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Discussion Starter #1
Hey guys,
A couple of weeks ago while on the highway my girlfriends 1996 Outback (Auto, 2.5) slowly lost power and overheated. Popping the hood, revealed an empty radiator and a coolant reservoir full of delicious chocolatey milky oil and coolant, so we towed it home and I replaced the head gaskets.

The take apart and reassembly went pretty easily (tons of helpful posts and links :29: ) but when I got to the point where I was ready to start the engine it wouldn't fire. For reference, all parts were installed except for the lower air box, washer reservoir and belts on the accessories.

The first attempt at starting (and occasionally if the car has been left to sit for a day) resulted in a single backfire, with a slight sulphur odor and a little smoke drifting out the intake. The motor turns over normally, but there is no further sign of ignition.

My first suspicion was jumped timing, but I've verified that the cam sprocket double marks align, and the mark on the crank sprocket points to the notch on the crank sensor mount.

Compression is good on all four cylinders (~150 psi), and I get a solid spark from all coil terminals (wires and plugs were replaced). I've verified that fuel is being delivered to the rails by pulling the return line and turning the ignition on.

I've cleaned and reseated the grounds at the rear of the engine and on the intake manifold and rechecked all electrical (and vacuum) connections. I've been using a OBD2 scanner, and the ECU is reporting no faults. If I disconnect sensors (TPS, IAC for example) or fuel injectors it faults, as it does if I attempt to start the engine with either the cam or crank sensors disconnected. The position sensors appear to be working (generating measurable AC voltage, and not faulting).

Pulling the spark plugs shows them to be wet with fuel, but I haven't noticed much in the way of fuel odor from the exhaust. After work today I'm going to check for voltage at the injectors while cranking the engine.

One thing I did notice that disconnecting the MAP or AFM (and the vacuum solenoids located behind/beneath) does not result in a fault. Is that expected, or should I be looking into that?

I'm pretty stumped at this point, and hope that you might have some suggestions or Outback specific knowledge that could help get my girl's car back on the road (and me out of the doghouse.) Thanks in advance!
 

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back fires are usually a timing issue. but if you re sure you got it right...

did you get the fuel lines reconnected correctly? that will cause a no start situation.

did you disconnect the wire harness to the injectors?

try starting with the gas pedal to the floor.

try a little starting fluid.

read the codes.

install the entire air plenum, and filter.

look under the plastic intake plenum and double check the large 1 inch hose going to the IAC on the intake manifold, near the pcv valve.
 

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Discussion Starter #3
back fires are usually a timing issue. but if you re sure you got it right...

The marking are all looking good after many attempts to start. I'm going to pull a valve cover to recheck that he cams are installed in the proper location. I'm pretty sure they're all right, but I'm grasping at straws at this point.

did you get the fuel lines reconnected correctly? that will cause a no start situation.

I believe so. The top line on the fuel rail is connected to the fuel filter, and the middle line goes to the grey return line on the firewall, and the lowest, smallest line goes to a similar line on the firewall.

did you disconnect the wire harness to the injectors?

Yes, when the intake manifold was removed. It is now connected, and the OBD faults report correctly when each injector is disconnected.

try starting with the gas pedal to the floor.

No change.

try a little starting fluid.

I'll have to pick some up, but spraying carb cleaner into the manifold didn't result in any poping or signs of ignition.

read the codes.

The ECU doesn't throw any codes when all connectors are connected.

install the entire air plenum, and filter.

No change.

look under the plastic intake plenum and double check the large 1 inch hose going to the IAC on the intake manifold, near the pcv valve.

Connected with no signs of damage.
I'm really starting to suspect that the airflow metering system might be the culprit. It's obviously been replaced in the past (it's got salvage yard markings on it), and the ECU doesn't seem to notice when it's not connected. I've verified that it's getting 12v, but I want to bench test it.

Does anyone have pin-outs and expected resistances? And can anyone verify that the ECU should throw a code if the MAF connector is unplugged?
 

