Bad resistance wire causing no spark at coil?

[joejoegabbard]

I?d like to start by reiterating what other first-timers have stated on this forum ? what a great resource! Thank you all!

I am working on a 1987 Stingray w/ 2.5L (120hp) Mercruiser I/O, Alpha 1 Sterndrive. The engine serial # is B733336 ? a GM straight 4.

The boat ran pretty good last year with the exception that the engine would start surging after the boat was warmed up for ~10-20 minutes (but ran fine when first running). It would almost stall out, but when I let it sit for a while, it would run great again, but only for 10-20 minutes, and then back to surging. At that time, I thought it was fuel-starved, or maybe debris in the gas and/or tank. I rebuilt the carb (3.0L on top of the 2.5L) and thoroughly checked the fuel system (from tank to and through carb) for debris and obstructions. When I put the boat away for the winter (properly winterized), the surging problem was not resolved.

Fast forward to this Spring. When I tried to crank her up (summerize!), I got the dreaded ?no spark?. After working through the troubleshooting tips on this forum, I (humbly) come and ask for help.

The details of my troubleshooting efforts are as follows. No spark at the coil (tested by both holding coil plug wire close to ground and newly purchased high voltage spark tester). I am getting +12V at the + and ? side of the coil with ignition on, points open. I do not have a deadman?s switch. I disconnected the white/green wire at the shift interrupter switch terminal block, and still no spark at the coil. I needed a tuneup anyway, and after reading so many recommendations to ?do a tune up?, I installed new dist. cap, rotor, condenser and points. I don?t (currently) have a tool to set/measure dwell, but did use feeler gauge to set point gap to .022 per service manual. Still no spark at the ignition coil.

Now I get to the resistance wire (sorry for the long post, but I?m assuming more detail is better than less, as long as it is focused!). Using a multimeter, I measure ~1.2 ohms by putting neg end of multimeter on the purple wire connector taken from the choke, and putting the pos end of the multimeter on the purple resistance wire taken from the + end of the coil (disconnected from the + side of the coil), BUT shrunk wrapped together onto one circular connector along with the +12V purple/yellow wire from the starter (not sure if this matters). Also, I am only getting ~5.5V across the coil with the points closed.

And now the questions? 1) Would a reading of +5.5V across the coil with points closed explain why I have no spark? 2) If my resistance wire is bad, only reading 1.2 ohms (as opposed to 1.8 ? 2.0), wouldn?t I see MORE current at the coil (not less)? Lastly, and this may be a little far out, but could my engine surging last summer have been an indication that my coil / resistance wire were off, or going-bad if there is such a condition, and thus I was missing spark here-and-there as the engine and coil warmed up?

Thanks in advance.

 

[Don S]

Re: Bad resistance wire causing no spark at coil?

The resistance wire has nothing to do with the ignition when cranking the engine. The coil gets power from the starter. If you have ~12V while cranking, then you should have spark.
When you set the points, was the points set while open on the high point of the distributor cam?

 

[joejoegabbard]

Re: Bad resistance wire causing no spark at coil?

The resistance wire has nothing to do with the ignition when cranking the engine. The coil gets power from the starter. If you have ~12V while cranking, then you should have spark.

I should have been more clear. All troubleshooting was done with ignition ON but not cranking (start?) position. I can check while cranking tomorrow.

When you set the points, was the points set while open on the high point of the distributor cam?

Yes, points set while open at high point of cam.

 

[JustJason]

Re: Bad resistance wire causing no spark at coil?

if the keyswitch was set to the on position for more than a few minutes with the points closed then you fried your condensor... and possibly your points too

 

[Don S]

Re: Bad resistance wire causing no spark at coil?

Have you checked the high tension lead to the coil?

 

[joejoegabbard]

Re: Bad resistance wire causing no spark at coil?

Back at this morning...

If you have ~12V while cranking, then you should have spark.

I'm only seeing ~1.5V across the coil while cranking (with new points set to proper 0.22 gap). I have 12V at each + and - side of the coil when key in on position (but not cranking)

if the keyswitch was set to the on position for more than a few minutes with the points closed then you fried your condensor... and possibly your points too

I gathered that from reading other posts, so I've been doing points-closed testing for at most 20-30 seconds. Would that fry the condensor?

Have you checked the high tension lead to the coil?

