Pump Voltage...

[Rosey1968]

So I am trying to check my fuel pump voltage... I dropped the tank to inspect everything so the tank is out of the car.

I do have a Racetronic hotwire kit from 2011... which wire is the correct one? This is the plug into my fuel sending unit:

The purple wire in 8.6 with key on, engine off. this seems low... is it due to a lack of a solid ground? I was grounding to the grounding strap that is attached to the body and take (when in the car).

The hot/red wire at that goes into the Hot Wire relay is 12.6 with the key on, engine off.

Any advice woudl be apprecaited.

Thanks.

 

[Steve V]

Red is power, purple is for sending unit.

 

[Rosey1968]

If I am not getting power to the red is my relay shot?

 

[Chuck Leeper]

If I am not getting power to the red is my relay shot?

Not necessarily. With KOEO, the ecm only triggers that power for about 4 secs. If you don't "catch" it, you will see 0.
The power will not return, until the ecm sees engine rpm.

 

[dynoman]

You can use the jumper behind the alternator to apply power to the hot wire relay and pull it in then check voltage . Do you have the upgraded intermediate harness from the hot wire relay to the bulkhead connector at the top of the tank ? Also check the yellow bulkhead connector for burned or corroded pins . I would also run a dedicated 10ga. ground from the battery back to the tank connections , don't rely on chassis grounding .

 

[Rosey1968]

Chuck, you the man. Perfect advice and much appreciated. I rechecked and all is good.

Dynoman... I do have an upgraded/newer harness. I will take you advice as well and run a ground to the back.

My pump us going so I have a new one on the way... hopefully I will be driving by weekend.

Thanks again for the advice.

 

[TurboBuRick]

There is no need to run a ground wire all the way to the back. Just make sure the ground strap from the motor to firewall is good. The body of the car is essentially a big conductor. Just have to link it to the motor.

 

[Boost231]

I disagree 100 percent. A solid ground back to the battery is the only way to go. Grounding any other way is half ass

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[Pronto]

I ran a 10 gauge ground (same size as the power) up to the that link on the fender. No big deal to do and I know now there is a proper ground for the pumps.

 

[SS/GN]

I run a separate ground (braided strap) from the negative cable on the block to the frame.

 

[Chuck Leeper]

https://www.bing.com/search?q=Volt drop tests&form=SWAUA2
Read up, and try it.
Also, try testing the grounds, w/ a ohm reading. Might be surprised at what was thought to be "clean" grounds, are not.
Yrs back, my Hemi car had a poor start issue. A volt drop test revealed 3 V drop, on the starter circuit.
This was a new system, w/ the heavy cables at 1/0, etc.
The batt ground was on the chassis. {6T5 Belvedere is a "unibody" car, and had an elaborate frame tie system.}
A 1/0 neg cable was run from the batt, to the block...WALA! Great starter rpm.
When we install main power cables at the shop, we drill a small hole in the terminal, crimp them, then solder them, thru the hole. HD shrink wrap follows.
We do not solder small wiring connectors. They are crimped w/ the CORRECT crimper, shrink wrapped w/ hi Q shrink tube.
30+ y/o harnesses are usually pretty much junk, and are treated as such.
Back under my rock...

 

[dynoman]

I'm actually surprised that a heavy ground wire wasn't part of a hot wire kit to complete the circuit.

 

[TurboBuRick]

The body of the car can carry a ground better than a wire. That’s why there is no ground wire on a hot wire kit and also why the engineers did not run ground wires from the factory.

 

[TurboBuRick]

I run a separate ground (braided strap) from the negative cable on the block to the frame.

That grounds the frame but not the body. There need to be a braided strap from engine to firewall for the body. There was a factory strap that went from engine to firewall. On most cars I see this is either loose, disconnected or missing all together.

 

[SCOOBY DOO]

The body of the car can carry a ground better than a wire. That’s why there is no ground wire on a hot wire kit and also why the engineers did not run ground wires from the factory.

I'm assuming you're referring to the strap from the firewall to the transmission bellhousing?

 

[TurboBuRick]

Yes roger that. Bellhouse bolt or a intake bolt.

 

[Jerryl]

Or you can do what I did on the ground side of the circuit, and quit worrying . . .

Ran 10ga stranded copper (used through out this project) from pump hanger to firewall. All soldered connections.
Ran braided line from engine to firewall (Same bolt as 10ga)

Ran 10ga from hanger to frame.
Ran 10ga from frame to body.

Done. Hahahaha

 

[TurboBuRick]

Jerryl, not everyone has a rustbucket like you and Boost231 with no good metal to catch a ground.

I think you guys better run another ground wire back there just incase.. J/K

 

[Boost231]

We don't have rust. these Arizona cars have dry rot. Lol

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[TurboBuRick]

I know that LOL. Just poking fun