BIG No start problem, please help

[ZR1 MK]

Keep in mind, a proper spark is much harder to create under compression. At this stage, investigating Tylers senario may be the best thing to do.

[8upZR1]

I went through the diagnostic procedures that Tyler's pages outline. At least all of the ones that I could do without special equipment that I do not have, such as oscilloscope. The pages say that if spark is present then there is no reference signal from the ignition module and it must be replaced. I have tried a brand new in box, never used ignition module and no dice. My other ignition module only has about 10 hours of operation on it. I have noticed though, that when I try to start the car with the MSD hooked up, the light on the MSD indicates an interuppted signal. However, instead of staying on, the indicator begins to flash showing that the system is operating properly. I have checked for continuity between the ignition module wires and the ECU and everything looks good, all harness connections look solid. I noid lighted the injector harness and everything looks peachy there. I am dumbfounded, however leaning towards suspecting the ECU.

[Tyler Townsley]

Remeber less than 400 rpm all spark timing is done in the dis module. That was why I bought the tester. I already had an ecm I knew was good and it made no diference. If you are still stuck next week I can add a scope to the ISS tester and I have a good 90 ecm somewhere. Another thing to check is pull the eprom, clean the contacts. and make sure it is seated properly.

Tyler

[8upZR1]

But I am getting sparks, and I know that these modules are good, so I am thinking that the sparks are merely coming at the wrong time. The ECU apparently handles the advance so my guess is ECU. Maybe its just a chevy thing.

[Tyler Townsley]

Originally Posted by 8upZR1

But I am getting sparks, and I know that these modules are good, so I am thinking that the sparks are merely coming at the wrong time. The ECU apparently handles the advance so my guess is ECU. Maybe its just a chevy thing.

Not true. You need to read this page to understand the spark operqtion.

http://www.sirgalahad.org/tyler/prototype/page17.jpg

At start the ecm is signaling the dis to operate in bypass mode, which means the ecm is out of the loop. It would very unusal for you to have 2 bad dis modules but that is what happened to me. The one module would generate spark below 400 rpm but fall apart above that. Also check all your grounds especially those pretaining to the ecm ignition modules. Ohm them each to ground

Tyler

[Tyler Townsley]

This may help trouibleshoot the ecm:

http://www.sirgalahad.org/tyler/misc/90ecm1.jpg
http://www.sirgalahad.org/tyler/misc/90ecm2.jpg
http://www.sirgalahad.org/tyler/misc/90ecm157.jpg
http://www.sirgalahad.org/tyler/misc/90ecm158.jpg
http://www.sirgalahad.org/tyler/misc/90ecm159.jpg
http://www.sirgalahad.org/tyler/misc/90ecm160.jpg
http://www.sirgalahad.org/tyler/misc/90ecm161.jpg

Missing last page will post it when I get my trailer back.

Tyler

[Z Factor]

Originally Posted by 8upZR1

I am new to this site

Hello and welcome tp the forum.

I see you have been getting a lot of good advice as usual.

Nice posts TT, worthy of some reputation points.

[8upZR1]

Thankyou Tyler for the ECM diagnostic material. I will look it over tonight and hopefully put it to good use tomorrow.

I was wondering if by some cruel chance of fate, that my cam timing somehow slipped on one bank, that this could be the cause of my problem. I rechecked the timing when I was done torquing down the cam bolts but I am some how second guessing my work now. If one cam slipped on the sprocket say 50 degrees or so would the motor not start? Would the other side of the motor not operate correctly? If a cam slipped that much would I not have valve piston issues? I am absolutely positive that the cam timing is spot on and that it has not moved but this no start deal is driving an urge deep within me to tear the motor apart and double check just so that I can sleep more soundly. But then another part of me says I will commit suicide if I tear into the motor, find the cam timing OK, have to do all that work again and still have this no start issue. Maybe I am having issues. If there were a cam that could possibly have slipped it would 100% definetely have to be the drivers side intake cam, as a small 15 degree segment of the snout of the cam was broken off during the install. I had the timing plate pinned onto the gear and wanted to see what the cam timing would be if I retarded the cam all the way with only the play in the system. My thought was that if the bolt failed somehow then the cam would retard to the end of the adjustment range within the hole I used for the cam timing pin. When I manually retarded the cam to the end of the adjustmewnt range a happy little peice of the cam snout broke off. It was half radius half flat. I just reset the timing to where I desired it to be and then torqued the cam bolt down, figuring it would be strong enough to hold the timing. I do this all the time for DOHC Ford modular engines that are used for drag racing, just leave out the keyway and torque the bolt down. It lets you have more adjustment of the cam timing then the single keyway will allow. I have never had a slippage issue and these motors rev to 9K.

I was thinking back to when I took the motor apart and was thinking that I might have just maybe dropped the ECM onto the floor by accident. Are trhese things shock proof? Most likely I did not drop the thing but anything is possible.

[8upZR1]

I have just tried an ECU from a ZR1 that works, and it was not worth the effort as it had no effect. This problem has me totally baffled.

I was wondering if anybody who has O2 sensor or A/F ratio gauges in there car could tell me what they read when the car is cranking?

[ZR1 MK]

Originally Posted by 8upZR1

If there were a cam that could possibly have slipped it would 100% definetely have to be the drivers side intake cam, as a small 15 degree segment of the snout of the cam was broken off during the install.

What cam bolts did you use?
What torque tool and method did you use?
What exactly is the extent of the cam damage?