Hard starting/cranking 155 part#2

[68ragtop]

A couple years ago I bought a 2002 4tec n/a 155 with only 50 hours on it.

Like most of my skis I bought this one not running. It suffered a locked up impeller/pump & when the previous owner tried to re-start it the ring gear broke loose from the flywheel. Yes, that was a weird one......
Some of you guys might recall that thread....

So, I rebuilt the pump, replaced the flywheel & got it on the water again running great. But, it would not restart very well when it was warmed up. After a bunch of testing the starter was found to be weak & most likely overheated from repeated attempted restarts with the locked up pump.

I replaced the starter & it was much, much better, but after spending hours on the water, I realized it was still happening when it was at full operating temperature. Even though my battery tested good, I also bought a 400CA AGM battery thinking that might help, but it didn't. The compression on this engine cold is around 185 per hole. when its hot @190 on the IR gun & bucking the starter the compression reads over 200psi. Even in flood mode with no fuel & ignition, same thing. so it's just a fight between the starter & the compression & the compression wins 80% of the time. been living with it every since. leave it cool down for 5 minutes & there is no problem.

Fast forward to this summer & I bought another 155 Project ski. Ironically it's the exact model & year. So just for giggles, I swapped everything over from the new project ski. I mean everything! Starter, solenoid, starter wires, fuel injectors, ECM, throttle body, etc. No change at all!

I have been really hoping to find another 155 owner that could tell me what their compression is when the engine is hot to see if its the same. I have a feeling this 200psi might be abnormal but am not sure why its happening.

One thing I did find was the camshaft was about 1 degree retarded. I then retorted the camshaft to the end of the adjustment slot (which is was almost there already) & it only dropped the compression a few psi if anything.

Can anyone tell me if these 155's should have that much hot compression? I am guessing nobody as ever bothered to check. I wonder if its possible that having the camshaft retarded might lower compression a little, but maybe raise the running combustion temperature? could the late fuel & air charge into the cylinder make a temperature change? Thats about the only thing I haven't tried, but only because that would raise the static compression.

Any thoughts?

 

[68ragtop]

After making the post it got me to dig into it again..

I decided to set the cam to zero just like the manual shows. This did raise my static compression a bit.
now its at 185-190 cold. But, surprisingly the hot compression is staying at 200, not higher. so advancing the cam back to factory specs didn't seem to make anything worse, but unfortunately it didn't help much either.

It Still struggles. I also paralleled a deep cycle 850cca amp battery with my heavy 4ga jumper cable set & it no doubt starts much better & spins over faster too, but even with all that amperage, it still will hesitate & not crank on some tries while its hot.

Starter gets heat soaked up to about 165 degrees. Probably normal range as everything around it is that warm. I am sure that is part of the equation. The hotter the starter, the less efficient it becomes.

 

[68ragtop]

Well, I am now at the conclusion that what is happening is heat induced ignition of the compressed fuel vapors. On one of my hot engine compression tests the engine bucked & simultaneously blew an o-ring out of my compression testers fitting. When I tandem up an additional battery for more cranking power, the engine will momentarily sputter a bit as if it was trying to start. This of coarse is in flood mode with the throttle wide open so there is no additional fuel or spark at this time. Going to try a round of direct sea foam to see if it will break some of the carbon free on the piston. Kinda doubting this will do much. Otherwise it looks like I will have to pull the head & clean it up manually.

Sorry for putting this thread in the Build section on a stock engine. Just wanted to tap into the thoughts of the guys who are messing with the engines at a deeper level

Any thoughts? I'll update on the seafoam treatment & I'll see if I can get any picts before & after of the piston domes. Not expecting it to do much of anything as I know chemdip is about the only thing that removes carbon other than manual labor.

 

[68ragtop]

Just thought I would put a close to this thread in case anybody is searching & lands on this thread. Basically what I have come to realize is these 155's just have a heck of a lot of compression. This one was at 185 cold & near 200 hot. Between fuel & exhaust vapors getting back in the combustion chamber when sitting & the slow cranking speed of the 4tec, everything has to be spot on to start easy. I was able to reduce the amount of carbon build up on the piston domes using seafoam top end treatment but the biggest culprit was the battery. I had a good battery that tested good even under a carbon pile load test. But, a fresh AGM was still better & with that changed the problem was 100% gone. It was never that big of a deal, but now I have come to realize the health of the battery & starter are the biggest things. I'm guessing these machines had starting issues back in the day from time to time with the original 330CCA batteries. Googling the issues I was having I was finding similar symptoms with other 155 owners & it usually came back to the battery / starter & quality of gas. Hard to believe it was that obvious, but I made the assumption my battery was perfect just because it "passed" the load test. It was not.