1984 Mercruiser 470 - No Spark at Cap

[nalloco]

I have a 1984 Mercruiser 470 with no spark at the cap...start with that.

I have replaced the following:

Coil
Cap
Rotor
Condensor
Points
Plug Wires
Battery

I have 12 volts going into the + side of the coil with the key on and also 12 volts coming out of the wire from the coil to the top of the cap. The wire going to the top of the cap, the power fluctuates at turn over, drops down to about 8 or so...which should be normal. The motor turns over just fine, a little rough after trying a few times, but i am sure the battery is a little tired of trying with no results. Can anyone help me? I realize that there are 100 different posts on no spark for mercruiser, but I have tried everything that I have read. I am wondering if someone out there knows of something stupid that I could be over looking....

 

[rbh]

Re: 1984 Mercruiser 470 - No Spark at Cap

hey there-
what did you gap your points to?
gap to your motors spec, charge your battery so when you get it going you dont fry the altinator, and get some one to turn the engine over while you check for spark from one of the leads. if no spark ensure the coil wire is firmly planted in coil as the boot sometimes holds it out?
rob

 

[nalloco]

Re: 1984 Mercruiser 470 - No Spark at Cap

I will check the gap on the points today, not sure what they are at right now, my Father-in-law jumped in and put them in. Would this keep the cap from producing any spark at all? Are there any other causes that you can think that might keep it from sparking if they are gapped correctly and cleaned nicely?

 

[rbh]

Re: 1984 Mercruiser 470 - No Spark at Cap

if he gapped them and did not tighten down the screw tight enough they just might have closed up?
rob

 

[stonyloam]

Re: 1984 Mercruiser 470 - No Spark at Cap

Would this keep the cap from producing any spark at all?

YES. If the points do not open (or do not close) you will have no spark.

 

[searay3]

Re: 1984 Mercruiser 470 - No Spark at Cap

you will have to check the points side for a short to ground to verify it has the ability to spark. Remove the wire from the neg side of the coil. With a meter set to ohms, put a matchbook or paper between the points contacts or turn the motor until they are open. One lead to the wire and the other to a good ground. there should be no continuity. If there is, remove the wire form the points, as well as condensor. check the insulated side of the points. One lead to the points the other to ground. Again there should be no continuity. If there is the points are shorted or improperly installed. If there is not, the wire from the coil is shorted where it enters the distributor body. Tachs can also short out the ignition. remove that wire as well from the neg side of the coil. The condensor can short and kill the ignition. Remove that wire from the points while testing. Something there is shorted. only one side of the points should have a connection to ground (engine block).

 

[nalloco]

Re: 1984 Mercruiser 470 - No Spark at Cap

Thanks everyone for your suggestions, I am going to be working on the boat this afternoon when I get out of work. I will be back to post results of all attempts to get this old boat running. Thanks again!

 

[nalloco]

Re: 1984 Mercruiser 470 - No Spark at Cap

Ok guys...Great news! I got her to spark and fire up. I am assuming it hasnt been run in a while, so it was tough to keep going. And of course, there is a but...Now that I am getting spark air and fuel, it is very hard turning over, could this be a cause of a bad starter or a bad starter selenoid? Any ideas? It cranks very hard and every once in a while it will crank really quick and fire right up, but then it sounds as though the starter is getting stuck in gear and not pulling out. Does that make sense? Let me know.

Thanks!

 

[kamby]

Re: 1984 Mercruiser 470 - No Spark at Cap

Its not uncommon for starters that sit to have issues especially marine starters. Often times the pinion gear wont suck back into the starter casing and run with engine ruining the starter. When it does it pull it off teh engine and see if its still stuck up. If it is your looking at a rebuid. Probably full of rust and gunk from sitting.

Good luck

 

[nalloco]

Re: 1984 Mercruiser 470 - No Spark at Cap

Would that cause it to turn over hard?

 

[kamby]

Re: 1984 Mercruiser 470 - No Spark at Cap

Hard to say, is it just turning over slow, engine making noises, starter clunking. Could be bent starter gear. If a starter is still spinning when the engine is running you can ruin it real quick.

Start simple, check battery cables for corrosion, make sure there good solid connections. Make sure your getting good ground to engine block. Batteries are nice and charged and have the proper cranking amps for the engine. Lets see it could also be a valve lash issue requiring adjust ment. Worn out tired starter.

1st thing id check is the electrical cables. Have batteries tested if they havent been in a while. If it still does it, yard the starter out take it to a shop and tell them what its doing and see if they will crack it open to check for rust.

Had a Marine 350 engine that the starter moved really slow, after replacing the cables took it into shop and found the whole starter body full of solid rust. Sometimes it would start sometimes it wouldnt.

 

[stonyloam]

Re: 1984 Mercruiser 470 - No Spark at Cap

The same thing was happening on my 470. Turned out that the armature shaft had broken (under the windings) and the armature was rubbing on the field coils. This caused the starter to turn over slowly. Happened on two starters. Has been fine for the last 10 years. Good luck.

 

[nalloco]

Re: 1984 Mercruiser 470 - No Spark at Cap

What and where is the armature shaft?

 

[kamby]

Re: 1984 Mercruiser 470 - No Spark at Cap

Its inside the starter, when the windings and stuff get excited they cause the armature to engage and spin, which happens to spin the flywheel starting an engine or atleast turning it over.

If your having doubts remove the starter and take it in for testing, shouldnt cost anything. And if its bad have it rebuilt or get a new one.


Check this video out, about 12min and gives a run down of the starter and what can go wrong.


http://www.youtube.com/watch?v=CxjPpytfnv0

 

[rbh]

Re: 1984 Mercruiser 470 - No Spark at Cap

so why no spark?

 

[nalloco]

Re: 1984 Mercruiser 470 - No Spark at Cap

so why no spark?

I think it was a number of things, from bad connections to just making sure everything was right. Double checked the gap on the points, had to adjust and clean them, replaced the condensor again. I think it was just a combination of all of that stuff plus not being started in a year. Now I am going to take the starter out tonight and have it checked tomorrow. Hopefully I wont have to replace that. $250! That is a quarter what I paid for the whole boat! Thanks everyone for all of your help, it is greatly appreciated. Seems to me that everyone on here knows what they are talking about. This is my first boat that I personally owned, although I have grown up around them...we'll see what the first summer of boating brings me! Thanks again!

 

[nalloco]

Re: 1984 Mercruiser 470 - No Spark at Cap

Good news guys! I took the starter apart, cleaned all the contacts and got all the rust and crap out of it. Put it back in, tightened everything down...Motor is running like a champ! She purrs like a little kitten. Just got a little interior remodeling to do and she'll be like a new boat. Thanks so much for everyones help, I really appreciate it!

 

[kamby]

Re: 1984 Mercruiser 470 - No Spark at Cap

Glad to hear u got it going. Hope you have lots of fun with her. Now for the maiden voyage to see how the engine performs and how the drive does.

Congrats..