1980 Chrysler 105 cranks but will not fire

[jon705]

I have a 1980 Chrysler 105 outboard that is giving me problems with starting. It cranks just fine, and I'll get the occasional backfire, but it will not fire up and run. Here's what I've tested:

1. Battery is new, has good charge, voltage-drop tests fine.
2. I get a 12v reading at the blue (ignition circuit) wire with key in run position.
3. Gas in the tank is old - don't know how old but I've squirted fresh 50:1 mix with a spray bottle directly in the carbs without firing success.
4. Spark is present on all four cylinders as tested by pulling each one and holding near engine block during cranking. They all make a bluish arc - is there such thing as a bad or weak spark?
5. Plug tips are shiny (not sooty) but are wet with gas when I pull them.
6. Choke works when pushing key in.
7. Another thing I thought I should mention is there is quite a bit of unburned 2 cycle oil coming out of the prop area.

What other tests can I run or items should I test to get this running?

Thanks in advance!

 

[JB]

Re: 1980 Chrysler 105 cranks but will not fire

Most likely suspects:

1. Sheared flywheel key.

2. Wires on wrong plugs.

 

[moparman]

Re: 1980 Chrysler 105 cranks but will not fire

How fast does the motor spin over? Even though it has spark from the plug wires,firing in the cylinder under compression at a slow cranking speed will produce a weak spark. moparman

 

[jon705]

Re: 1980 Chrysler 105 cranks but will not fire

Most likely suspects:

1. Sheared flywheel key.

2. Wires on wrong plugs.

What do I look for on the first?

Thanks,

--Jon

 

[jon705]

Re: 1980 Chrysler 105 cranks but will not fire

How fast does the motor spin over? Even though it has spark from the plug wires,firing in the cylinder under compression at a slow cranking speed will produce a weak spark. moparman

Not sure exactly what the cranking RPMs, but the new starter motor I bought for it turns over at a pretty good clip.

Also since posting this I have cleaned both carbs but still won't fire up. Any other ideas?


Thanks,

 

[jerbear56]

Re: 1980 Chrysler 105 cranks but will not fire

Before you spend any more time and money on it, run a compression check.

 

[JB]

Re: 1980 Chrysler 105 cranks but will not fire

Backfires only happen when you get spark with the exhaust ports open. That means bad timing. That is usually caused by the flywheel not being in time with the crank. That usually means that the key that keeps them in time has sheared and the flywheel has slipped.

Nothing. . .nothing. . .else will fix it but to pull the flywheel and replace the key.

 

[jon705]

Re: 1980 Chrysler 105 cranks but will not fire

Backfires only happen when you get spark with the exhaust ports open. That means bad timing. That is usually caused by the flywheel not being in time with the crank. That usually means that the key that keeps them in time has sheared and the flywheel has slipped.

Nothing. . .nothing. . .else will fix it but to pull the flywheel and replace the key.

If the rain holds off tonight I will be removing the flywheel and checking the key. My guess is it sheared off as the flywheel nut was not torqued. I have an assortment of replacement keys so hopefully one will fit and I can actually hear this thing run! I'll post what I come up with. Thanks!

Well the rain held off but I didn't have the right size bolts to fit in the three flywheel holes for the puller - so tonight will hopefully be the night.

 

[jon705]

Re: 1980 Chrysler 105 cranks but will not fire

Before you spend any more time and money on it, run a compression check.

Compression is 105-110 on all four cylinders.

 

[jerbear56]

Re: 1980 Chrysler 105 cranks but will not fire

Your compression is way too low. Should run 145 to 165 pounds. Try re-torquing your head gasket and see if it comes up.

 

[jon705]

Re: 1980 Chrysler 105 cranks but will not fire

Your compression is way too low. Should run 145 to 165 pounds. Try re-torquing your head gasket and see if it comes up.

I'll try that. Probably won't have time until tomorrow evening. I read in another post that anything above 100 should be fine as long as all cylinders are within 5% of each other. Does the latter comment apply to a smaller motor?

 

[moparman]

Re: 1980 Chrysler 105 cranks but will not fire

that should be enough to fire it [ your getting a backfire right?], I agree with JB, especially if the flywheel nut is loose,torque should be 92-105 I believe,but if some one has the torque value handy ....... MOPARMAN

 

[jerbear56]

Re: 1980 Chrysler 105 cranks but will not fire

Head bolt torque is 240 inch lbs, or rounded, equals 19 ft. lbs. Flywheel nut torque is 90 ft. lbs. That's straight from the factory service manual.