Is this is the black wire that goes from - side coil to the center of dist? If so, I'm seeing 12V at the end of that wire (dist side) with key in on position (not cranking). Should I be performing a different test on that wire? Thanks in advance.

 

[joejoegabbard]

Re: Bad resistance wire causing no spark at coil?

I (embarrasingly) need to correct myself...

I'm seeing 12V at the end of that wire (dist side) with key in on position (not cranking). Should I be performing a different test on that wire?

Above, I am referring to the small black wire from - coil terminal to dist, NOT the heavy qauge "spark plug like" wire that sends the high-voltage from center of coil to center to dist cap. Using high voltage spark tester, I'm not seeing any spark at the center of the coil (without using the high tension wire, just measuring straight out of the center of the coil). You might recall that I'm only getting ~5.5V across the + and - of the coil with key on, points closed (not cranking), and that my resistance wire reads 1.2 ohms.

 

[Don S]

Re: Bad resistance wire causing no spark at coil?

Have you checked the high tension lead to the coil?

Is this is the black wire that goes from - side coil to the center of dist? If so, I'm seeing 12V at the end of that wire (dist side) with key in on position (not cranking). Should I be performing a different test on that wire? Thanks in advance.

No, the big coil wire that goes from the coil tower to the center tower of the distributor cap.

 

[JustJason]

Re: Bad resistance wire causing no spark at coil?

Ok... try this.
Disconnect anything on the - side of the coil.
Put the negative lead of your DMM (digital multi meter) on the battery negative post.
Put the positive lead of the DMM on the coil +
Whats your reading?
If under 10 volts replace the ballast resistor
If over 10 volts make up a piece of test wire with aligator clips on both ends. Clamp one end on the coil -
take the other end and rapidy tap it on a good ground, the battery - if available is best. Hold the coil high tension lead 7/16ths of in inch off of a good ground with insulating pliers (ie plastic)
Do you have spark? If yes then you have either a problem in your points system or tachometer if the boat has one.
If no, you have a problem with the coil or the high tension lead.
Not much to it after that.

 

[joejoegabbard]

Re: Bad resistance wire causing no spark at coil?

I had a new ignition coil, but was waiting to try it. Put it on, and now I have spark at coil and at plugs (although its not clear how strong of a spark I have).

I'm getting the engine to turn over, but is backfiring through the carb. It almost got going once. I did not change the position of the dist., so I *shouldn't* have messup the timing. right?

Any suggestions on why it won't get going? Could it be that my spark is not "strong" enough?

thanks again

 

[Don S]

Re: Bad resistance wire causing no spark at coil?

Did you get the spark plug wires mixed up when you replaced the cap?

 

[joejoegabbard]

Re: Bad resistance wire causing no spark at coil?

I thought the same thing, I double checked the order with the manual -- looks correct, 1-3-4-2

I winterized it myself last winter for the first time. Is it possible to have OVERfogged the engine? I fogged the carb till the engine died, and then fogged each spark plug "hole".

 

[Don S]

Re: Bad resistance wire causing no spark at coil?

You have new spark plugs, so the fogging oil should be a problem. You could check by pulling the plugs and cranking the engine over a few times to get rid of any excess oil, then clean the plugs and try again. But oily plugs will not cause it to back fire. Did you pull all the plug wires off the distributor cap when you changed it? or do just one at a time.
Did you see where the rotor is pointing on the cap when #1 cylinder is up on TDC on the compression stroke?

 

[chiefalen]

Re: Bad resistance wire causing no spark at coil?

maybe the dist.cap is turned 180 around.maybe the dwell is off.

 

[Don S]

Re: Bad resistance wire causing no spark at coil?

maybe the dist.cap is turned 180 around.

They will only go on one way. Just like any distributor cap.

maybe the dwell is off.

He doesn't have the meter to check it. So without the ability to test things, we have to guess, and throw money/parts at it, and hope it works eventually.

 

[Coors]

Re: Bad resistance wire causing no spark at coil?

Harbor freight has them for $5, and they actually work good.
I bought one to throw in the boat toolbox...

 

[joejoegabbard]

Re: Bad resistance wire causing no spark at coil?

Just checking back in with those who posted to help.

Its looking like a timing issue since I'm backfiring through the carb. I'm having my mechanic (more experienced than I) check my points install, and will correctly set the dwell. It will be a day or so, but I will post again WHEN I get it running... if nothing else to get appropriate closure on the thread.

Thanks again to all.