1998 Mercruiser 3.0LX Delco EST Ignition Cannot Enter or Exit Base Timing Mode

[baseballa51]

I feel like I'm beating a dead horse with all the posts I've read about timing and the proper procedure. I have ALL new ignition components, including plugs and wires with about 20 hours of run time. I have been battling running rough for a while, so much that I never take the boat out. When I attempt to enter base timing mode, nothing changes with the RPMs, and wants to stall out as I approach the proper timing mark while rotating distributor. It only runs well way out of spec on timing (~20-25 degrees BTDC at idle). Last week I troubleshooted again and noticed it was not advancing with RPM at all. I replaced the inexpensive ignition control module with a reputable manufacturer (Sierra) thinking that was the issue with the inability to accurately base time and not advancing. Well here we are and it's exactly the same symptoms. I have verified the schematic with my multimeter, tested components, followed instructions to a T. It has new fuel pump, rebuilt carb, filters, fuel water separator, basically everything that can be bolted to the engine has been replaced within 20 hrs of runtime. I've spent weeks researching and looking at hundreds of forum posts and countless videos. I am completely stumped. Any help at all is appreciated.

 

[alldodge]

A timing light will let you know there is spark but not that there is enough to ignite. Use a spark gap tester and see if your getting at least 1 1/8 inch spark and it's white or blue

Dump the contents of the fuel filter in a clear container to see if there is nothing but clear gas. If the fuel pump filter bowl is clear look before dumping to see if it's full and is clear

 

[baseballa51]

A timing light will let you know there is spark but not that there is enough to ignite. Use a spark gap tester and see if your getting at least 1 1/8 inch spark and it's white or blue

Dump the contents of the fuel filter in a clear container to see if there is nothing but clear gas. If the fuel pump filter bowl is clear look before dumping to see if it's full and is clear

Thank you for your reply. After troubleshooting the no start for a few hours today I gave it a whole bunch of gas and starting fluid and it fired up and stayed running. I have since edited my post but I will check the arc length of the spark coming from the plugs. Not sure if it is still applicable at this point, though. I've never had a problem starting the engine before, but it's always running rough.

 

[baseballa51]

I never would have fixed it if i didnt keep some old parts. the metal tab on the old rotor cap I noticed was longer than the tab on cap of the new distributor. I changed the cap to the old one and it immediately went into base timing mode first attempt and started retarding and advancing. so the tab got closer to the spark plug terminals and was causing a bigger arc across it. the module wouldn't recognize the arc from the new cap, even though it came as a complete kit. wild.

 

[dubs283]

If the ignition only runs at idle with the timing at 20-25 degrees btdc then the issue is either the firing order is incorrect, the tune up components are of an incorrect/inferior quality, the fuel supply has an issue or the engine mechanical system is faulty

Funny story, had a 350 sbc rebuild that would only run at idle with the timing set around 30 degrees btdc. Tried multiple different firing orders (was an old chris craft motor) and found that this particular rebuild would run at idle with 30 degrees of timing advance with four different firing orders. Wouldn't hold an idle at normal timing. Rebuilder claimed the carburetor rebuild was at fault. After they came to the shop twice and finally retrieved the engine we got it back and it ran at idle with 8 degrees btdc timing. Never got an explanation as to what the issue was