compression test quckie

[SirEnvy]

Default Re: Compression test by JB

Just make sure your ignition is disabled with the plugs out and cranking over. I've seen some mtrs go "boom" if this is not done.


This was in the top secret forum, and I am confused. Why would I need to disable the ignition and worry about the plugs, if the plugs are OUT of the motor, or if the wires are all disconnected.

 

[jonesg]

Re: compression test quckie

If the cyl's happen to be flooded with raw fuel and you leave plug wires dangling in front of the openings and sparking to the block, you will be spraying atomized fuel directly at sparks, you'd get an education pronto.

 

[SirEnvy]

Re: compression test quckie

If the cyl's happen to be flooded with raw fuel and you leave plug wires dangling in front of the openings and sparking to the block, you will be spraying atomized fuel directly at sparks, you'd get an education pronto.

So the moral of this is to be careful, and think about covering wires, or removing wires from coil to prevent a BOOM

 

[F_R]

Re: compression test quckie

No, the moral of the story is disable the ignition. Some, but not all, ignition systems will be damaged by trying to jump a spark gap that is not there. If nothing else, it is a severe strain on the coil(s).

Easiest way to disable the ignition is pull the lanyard, if there is one. Another simple way is ground the plug wires. If you do this often, make a set of wires with alligator clips on both ends. One alligator in the plug boot, other end to ground on the block or something.

I have personally shot fire out of the plug holes about six feet. Good thing I wasn't standing in the way.

 

[SirEnvy]

Re: compression test quckie

and what if I leave my plugs in? And take one out at a time...same thing?

 

[JB]

Re: compression test quckie

and what if I leave my plugs in? And take one out at a time...same thing?

Your results will be severely distorted.

 

[1946Zephyr]

Re: compression test quckie

I have personally shot fire out of the plug holes about six feet. Good thing I wasn't standing in the way.

I once did this to my lawnmower. The cylinder flooded out with gas, so I took the plug out and yanked the cord, to blow it out. Needless to say, I had a nice flame thrower, when the lead sparked on the cylinder head.

Half of my lawn did not need mowing that time.

 

[Jayrock]

Re: compression test quckie

Just follow the directions in the sticky. If you have to be convinced to do so, it is even more important to FOLLOW THE DIRECTIONS CLOSELY. Or you can injure yourself, or your beloved outboard. Not to mention just wasting your time with a flawed test. Good Luck, and have a fire exteguisher within arms reach at all times while goofing with any gas powered engine.

 

[ebrich2]

Re: compression test quckie

one other thing my merc manual said do when doing a compression test is to dis-connect the fuel line to the engine along with pulling all plugs.

 

[SirEnvy]

Re: compression test quckie

man, I am kind of nervous, first time doing this...I dont even know if this is my problem. I had a compression test about 2 months ago, and the mechanic said it was GREAT...im going to my local hardware store and getting some wire and alligator clips and making my own ground, and then clipping it to the wire(inside the wire) and to the nearest screw on my outboard.

 

[SirEnvy]

Re: compression test quckie

Im working on a 1985 Evinrude 150...I dont think there is a lanyard.

 

[SirEnvy]

Re: compression test quckie

Can I buy a remote starter switch with alligator clips, then clip them on the screws of the starter? By doing this, I can leave the key in the off position and not worry about spark?

 

[wifisher]

Re: compression test quckie

Can I buy a remote starter switch with alligator clips, then clip them on the screws of the starter? By doing this, I can leave the key in the off position and not worry about spark?

yes

 

[JB]

Re: compression test quckie

The jumper (or remote starter) connects from the +12V input at the solenoid to the small stud where the wire is coming from the ignition/starter switch, Sir Envy. The idea is to energize the solenoid with low current. If you try to jump the +12V directly to the starter you will start a fire.

Follow the instructions and you will be fine; it is not rocket science.

BTW, there would be no harm in disconnecting the fuel line but there will still be fuel in the carbs, so don't get the idea that hazard from fuel is removed by doing so.

 

[SirEnvy]

Re: compression test quckie

The jumper (or remote starter) connects from the +12V input at the solenoid to the small stud where the wire is coming from the ignition/starter switch, Sir Envy. The idea is to energize the solenoid with low current. If you try to jump the +12V directly to the starter you will start a fire.

Follow the instructions and you will be fine; it is not rocket science.

BTW, there would be no harm in disconnecting the fuel line but there will still be fuel in the carbs, so don't get the idea that hazard from fuel is removed by doing so.

Okay 10-4...im just going to ground the wires to the nearest screw on my outboard...there are plenty near the coil so I will just ground to that.