setting timing @ cranking speed

[20vector]

hello all.. i got a 1998 200 efi mariner and when i set my WOT timing i left #1 plug in only and set timing. my buddy says im suppose to take all plugs out to set WOT timing. didnt think it would be much difference but checked it after i set it with #1 plug in and took plug out and checked timing again and was like 4? to 5? difference. of course it was spinning alot faster. so if someone knows the right way please let me know. another thing when spark testing at 3/8" gap spark jumps good. at 1/2" gap i think only #1 spark was jumping. is 3/8" gap for spark to jump enough or is it telling me something is getting weak and if is what is it likely? thanks all in advance

 

[fisherman81654]

Re: setting timing @ cranking speed

hello all.. i got a 1998 200 efi mariner and when i set my WOT timing i left #1 plug in only and set timing. my buddy says im suppose to take all plugs out to set WOT timing. didnt think it would be much difference but checked it after i set it with #1 plug in and took plug out and checked timing again and was like 4? to 5? difference. of course it was spinning alot faster. so if someone knows the right way please let me know. another thing when spark testing at 3/8" gap spark jumps good. at 1/2" gap i think only #1 spark was jumping. is 3/8" gap for spark to jump enough or is it telling me something is getting weak and if is what is it likely? thanks all in advance

I don't know about your spark plug gap issue,as far as timing goes,Take out all plugs and ground them,EXCEPT number one plug.
The reason is,you have less drag on the starter. You also want to have a fully charged battery when cranking.

 

[Texasmark]

Re: setting timing @ cranking speed

I don't know about your spark plug gap issue,as far as timing goes,Take out all plugs and ground them,EXCEPT number one plug.
The reason is,you have less drag on the starter. You also want to have a fully charged battery when cranking.

When he says ground them, he means ground the outer shell of the plug. This forces the 40kv unloaded high voltage jolt to the plugs to be limited by the voltage necessary to jump the gap which may only be 15kv or so and in doing that, you relieve the load on the starter so that it can spin your engine faster and relieve the stress on your ignition as it only has to tolerate 15kv rather than the unloaded 40kv that Merc says their ignitions can produce.

HTH,

Mark

 

[20vector]

Re: setting timing @ cranking speed

hello all. i took all plugs out except #1 and all plug wires instead of just grounding them i connected them to a spark gap tester. when i checked how good my spark was few years ago they were jumping the 1/2" on the test board. when i was setting my timing i went ahead and hooked all coil wires to the spark tester just to have the spark going somewhere. didnt really plan on checking how good my spark was but when i was done setting timing and was about to disconnect everything decided to look and see how my spark was, since a week ago i disconnected my idle stabilizer and my detonation controller assembly. you know how those spark testers are, they have like 4 lines you can set the slide at to see how far the spark is able to jump. i know perfect is if it can jump the 1/2" mark. mine wouldnt jump that far. but set at the 3/8" mark had good spark jumping on all cylinders. was wondering if jumping 3/8" is good enough? also when i was doing this i had ecm disconnected as per the book says when setting timing. didnt know if ecm disconnected gave it weaker spark or not? thanks again everybody...

 

[CharlieB]

Re: setting timing @ cranking speed

ECU should have NO effect on the ignition system.

Cranking speed directly affects spark as the stator has a minimum RPM of 300 to generate sufficient energfy to operate the ignition system.

A 7/16 inch spark is the minimum set by the book, if your ignition cannot throw a hot blue arc across a 7/16 inch gap you may want to start checking things.

First, cranking RPM, worn starter brushes, dry starter bushing, dirty battery cable connections, or a combination of the above, can contribute to weakening cranking spark, yet not affect power output once the motor is running.

Do NOT assume that the ignition system, or stator is failing without checking and PROVING something wrong.

If your WOT RPM is fine, you do not have an ignition problem, it is more likely a starter or battery cable problem.

 

[hl]

Re: setting timing @ cranking speed

While reading this tread I was wondering why is necessary to ground the plugs that are taken out while checking timing?

 

[fisherman81654]

Re: setting timing @ cranking speed

While reading this tread I was wondering why is necessary to ground the plugs that are taken out while checking timing?

To prevent ignition damage.
What would happen if you didn't ground them? Maybe nothing bad or maybe damage the one of the electrical componets. I have done it both ways before I learned the proper procedure,which is ground the plug wires or plugs.
I have seen this question answered more in depth on the fourm,don't remember the post title.

 

[jeffersondodson561]

Re: setting timing @ cranking speed

hello all.. i got a 1998 200 efi mariner and when i set my WOT timing i left #1 plug in only and set timing. my buddy says im suppose to take all plugs out to set WOT timing.

What is your serial number? What wire colors do you have coming out of flywheel, do you have an altenator? Just asking becuause you you only have yellow wires or green wire with a tracer color coming from out of the flywheel or have an altenator the ECU may be control maximum WOT timing?

 

[hl]

Re: setting timing @ cranking speed

I have not tried it yet. Just reading to learn more about timing. As I was reading I learn that not grounding the plug wires could damage the CDU. I hate to ask a stupid question but what is a CDU?

 

[electricjohn]

Re: setting timing @ cranking speed

capacitor discharge unit aka switchbox.