Needs ECM?

[88SubieSnack]

1988 SPFI

Crank no start condition.

Has code #14 stating fuel injector issue. The day this happened it ran fine three different times within the hour when moving for our plow guy. Then cranks but doesn't start to go to lunch. Found no injector noid light while cranking which points me to the ECM driver for the injector. Injector and ECM unplugged I have good continuity and 0.04 ohms of resistance. I am condemning the ECM at this time and would like your input on this. I feel certain.

Other Notes:

Before all this on the same day the engine died as I was turning my A/C on and then it restarted and fired. Not thinking much of it at the time. Then later to go to lunch, crank no start. I think that's a coincidence of me turning the A/C on and it dieing. A/C is a different circuit except for the signal to the ECM.

Engine will run good on supplemental fuel if I keep my foot on the throttle, atleast halfway.

Fuel injector resistance = <2.0 ohms

Direct fuel pressure = 50+ psi

Running fuel pressure = 40 psi

Timing = OK

Has great spark

My diagnosis points me to the ECM and I have heard they will fail. Identifix has a case on this for a vehicle with 230,000, I'm at 209,000. 

What do you think, any suggestions?

-Will

 

Edited January 12, 2022 by 88SubieSnack

[DaveT]

Fuel pressure should be 21PSI.  40 is way high.

You can check the injector -

Remove the intake boot so you can see the throttle plate.  Unplug the injector, and use wires / spare connector to make it easy to momentarily tap 12V from the battery across the 2 pins.    crank for a couple seconds to get fuel primed.  If the pump and regulator are good, it should hold for a few minutes.

The injector should click, and you should see fuel spray.  A pretty good blast. 

ECM fail.....  Of course, anything can fail.  I've been running these SPFI EA82s since about1992, and have never had an ECU failure.

I had a wire in the engine harness break, mid run, that intermittently disabled the IAC valve.  This caused a won't idle drive ability problem.  It would drive & run as long as I did not release the throttle completely.

 

[somick]

At the ECM connector try to find a wire that sends voltage to the injector and connect a test light to it.  If it lights it could be a broken wire like Dave mentioned.

 

Good luck,

Sam

[88SubieSnack]

Thanks Dave, I'll verify my fuel pressure readings again, however fuel pressure is plenty. I too might be skeptical about the ECM since it will run with my foot on it, but noid light will not light up... Idle control valve is good, has good continuity and is not shorted. 

More testing tonight after work.

[88SubieSnack]

I'll check that too Sam. Going to diagnose further tonight and I'll send an update.

Thanks!

[88SubieSnack]

Sam, I verified no voltage from ECM power supply to injector, pin 43 of F107 ECM connector. Injector has good ground, pin 48 of F107 ECM connector. Pointing back to my noid light not lighting up while cranking.

Would another component cause the loss of supply voltage?

Dave, fuel pressure is correct. I misread my notes from days past.

 

I have an ECM on the way.

Note:

I had a bad throttle position sensor prior which I have now replaced and adjusted to spec so I know that cannot contribute to a no start.

Thank you!

 

[DaveT]

There are 1 or 2 power wires to the ecu,  it would be good to check them.

[88SubieSnack]

Update:

Checked all power and ground wires to ECM and they're good. Checked multiple power and ground wires to vital sensors and they're good. Lab scoped the crank angle sensor and have a nice square wave, also lab scoped the throttle position sensor and have a nice cascading wave. All this just to confirm everything is in good working order. Still no power output to the injector except with my foot on the throttle, atleast halfway. Had a test light on the injector power supply circuit at the ECM and the light was very dim and fading as I let off the throttle, and brightened up attempting full throttle but it sure was sputtering. I am now convinced the ECM is failing/going bad/has failed. I got a new one coming and we'll see what happens, certain it'll run.

Thanks for the feedback! 

[GeneralDisorder]

Certainly possible. This is happening a LOT with 25+ year old electronics. My old loaner car was a '90 legacy that had about 6 codes that would never clear. We installed a LINK ECU and never had another issue. Car has 340k+ on it now. 

Aging electronics will continue to be an issue going forward. I would investigate and pursue any options for replacement NEW electronics. I know for a fact the LINK ECU's support the Subaru 360 optical distributor since it's identical to the Nissan 360 opto. 

GD

[88SubieSnack]

Well my ECM is good, everything is good actually! I found my fusible wire link corroded and hanging on by a single wire in the fuse block by the battery. And so I fixed it and BAM! He runs very well. I returned the ECM I bought too. Everything I tested proved the ECM was the culprit. Interestingly enough I measured voltage at both sides of that fusable link with my meter. However it wouldn't illuminate my test light. Anyways Yay! On to other Subaru things.