big pop, no start

[ryan george]

A little history. 2 falls ago i popped my first head gasket after owning the car for 20+ years (no log, powerlogger didn't record the run). I run mid to high 20's for boost, so i don't baby it. That following spring i decided it was time to upgrade since the head gaskets needed replaced. Had Dan @ DLS rework the stock heads for a roller cam and do some cleaning up to the heads to get more flow (not a full port job, told him i wanted a mid 10 sec car so that's what he recommended). After a few problems with the install, I had the car back. Did the required break in time. Then, decided to run straight race fuel instead of alcohol as I didn't trust the alcohol system with the boost in the high 20's. This included a new chip from Eric at TT.

Was working on tuning (I'm not the greatest, admittedly, always fat,, haven't had help from anyone but I do try), starting with boost in the low 20's and working my way up. I had probably made 8 - 10 hard pulls up to about 105-110mph with no knock (none expected with the race fuel) over the course of having the car out 5 or so times (don't recall). I have also had an oil leak issue that coated the underneath of my car since the rebuild. Have not been able to trace it, but I think it's the breathers on the new head covers. I opened them slightly as a few directed on here, but to no avail. Recently, I cut them completely open as my others were, but with the car being down, no idea if that fixed the issue.

So...I have a buddy over helping me work on a shower and we get it done and since he's never been in the GN before (it doesn't get out much) I decided to take it out for a spin. It was running good. Launched hard on no or very little boost. Drag radials broke loose a little ways out then grabbed. Felt like they may have broken loose a little again. Then a big pop and the engine dies. I'm able to get it off the road and figured that my stupid up pipe had blown off, no big deal. Check, and it's on tight. Try cranking the car over and it cranks and cranks but nothing. Plug wires are connected. I have fuel pressure. ECM connections are tight. Cam sensor was suggested as another possibility, but I pulled the cover and it's tight. I just now (after probably 8-10 months) started to go down the no start tree on Steve's Vortex Buick site, but I don't have an injector test light (yet), so I thought i'd check on here to see if anyone quick ideas i can check. I did the spring oil change and just put in a new O2 sensor, but that's it so far.

Haven't done anything with the car for this long because I've been busy, but mainly really, really frustrated and disappointed. Just feels like ALOT more money pissed away for nothing. I've had the car for almost 25 years now and I unfortunately keep finding myself asking why I don't sell it. That sucks.

Appreciate suggestions. Thx.

 

[Chuck Leeper]

"Big pop", as in a backfire thru the intake??
Does the cam sensor rotate when cranking?
Timing chain?
Have you pulled the v covers?
Ckd the crank sensor?

 

[ryan george]

Something like that. Thought the uppipe blew off, definitely up front. No on other items. Some a bit beyond me but will research. Timing chain is new. Wouldn't know what to look for if I pulled the valve covers, to be honest. Glad you're back, and thanks.

 

[Chuck Leeper]

Thanks!
A look at the valves may show some bent push rods. [especially, if the chain took a dump.]
Take a look at the balancer. Is it tight? If the backfire was severe enough, the crank may have issues, thus the sensor could be affected.
When cranking, does it sound as tho the engine is "freewheeling"?? [No/low compression.]

 

[whitehot1]

I had a turbo regal do that before made a loud pop and the engine shut off would not restart, i got lucky since i had a crank sensor in the trunk with some other spare parts i carried around with me so i was able to replace it there on the side street. Not the best of working conditions laying in the grass on my back but it saved me a tow bill.

You can remove the cam sensor and look down in that hole it sits in and check the timing chain but you will have to reset the cam sensor when you reinstall it.

 

[ryan george]

Thanks!
A look at the valves may show some bent push rods. [especially, if the chain took a dump.]
Take a look at the balancer. Is it tight? If the backfire was severe enough, the crank may have issues, thus the sensor could be affected.
When cranking, does it sound as tho the engine is "freewheeling"?? [No/low compression.]

Will check on those items. Wifes bday so limited time today. Seems normal turning it over.

 

[pacecarta]

id check the cam sensor for spinning ,
take the cap off and grab the reluctor disc and see if it moves , it shouldnt but my guess is it does now may have sheared the roll pin or the screw at the top loosened

 

[ryan george]

I had a turbo regal do that before made a loud pop and the engine shut off would not restart, i got lucky since i had a crank sensor in the trunk with some other spare parts i carried around with me so i was able to replace it there on the side street. Not the best of working conditions laying in the grass on my back but it saved me a tow bill.

You can remove the cam sensor and look down in that hole it sits in and check the timing chain but you will have to reset the cam sensor when you reinstall it.

Thanks, will search to see how to test the crank sensor.

 

[ryan george]

id check the cam sensor for spinning ,
take the cap off and grab the reluctor disc and see if it moves , it shouldnt but my guess is it does now may have sheared the roll pin or the screw at the top loosened

No, does not move, well, ever so slightly. Checked today. Thx.

 

[whitehot1]

Here is a quick troubleshooting method that may save you some time.

Long ago, Jim Testa posted a "How To" get started in the trouble shooting. It is well worth reading in order to apply some logic to the process.

Below is a short cut derived from Jim's article. The below simply applies logic to the No Start troubleshooting trees and can save you a lot of time.

If you have:

no spark, but have injector pulse - Check the Ignition Module (also check the CCCI and ECM-IGN fuses)

have spark, but don't have injector pulse - Check the Cam Sensor or ECM

have no spark or injector pulse - Check the Crank sensor or the Ignition Module (and fuses)

 

[ryan george]

It's taken me a bit to get back to you, but wanted to say thanks to you guys for the diagnostics suggestions. Turned out to be the crank sensor. It was totalled. Of those 3 'towers' on the sensor with the 2 slots in between, only 1 of the 'towers' was left and it was just dangling. Brian Lorenz also contacted me once he saw my thread and gave plenty of advice. Took me a bit to get it all figured out, but I learned something and did it myself, so all is good. Car fired up on 2nd crank after sitting since last summer. Again, thanks for the help...

Ryan