1994 N/A Legacy Intermittent Starting Problem

[Jessekrs123]

Okay, so I am really becoming frustrated with my car, and I am beginning to miss school because it will not start sometimes.

I sometimes fail to get spark. The car will crank but it fails to get spark so no start.

Sometimes the car starts right up, no problems. Once I get the car started, it will not stall or anything. I've driven it for over 1 hour after I got it started up and it never randomly lost spark.

I have power going to all of the following ignition components with the key 'on':
- Igniter
- Coil

I do not have power going to all of the following ignition components with the key 'on':
- Crank position sensor
- Cam position sensor

I am not getting a CEL, because from what I understand, the CEL for either sensor is only tripped if it is receiving a signal from the other sensor. And in my case, both sensors are not getting power, so there is no signal to set off the CEL.

I have checked all fuses, they are all good.

I had to move my ECU ground from the rocker cover to the intake manifold, but that ground checks out good, plus I have a wire from the negative battery terminal going to the ground.

I checked and made sure that the connectors for the crank and cam sensors are grounded, they are grounded properly.

I am next going to check continuity between the sensor's connectors and the ECU.

Something funny that I have noticed is that when my car will not get spark, when I unplug my IACV, I can hear the relays clicking and the injectors priming like I had just turned the car to on.

1. I understand that sometimes the ignition relay goes bad on these things, and I am wondering if a bad relay would have anything to do with not having power to my crank and cam sensors. Would a bad ignition relay only effect spark when starting or would it effect spark while running? Because once the car gets running, I do not lose spark.

2. I am pretty sure I should be getting power to the cam and crank sensors with the key on, what gives these sensors power?

This is becoming very frustrating, I am missing school and work because I cannot get this thing started sometimes.

Any help is greatly appreciated, I just want my car to start up and run every time I need it.

[Legacy777]

How are you testing for spark?

Have you pulled the plugs to verify whether there's fuel?

How long has the car been doing this? Has anything changed/been done recently as far as maintenance or other work?

Any other history would be helpful.

[Jessekrs123]

I test for spark by sticking a screw driver into the plug wire and putting the screw driver near some kind of metal. When I do test for spark when I am not getting any, spark seems to show up when the relays click.

There is most certainly fuel, no doubt about that. Fuel pump, injectors all prime. When I have no spark, I can smell fuel because there is no spark to burn it off.

It just started recently doing this, the car was running fine since August 20 when I grounded the ECU properly, now all of a sudden it is intermittently starting.

I recently put a new starter on after the other one died, that is not the cause of any problems because my car started fine after the new starter was put in.

I recently replaced the blower motor relay because my heat was intermittent, and that fixed my heat problem. When I was replacing the relay, I tested the connector that the relay goes into, and I had accidentally touched my test light to a 12v power on the connector and hit the side of the ECU at the same time, and it caused a spark. I ended up blowing out the 2 fuses for the blower motor, but even after that, the car had no problem starting.

What would cause my cam and crank sensors to not get any power? I am looking through my diagrams and all that it shows is that the two sensors tie into the MPFI system, it doesn't point out anything specific. Everything else checks out good with those sensors, the car runs SOMETIMES, and once it begins running, it does not stall or anything.

Also when this started happening, like I said before, when I unplugged the IACV, I can hear the relays clicking and injectors priming like I just turned the key to 'on'. For about 3 days, my car would only start if the IACV was unplugged, and once I got it running, I would plug the IACV back in and it would run fine. Now unplugging the IACV doesn't help.

[Legacy777]

You are not going to be able to get a voltage reading from the crank/cam sensors. These sensors are a reluctor type sensors, where a small voltage is created when the crank or cam gear/pulley passes by the sensor. You would need an oscilliscope to see the voltages from these sensors.

I'm not sure what to say about the IAC valve, it gets its power directly from the ignition relay. It's possible the ignition relay is worn and can only draw so much current through it, and won't allow enough current to be drawn through to start properly.

[Jessekrs123]

I will get a new relay and put it in and see what happens. I really hope this is the problem because I am at my breaking point.

[Jessekrs123]

I replaced the ignition relay and the cam position sensor and now all is working. I got the cam sensor for free so might as well put it on. Haven't had a problem since. Now the only sensor that hasn't been replaced - TPS. Wonder if that will be my next problem...

[Jessekrs123]

I hate to resurrect this thread, but I have yet again ran into the same problem. I have definitely traced the problem to the ignition relay or ECU.

I have checked the connector that connects into the relay, it is grounded and I am getting constant power to the yellow wires, and ignition 'on' power to the green wire. The ignition relay is brand new, and I am still failing to get spark.

Looking through my wiring diagrams, I noticed that there is a diode that goes from the ignition relay and it goes out to the starting/charging system, coil and ignitor. From what I have researched, diodes are made to send power in one direction, and some symptoms of failure include shorting out, and burning out which could cause intermittent problems. When failing to start, sometimes the ignitor would not be getting power.

All grounds check out, all of my circuits from the ECU to sensors are all closed, and still getting no spark.

Has anybody had a problem with this diode, or would you think that maybe my ECU is bad? If anyone has experience with this diode, please post. I am getting really tired of taking my dad's Jeep everywhere because my car will start only sometimes.

[Jessekrs123]

Bump, pleeeaaase somebody give me some input before I take a sledgehammer to this car.

[Jessekrs123]

I am pretty sure I just found the problem. My coil is bad. While testing the car would only start if ONLY the 2 spark plug wires in the front of the coil were plugged in. My problem was the coil that went to cylinder 4 was messing up, jumping spark everywhere, possibly to the other coils. I had an old coil from my old 93 wagon, put that on and the thing started right up.

I'll have to wait it out for a week or two with plenty of cold starts to see if this has fixed the problem. I am hoping that it did. I am testing out my bad coil right now to see if it is indeed bad.

[Legacy777]

Good to hear. Hope it is the coil and it's fixed.

[Jessekrs123]

Oh well, that fix lasted 1 day. The problem came back. If it comes to the point where I am going to have to go through all of my wiring, I am just going to drop an EG33 in and throw in the SVX ECU harness in there while looking for the culprit. I really cannot figure this out, I have been through everything I can think of regarding this problem.

[bry]

To me, it sounds like ECU is not reading voltage waveform from your inductive cam and crank sensors. The crank sensor is tied into both fuel (pump and injector pulse), and ignition timing. When it doesn't work, your car is completely dead. You might swap a low-buck ECU from a pick-a-part car and see if that cures the problem. Expansion and contraction due to temperature changes can cause varied contact in the electrical circuit.

Here is how to check voltage and ground at ECU:


Crank & Cam Sensor Test (cam is same as crank). Be sure to switch your voltmeter to AC. Note that you will only get a voltage if the engine is cranking or running:


Coil & Igniter Test:


ECU Voltages For Various Sensors:


Trouble Codes:

[Jessekrs123]

Thanks, I have tested some of this stuff, but not all of it. I will go through it all again.

[beefwagon]

dude always checkwhat you first worked on go back to your ecu ground and double check that its still got a solid ground, maybe solder it or put in a self tapper into the body also go get a waste spark coil off of a 96 dodge neon it will increase performance and also gas mileage they can be had for cheap at the yard much cheaper than a new one

[mike-tracy]

dude always checkwhat you first worked on go back to your ecu ground and double check that its still got a solid ground, maybe solder it or put in a self tapper into the body also go get a waste spark coil off of a 96 dodge neon it will increase performance and also gas mileage they can be had for cheap at the yard much cheaper than a new one

Check the post date bro