1973 k10 intellitronix fuel gauge issue

[Mike_The_Grad]

Hey everyone, i recently performed ls swap on my buddy's 73 k10. I also installed intellitronix analog gauges. I'm having issues with no voltage meter reading at all. Fuel level gauge is reading different readings all of the time. Sometimes needle is pointing straight down, sometimes 3/4 tank, sometimes 1/4 tank. All of this happens within a few minutes of driving. I ran out of gas on Friday and was stranded for 2 hours. Gauge was reading 1/4 tank. I'm using 87 tbi tank, 87 tbi sending unit with 255 lph walbro pump. Sending unit wiring is as follows. Sending unit ground with eyelet to frame rail clean no piant star washer nut and bolt. Pump harness 2 wire pigtail is fitech fuel pump relay wire to positive wire of fuel pump, negative wire of fuel pump is connected to signal wire of intellitronix fuel level gauges. Intellitronix fuel level gauge ground wire is connected to frame rail clean no piant star washer nut and bolt tight. Frame rail grounded to negative post of battery. Heavy duty ground straps from both cylinder heads to framerail, frame rail to battery negative post, cab to frame rail with ground straps. Fuel tank to frame rail with ground wire clean no paint and tight with star washer. Oil pressure gaugereads correctly and so does water temp gauge. Speedometer needs calibration and so does tach. But voltmeter gauge shows nothing all the time no matter what. Any help??

[Mike_The_Grad]

I also rewired entire vehicle with american autowire classic update series kit. Have zero issues. All lights work. Engine runs great have power everywhere it's needed. I also used my test meter to check continuity on gauge fuel gauge circuit and fuel pump and fuel tank sending unit circuit. I have continuity from fuel pump positive to fuel pump negative wire harness from sending unit. I have continuity from fuel pump positive to vehicle frame negative. I have continuity from tank to frame. I don't have continuity from fuel pump negative to vehicle frame. But I do have resistance value of 83.7 ohms. From negative of fuel pump to vehicle frame. How can I have resistance value but no continuity? I'm not electrician. But I can listen and follow instructions. This is the first time I've ever had any issues with a gauge not working properly. And I've rewired at least 10 trucks. Installed dakota digital, classic instruments, new vintage and intellitronix digital gauges, ls swap, sbc engines, some with fuel injection. Trouble shooted stock gauges and vehicle wiring. But this one has me stumped.

[leegreen]

>negative wire of fuel pump is connected to signal wire of intellitronix fuel level gauges<

that does not sound right

[Mike_The_Grad]

I agree 100% but where do I pull my fuel level sender signal from then? Key on sending unit wire disconnected from the gauges. I get
6.7Mv against vehicle ground.

[leegreen]

I know nothing about your specific gauges, but the '87 tank works like this, so unless you are supposed to change sender units your gauges must work like this too:

Power to the gauge, then the gauge signal wire grounds through the sender resistor and to the grounded portion of the sender assembly. And the sender assembly needs a good ground to the frame.

grounding the pump through the sender unit signal wire as you describe means you are grounding through the variable resistor of the sending unit and possibly through the gauges. neither is meant to ground a load like a fuel pump.

Ground your pump to the metal portion of the sender assembly and use a heavy ground wire from sender assembly to the frame - the walbro pump will draw more amps than TBI did

[Richard]

Originally Posted by leegreen

I know nothing about your specific gauges, but the '87 tank works like this, so unless you are supposed to change sender units your gauges must work like this too:

Power to the gauge, then the gauge signal wire grounds through the sender resistor and to the grounded portion of the sender assembly. And the sender assembly needs a good ground to the frame.

grounding the pump through the sender unit signal wire as you describe means you are grounding through the variable resistor of the sending unit and possibly through the gauges. neither is meant to ground a load like a fuel pump.

Ground your pump to the metal portion of the sender assembly and use a heavy ground wire from sender assembly to the frame - the walbro pump will draw more amps than TBI did

Agree, was just about to post almost this same response. I looked up the gauges used and the fuel gauge is designed to use the stock sending unit.

[Mike_The_Grad]

It is a stock sending unit from a 87 tbi truck. I reconnected everything and changed the ground wire from the gauges. It seems to be working now. But my voltmeter doesn't work at all. It hasn't worked prior to the fuel gauge issue either. It's just all the way to the left.

