legacycentral bbs

This is a 1990 DOHC. US spec. It just started misfiring on the freeway, cut out and never started again.

12v at positive wire to coils. No voltage on either signal wire to the coil.

No signal from ECU to ignitor. No spark at plugs. Grounded out a spare plug, screw driver, and wire and never got spark.

Fuel pump sees 12v (turns on in key pos. 2) but sees only 9v on and off during cranking. It goes back and fourth 0-9v at equal intervals with the fuel pump relay clicking on and off...

I havent checked the codes since I havent learned how yet. I pulled the positive cable off the battery to reset the ECU and still no start. I probably erased any codes doing this, right?

I have 12v coming off both the yellow/red wires on the ignition relay.

The tachometer does not move during cranking. Normal?

How would you guys go about diagnosing this prob?

Your first sentance has me confused. I dont even think there were any subaru's sold in america in '90 with DOHC heads let alone a legacy.

Well, its a 16v. I guess there is only one cam per head come to think of it. I just got thrown off because my haynes manual specifies there is a dohc, sohc, and turbo.

Got any tips on why the igntion isnt working? Or if the fuel pump relay should be going on off during cranking.

ah I see. No idea about the starting stuff not too good with that. I'm only here for symantical errors

It sounds like maybe either your crankshaft angle sensor or camshaft angle sensor (or both) stopped working.

The fuel pump turning on and off sounds like what happens in test mode (when the green connectors under the dash are connected). Do other relays and solenoids click on and off repeatedly as well?

The check mode connectors are all disconnected. There are 2 green and 2 gray right?

I wouldnt be surprised if its the crank sensor. How do you test the cam and crank sensors? They passed a resistance test. And I swear I got 1v on and off from the crank sensor, but its a little bit foggy right now. Either way....please let me in on where to get them cheap in case I need them.

The igniton relay stays steady. What other relays/solenoids are you referring to?

Does anybody have a wiring diagram for the TCU? I need to check something on there too.

Thanks

There is a mating pair of green connectors (test mode) and black connectors (read memory):

http://www.surrealmirage.com/subaru/engine.html

You need an oscilloscope to properly evaluate the signals coming from the sensors. With just a voltmeter all you can do is look for oscillating signals as the engine is cranked.

Your best bet for cheap replacement sensors would be a junkyard, I think.

In test mode the ECU should cycle the fuel pump relay, the radiator fan relay, the IAC valve, the A/C cut relay, etc.

This might help with the TCU stuff:

http://www.main.experiencetherave...TCU_I-O_page1.jpg
http://www.main.experiencetherave...TCU_I-O_page2.jpg

pics of the connectors

http://www.main.experiencetherave.com:8 ... cuhide.jpg