Hello everybody.My sons 87 4Runner will not start. I have put a noide light on the injectors harness and there is no pulse. It flashes a trouble code 4. The book says it is the water thermal sensor. Will this interfere. The book says the computer has to have sensor signal input for it to work. The wiring diagrams show inputs but I don't know if it is a signal voltage or battery voltage. PLEASE HELP. If my computer is bad ,does any YOTA guys have an extra you don't need????????????? JIM

 

The thermal sensor tells the computer if the engine is warm or cold. if its bad it can make your truck very hard to start or not start at all, i have no idea how to test the thermal sensor, but if you need to replace it you can get one at partstrain.com for 117.00 dollars.

 

how bout the EFI fuse?

just throw'n out possibilities...

 

If your talking about the ECT (engine coolant temp sensor) then just unhook it and the computer will think its -20 and run full rich. This might help
http://personal.utulsa.edu/~nathan-b...40engineco.pdf

Also I checked kragens website and it shows ECT sensors for around 30 dollars.

 

Don't mess with the ECT sensor if you don't have injector pulse. It won't make a difference.

When you used the test light, did you put it across the injector terminals? IE - unplugged the injector, cranked the motor, and didn't see it pulse?

Next test:
With the ignition on (not running/cranking) test between one terminal of the injector pig tail and ground. One of the terminals (test both) should indicate 12v.

If not, you've got a current supply problem - probably EFI fuse.

If you have 12v, you have a trigger problem, probably ignition related. Start with the distributor pick up.

What's the history on the truck? Was it running and just died or were you guys working on it?

 

I checked with multimeter and I have injector pulse. I have a code 7 and 11.TPS I pulled EFI fuse but they will not reset???????????????