100hp 1972 ign problem

[thejeepster02]

Hi Folks
I have a Model 100293r, ser J07206

I had a mechanic at my marena check why she will turn over but wont start.
He said I had no spark and the parts are not available, I dont believe i cant get parts. for some reson he dosnt want to work on it.
I have enough experance to replace parts but not figureing out which one.
Im thinking of replacing all the ign. parts but i have no manual for part numbers.

any common problem i can look for?

any help would be great

 

[Joe Reeves]

Re: 100hp 1972 ign problem

Remove the spark plugs, check the compression (gauges are cheap). What is the compression on each cylinder?

The following may be of interest to you. Hopefully you have some mechanical expertise...... and if not, just go slow with your efforts.

(Voltage Drop To Battery Capacitance Discharge)
( Pulsepack When Electric Starter Is Engaged)
(J. Reeves)

On the older Battery Capacitance Discharge ignition systems (1968-1972), the electric starter reaches a point, even with a top notch battery, whereas the starter will draw excess voltage/current/whatever which results in a voltage drop to the pulsepack. The cure is to purchase a diode which is capable of handling 12 volts and installing it between the starter terminal of the starter solenoid (NOT the battery cable terminal) and the wiring terminal that supplies voltage to the pulsepack.

The diode must be installed so that the current flows from the starter terminal of the solenoid to the pulsepack... NOT vice versa. When that diode is installed in this manner, when the key is turned to the start position, the voltage that is applied to the starter is also applied directly to the pulsepack via the diode effectively eliminating the voltage drop and energerizing the pulsepack with the required voltage needed for its proper operation.

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store
********************
(Battery Capacitance Dischage Powerpack Test)
Various OMC Engines - 1968 to 1972)
(J. Reeves)

Purchase a small 12v bulb at your local automotive parts store (the 12v bulb is to look like a flashlight bulb, not a headlight bulb). Solder two wires to that bulb, one to the side of the bulb (ground), and the other to the positive point. You might use a bulb of a somewhat lower voltage to obtain a brighter glow... just a suggestion.

Remove the spark plugs. With the key in the on position, make sure that you have 12v going to the pack at the terminal block (purple wire). Now, connect the ground wire from the bulb to any powerhead ground. Connect the wire from the positive point of that bulb to the powerpack wire that is connected to the coil wire on the terminal board (blue wire).

Crank the engine and observe that bulb closely (CLOSELY!). If that bulb glows even the slightest bit, the powerpack is okay. It may be a very dim glow... just so it glows! If it doesn't glow, the pack has failed.

Keep in mind, that type powerpack (Battery Capacitance Discharge) demands a top notch battery of at least 70 amp hours. Any less will, in time, cause powerpack failure.

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

 

[thejeepster02]

Re: 100hp 1972 ign problem

Should have said this in the first message. Before it wouldnt start at all. it would run for about 15 seconds and die. it wold always start right back up, but die again. now it wont start at all.

 

[tashasdaddy]

Re: 100hp 1972 ign problem

do the test Joe recommended, and check compression. and report back. make sure it is viable to repair. Joe is the man i turn to when i have a question on the older engines.

 

[thejeepster02]

Re: reply to Joe on 100hp 1972 ign problem

Re: reply to Joe on 100hp 1972 ign problem

Hi Joe
I checked the compression as asked.
3 showed 105 and 1 showed 107.
whats that tell me??

thanks

 

[WillyBWright]

Re: reply to Joe on 100hp 1972 ign problem

Re: reply to Joe on 100hp 1972 ign problem

That tells you not to worry about bad compresion.

Here are a couple of easy checks. Rotate the flywheel til the #1 piston (top-right looking from behind) is at top dead center. Without cranking and with the #1 sparkplug out and grounded against the block, have someone turn the key on and off several times and check for spark to the #1 sparkplug. If you get spark when the key is turned off, your amplifier might be okay.

At night or in a darkened garage, have someone try starting it and watch under the flywheel for errant sparks (if it starts, shut it off immediately unless it's on muffs). It's fairly common for spark to leak out at the distributor terminals and not reach the sparkplugs. The sparks jump between one or more terminals and the spinning flywheel. You can't see it in daylight, but it's plain as day at night.

 

[Joe Reeves]

Re: reply to Joe on 100hp 1972 ign problem

Re: reply to Joe on 100hp 1972 ign problem

On the 1972 models, the compression is usually up around 125 psi BUT it will vary with different gauges. The fact that the compression readings are very close is a good sign. I suspect that reading will increase after the engine is run for as short time.

 

[thejeepster02]

Re: 100hp 1972 ign problem

ran some test today.
Have power to the purple wire to the power pack. checked the blue wire which goes to the coil, while cranking..I see nothing.

NOTE.. with the key on, i can hear off and on sparking. it sounds like its coming from under the fly wheel. I pulled the coil wire off and it sounds different but still there.

Still need some help..

 

[F_R]

Re: 100hp 1972 ign problem

Aha! Remove the coil wire from the distributor cap (it unscrews, take the coil off and turn the whole thing, then remount the coil) and recheck for spark right off the coil wire. Sounds like it's getting lost in the distributor cap.

 

[thejeepster02]

Re: 100hp 1972 ign problem

is the distributor under the fly wheel??

 

[F_R]

Re: 100hp 1972 ign problem

Yes

 

[thejeepster02]

Re: 100hp 1972 ign problem

any special advise on getting the fly wheel off, or is it a easy task

 

[F_R]

Re: 100hp 1972 ign problem

It's easy if you have the proper tools. You need a three-bolt puller, most use an automotive vibration damper puller. But not an el-cheapo one. You are really going to stress it. Get a set of grade-8 screws for it. Lesser grades will break. It attaches to the 3 screw holes near the center of the flywheel. Attach it and give it heck. It will come off with a pop when you pull hard enough.

When you reinstall the flywheel, make sure the taper and shaft are both clean and dry. Use a torque wrench to tighten the nut to 70-85 ft/lbs. This is vitally important!

 

[thejeepster02]

Re: 100hp 1972 ign problem

I bought one at advanced auto supply, $19.00.
It was the only one they sold. The holes line up but the bolts that came with it wont go in. I do want to get the grade 8 hardend as suggested but do you know what size bolt it is. I tryed all my odds and ends that I had. I cant believe this old of a motor wold be metric.
Hope someone caqn help

 

[thejeepster02]

Re: 100hp 1972 ign problem

Forgot to ask, is WD40 ok to use on the fly wheel??

 

[Joe Reeves]

Re: 100hp 1972 ign problem

You say that you checked the blue wire going to the coil. How exactly did you check it?

 

[thejeepster02]

Re: 100hp 1972 ign problem

I used a 12volt test light and then a digital meter, while cranking, I seen nothing

 

[F_R]

Re: 100hp 1972 ign problem

I Think they are 5/16 - 24 but might be 5/16 - 18. I have a set of both, but am having a brain lockup at the moment as to which fits which.

 

[thejeepster02]

Re: 100hp 1972 ign problem

Wanted to cllarify,,, The sparking was with the key on only. NOT running or Cranking

 

[thejeepster02]

Re: 100hp 1972 ign problem

Once the fly wheel is off, what am I looking for, A cracked distributor cap??