3.7L 1989 Alpha One ignition problem

[grady86]

I have a 3.7L Mercruiser Alpha One, year 1989, 165 HP, 224 CID. 2 barrel carb, pointless distributor ( see picture ). As of right now, I am not getting any spark, even with a brand new rotor and distributor cap. Backing up a little, the motor recently went from running great to not running at all, i.e. no spark at any spark plug, so I checked under the distributor cap and saw the rotor was destroyed ( see picture below ). After replacing rotor and cap, the no-spark issue still remains. I used a strangers' advice and used a wooden dowel to check the #1 spark plug's top-dead-center position in relation to the rotor position. Although this didn't seem to be a very exact method because I'm not sure how to know which is the exhaust and which is the compression stroke, the rotor was pointing directly at the #1 spark plug position on one of the two top-dead-center strokes. Another bit of information is that the ignition coil is sparking normally on the high tension lead when grounded to the engine, although with the ignition switch in the on position, the coil gets ridiculously hot for some unknown reason... not sure if that is normal, but I don't remember it ever doing that before. Thanks in advance.

Sincerely,

Grady

 

[grady86]

No Title

 

[wrestling coach]

OK. FYI. To get on a compression stroke remove the #1 spark plug ( closest to the front of the engine ) remove the coil wire, place your thumb over the spark plug hole as somebody bumps the engine using the key. When your thumb gets pushed off that spark plug hole with a rush of air you are on a compression stroke for #1 cylinder.

 

[stonyloam]

OK, if you are getting spark from the coil then it is a matter of getting the rotor pointed at the right plug lead and it should work. Just find #1 compression as the coach says. If you have an Ignitor 1 I think it will draw corrent with the key on, so that may be the cause of the hot coil.

 

[MikDee]

Okay, how about this, TDC on the crank where it is now, could be ready to fire on #4? Turn the crank over 1 more turn to TDC again, and it's ready to fire on the alternate opposing cylinder #1.

If you could take off the valve cover, you would see when both intake, & exhaust valves are totally closed on Cyl #1, and when on Cyl #4 as well, that would show which Cyl is on TDC compression at the time.

 

[grady86]

Update:

I used the pressure method to determine the compression stroke as wrestlingcoatch mentioned. What I ended up using was a standard compression gauge, minus the gauge. this made it easy to tell when the compression stroke was starting. Once I started feeling pressure, I switched from using the ignition switch to manually turning the flywheel and using an old graphite arrow shaft in the cylinder, turning the flywheel slowly until the arrow shaft stopped moving upward.

After I was satisfied that my #1 cylinder was "TDC", I marked the position the rotor was in and sure enough had to adjust the distributor housing. However, this seemed to be just fixing an earlier adjustment I had made before I used the "dowel" method and simply waited until I felt the first "puff" of air, which surely wasn't top dead center but was rather the very beginning of the compression cycle. So.. to clarify, I most likely was just fixing an unnecessary adjustment I had made while using improper methods.

Anyway, after I was happy that my rotor was pointing directly at the contact for spark plug #1, I tried starting. Nothing. Additionally, no spark from high tension lead anymore. 12V reading on the ignition coil at the + terminal. approx. 1 Ohm of resistance across primary coil, 10K Ohms across secondary coil. Oh, almost forgot, I noticed none of my instrument gauges were activating, so I checked ignition switch fuse and sure enough it was shot. Replaced it (20A fuse) and all gauges work perfectly, but didn't fix anything else.

Right now I am leading toward replacing the coil... however, before I do that does anyone know a reliable way to get tolerance readings for resistance? Google is failing me, it's a cylindrical mercruiser coil part number 392-805570-1.

 

[MikDee]

I told you, you can use a hose,,, Plus, once you start to get compression, just move the crank pulley to the TDC mark, then just take out the Dizzy some, and drop your rotor in at #1 Distributor cap post. I thought it might be a bad coil from the beginning.

 

[grady86]

Update :

New coil came into Napa today. After installing the coil, she fired right up! I still had to adjust the timing a bit, but once it was running smooth, I let her sit and get up to normal temp. All seems normal (minus an annoying intermittent whining noise coming from somewhere near the distributor).

A little bit of information that I forgot to include earlier: When I said my rotor was destroyed, not only was notch retaining the rotor to the distr. shaft broken off, but the top spring contact was also partially missing. The resistance readings on the secondary windings of the faulty coil were approximately 2000 Ω higher than in the new coil (10k Ω vs. 8k Ω respectively). It would seem that this caused excessive voltage to be imparted to the rotor, although this doesn't make much sense to me (more resistance = less voltage, right?)

Anyway, thanks everyone for the input, I learned a ton about my ignition system thanks to your help. I will no doubt be back, humbly requesting support. Cheers!

 

[grady86]

Update :

New coil came into Napa today. After installing the coil, she fired right up! I still had to adjust the timing a bit, but once it was running smooth, I let her sit and get up to normal temp. All seems normal (minus an annoying intermittent whining noise coming from somewhere near the distributor).

A little bit of information that I forgot to include earlier: When I said my rotor was destroyed, not only was notch retaining the rotor to the distr. shaft broken off, but the top spring contact was also partially missing. The resistance readings on the secondary windings of the faulty coil were approximately 2000 Ω higher than in the new coil (10k Ω vs. 8k Ω respectively). It would seem that this caused excessive voltage to be imparted to the rotor, although this doesn't make much sense to me (more resistance = less voltage, right?)

Anyway, thanks everyone for the input, I learned a ton about my ignition system thanks to your help. I will no doubt be back, humbly requesting support. Cheers!