1986 Thundercraft Distributor??

[Chiboka]

I have a 140 Mercruiser 3.0L engine in my 1986 Thundercraft. The engine will not start. After taking off the distributor cap & cranking it over the rotor does not turn. I believe it could be the gear that rotates the distributor shaft. Can this be changed with out pulling the engine by just dropping the oil pan?

Any help with this would be appeciated.

Thanks

 

[Maclin]

Re: 1986 Thundercraft Distributor??

It could just be the gear on the distributor shaft itself. There is a hardened rollpin that keeps the distributor shaft turning with the gear. The first thing to do is remove the distributor and look at that.

Note the rotor orientation, also mark the distributor base and the block, and do not allow the engine to turn over while the distributor is out, this will be helpful when re-installing.

 

[Don S]

Re: 1986 Thundercraft Distributor??

Note the rotor orientation, also mark the distributor base and the block, and do not allow the engine to turn over while the distributor is out, this will be helpful when re-installing.

I think at this point, it doesn't matter, the engine is turning and the distributor shaft isn't, who knows what it's pointing at now.
To reinstall the distributor, he will have to get the engine on #1 TDC and reinstall the distributor correctly. Not hard, just has to be done.

 

[Chiboka]

Re: 1986 Thundercraft Distributor??

I'll look at that and see this weekend. If it's that, which I think it is. It probably will not be too costly. I downloaded some diagrams off the net too help.

If the gear came off were would it have gone? In the oil pan? Is that gear plastic or metal.

Thanks for the quick response.

 

[Chiboka]

Re: 1986 Thundercraft Distributor??

The engine died while throttling up too almost full speed.

 

[Chiboka]

Re: 1986 Thundercraft Distributor??

Thanks DonS for the info. By the way what does engine on #1 TDC mean and how does one start this process.

 

[Maclin]

Re: 1986 Thundercraft Distributor??

I think at this point, it doesn't matter, the engine is turning and the distributor shaft isn't, who knows what it's pointing at now.
To reinstall the distributor, he will have to get the engine on #1 TDC and reinstall the distributor correctly. Not hard, just has to be done.

Right, I was thinking too much about someone like a forum searcher only catching part of this and pulling a distributor for the first time.

The TDC thing is not too hard and is unavoidable now as Don said. Sorry for the misdirection.

 

[Chiboka]

Re: 1986 Thundercraft Distributor??

I have a good mechanical understanding but this would be my first time with this type of repair.

 

[ziggy]

Re: 1986 Thundercraft Distributor??

what does engine on #1 TDC mean

this means that you need to bring the #1 cyl. to the top of its bore, on the compression stroke. both valves closed. remove all the plugs and put yer finger (or a compression gage) over the #1 sparkplug hole. rotate the engine and when #1 is on a compression stroke ya will feel it trying to blow your finger off the hole when your coming up on the compression stroke. then observe the timing mark and bring the harmonic bal. to 0. this will be top dead center of the compression stroke of the #1 cyl...... install the distributor with the rotor pointing twards the #1 spark plug.....

 

[Chiboka]

Re: 1986 Thundercraft Distributor??

Thanks

What is bring the harmonic bal. to 0. mean.

 

[Haut Medoc]

Re: 1986 Thundercraft Distributor??

Thanks

What is bring the harmonic bal. to 0. mean.

It means bring the timing mark on the harmonic balancer to '0' degrees on the timing tab....
= Top Dead Center.......
Without knowing basic stuff like this, I would say you are out of your league on this repair, but keep asking questions & we'll learn ya.....

 

[Chiboka]

Re: 1986 Thundercraft Distributor??

I understand that.

If the gear fell off the distributor were would it end up? Could it fall inside the motor?

I'll take a closer look at it this weekend. I just wanted too have all the right knowledge from here before I get into it. This way it should be staight forward.

I will probably look at it tomorrow afternoon seeing I have an extended long weekend.

If there is some thing else I should be aware of please let me know.

I was very unlucky this passed weekend my Seadoo, small fishing motor & boat broke down all at the same time. Bad Luck.

Thanks Mariners

 

[Maclin]

Re: 1986 Thundercraft Distributor??

The gear would not fall off, it would just spin on the cam's gear without turning the distributor shaft, or only turn it slower or be real jerky.

This may not be the problem, but the distributor has to come out anyway if the problem is deeper so might as well pick the lowest fruit first and not get the ladder out yet.

If the distributor gear and roll pin are intact (you turn the bottom of the shaft and the rotor follows, and you can see both ends of the rollpin thru the gear) then it could be a broken timing belt. When cranking does it crank relatively smoothly or have a definite lope that is the same each revolution? When the timing belt goes the cam is not turning and the valves remain open or closed depending on where they are on their lobe when the cam stopped turning. This makes for a definite lope as the starter turns, slower then faster and the same rhythm each time the engine makes a revolution.

 

[Chiboka]

Re: 1986 Thundercraft Distributor??

When it turns over it is smooth. I will take a closer look when I take it a part again. If I cannot figure it out then I will surely come back with more details.

Does this year of motor have a timing belt or chain?

 

[Haut Medoc]

Re: 1986 Thundercraft Distributor??

When it turns over it is smooth. I will take a closer look when I take it a part again. If I cannot figure it out then I will surely come back with more details.

Does this year of motor have a timing belt or chain?

Neither, it has gears.....

 

[Chiboka]

Re: 1986 Thundercraft Distributor??

I just looked at a schematic. Too see & it is gears. No belt.

 

[Maclin]

Re: 1986 Thundercraft Distributor??

Yup, forgot, sorry again. Work is interfering with my posting time.

 

[Chiboka]

Re: 1986 Thundercraft Distributor??

No problem Maclin. I'll take a closer look at the distributor setup to see if everything is in tacked. Might as well change the points & rotor well I'm at it.

Cheers

 

[Chiboka]

Re: 1986 Thundercraft Distributor??

It was the gear that came off the distributor shaft. Replaced the split pin & set the timing and everything is good again. Now on too my next problem the Seadoo. I'll jump over too the PWC section.

Thanks goes out too everyone who helped me.

 

[Maclin]

Re: 1986 Thundercraft Distributor??

Good deal, glad you did not have to dig any deeper, good job!