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Questions and Answers

Toyota Truck Eats EFI Relays

Q. Hello, I have been battling a horrific electrical problem on my 1991 Toyota LandCruiser. It goes through EFI Main Relays like they were kleenex, especially lately. I read online that this is an inherent problem with some of the early FJ80 Cruisers since the wiring was too small of a gauge from the factory.

I came across this site (scroll to bottom of that site's page) that showed a similar situation... Tech Tips > July 2001. So I replaced the 5"-6" wiring that came from the harness with a 10 AWG wire, much beefier!

This seemed to solve my woes for about five weeks. Then once again, I'm blowing EFI Main relays once the vehicle is driven for longer than 15 minutes. The vehicle will crank strong, but won't start until I replace the Main relay with a new one. Then immediately it cranks. Lately I can't even drive to the supermarket without having a no start/dead relay when leaving market.

I read your article on how Hondas have some similar problems and prayed that you might be able to add some insight to my dilemma. What might be causing this overheating/resistance? Problem of the relays? Once a relay gets "fried", two of the contacts show signs of the overheating and the relay is toast.

ANY help would be much appreciated. I love the LC but I am seriously considering parting ways due to this one puzzling problem.

Thank You!
Frank

A. I don't know if this a chronic problem with this vehicle or not. According to Toyota, it's not. But in any case where a component is burning out in this manner, it's almost always due to a high current flow.

The EFI main relay serves as a source of battery power for several components including the Circuit Opening Relay, (which powers the fuel pump), the fuel pressure up VSV and the ECU. So any one of these components could be drawing higher than normal current and causing the EFI relay to burn out.

That yellow/red wire, pin 4, that they refer to goes to, according to my wiring diagrams, the ECU, Circuit Opening Relay and the check connector. Power from the battery comes in from the red/yellow wire at pin 2. The activation signal comes from the ECU to pin 3, red wire, then to ground through the brown wire at pin 1. So I would have to guess that the fuel pump is the critter that's drawing too much current. I think the best way to test this theory is to bypass the EFI Main Relay and Circuit Opening Relay. Run a wire from the battery to the fuel pump with an inline 15 amp fuse and run the car like this. If the EFI Main Relay doesn't burn up, you know for sure it's the fuel pump. Keep in mind that the fuel pump will run all the time wired like this, so you will have to disconnect it when stopped.

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