[leegreen]

check to see if the volt meter has power and ground and if you get a voltage reading from those two wires with a multimeter

[Mike_The_Grad]

So am I supposed to ground the fuel pump to the frame? I'm confused. I only have 3 wires total for my fuel sending unit assembly. 1 black with an eyelet attached. And a 2 wire weatherpack terminal connector. 1 wire is grey and the other is purple.

[leegreen]

The connectors / colors on a '87 TBI fuel sender and an autowire classic wiring kit may not match up perfectly.
Can't tell if that is another connector on inside of the sender unit and what wires go where.

What you need:
two wires to the assembly, one ground from the assembly
One wire from fuel gauge goes to sender unit and connects to the variable resistor on float switch - this circuit grounds to the sender assembly

One wire from fuel pump relay to the sender assembly and connecting to the red wire from fuel pump. The fuel pump ground needs to go to the metal parts of the sender assembly, there may be a terminal for it to connect to or you need to make something.

The ground wire from the top of the sender assembly needs to go to the frame, I'd run a heavier wire, solder the connectors and put some conductive grease on the connections at both ends of the ground wire.

[Mike_The_Grad]

The American autowire kit has just 1 wire for the sending unit sensor reading. It's a tan colored wire labeled gas gauge. I have that wire connected to the negative of fuel pump and yo the signal wire of the intellitronix gauges. I just downloaded the instructions for dakota digital Grafix gauges because my friend just ordered them for his 67 c10. Yes they are different manufacturers and different eras. But I the dakota digital gauge instructions it specifically states:

For fuel level sensors that are attached to an electric fuel pump, or if you have an electric fuel pump in the tank, make sure that the fuel pump is externally grounded to the vehicle chassis. Attempting to ground the fuel pump to the Dakota Digital Control Box will result in erratic operation and damage to the Control Box.

Sounds like it would be the same for any type of aftermarket digital gauges. If this is the case, where the heck do I pick up the fuel sensor level reading from??? I've only got 3 wires to choose from. 2 for fuel pump positive. And negative. And the other black wire with eyelet for grounding to the frame.

[87chevy.com]

Originally Posted by Mike_The_Grad

The American autowire kit has just 1 wire for the sending unit sensor reading. It's a tan colored wire labeled gas gauge. I have that wire connected to the negative of fuel pump and yo the signal wire of the intellitronix gauges.

sounds wrong. if wired like you are saying, it will never work. its going strait to ground and may be getting current that can damage gauge.

if wire is marked gas gauge, it gets connected to only fuel sending unit wire. that simple

sounds like a few wires not wired correctly. this can damage the gauges or sending units. double check wires with volt meter

[Mike_The_Grad]

Anyone have the fuel system wiring diagram from 1987 r10 tbi? Including fuel pump, gauge, ground circuits.

[leegreen]

I'll repeat

1 wire to fuel sender from gauge.
1 wire from power to pump
ground the pump to the sender assembly
ground the sender assembly to the truck

---------------

you don't add any power to the sender, it provides a variable ground the gauge reads as fuel level.
if you connect the gas gauge to the ground of the fuel pump the gas gauge will see 12V, it won't work, it might get fried. If you are also grounding the fuel pump through the sender resistor I think you risk sparking at the resistor inside the tank. The fuel gauge sends a very low voltage to the sender, not a full 12v

[87chevy.com]

Originally Posted by leegreen

I'll repeat

1 wire to fuel sender from gauge.
1 wire from power to pump
ground the pump to the sender assembly
ground the sender assembly to the truck

---------------

you don't add any power to the sender, it provides a variable ground the gauge reads as fuel level.
if you connect the gas gauge to the ground of the fuel pump the gas gauge will see 12V, it won't work, it might get fried. If you are also grounding the fuel pump through the sender resistor I think you risk sparking at the resistor inside the tank. The fuel gauge sends a very low voltage to the sender, not a full 12v

the Ground cable is for both sending unit and fuel pump. attach that ground cable to frame . Also make sure you have proper grounding throughout - Ground cable cab to frame, battery to frame.

if a volt meter gauge does not work, it should only be 2 wires, power and ground. trouble shoot what your missing