a few tuning questions

[jeff_smith_0423]

Re: a few tuning questions

well maybe i'm dead on both accounts...

I borrowed a tester from an AutoZone nearby and tested the top three cylinders. The engine was cold when i did this as i dind't want to risk further damage to the powerhead by warming it up. The top two cylinders have almost zero compression. I was able to get about 70 from the third.

Also, the top two have no spark. Had a neighbor watch the spark tester.

Should I attempt a decarb with seafoam or am i just screwed?

 

[achris]

Re: a few tuning questions

That wire with the insulation missing is a trigger wire. There are 2 triggers, each fires 2 of the cylinders. One cylinder fires when the trigger pulse is negative and the other cylinder fires when the pulse is positive. If you lose one wire of a trigger, you lose 2 cylinders. The failed insulation will probably go all the way up the sleeving, and there is probably insulation gone off the other wires too. Moving the wires as little as possible, remove then from the switch box and check with a multimeter to see if any run to ground. It's a bit of a pointless (no pun intended) exercise to check the triggers wire-to-wire because they are just a coil and will show a 'short circuit'. You can check that you have no continuity between the 2 triggers though...

Compression problem. Take the top transfer port cover off and have a look at the piston skirts. Transfer ports cover is on the starboard side of the engine. Only 6 (I think) small screws hold it on and you'll be able to see the rings and also the piston crowns. One cover does two cylinders.

Chris...........

 

[jeff_smith_0423]

Re: a few tuning questions

Great suggestions. The trigger issue seems like the solution. My neighbor has a multmeter so once i get ahold of him, we'll test that out.

What should i expect to see when i remove the transfer port cover? If rewiring that triggger fixes the problem should i get it running and do a decarb first, check the compression afterwards, and then move forward with this? It looks like i have to remove the entire switchbox and fuel pump to gain access. I'm afraid i could screw up more just by digging into it.

Oh - and the top two piston tops look pretty carboned up, but i guess that is to be expected.

 

[achris]

Re: a few tuning questions

If you have zero compression, it ain't carbon! If I saw zero on 2 cylinders the first thing I would suspect would be that I screwed up the test. But that's me. So, go out and do the test again. It doesn't matter that the engine is cold.. You will get good readings. If you still see zero on the gauge, stick your finger over the hole and verify that you really do have no compression. You see the theme here? Make sure the throttle is full open when you do the test.

Cheers,

Chris.............
I'd buy/build a remote starter switch. That way you can do all the testing by yourself and don't need a 'key-man'.
It's just a press button momentary switch with a couple of wires with alligator clips on (we use crocodile clips in Oz ). I stuck the switch into the top of a 5 inch length of polypipe and wrapped a bit of insulting tape around it. Make the wires about 10 guage and you'll never have any problems. You hook one clip to a 'hot', usually red, and the other to the solenoid coil wire (solenoid has 2 smaller wires, one to ground, the other from the key. That's the wire you want, the one from the key. It won't be black!) on the starter solenoid, usually yellow.

 

[jeff_smith_0423]

Re: a few tuning questions

i'm sure there is operator error / suspect tool involved in the compression test. When i do the first two cylinders, the guage bounces a little bit between the 0-10 psi range, and the third cylinder will bounce with each cranking stroke up until the 60-70 range - BUT the guage is definitely not holding air. goes back down to zero as soon as i stop cranking. I don't see how i was able to get this motor running this morning on two cyls with no compression, the third with 70, and who knows what on the fourth. Can't get the mercury guage ordered until monday.

Thanks for answering my "remote start" question in advance - it was going to be my next question.

I've got the multimeter and hopefully my service manual can tell me what i need to do with it. It just looks like a label full of gibberish to me

 

[jeff_smith_0423]

Re: a few tuning questions

Oh, and i just did a rough test with my finger in the spark plug hole. Cranking the flywheel around by hand DOES force air against my finger and escape outwards.. same on the other two accessible cyls.. so there is SOME compression there. It doesn't seem like the piston is just in the sleeve with no ring whatsoever.. but, i guess i'll see that once i get the transfer port cover off.

 

[achris]

Re: a few tuning questions

I've got the multimeter and hopefully my service manual can tell me what i need to do with it. It just looks like a label full of gibberish to me

Oh dear, it looks like reality is on the blink again... - Marvin, the paraniod andriod.

Find a book on basic electrics. If you haven't used a multimeter before then you won't know what you're reading or what you're looking for....

Chris.............

 

[achris]

Re: a few tuning questions

Why are you waiting for the compression gauge from Merc? Just buy a gauge with a flexible neck (rubber hose) that any backyard mechanic would use. It doesn't have to special because it's marine (one of the few things ). As long as you can screw the end into the spark plug hole you'll be right.

Cheers,

Chris...........

 

[jeff_smith_0423]

Re: a few tuning questions

A couple things for you all.