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Discussion Starter #4
Update: I just traced the MAF circuits back to the ECM. No shorts to ground, and good continuity.

Can anyone confirm or deny the following:

A disconnected MAF sensor should generate a P010X code.

The car should not run (no fuel injector pulse) without a MAF reading.
 

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Carb cleaner will help stall an engine, not help start it.

If the plugs have fuel on them it sounds like a spark issue, which would point to timing. Do not verify spark by holding the plug next to the exhaust manifold. You Errol get the smoke of your life. There is enough current running in there to kill someone.
 

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yes, if starting fluid does not get the engine to fire you have a spark issue.

you probably have the timing correct, but just for all the rookies, the ARROWS are not the timing marks. NOT the ARROWS, NEVER the ARROWS. the timing marks are the ''hash'' marks, the straight lines on the outer edge of the cams and on the ''tabs'' of the rear of the crank sprocket. these marks line it up correctly while all 4 pistons are at mid stroke. this eliminates any chance of piston / valve collision.

you can check the timing by lining up the arrows in the 12 oclock position, but you cannot see the marks on the crank sprocket with the crank pulley in the way. i don't think. (i usually paint a mark on the pulley when i have it off so i can check timing with the pulley on.)

if spark is the issue, is the crank sensor plugged in? crank controls spark, cam controls fuel.
is voltage getting to the coil? weak voltage may give a spark but not a strong enough one.

the front of the coil fires the front cylinders and the rear the back 2. the igniter feeds the coil in the same manner.

did you get the correct cam sprocket on the driver side? if you mixed them up it will never run. but i would also think it would never mis-fire. the lower cam sprockets, if DOHC, and the passenger side cam sprocket do not have the ''lugs'' / reluctors that the cam sensor is looking for.
 

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The poster did say that he has good compression. Compression numbers would be off if the timing was badly off.

If it were me at this point. I would pull the plugs and let them dry out. Then turn the motor over and blow out all fuel. Then try again.

Verify all plumping for the IAC is correct. Verify that temp sensor is connected.

Do you have access to a scanner?
 

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Discussion Starter #8
Okay, spent some more time on the car.

I am confident in the timing. The double marks on the intake and exhaust cam gears are pointing at each-other, and the crank sprocket arrow is pointing at the notch. All are spot on. I even pulled the valve covers, and and the cams (and corresponding sprockets) are installed in the proper locations.

Tried spraying starting fluid into the manifold (plenum pipe, MAF sensor and airbox removed) and attempted to start the car with the throttle closed and WFO. Besides the nice smell and slight buzz, nothing happened.

IAC plumbing looks good, and it was not removed from the intake manifold during the HG replacement. I'm going to check the voltage coming from the igniter in a minute, but I do get a solid blue spark when I ground a plug against the intake manifold.

But I'm still really concerned about the ECM and the MAF sensor. It doesn't produce a OBD fault if I disconnect the MAF connector, and if I short either of the signal pins to ground I don't get a fault either. This really doesn't seem right.
 

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Discussion Starter #10
Yeeeeeep. Just found a manual with better illustrations and came to that realization. Why two marks Subaru? Why? I'll put the timing belt back on tomorrow and see what happens.
 

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Discussion Starter #13
Okay, timing set on the correct mark, still not firing. Still wondering about the lack of fault codes when the MAF sensor (and pressure/switching solenoids behind it) is disconnected. Can anyone tell me if this is expected? Should the engine be able to start with the MAF sensor unplugged?
 

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I would now be worried about valve damange. Check your compression again.

Some cars will start without the MAF. It depends on the car.
 

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Discussion Starter #15
Getting ~150-175 PSI on all cylinders (rising on each subsequent test). Car also started tonight with starting fluid sprayed in the intake and ran for about 5 seconds (killed it b/c radiator is out and it's puking ATF.

Time to put the radiator back in and see what happens.
 
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