Inline Six Cylinder No spark on #1 and #3

[Rabbitdawghunter]

I am working on a Merc Inline 6 cyl, Serial #A935424.<br /><br />What year model is this ?<br />What is the part # for the Merc Service Manual?<br />What could caus loss of spark on 1 and 3 .<br />What is the complete ignition troubleshooting procedure for this engine?<br /><br />I have already tested with DVA at the coils and #1 and #3 only have .3 to .4 volts. All others around 140 to 150 volts.

 

[Rabbitdawghunter]

Re: Inline Six Cylinder No spark on #1 and #3

I forgot to mention that this engine is a 90 HP

 

[Clams Canino]

Re: Inline Six Cylinder No spark on #1 and #3

It's somewhere in the 80's, they are all the same anyway. Not sure of the Merc part number, I have a Seloc for that era. You FLMD can get you a Merc one though. <br /><br />I'd bet on the upper switchbox being the problem. Try disconnecting the little blk/wht bias wire between the boxes and retest. If you get the same result, you can bet on the top box. Reverse the two boxes and see if it follows.<br /><br />-W

 

[dolluper]

Re: Inline Six Cylinder No spark on #1 and #3

An 86 ---6cyl---90 reads A90 so yours is newer than 1986 0r 1986

 

[mellowyellow]

Re: Inline Six Cylinder No spark on #1 and #3

follow clams good advice and swap switch boxes.<br />if no spark follows...

 

[Rabbitdawghunter]

Re: Inline Six Cylinder No spark on #1 and #3

Yep, the spark changed places with the swap. Also this has high speed/low speed stator that will give voltages of about 32 and 290 or so does it not?<br /><br />Is there a place other than through the dealer that I can get a copy of the serial number guide, I have everything up thru 1976 from Oldmercs.com but I need to fill the gap between 76 and when they started putting the year on the ID plate. (That was late 95 or so wasn't it)?

 

[dolluper]

Re: Inline Six Cylinder No spark on #1 and #3

Try this link hit 95hp to see ends at 86<br />www.maxrules.com

 

[Kiekhaeferscurse]

Re: Inline Six Cylinder No spark on #1 and #3

I thought the old rule of thumb was loose spark on one cyl its a coil, loose spark on two holes its the trigger, on 3 holes its a pack, no spark at all stator, or kill circuit but I've been fooled before and will be again

 

[Clams Canino]

Re: Inline Six Cylinder No spark on #1 and #3

Actually most of that is wrong. for several reasons. Except the stator part.<br /><br />-W

 

[Kiekhaeferscurse]

Re: Inline Six Cylinder No spark on #1 and #3

I'll explain my reasoning, if you explain yours clams, I love a good debate, but perhaps we should start a new thread on it?

 

[Rabbitdawghunter]

Re: Inline Six Cylinder No spark on #1 and #3

#1 and #3 are not a trigger pair are they?

 

[rodbolt]

Re: Inline Six Cylinder No spark on #1 and #3

nope<br /> you get a prize ]

 

[dolluper]

Re: Inline Six Cylinder No spark on #1 and #3

Yes start that thread it would be a real goog one

 

[rodbolt]

Re: Inline Six Cylinder No spark on #1 and #3

for me its to quick and easy to test stator and trigger inputs verses switchbox outputs. gives a quick way to isolate the problem.

 

[Rabbitdawghunter]

Re: Inline Six Cylinder No spark on #1 and #3

What's your opinion on the rule of always replacing both swithchboxes. How much of a chance are you taking to just replace one?

 

[rodbolt]

Re: Inline Six Cylinder No spark on #1 and #3

hello<br /> it is a reccomendation. however sometimes a customer just does not have the money. they are not cheap. seems sometimes a failed box can damage the other box. but they quit giving them away so yes I have replaced just one. sometimes a few weeks later I will have to replace the other one but sometimes not.

 

[Clams Canino]

Re: Inline Six Cylinder No spark on #1 and #3

No debate to it... <br /><br />If you lose spark on one cylinder it's most likely one SCR in one switchbox, then a coil.<br /><br />If you lose spark on two the trigger is ONLY indicated if they are the two cylinders that are on the same trigger winding. Past that it's back to the switchbox.... again. Since he lost #1 and #3 that voided the trigger theory right out out of the gate.<br /><br />Three outages on 1 box it's the switchbox OR trouble with the stator lead feeding that box.<br /><br />And lose them all, yes it's most likely the stator. <br /><br />-W

 

[Rabbitdawghunter]

Re: Inline Six Cylinder No spark on #1 and #3

Clams not trying to be a smarta!! but this is only a pair out on one switchbox, that are not a trigger pair and considering what you just said wouldn't I need to see #2 gone also for it to be the switchbox. The stator voltage inputs are good. I'm assuming that switchbox can lose 1,2 or 3 cylinders assigned to it because of internal shorts and you would have to rely on the input and output values to make that determination.

 

[Rabbitdawghunter]

Re: Inline Six Cylinder No spark on #1 and #3

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[Clams Canino]

Re: Inline Six Cylinder No spark on #1 and #3

Originally posted by Rabbitdawghunter:<br /> Clams not trying to be a smarta!! but this is only a pair out on one switchbox, that are not a trigger pair and considering what you just said wouldn't I need to see #2 gone also for it to be the switchbox. The stator voltage inputs are good. I'm assuming that switchbox can lose 1,2 or 3 cylinders assigned to it because of internal shorts and you would have to rely on the input and output values to make that determination.

You are 100% correct. But unless we are speaking in different dialects of English, I said nothing that wasn't in 100% agreement with what you just said.<br /> <br /><br />-W