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Closet Powerboater
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Discussion Starter · #1 ·
I've been told that I'm not firing on all cylinders.:D

When I bought my boat 2 years ago I had the Perkins 4-108 surveyed and the mechanic said one of the cylinders wasn't firing. He noticed at the time that we were over-propped and he figured the injectors got coked up with carbon. He said it might take an injector service to fix the problem or, if we pitched the prop down and ran it hard for a while it may just fix itself. We tried option 2. We took 3inches of pitch off the prop and ran it hard for quite a few hours, especially on a 3 week trip.

Now, I want to know how do I figure out if I'm firing on all cylinders? i.e. did I fix the problem or does it remain?

MedSailor
 

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337 Posts
Buy a laser thermometer and point it at each cylinder head right next to the injector. If the cylinder is not firing, the temp. reading will be much lower.
 

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That will help diagnose your 4-108, but if your friends are saying you aren't firing on all cylinders, they probably know best!
 

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Closet Powerboater
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3,925 Posts
Discussion Starter · #4 ·
Buy a laser thermometer and point it at each cylinder head right next to the injector. If the cylinder is not firing, the temp. reading will be much lower.
That sounds like it could work AND it involves buying a new toy with the word "LASER" in the title!:D Seriously though, won't the block equalize in temperature quite quickly, being metal and all? Should I run the test after a set number of minutes ie during warm up?


Any suggestions on where to buy one of these phazers?

MedSailor
 

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Telstar 28
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993 Posts
Try here
Not laser, but infrared, only $46.
 

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Don Radcliffe
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398 Posts
For free you can let the engine idle, and crack the fuel injector inlet pipes one by one. If the cylinder was firing, the engine will slow down and run rougher when you loosen the nut on the injector pipe.
 

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Closet Powerboater
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3,925 Posts
Discussion Starter · #7 ·
For free you can let the engine idle, and crack the fuel injector inlet pipes one by one. If the cylinder was firing, the engine will slow down and run rougher when you loosen the nut on the injector pipe.
A phazer toy is cool, and I LOVE another excuse to buy a tool but learning how to diagnose it with nothing more that what I have onboard is what it's really all about. THANKS!

MedSailor
 

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The slacken of the injector HP connection is the best wah and have a roll of Kitchen tissue handy to catch the drops.

This is actually best done under load so that a poorley set fuel pump doesn t mess up the experiment. IE run the engine in gear and then slacken of the connections one by one and retighten before moving to the next. If there is no change in engine note when one is slack and spraying fuel then that cylinder is not working. Next remove that injector and check you have compression in that cylinder . If lots of compression then it could be an injector problem or pump problem. If no compression then valves or rings.

You need to ensure the engine does not start so may have to slacken of the other injector connections and catch the fuel with tissue.
 
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