98 GTX RFI losing running on one cylinder

[JAB6]

Hi Everyone,

I took my 98 GTX RFI out today and it was running great for about an hour and a half. At this point I lost the rear cylinder. I checked the plug and it was damp with oil but i couldn't tell if there was fuel. I checked for spark and that was good, I even changed the plug but it didn't fix the problem. It almost seems as if the fuel is not getting to the rear cylinder. I've tried to take it to a dealership and they are stumped by the problem. This is a repeating problem and it usually happens at random intervals. Most of the time it is after an hour or 2 of running. The worst part is I pull it out of the lake and drive it the half hour trip home and it starts right up and runs normally. This has been bothering me/ ruining my trips to the lake for a couple years now. I'd really appreciate any advice you can give me.

Thanks,
Justin

 

[nswillin]

Start with a compression test. That piston could be on it's way out. Could be that there is no problem at first until it heats up and then starts acting up. Start there and post what you get.

 

[custompartsguy]

yeah I would say the same....do a compression check first...then if good I would possibly think about having the carbs rebuilt

 

[JAB6]

Compression Results

I just checked the compression it was 140 psi in the front cylinder and 145 psi in the rear cylinder (the problem one). The engine was cold for this test. I believe these are good numbers from what I have read in other posts on the forum. As far as rebuilding the carbs, it is fuel injected and I recently cleaned the injectors to try to remedy the problem without success.

 

[custompartsguy]

sorry I didn't notice the rfi in your post....get that engine hot and do a compression test on it please then let us know what figures you have on an hot engine....

 

[custompartsguy]

Reason I ask for the engine to be hot for the test is because that is whe you are having your problems, get it hot and if possible get a reading when you loose that cylinder

 

[JAB6]

Hot Compression Test

Ok so today i took the ski out for about an hour and a half. And I couldn't get it to stay a cylinder down long enough to get a compression check. I did check the compression on a warm engine and it was 135 for the front and 140 in the rear.

I'm going to summarize the ride just to see if it gives you all any insight. I rode for about a half hour at higher Rpms, then I ran it at a little lower RPM and it started acting up for about 5 seconds but then it came back to full power and ran it constant for another hour. During this time i never really went below 3000 or 4000 RPM mostly above 5000. When returning to the dock I had it at full throttle and i heard a Long single beep, (the fuel was getting low, could this be a warning for that?), it has never done this before. It continued to run fine until i got closer to the dock and allowed it to idle for a minute or so. The rear cylinder began to cut in and out and finally after about 2 minutes of giving it about half throttle the rear cylinder came back to life. I checked the compression and got the above results.

I really appreciate your help,

Justin

 

[custompartsguy]

1 long beep, or 1 continuous beep? 1 long beep, safty lanyard on switch more then 10 mins without starting engine,badd connection,wrong lanyard,defective lanyard,dreid saltwater in safty lanyard cap, improper operation of mpem or defective wiring harness

 

[JAB6]

Beep

It was a single long beep, probably 1-2 seconds in length. Nothing showed up on the info center, and this was about a minute before i began to let it idle. Other than hearing the beep the ski didn't act any different.

 

[Dennis]

Lost Cylinder

Switch fuel injectors and see if the problem goes to the front cylinder.
Good Luck, DAWG

 

[custompartsguy]

let me ask you a question, the only time you have a problem is when you are riding it and it never stays that way long enough to check the problem....so with that being said, how do you know that the rear cylinder is the problem and not the front one?

Same for changing the injectors around what will that do if you cannot get it to give you the problems long enough to check it?

It could be an injector giving out, to check that as an intermitant problem...I would just try and find another set of injectors and put them in to test the system, then test ride and see if that fixes the problem.

 

[custompartsguy]

The rear cylinder began to cut in and out and finally after about 2 minutes of giving it about half throttle the rear cylinder came back to life.

Please give me details as to exactly what it is doing at this time and how you checked it to find which cylinder is having the problems. Is the ski reving up and down like it is searching for an idle during this time? If so being fuel injected it does have a throttle position sensor right? If it is like I just stated and does have a tps sensor on it, if it starts going bad it will search up and down for an idle.

single or twin throttle bodies?


I need more info to help you further....

 

[JAB6]

More Details

Usually this occurs and ends my day at the lake, it stays that way until I take it the half hour trailer trip home and I start and check it and it runs fine. It just so happens when I had the tools with me to check the compression that I couldn't get it to last long enough to take a reading.

I know the rear cylinder is dead because while it is happening I can remove the rear plug wire there is no change in performance. If i remove the front plug wire the engine dies. I've also removed the rear plug wire when it was running correctly and it performs like it does when it is having the issue.

There is no searching for idle and it has a single throttle body.

 

[custompartsguy]

try swaping injectors

 

[custompartsguy]

any luck yet?