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'95 Legacy Intermittent Hot Start Problem


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My '95 Legacy 2.2 occasionally won't start after it's been driven.  Engine cranks ok, just doesn't fire.  Let it sit for up to 45 minutes, starts right up just like nothing was ever wrong.  It'll do this maybe once in 10 or 15 trips, hot or cold weather - same.  No CEL.  Coolant temp sensor, right?  Replaced it.  Same problem.  Next, following leads from my Subie guy and posts on numerous forums, swapped in another  ECM, then replaced the knock sensor, then swapped cam position sensor with my '97Outback hoping to transfer the problem to it.  Nope, still the Legacy.  I've checked spark and fuel delivery when it's doing it's no-starting thing and both OK.  Seems to be a common but elusive problem.  Any ideas?

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injector resistor on the passenger side firewall. the ceramic thingee in the aluminum housing. perhaps it is failing intermittently when hot. Just a hunch.

 

Also, there is an ignition amplifier module on the firewall. Although different than an ea82, this does happen with the ign amlifier on ea82's so the same logic can apply. Perhaps suspect this first. Good luck

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try swapping the crank sensor just to rule it and the cam sensor both out.

 

fuel pump?  they don't fail terribly often but hey it is 20 years old now.

test for fuel next time it does it.  either just pop the fuel hose in engine bay and see if anything comes out or rig up an actual fuel pressure gauge.

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It's probably the coil pack. Coils on most things (cars, boats, small engines, etc) fail in this fashion. A friend of mine just went through this on his forester.

Basically since it's mounted on top of the engine the hottest it gets is just after the engine is shut off. No more coolant flowing, so everything gets heat soaked under the hood and gets pretty hot. Coils generally fail because of heat related issues, so that's what I would have replaced first.

 

The other deceiving thing with a failing coil, sometimes you'll get weak spark, but it's not sparky enough to actually run an engine. It takes a much higher voltage to ionize compressed air/fuel than ambient air pressure.

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