88 harness in 89

[khriz_mk3]

I have a 89 supra turbo and had a new engine installed in it and now it starts but wont stay on it turns out i need a new wire harness. someone told me the harness from an 88 will work if i change the ecu as well. i wanted to know if this would really work or not. really want my supra to run so please need help

[Supra_Freak_7m]

Before embarking on serious changes to your cars wiring. Would you mind providing more info as to why you feel you need a new harness?? i.e. lots of splices, wrong harness for the engine

Also, Would you mind elaborating on the source of this "new" engine. Is it from a different car? Is it a JDM Engine? Is it the original engine that has been rebuilt?



As for the original question, More than likely not. The reason being, the multitude of harnesses used in 89 cars. As far as ECU to Engine. There are no problems. There are several plugs on the ENGINE side of the harness that don't plug into the ECU. These plugs attach to the CAR HARNESS.


Most notable of these is the B1 Plug. It is the largest of plugs that DON'T plug into the ECU. This connector goes from the ENGINE HARNESS to the CAR HARNESS. It has numerous important connections such as the ignition switch, starter solenoid wire, gauges, and other such dash related stuff.

A Comparison of pre and post 89 connectors.

http://members.shaw.ca/boltz/7MGTE-S...TE,%205MGE.htm

Now, here is where it gets tricky. An 88 harness B1 Plug may plug right into an early 89 CAR harness, however, I don't think the wire functions match up 100%. I put an early 89 harness into my 87 car and had to change 2 wires and everything else was golden. A later 89 harness would require much more significant modification to make work to the point of chopping the whole B1 plug and re-doing the whole plug.

Step 1: With the battery disconnected. Place your 88 harness in the passenger floorboard. Try to plug your 88 Engine Harness B1 plug in to your 89 Car's Dash harness. If it slides right in and clicks. You may be able to de-pin a couple of wires and move them in the plug to make things work correctly. If the plugs are not compatible. I suggest you find an alternate 89 harness as the differences will be significant.

[khriz_mk3]

Its a JDM engine. I've had multiple mechanic's tell me its the wire harness. That is there is no pulse in the injectors. They say the harness it has now has been cut too much and has too many plugs missing.

[btwilson86]

No pulse to injectors could be a faulty (or missing) injector resistor pack. Make sure that the metal box next to the drivers side strut tower is plugged in to the wiring harness.

Have you pulled your engine codes yet? Even if the lights off, codes may be stored in the computer that could help diagnose the problem. I personally think a bad harness is a long shot, especially since the car will temporarily run

[khriz_mk3]

That's the small grey box right? It starts up if you inject starter fluid in it. However as soon as you stop the car stops. The mechanic said it was the harness that was missing a lot of sensor plugs which is why the injectors don't work.

[btwilson86]

Yeah, it should be a small gray metal box with a round yellow connector. There's a similar box on the passenger side fender- that's the fuel pump relay. Your engine harness may have gray plugs that connect to those.

If you put a jumper wire between the B+ and FP terminals in the diagnostic box (by the fuse box behind the battery) and turn the key on, do you hear fuel running through the fuel rail?

When you say its missing sensor connectors, are they still connected some way to the sensors or are the wires not connected at all?

Do you have a JDM harness on your engine or a US harness?

What ECU are you using?