No power to fuel pump

How would i check this?

 

https://www.engine-codes.com/p0450_toyota.html

 

Substitute a load for the pump. I would use a headlight bulb. Connect one side to battery positive and the other side to the fuel pump ground circuit and see if it lights up bright. You can then test the voltage difference between the ground and battery ground post.

 

Relay is in the area you mention

If you have been running the pump at that low voltage quite possible it burnt up from being run under voltage.

Gotta find the cause of the low voltage first .

 

That is interesting My EWD does not show that relay Must have done away by 2000

 

Say i did short the wires/fuse/relay. Would i need a new electrical harness from the ecu?

 

Only if The Fire Company showed up at that point a wiring harness is not a issue Fire Sale

Look for melted insulation melted connectors and plugs

If you put 12 VDC into the circuit and by passed the Circuit protection caused a short or had a short wires will be hot till one burns through and opens the circuit We would all Hope the circuit opens before the Truck catches fire.

Best answer it is possible!!

 

Sorry confused on whatbyou mean by fire sale. Are you saying the only way harness is f***ed is when it catches fire?

 

Close Enough

 

Sounds like several different problems in this thread. Fuel pumps have built in check valves so that 1) that later model Toyota engines where the circuit opening relay is controlled by the ECU will start on existing fuel pressure really before the fuel pump starts pumping. &
2) so that fuel doesn't drain back into the tank ( fuel system loses it's prime) if the vehicle sits for any length of time. That sounds like what is happening in a couple of above mentioned problems. Lower voltage on a fuel pump will not hurt it...early Tundra's and Lexus' used resistors with a relay to slow down the rpm of the fuel pump to lower fuel pressure when the engine didn't need full pressure. Today these vehicles use a separate fuel pump ECU to control this.
Also when troubleshooting electrical problems...broken wires can still give voltage readings, but will not carry current. For example if a wire has 12 strands, but 11 are broken, you will still get a voltage reading even though that one strand won't carry the current required by a curcuit.

 

If you want to try to bypass it just to be able to drive places, there's a wire under the driver side step plate you can splice into +12V. I can take mine off for a pic if wanted

 

Was this problem ever found? I have a 2004 3.4 that is doing the same thing. 12 volts going through the c/open relay and 4.5 volts at the pump.

 

Welcome to TacomaWorld
OP logged out 6 years ago but fixed it
https://www.tacomaworld.com/threads/no-power-to-fuel-pump.289927/#post-7271737
If you're asking another member tag the name
@jcp09

 

Was the problem ever found I have a 1997 Tacoma 2.7 voltage drop at the under dash relay