge sending unit location.

Although, I don't understand why it has the loop from one side of the connector to the other... (per the diagram)

Here is the rest of circuit #30

 

[dyeager535]

That "typical 1981-87" stuff is garbage.

Should be able to put the pink sender wire to the proper one for the gauge though, yes.

That instrument panel connector is garbage, voltmeter issue might be solely from that connector. I hard wired mine as I was sick of all the intermittent problems with the cluster.