Head scratcher.

[GatorGreg]

A little background first. 94 GTS, engine rebuilt 3-4 years ago. Just got it going a few weeks back from sitting over the winter. After 3 hours of draining and replacing fuel etc. got it fired up and went on test ride. Blew out the wear ring after the first 5 min, removed all the debris from the prop and limped it back to the dock. Trailered the ski home and started ordering parts. Replaced the wear ring and pump oil. Also, replaced the old gray fuel lines, rebuilt the carb (reset the adj screws to factory), cleaned fuel selector, installed inline fuel filter. Replaced large oil supply and return lines to cyl block(running premix/blocked off). Charged the battery. Also some other various cleaning & repairs. I did not fire it up in the driveway on the hose because I left the kill lanyard at the boat house. :banghead:

Here is the weird part. I took the ski down to the ramp to start the setting the idle and low speed adjustments but could not get it to start. I used the plastic bag over the intake, could see the inline filter fill up and then smelled the fuel. Still no dice. I pulled the plugs and check for spark, checked good. Cleared the cylinders out with the plugs removed. Reinstalled plugs, still no go. This went on for a good hour while standing thigh deep in tanin stained gator infested canal water. Pulled the ski back to the house so that I could fight with it on dry land. Messed around for another half hour with no luck. Ran up to the local parts store and rented a compression gauge. With both plugs out was only getting 90psi tops on both cyls. (did not know to wot, until I seen it on another thread this morning). At this point I'm resigned to doing a top end. Put it all back together and walked away to work on some other things. About 4 hours later I just happened to walk past the ski again and for some reason I grabbed the choke knob and hit the starter button and it came to life. Was able to run it on the hose for a couple of minutes and eventually put it back in the water and motor it 1/8th mile to the dock, will tune the carb another day. But what gives? I'm not sure why this kicked my butt for hours only to start up later, did I flood it out? Any ideas?

I'm going to recheck compression with wot in the next few days when I set the carb.

Thanks to everyone on this forum, I've been turning wrenchs for years. From cars to fighter jets to bulldozers. But, I learn something new from this site everyday. Thanks again.

 

[bigJake]

I don't want to hijack the thread, just add a question. I know to do the compression test with WOT (because KustomKarl gave me instructions a couple years ago when I did my first compression test) but I don't know the technical reason behind it? I just like to have an understanding of WHY I'm doing something? Thanks.

 

[KyleB]

Jake, the reason why you test with WOT is so the butterflys in the carbs will open up all the way and give each cylinder the most air possible to compress. That's the way I understand it. Hope this helps.

Kyle

 

[Dr Honda]

Jake... Kyle is right on the money. It's not always necessary to hold the throttle open, but it's the "Normal" way to check, to get good cyl filling.

Greg.... well... 90 psi... that engine is done. It will start on the trailer because there isn't a load on the engine... and there is no water in the exhaust. (not enough to put pressure on the engine) If the gauge is right... it's not going to start in the water. It just can't compress the air/fuel enough to get good combustion.

FYI... that engine should be seeing 145 to 150 PSI cold.

Sorry.

 

[bigJake]

thanks for the clarification guys. Sorry about your engine Kyle, that really sucks.

 

[GatorGreg]

Dr. thanks for the help. I think I was checking compression wrong (not wot). It did start in the water and run, I did not take it up to high rpms because I was in a no wake zone going down the canal, but I was able to goose it a few times and got a good response. I'm just confused why it was so hard to start when I was working on it, then started easily a few hours later with no tinkering!!??

I've always had issues starting both my skis during a cold start. What is the proper procedure for a cold start? I normally hold the choke closed and squeeze the throttle a couple of times while cranking. But sometimes it takes 4-5 thirty second starter cylcles to start. If the engine is warm I usually crack the throttle a little and it will fire up.