# Car will turn over but not start! fuel good w/ spark



## richvass (Dec 3, 2009)

Hey guys,
I have a z24 1991, auto with 356000 kms on it. She has a v6 multi-port engine.

Brief History:
She was running pretty well, except when I tapped the gas when idling...she'd drop a little and then ran like nothing was wrong. I'm pretty sure its jst a dirty Throttle Body, which I was planning to clean anyway.
Recently, I also cleaned the Mass Airflow Sensor because it was acting up a little during idle.

Problem:
Now, she will turn over but will not start. I was sitting in a parking lot with a friend for about an hour when all of a sudden it jst died. No sputtering or any other signs that she was going to go dead. RPM gauge jst dropped and I couldn't start her again.
Actually after about 20 minutes, I tried and it started for half a second before it died again.

Fuel Pump is working (I hear humming) and there is fuel on the fuel rails. I haven't had a chance to test exact pressure, because it almost got me in the eye from the port so I assumed pressure was OK. I also didn't want to invest 80 bucks in a gauge before I got the smaller things out of the way. And I never saw any symptoms of the fuel pump going bad, since it cut out without a warning. This leads me to assume it was a crucial sensor, relay, fuse or something electrical (correct me if I'm wrong).

I have spark on all 6 plugs...nice white/blue sparks. When I spray Quickstart into the throttle body, it will run until I stop spraying. So again...I'm assuming compression is alright.

I also have 12V to the Injectors (both connections) and the Resistance on the Injectors checks out. 

ECM: I changed around with an 89 beretta that I know was running fine and that didn't help either. So I'm assuming my ECM is still good.

Possible Problems:
-Crankshaft position sensor: after battling with it for some time, I was able to remove it. The sensor had cracks along the side. I'm waiting to pick up a new one to make sure that isn't the problem. Some say that if the Crank Sensor is bad, I wouldn't be getting sparks either. Others are saying that they had same problems, and replacing it helped. Which is true and has anyone had similar experiences?

Bad Ground:
Could it jst be a bad Ground? (to the ecm? and how might I check that?)

Anything else:
Are there any sensors that might be obvious to anyone, that the ECM needs to send an ignition pulse and might fit what happened to my car? Oil Pressure sensor and Coolant Temp Sensor?

I would really appreciate any help.
Thanks in advance.


----------



## octaneman (May 13, 2009)

Hi richvass

The crank sensor has gone bad when there are signs of damage are present on the sensor. The computer does not know when the piston is at TDC on the power stroke so the engine will not start. Replace the crank sensor and attempt a re-start.


post back your findings.


----------



## richvass (Dec 3, 2009)

Here is the funny part. Replaced the Crank Sensor. Tried to start it for a second with no success, then remembered that I had unplugged the knock sensor to gain access. Then noticed that I had broken the plug so I still kinda forced it in so it would make a connection.
Then I attached a make shift noid light to one of the injector plugs (ie a 12V brake like, one connector going to the pink and one grounded to the block) and had replaced the battery, because the other one had drained on me...and voila, it started. Was idling rough and lacking power (which I assumed was the knock sensor connection), but more importantly the check engine light came back on.

I drove it all day around town to pick up a pigtail for the knock sensor to replace. When I got home in my drive-way...same problem. It suddenly jst died as if I turned the key 'off'! Couldn't get her working and was back at square one.

I believe that the key to my problem lies in the Check Engine light going on and off. When the car ran for the day...the light was on and gave me 'bad knock sensor' code. Now, the light doesn't come on and I can't diagnose using the ECM stored codes.

Since the Check Engine doesn't come on, I'm guessing the ECM isn't really getting power. Could it be a ground that is causing the ECM not to send Injection Pulse? Did I maybe give it proper ground for a second with my jury-rigged noid light, which made it work for a little bit? (same trick doesn't work anymore)


----------



## octaneman (May 13, 2009)

The injector pulse is controlled by the computer, you grounded your make shift noid light to the chassy and this was a mistake for it has shorted out the computer injector circuit. The pulse is switching action done by the PROM's oscillator not by grounding the signal, you will have to check your fuses to the ECM because the check engine light runs off the fuse box. Replace any burned out fuses. If your check engine light comes back on remove the codes and please post them. If your fuses check out OK and you're still not getting pulse width, then the computer will have to be replaced along with the knock sensor.


----------



## richvass (Dec 3, 2009)

Thank you soo much for your input!

My questions is, would I still be getting power to the injectors if I shorted out the ECM itself, would I still be getting power to my Injectors?

And I will replace the ECM, because I have an 89 beretta which does work with the same ECM. Jst going to switch out the PROMs. 

But when I checked both connections with my multi-meter grounded on the Chassy...I have 12V running to both. When I plug in my "noid" light into either connection, it glows bright.
So does the ECM have the circuit grounded at all times and takes away ground when pulsing the Injectors? or does it only ground the connection when it pulses the injectors?


----------



## richvass (Dec 3, 2009)

Honestly, I was in denial. But changing the ECM from my beretta and swapping out the PROM helped. Its running really well now.

I did notice something else though which brings me back to maybe a bad ground or connection:
I was sitting at the intersection with my left signal light on...and noticed that when the light came on...rpm would jump maybe 100 rpms and drop as soon as the light was out. It would jump to the same rythm as the signal light. Very strange.

Thank you again for all your help!!! I can only hope that this thread will be useful to someone else out there. And having ALLDATAdiy....jst amazing!


----------

