Compression, spark, and fuel still no start
 

I bought this car in a non running condition. It needed a starter cause the old one was burnt up.

2007 CTS 2.8 first timing chain style.


I replaced the started and it would try to start but wouldn't. I checked compression at cylinder 3 and 6 and both was around 60 psi. I tore into it and found what I thought was the timing being off but now I'm not so sure. There's new head gaskets and the cylinders were horrible soaked in fuel. None the less long story short I put a new timing assembly on and added a little oil and I have between 120 and 140 on all 6 cylinders.

When cranking my scan tool shows roughly 150 rpm without injector pulse and when I have everything together when I first try to start the car my rpms will jump up to 350-450 area and then quickly dies back down to around 270.


To me it's like the ignition system is possibly working correctly only for the first few cranks. and then dies out. Cause when I graph it the jumps are like 150, 250, 350 and then bounces between 250 and 280. Like it hit for 3 cylinders and then doesn't anymore.


I have a crank sensor on it's way but has anyone experienced this? I'm wondering if it's the ecm or if it needs reprogrammed or what.

Just hoping someone has experienced this.

anybody know what the cranking rpms should be?

no plugs showed 202 rpm. Fully charged 2 month old battery and new starter.

Thanks for the help guys.

Jeremy

Codes? Fuel pressure? Injector pulse? What is battery voltage when engine is cranking? since it not very old it should stay over 10.5 volts. Will it start or "hit" if you spray ether, silicone, WD40 in air intake? if it does it should be fuel related. Because of multiple coils and modules you should use spark tester to verify spark on both banks. If you have rpm signal at PCM crank sensor maybe ok.

The car has a brand new battery brand new starter and battery charger on it to make sure it was fully charged. It cranks over fast like it should spark plugs are wet it's trying to start but acts like timing. Sprain ether does absolutely nothing. If anything floods it out. I'm getting fuel and spraying ether doesn't help so I haven't bothered with checking fuel pressure and the plugs are wet so no need to check injector pulse. What's the odds that the crank sensor is only picking up half of the signal or partial or could it be the ECM not doing it correctly

this post doesn't exactly match first one. If fuel pressure is too low there won't be enough fuel to start, yet enough to foul plugs. there should be a code stored if crank sensor comes and goes. You could re-check timing chain install. Cam sensor could cause no start it signals where #1 TDC is for ignition and injection timing. It also can set code

How does it not match. Both times I've said that plugs are wet and ether doesn't help. So it's not a fuel issue.

I'm 90% sure it's ignition system. I'm the 3rd guy to work on it cause the first 2 couldn't figure it out.

At this point I'm leaning towards a ecm or reprogram but I don't want to just throw money around.

Also correct me if I'm wrong. If my timing was off wouldn't the ecm pick up the mismatch cam timing since it has 4 cam sensors and throw a code.

Secondly if I was off on my timing I'd have no compression. 120 to 140 psi. And my leak down test shoes air moving past my rings. Into the block. I'm hoping they will reseat properly when it fires or warms up since I'm doing a test on a engine that has been fuel washed 100+ times and cold.

How does it not match. Both times I've said that plugs are wet and ether doesn't help. So it's not a fuel issue.

I'm 90% sure it's ignition system. I'm the 3rd guy to work on it cause the first 2 couldn't figure it out.

At this point I'm leaning towards a ecm or reprogram but I don't want to just throw money around.

Also correct me if I'm wrong. If my timing was off wouldn't the ecm pick up the mismatch cam timing since it has 4 cam sensors and throw a code.

Secondly if I was off on my timing I'd have no compression. 120 to 140 psi. And my leak down test shoes air moving past my rings. Into the block. I'm hoping they will reseat properly when it fires or warms up since I'm doing a test on a engine that has been fuel washed 100+ times and cold.

Am I wrong for thinking my compression is/will be fine?

It seems there should be codes set, since there are not, There is a reflash for carbon and timing chain issues. The cam sensor will whether #1 or #4 is ready to fire. Ok you are # 3 so that means all the simple stuff should have been looked at and it's possible ecm has been reflashed. It also means you need to verify everything that may have been taken apart and put back together, including checking connectors and ground wires. I would run a leak down test on all cylinders since you posted engine had new head gaskets. It is a interference engine. You could swap a ecm from another 07 2.8 cts that will start and see if it will start. Technically it would need to programmed to the vehicle but to fire it off you should not. Here is a link to a TSB related to chains

https://www-odi.nhtsa.dot.gov/acms/c...52863-6133.PDF

Slowroll I think I found my issue. I just can't seem to find any data to back it up.

Crank position sensor is a 2 wire sensor. Gets power on one side and the other side is signal.

Wires are white and purple

I am getting 2.36 ​​​​​​volts on my white wire with ignition on and while cranking. I'm 99% sure that it's supposed to be a 5 volt reference.

Just like the tps map and other sensors.

So I believe my issue is the pcm not supplying enough voltage for a stable strong signal which would explain why I have felt it was a ignition issue.

Dealership said they couldn't find in the computer anywhere that specified what the voltage should be but he agreed it should be 5 volts

If you go to no start chart there should be a spec. You should not get a reading over 4.5 or below .05. When engine is cranking the interrupter is passing by sensor and signal is going high to low. Voltmeter will read an average voltage. There should be a pin out chart in the service information. it will have key off, key on, and cranking at the different pins.