LC100 won't crank - No power to the fuel pump (2 Viewers)
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It has been mentioned about the efi relay. If your check engine light is working and the security light goes out when inserting the key, then it's safe to say the efi relay is working. You could always check to confirm 12 volts coming out of the relay in case you have a voltage drop.
If you're not getting any faults then move to the fuel pump control circuit.
Today, while running some diag on another matter today it led me to run some voltage checks on the fuel pump/ecu circuit. Not sure if you are aware that there is a fuel pump ecu in the interior left rear quarter behind the trim panel next to the tail light housing and bottle jack. This circuit is fed thru thr efi relay and sends the signal to the pump, and main ecm.
There are 5 wires from the harness to the pump ecu. Disconnect the harness at ecu to test the following and follow the voltage checks on pages 315-318 in the repair manual.
Black-white = ground
Black-yellow = B+ 12 volts main power (efi relay)
Black-red = fuel pump -
Black = fuel pump +
Green-white = fuel pump control switch (inertia switch)
Green-red = DI fuel pump control at ecm
Sadly I wrote these down from memory after spending a lot of time working thru the manuals and the meter.
In my case, my pump was locked up and had high resistance (3.7 k ohms) between pump pos and pump neg.
You have confirmed your pump is working but you may find the problem elsewhere in the control circuit by running the above checks.
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You can pull the rear seat and carpet and energize the pump directly - at the pump. Unless it was corrected, the 2000 model year FSM has the polarity backwards for applying voltage to the pump.
You are correct, I wrote it incorrectly. The bk-rd is negative and the bk is positive.
Every other bk-rd wire in the loom is positive, don't know why Toyota decided to change it for the pump.
The pump can also be energized from the fuel pump ecu connector. I found it easier and also since I was already there metering the rest of the circuit. You don't have to remove the entire panel. Just pop the panel off at the rear to access the ecu. I removed the 2 bolts to the ecu so I could feed it thru the jack access panel, made it very easy to meter the harness.
cbbr
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- Thread starter
- #26
Thanks - I already energized the pump directly from the battery to do a pressure test and rule out a bad pump. It is fine. And I jumped the relay, so that's ruled out. I need to energize the pump from the engine bay if possible so I can look for line breaks/shorts. I appear to have either an electrical break/short/ground issue or an ECU issue. At least that's what I think. ECU & electrical issues are a real blind spot for me - I have zero experience with them.
The reason I suggested throwing a meter on the fuel pump ecu is because it will check the entire circuit, from the ecu, efi relay, fuel pump switch, ecm, and the entire harness in between the modules.
Does the fuel level gauge work? On my 01 tundra, I ran out of gas once and the ecu killed the pump to stop it running while dry.
Sean
Sean
You may find some useful info here.
forum.ih8mud.com
Fuel gauge with full tank reading empty/ flashing low fuel light. Engine dyes two miles later.
99 100 series new fuel pump for E85 fuel two months old. No previous issues… Stop for gas 1/2 tank, top off and leave. Fuel gauge reading full then went empty and low fuel light was flashing… so odd. Stop / shut down restart and same fuel gauge go up, then down and low fuel light flashing. Ok...
forum.ih8mud.com
The connectors must be in place and metered from the back side.
Don't recall what E9(20) is but Conn A5(31) is a ground.
I do know the E9(20) is not related to the fuel pump circuit, if that's what you're hunting for.
What is it you're after by pinning those two wires?
Don't recall what E9(20) is but Conn A5(31) is a ground.
I do know the E9(20) is not related to the fuel pump circuit, if that's what you're hunting for.
What is it you're after by pinning those two wires?
cbbr
SILVER Star
- Thread starter
- #34
I have the Fuel ECU out and have metered a few wires from the harness. The battery (as a check) is at 12.24V. Black-White to Black Yellow is 12V. Black -Yellow to Body is also 12V (expected). I don't have anyone to turn the key, so more later.
After reading what @kevgentile wrote above, I tested the resistance between Black-Red and Black at the harness and got 4.17 K Ohms. That confuses me as you said that your pump was locked up. When I ran a line from the battery directly to the pump, the pressure at the rail was 45psi, so the pump worked that way.
After reading what @kevgentile wrote above, I tested the resistance between Black-Red and Black at the harness and got 4.17 K Ohms. That confuses me as you said that your pump was locked up. When I ran a line from the battery directly to the pump, the pressure at the rail was 45psi, so the pump worked that way.
cbbr
SILVER Star
- Thread starter
- #36
Those reading didn't sound right... So remembering @SteveH reply above, I started looking at the wire under the rear drivers door. When I unplugged the harness there, 289K miles of crap dropped out. A little electrical cleaner later, the resistance is 1.3 ohms at the ECU harness and the truck fired right up. Success!
Thanks to all of you for putting up with my complete incompetence and continuing t help me through this process. Now for mods that I understand...
Thanks to all of you for putting up with my complete incompetence and continuing t help me through this process. Now for mods that I understand...
Good Job!
That's why I mentioned checking everything back at the pump ecu. It allows you to check the entire circuit. The high resistance you measured on the pump side was an indicator that there was an issue with either the pump or the harness. Because you verified the pump was operational that only leaves the harness.
In my situation, I jumped my pump at the ecu connector and had no pump activity.
