legacycentral bbs

So everything is connected, bolted together, fluids where they should be.

Go to start the car and it turns over, i have no spark

I checked, rechecked and checked again. All the wiring i can clearly see is reconnected. What could cause the coil pack not to send spark?

-Brian

What exactly did you do with the engine?

The first thing I would do is check the fuses.

Does the Check Engine Light turn on when you first put the key in "ON" but before you start the car? If not, then the ECU's not getting power.

If the ECU is on but you have no spark, the first things to check are the cam sensor, crank sensor, ignitor, and coil pack.

I removed the motor to do the head gaskets

2 months later, its all back together.

I dont remember seeing the check engine light, i will check again as its not something I was paying attnetion to.

CEL does come on with the key. So i guess the ECU is getting the power it needs.

Im checking the .pdf version of the service manual, and the wiring diagram isnt much help to me.

I do know, there were 3 plugs on the backside of the motor, center near the throttle body. two were 3 spade plugs, one was a single spade plug.

When removing the motor, i failed to disconnect these 3, and I ended up ruining them. One of the 3 spade connecters just broke the locking tab. I now have it secured with a zip tie. The single spade connector tore from the wire, so I used a standard butt end connector and just reconnected them.

The third 3 spade connector was completely destroyed. the 3 wires comming from the harness side were exposed. I matched the colors and right now they are just connected to the pins in the engine side until I can find a better replacement. Im thinking these are the cam angle and crank sensors??

^^^Yes, the 2, three spade connectors are for the cam and crank sensors. The single wire is for the knock sensor.

Those 3-pin connectors are for the cam and crank sensors. If I remember right, the sensors have long wires permanently attached; you probably damaged one or both sensors when you yanked 'em, unfortunately.

If it's just one, checking the ECU trouble codes should tell you which one.

The single-pin connector is the knock sensor connector, I think. That wouldn't keep the car from starting.

This is why I wanted one of your scan tools Vik

I sure hope I didnt damage anything internal.

Well, you can read the trouble codes without a scan tool for now.

If you did damage one of the sensors it's not that big a deal -- just get a replacement. Maybe Frank can help you with that.

Im lookin at the wiring diagram and its not telling me which wires are which.

It labeles Y W B (yellow, white black i assume) however it doesnt tell me which wires do what.

I wanna be able to test the wiring to see if its getting a signal from the sensor.

The yellow wire is the shield, so look for a signal between the white and black wires.

But first check for ECU trouble codes.

Whats the "shield" do?

It's a metal braid that protects the signal wires from interference. It's grounded on the ECU end.

Vik...

I have the car wired for your laptop scan tool... and i have an old laptop that is setup with only the scan tool on it.

I dusted it off, and hooked it up. The scan tool recognized engine RPM when cranking the engine over. Does this work off the crank or cam sensor?

I dont have a multimeter at home, so this was just a quick test to see if the ECU is seeing any RPM, which indicates it does.

I was swapping the 3 loose wires around on the connector in every combination I could. A couple combinations the tach would just sit there and a couple the tach would kinda bounce when turning the engine over.

I'd like to check the ECU for errors, but i have a raging headache now, and i think im going to toss the towel in for the night.

Hm. I don't know whether the ECU would show nonzero RPM if the cam and crank sensors aren't both working. What does the ignition timing readout show?

It's possible the tachometer and RPM readout are just based on the crank angle sensor. I don't know.

Hope your head feels better. Drink lots of water and get lots of rest.

I checked all the variables with the scan tool, and everything reacted to the motor cranking over. Dont remember what the timing said, but it did retard timing (i wanna say something like 35 or 38 degree's).

I think it's supposed to be fixed at 10 degrees BTDC during cranking.

Ok so im at work talking to one of the mechanics I work with. He's gone thru training for auto's even tho we work on construction equipment... etc...

Anyhow, he was telling me that a car is able to run on only the crank sensor, and even if the cam sensor was disconnected the motor should still run, but would run like shit. From what he was saying, is vehicles are programmed to use the crank sensor for spark, and the cam sensor for timing. Mind you, he's never touched a subaru, so I can't put much truth to all this, but he has gone through more training than I so I cant call him a liar.

Is there any truth to this?

In theory I'd say that's more or less the truth, but I don't know how subarus are programmed, and if that'll work in practice.

Like Josh says, in principle it's possible for an engine to run without a camshaft position sensor. In fact, my roommate's 91 Escort doesn't have a cam position sensor at all. The crankshaft position sensor provides enough information because the ignition system uses waste spark.

However, our crank sensor doesn't actually provide quite enough information to run the engine, because it is rotationally symmetrical about 180 degrees of rotation. That would mean that there would be two possible positions of the crankshaft for any given reading.

It's theoretically possible for an ECU to make it work anyway by first trying one guess and then the other if the engine doesn't fire with the first one, but I don't believe our ECUs are that smart.

Did you ever check the trouble codes?

I printed out the trouble code chart, but havent checked yet. Dont have much time after work to work on the car (not to mention, after wrenching at work for 8 hours, the last thing I wanna do is come home and wrench some more)

I wanna check the ECU for codes, but I wanna replace that bad plug as well. This weekend I should be able to get to the junkyard and get that plug and I think i'll get an extra cam sensor as well just in case.

Big shocker here.... went and checked the codes and im getting 11: Crank Angle Sensor.

If i trace that wiring, the damaged connector is the one that leads to the crank sensor...

Guess i gotta just goto the yard and get the connector then try.

There ya go.

Just get the entire crank angle sensor -- a couple feet of wire and the connector are attached to it.

Yeah but it looks like that wiring is ran under the intake manifold. Im not about to pull the manifold to try and route that wiring.

Im sure the wire and sensor are fine. But I'll prolly grab it all from the JY while im there.

It's not as tight as it looks, just no room for your hands.

Tie a piece of wire or string to the broken connector. Unbolt and pull the sensor towards the front of the engine, pulling the string behind it. Once the connector clears the manfold and is free, untie that end of the string from your old sensor and tie it to the new one. Pull the far end of the string from the back of the engine to guide the new connector under the manifold. Patience and a bit of fiddling and you'll get it back in place. Bolt it down, plug it in and give her a whirl.

This my not work with a 'new' sensor that is really old. The wires will have taken a set and may not be flexable enough to snake back in.

Another tip is to wrap the string/connector joint in tape to smooth any edges out that may get hung up while removing or replacing it.

Good idea, thanks for the tip