Fuel pump issues

Hello, i am working on a 2013 Toyota Tacoma Sport v6 fuel pump and have ran into a couple issues. i have tested the fuel pump and it turns on when connect to 12 VDC. when connected to the wire harness i get 10.53VDC to the pump. (through the harness into the pump). my question is what else could i try to get that pump working. when cranking the truck it provides the power needed but does not turn on.
thank you

 

Have you verified the chassis ground near the fuel pump is in good condition? If the pump comes on with an external power source and not when you plug it in to the harness, my guess is you have high resistance, or a complete break somewhere.

 

Voltage drops are normal due to wiring length and various induced resistances like corrosion.

How are the battery terminals?

 

I verified the ground and was getting 0.3ohms. Witch is normal for grounding.

for the voltage drops i understand that and that’s why I’m confused as to why the pump will not start. But the battery is brand new i replaced it 2 weeks ago thinking that was the issue not the fuel pump

 

How do you know the fuel pump is an issue? Have you checked fuel pressure at the engine with a gauge?

 

I'm assuming you are checking the voltage at the fuel pump connection. Correct me if I'm wrong.

If you have 10.53 volts at the connection to the fuel pump and a good ground there is no reason for it to not run.

As a quick test you could squirt starting fluid into the intake for a short burst to see it it will crank.

Bypass the connector for the Fuel Pump Resistor ( in front of the battery ) with a shorting clip or wire and see if that is the issue.

 

That’s correct about the voltage. I did spray some starting fluid and the engine kicked over. Witch lead me to start with the fuel pump. I am reading the 10.53 volts at both the harness from the truck and the wires internal to the fuel pump. The thing is it should be starting the pump and it’s not. I have tried 3 pumps in there today alone one from rock auto one from Napa and the original that i though needed replaced. All work when connected directly to the battery with wires but not with the harness

 

Did you bypass the Fuel Pump Resistor?

 

Ya that's what I would put my money on now. Kinda goes back to my first reply

 

I didn’t. I’ll give that a try

 

I tried to bypass the resistor but the truck still did not start. Would i need some kind of resistance to start the truck or will the jumper be enough to start the fuel pump?

 

The jumper inserted on the harness connector just bypasses the resistor all together. It should work and the pump should run at high speed with the jumper in place barring there are any other problems.

This test just eliminates the resistor being a problem or not. If you bypassed the resistor and the condition did not go away then the resistor is not the problem.

 

I would start looking at the ground connections since you are getting 10.53 volts to the pump and it still doesn't run.

 

Load test both the power and ground circuits to the fuel pump. Checking voltage with a meter, and Ohm testing with a meter, can lead to false positive results. A single strand could be all that's connecting the circuit and it could pass.

Dig out an incandescent headlamp bulb (Not a LED, no power probes either) and use that to test both power and ground. A typical 55W bulb is ~4.5A on a 12V circuit, plenty safe for testing and to confirm a circuits integrity. If it doesn't light up bright, the circuit is compromised.