I performed the trigger test as indicated by my manual. Spec was 7-10 r X100. got readings of .788 and .766 so i think the trigger itself is good. I slit open the trigger wire sheathing and inspected another 3 inches. The insulation destruction ends about 2 inches in. So - i'm going to get some crimp splicers and mend that section of wire. Hopefully this gets those top two cylinders firing. I'm going to build a remote start switch today as well.

When it comes to electricity, I'm not a complete moron, just inexperienced. I can usually figure out test procedures and the like without much trouble - just usually need a little bit of guidance to get started.

As far as the compresion tester, I'm still going to wait for one that I can access all four cyls with. I tried in vain for about twenty minutes to get the tube-styled one to thread, but there just isn't enough clearance in the lower cowling for me to do so. I can't get a spark plug socket in there, and i can barely get my hands in to start threading the plug. I'm pretty cheap, so the thought of spending $40 on a tool that won't be 100% useful is painful to me. I'd rather spend a little extra, and have to wait a bit, if it's going to give me something that'll be more useful and appropriate in the future.

As for this rented guage, I'm taking it back since i can't believe for the life of me that it is working properly. 10-10-65 on an engine that was starting easily and idling nicely before this failure seems pretty suspect.

 

[achris]

Re: a few tuning questions

A couple things for you all.

I performed the trigger test as indicated by my manual. Spec was 7-10 r X100. got readings of .788 and .766 so i think the trigger itself is good. I slit open the trigger wire sheathing and inspected another 3 inches. The insulation destruction ends about 2 inches in.

Your resistance readings sound ok. Be aware that sometimes the insulation breaks down at the top too. Where the wires come out of the sheathing to go into the plastic trigger ring.

As for this rented guage, I'm taking it back since i can't believe for the life of me that it is working properly. 10-10-65 on an engine that was starting easily and idling nicely before this failure seems pretty suspect.

Agree....

 

[jeff_smith_0423]

Re: a few tuning questions

Yep. If this doesn't fix it, i guess the next step will be figuring out how to pull the flywheel to inspect the leads at the trigger.

 

[jeff_smith_0423]

Re: a few tuning questions

Well, i spliced into that trigger wire, reconnected everything, and the motor started. Pulled plug wire one - no change.

Shut it down, hooked up the spark tester, jumped the solenoid with a screwdriver since i couldn't find an appropriate momentary switch. No spark on 1 and 2, hot spark crossing about 1cm on #3.

Anything else i can test or try before tearing the flywheel off to visually inspect the trigger? Coils?

 

[achris]

Re: a few tuning questions

To verify that is the triggers, just swap the two trigger pairs on the switch box. Swap the top two trigger wires with the bottom two. If the fault follows the trigger wires, it's a trigger problem. If not, it's the switch box, (or coils, but unlikely you'd have 2 go at the same time).

Chris.........

 

[jeff_smith_0423]

Re: a few tuning questions

swapped trigger leads. no change. I might swap a coil from 3 to 1 just to rule out the coils before i spend what looks like $173 on a switchbox.

 

[achris]

Re: a few tuning questions

As you don't have DVA multimeter it will be difficult to check the output of the stator, but you can still measure the resistance of the coils. You could also swap them the same as the triggers. Worth checking and that will confirm 100% if you need a switch box.

Chris...........

 

[jeff_smith_0423]

Re: a few tuning questions

Compression tester came in today - kind of a wash because i still can't get to the #4 cylinder with it. I migiht be able to with a little more light and a little more finagling.

BUT - the guage read right around 130 on each of the three accessible cyls. I'm relieved. Relieved to the nth degree.

a little further testing and I'll get that switchbox ordered.

Previous searching has led me to believe that CDI is the best choice. Consensus here?

 

[achris]

Re: a few tuning questions

...
BUT - the gauge read right around 130 on each of the three accessible cyls. I'm relieved. Relieved to the nth degree......

I'm not going to say 'I told you so' , but that is good news....

As for switch box, I've always used OEM, so I can't comment of the after market stuff... I've heard both good and bad reports, same as OEM...

You pays ya money, you takes ya choice......

Chris.............

 

[hkeiner]

Re: a few tuning questions

A DVA meter is a good investment. In the long run, it is usually cheaper to troubleshoot/confirm a suspected ignition part failure using test meters than replacing expensive ignition parts on a hunch (educated guess). That is my experience anyways. Ebay is a good source for used stuff like a DVA meter. That is where I got mine pretty cheap.

 

[jeff_smith_0423]

Re: a few tuning questions

I certainly agree. I've been looking around for a decent DVA meter and plan to test as much as i possibly can before throwing money at parts. There is nothing i hate more than throwing money at problems. I was hoping to remove and resistance test all of the ignition coils today, and then test by swapping coil leads, but it's about six degrees here, and even in the garage, it's only about 15. I want it running but not that badly.

 

[jeff_smith_0423]

Re: a few tuning questions

..or maybe i should see if any of the dealers around here can actually test the components for me. Being land locked in central indiana, dealers are few and far between though.