As a sidenote, you really should mix up a fresh batch of gas using super unleaded. The 105 was originally designed to run on leaded gas, and unleaded gas was the third choice to run in that engine.

 

[jon705]

Re: 1980 Chrysler 105 cranks but will not fire

I went to try pulling the flywheel again last night and another bolt hole for the puller stripped. It's looking like that flywheel might be "impossible" to get off without me taking it to a shop. When I have some more time - Friday cause I'm out of town on business - I'll have to drill and tap the hole and give another go at pulling it.

This question probably deserves a new post, but I have the chance to pick up a working 100HP Johnson outboard for $250. Seems like I'm going to spend at least that to get the Chrysler running. I'm thinking about picking up the Johnson to swap on the boat, then work on the Chrysler at my liesure to get it running again for either a backup, or to sell. Any thoughts?

 

[JB]

Re: 1980 Chrysler 105 cranks but will not fire

"Working" isn't very specific, but if the Johnny is really in good shape it sounds like a good idea, but. . .

Does it include all controls and accessories?

If the Chrysler really does have a sheared flywheel key I don't see why you would need to spend over $250 to "get her fixed". You can fix her yourself for a lot less than that.

The main reason I like the idea of going to the Johnny is availability of parts, information and advice.

 

[jon705]

Re: 1980 Chrysler 105 cranks but will not fire

"Working" isn't very specific, but if the Johnny is really in good shape it sounds like a good idea, but. . .

Does it include all controls and accessories?

If the Chrysler really does have a sheared flywheel key I don't see why you would need to spend over $250 to "get her fixed". You can fix her yourself for a lot less than that.

The main reason I like the idea of going to the Johnny is availability of parts, information and advice.

i'm going to look at it this weekend. Not sure if it comes with controls. How interchangeable are they? Can I use the Chrysler controls for the Johnson?

If I knew exactly what was wrong with the Chrysler, or that the flywheel key was the issue I wouldn't even look at the Johnson. I just don't want to start throwing money at the Chrysler without knowing what will fix it, and then not having a backup..

When I get back to town I'm going to give the flywheel removal anothert try.

Thanks for all your input!

 

[moparman]

Re: 1980 Chrysler 105 cranks but will not fire

When you get back to the chrysler flywheel, make sure you have at least two times the dia of the bolt screwed into the flywheel holes to try to remove it [example: 5/16 bolt=5/8 depth ,3/8 bolt =3/4 deep in the hole ],as this will give you plenty of engagement and possibly stop stripping out the holes, and make sure your not flooding the motor when trying to crank it

 

[jerbear56]

Re: 1980 Chrysler 105 cranks but will not fire

Just go for the johnson. Simply put.

The reason the flywheel won't come off is because you aren't pulling it correctly. Tighten the puller bolts to where they are good and tight, then hit straight down on the puller screw with a hammer. Tighten the puller screw a hair, and pop it again. About the third smack, it will pop loose.

FYI, if you are very careful, you can use a wooden dowel to check the flywheel key. Pull all the plugs and put the pointer at tdc. On nunber one, put the dowel in the plug hole and VERY slowly turn the flywheel until the dowel starts to move with the piston. Mark the flywheel with a sharpie at the pointer. Then do the same the opposite direction and mark the flysheel at the pointer. Distance should be equal from the tdc mark. I've had to do this before when pointers have come loose or shifted and it works really well.

 

[jon705]

Re: 1980 Chrysler 105 cranks but will not fire

"Working" isn't very specific, but if the Johnny is really in good shape it sounds like a good idea, but. . .

Does it include all controls and accessories?

If the Chrysler really does have a sheared flywheel key I don't see why you would need to spend over $250 to "get her fixed". You can fix her yourself for a lot less than that.

The main reason I like the idea of going to the Johnny is availability of parts, information and advice.

It comes with controls and we are going to start it before I take it home. I'm going to pick it up tomorrow morning. Then I can start the fun of swapping it on my boat. I will then be able to work on the Chrysler from the comfort of my garage.