PCM Apex 5.7 ignition timing....

[broke_not]

Hi,

I'm just finishing up a long block install on a '98 Ski Nautique with a 5.7 GM PCM Apex engine. The engine uses a distributor, but the timing is controlled via the engine ECM. Before disassembly, I rotated the engine to TDC on the compression stroke for the # 1 cylinder.

I marked the distributor body and intake manifold, and also the rotor's position as well. Engine is back in the boat now, and I fired it up on the hose to check for leaks/monitor oil pressure, etc. The engine starts and runs fine, but there's a procedure to properly set the "baseline" ignition timing. Timing specs are listed in the operators manual, but no procedure for checking/setting it.

Anyone familiar with the Apex 5.7?

Thanks!

http://i16.photobucket.com/albums/b26/brokenot/boatproject026.jpg

[Dennis Rennie]

The timing may have to be checked through a scan tool.In automotive at 1000 rpm the scanner checks the cam retart.If it is 0 degree +/-2 degrees then it is set right. To compensate for negative reading,rotate the dist. counter clockwise.reverse this procedure for positive reading.This procedure may or may not apply to marine applications.Also what year is the motor.

[broke_not]

Thanks for the reply.

I did speak to a tech at PCM and found out that while a scan tool can be used, it's also possible to put the system into base timing mode with a jumper wire. On the diagnostic connector attached to the harness, a jumper wire is attached across the A and B terminals after the engine is already running. Once the jumper is in place, the timing is set the old-fashioned way with a timing light by rotating the distributor.

I sent the tech a link to the thread I started on a Ski Nautique forum asking the same question. I received a couple of different suggestions that the tech said could have damaged the ECM. There are several such processes out there and while they're very similar, it's important to get the correct info for the model in question. He said that the process he described to me only applies to '97 and '98 model Apex engines.

;)