No Spark Mystery

[andrewterri]

I am back to helping my friend that bought our old boat. It is a 89 mercruiser 3.0. The boat still has a points ignition. The problem is the boat has no spark. Seems easy enough to fix. However, When you turn the key on and crank the engine the negative battery terminal get extremely hot and would start a fire if not turned off or unplugged. When my friend told me this I told him to check all connections and grounds and clean any that are corroded. He did this and it fixed the problem. He did not know how to fix the spark issue so he brought the boat to me. I have changed the coil, replaced the points and gapped to .22 as the specs call for, I have verified the interrupter switch is not engaged and still can not get spark. I can not figure this one out. Can you guys please help? Any thoughts? I have the outdrive off from changing the lower shift cable and bellows so I can turn the engine over as much as needed without hurting the impeller. Is there any wire that is known to have problems after a grounding issue? I have checked the fuse at the ignition switch and it is good.

 

[Bondo]

Ayuh,..... Is there voltage at the coil's (+) terminal, when the key is in the On position,..??

 

[andrewterri]

Its 11.38 key on points closed. It slowly climbs up if you leave it there.

 

[achris]

With the points closed the voltage should be around 8v on coil positive. High voltage (near battery voltage) indicates the points aren't 'closed' electrically, or there's a break in the wire between to coil negative and the points. Or the points (or distributor) aren't grounded properly.

Chris........

 

[andrewterri]

So where would I look for the ground? The old points I replaced were at the same voltage, 11.38ish. So that makes me think a ground. The only ground wire is the one that goes from the distributor to the negative coil side right? I do not have the tach wire connected or the hour meter wire. Those should not have anything to do with it but wanted to mention it anyways.

 

[andrewterri]

Can the condenser cause the high voltage? It was not replaced with the points.

 

[achris]

Turn the key on, make sure the points are closed, measure the voltage between the distributor body and the negative terminal of the BATTERY. Should be zero volts. If it is, then the problem is between the points and the coil.

No, a shorted condenser would pulled the voltage down, and an open would allow the voltage to be at about 8 with the points closed.

Chris.......

 

[andrewterri]

Thank you achris, I will check that. If I show zero volts could I make up a jumper wire with alligator clips and hook it on the brass screw of the points to the negative side of the coil to bypass the ground wire from distributor? Wouldn't that tell me if that ground wire from the distributor that goes to the negative side of coil is bad?

 

[achris]

There shouldn't be a wire going from the body of the distributor to the coil negative. The coil negative should only have the wire to the NON-gound side of the points, the shift cutout switch and the tacho on it. What I'm saying it if the distributor body has lost its contact with a proper ground, then you'll get the indications you are getting (but those are the same indications as a broken wire between coil negative and points)...

 

[tank1949]

So where would I look for the ground? The old points I replaced were at the same voltage, 11.38ish. So that makes me think a ground. The only ground wire is the one that goes from the distributor to the negative coil side right? I do not have the tach wire connected or the hour meter wire. Those should not have anything to do with it but wanted to mention it anyways.

1989? Clean ALL grounds! Look for NON marine wiring used. Marine stuff is tinned and doesn't get green like the other solely copper stuff. Green is corrosion and is NOT good in a boat. Former owner of my current rebuild used non-tinned wiring for all his new instruments. Cheap and looks pretty for a while and then the saltwater environment (in my case near the Gulf) creeps in. Even in fresh water, pure copper will start to turn black over time and difficult to re-solder. Buy yourself a good multi-meter and back track all wiring/voltage. You will find the issue. I did on mine!

 

[andrewterri]

Thank you guys. I am going to check that as soon as I get home. One question though, where does the distributor ground at? Is it through the bolt and base plate that tightens it to the block?

 

[Scott Danforth]

file your points. you even need to file new points

file them, gap them, verify the dwell, install the cap, and then set timing.

 

[andrewterri]

Now I am really stumped. Achris, I did your test and I am getting 11.4 volts across the both terminals ( + - ) with the points open and closed. With the cap off I checked the metal plate of the distributor housing and it was zero volts with points closed. The point housing itself had 11.4 volts with the points closed too. Does anyone have any idea how I am getting 11.4 volts across both terminals open and closed?

 

[achris]

Now I am really stumped. Achris, I did your test and I am getting 11.4 volts across the both terminals ( + - ) with the points open and closed. With the cap off I checked the metal plate of the distributor housing and it was zero volts with points closed. The point housing itself had 11.4 volts with the points closed too. Does anyone have any idea how I am getting 11.4 volts across both terminals open and closed?

What are you using as the reference? ie, where is the black probe of the meter?

Saying '11.4 volts across the both terminals ( + - )' to me means you're putting the black on one of the terminals and the red on the other.

Let's go back to basics.

1. Remove all wires from the negative terminal of the coil.
2. Put the black probe of the multimeter on the negative terminal of the battery (it will stay on this terminal for all measurements).
3. What voltage are you getting on the coil +? What voltage on the coil -?
4. Use a short jumper wire and connect it from the battery negative to the coil -. What voltage at the coil +?
5. Same jumper wire, but this time from the distributor body to coil negative. What voltage at the coil +?

Chris......

 

[andrewterri]

I will go complete the steps now. How I tested was the black probe on the negative battery terminal the entire time. I tested key on points open and closed all 11.4 on positive and negitve coil terminals, however, I did not disconnect the Resistance wire and alternator wire from the positive side or the low tension wire from the negative side of the coil.

I am assuming my friend connected the coil correctly before I got the boat and assuming has never worked out good for me before. Does the purple wires go on positive side along with tac wire and the wire from distributor go to negative side of coil? Thank you guys again for your help and I am going to do all tests as you described now.

 

[achris]

Correct wiring for the coil on a 3 litre with points.


May also have another wire from the coil - to the shift interrupt switch. (Or it could be a splice in the harness)...

 

[andrewterri]

Achris, I completed the tests. The parameters were key on and points open. I closed the points after the test when I noticed they were open and repeated several tests and will note the results. The only wires that were attached to the coil were the positive resisance wire (two purple wires together) and the high tension lead that plugs into dizzy cap ( spark plug wire if my nomenclature is wrong).

NO WIRES ON NEGATIVE TERMINAL

+ terminal 11.37
- terminal 11.38

JUMPER WIRE FROM BATTERY TO NEGATIVE COIL TERMINAL

+ terminal 5.89
points closed = 6.01


JUMPER WIRE FROM DIZZY BODY TO NEGATIVE COIL TERMINAL

+ terminal 5.91
points closed = 6.04

 

[andrewterri]

Achris, The coil is connected correctly. Thanks for the diagram

 

[achris]

Those results are what I would expect. Are you looking for spark at the spark plugs ends of the HT leads from the distributor, or from the HT tower of the coil?

If you're still getting battery voltage (12v) on the coil - with the points closed (all test wires removed), then you have bad points or a break in the wire between coil - and the points terminal in the distributor...

Chris.....

 

[andrewterri]

I was looking for a spark by putting a lighted spark tester on a wire than hooking the other end on the spark plug. And yes, I have 11.4 volts on the negative side of the coil with all test wires unhooked and points closed. The voltage does not change on the negative terminal whether the points are open or closed.

The wire that runs from the stud on the points, to the distributor housing, than to the negative side of the coil felt like it was cracking as I bending and feeling it by the dizzy housing where it comes out. Can I replace that wire with another one? It seems like i could put a ring terminal on both ends of a wire and hook it up to from the points to the coil. Is there another way to test for spark besides a light up spark tester? I have also tried starting and moving the interrupter switch just to verify that is not it.