Working with a 93 LS400;
When I try to start the car it does not even try to fire. So I leave the key in the start position, then go to the EFI Relay under the hood and tap the top of it ( EFI relay ) and you can hear a noise under the plastic TRAC cover like something just powers up. I put my hand back on a round componet with a few wires going into it and I can feel that is what powers up. Not sure what that componet is. Then it will start up everytime and runs great. Shut it off and have to do over again everytime.
I took out the fuse/relay block and dissembled it only to find everything is making good connections.
If I wiggle the top of the EFI relay versus tapping the top of relay still won't start; only starts by tapping the top of relay.
Bought a new relay; same problem.
Any body have any ideas?
Many thanks in advance.

 

You need a wiring diagram, back probe that relay to look for volts coming out of that relay after its been energized. It sounds like you might have a connection issue or high ohms in the wire that supplying your EFI. You state that once you tap it the car runs? and wiggling the relay doesnt allow the vehicle to run. One more thing have you done any electrical work to the car?

 

thanks for the response.
I will back probe the relay.
I have not done any electricial work lately.

 

hope this helps. this one is for a 91 ls400, but i think it's the same.

PURPOSE
The EFI main relay controls the ECU power supply.

LOCATION
Located in the relay box on the left side of the engine compartment.

OPERATION
When the ignition switch is turned to the ON position, the relay coil is energized. When powered the relay contacts close, sending battery voltage to ECU terminals +B and +B1.