I have a 4 dr 4x4 blazer 4.3 and my gauge is reading empty. I pulled the pump out teasted the resistance on the sendin unit. Empty waz reasin 80 full 220 i read the the purple wire is signal black is ground which run to the pcm. I was told pin 19 is signal and pin 13 was ground. But when i got to 13 there was no wire could that be the prob or is that slot is empty

 

If the gauge reads empty with the ignition on, the signal wire is grounded somewhere. What year is your Blazer?

 

I have a 2001 4dr 4x4 4.3 i know i have a ground problem i tried to follow it ended by the transmission very hard to access very little room like a inch trying to find the ground on the pcm cause i read it would be pin 13 but no wire in the slot

 

Check the harness closely where it goes past the front driveshaft, it can rub through and short out. If the purple wire shorts to ground, that's the problem.

Connector #3 at PCM pin #13 is the purple signal wire.
Connector #3 at PCM pin #19 is the black wire.

IIRC connector #3 is the "clear" connector, (looks more like white to me)

 

I had the opposite problem mine was full all the time. here is what I discovered if it is a open circuit it reads full, if it shorted or grounded it's empty. you might try unplugging at the pump and see if it goes to full.

mine was a issue of the contact fingers wore off or broke off so the float arm was not making contact with the sensor.

 

To clarify.. the connector you were reading should have been the one that is NOT black, red or blue.
Pin 13 should be purple.

If nothing on pin 19, then read pin 13 -purple- to ground. Should not be below 80 ohms.

 

I had double check and pin 19 has the purple pin 13 nothing could the ground be somewhere else? I had jump sending unit ground to the frame and it worked could i just by pass grounding to pcm or does it to be grounded to pcm

This might sound stupid but is the iirc and its purpose?

 

IIRC = If I Remember Correctly

 

Is there a wiring digram for the pcm?