'98 GTX RFI fouling plugs

[dperkinstx]

I have a '98 GTX RFI that's suddenly fouling plugs on a regular basis. I install two new plugs, then take it for a ride. It runs great. We usually ride for about an hour. The next time I take it out, it starts running poorly and gets progressively worse until it barely runs. It won't keep running when idling through a no wake zone. I replace the plugs and it runs great again.

I've gone through three sets of plugs in the last few rides. What could be causing this?

 

[Dr Honda]

Your injectors are leaking. Time for a rebuild on them.

OR.....

The cable going down to the oil pump broke, and the spring pushed it wide open. (but then it would be smoking badly)

 

[dperkinstx]

Your injectors are leaking. Time for a rebuild on them.

OR.....

The cable going down to the oil pump broke, and the spring pushed it wide open. (but then it would be smoking badly)

I'm the kinda guy who likes to know how things work and I'm having trouble understanding your diagnosis. This ski doesn't mix the oil & fuel, so how can a bad injector cause the plugs to foul? If the injectors were bad, wouldn't I be down on power. When I install new plugs, the ski seems to run fine for a while.

I reached down and felt the oil pump move while working the throttle, so I know the cable isn't broken.

Thanks for your help.

 

[jhjesse]

Over time fuel injectors get varnished and clogged up causing the injectors to dribble gas instead of spraying (atomizing) the gas causing the plugs to foul.
I would replace the injectors or have the existing ones cleaned/rebuilt.
http://www.fiveomotorsport.com/0280150845-65lb
Website says discontinued, but I would call them anyway.

 

[dperkinstx]

I have two GTX RFIs, a '98 and a '99. The '98 is the one fouling plugs.

I had the injectors and fuel rails on both skis cleaned/rebuilt. I took them to this guy:
https://www.injectorrx.com

When I reinstalled them the following happened:
The '99 fired up on the first bump of the start button. It's running great! Funny thing is, it's injectors looked the worst (all rusted up). The injectors looked so bad I bought another pair, along with a fuel rail, on ebay. Since I paid to have the rusty ones rebuilt, I went ahead and reinstalled them. They're working great.
The '98 runs worse that ever. It's hard to start. It runs rough. It sounds bad. It won't idle. It does, however, seem to run better once I squeeze the throttle and get up to speed.

I decided to take the injectors from the '98, along with the two I just bought, back to the place I had them cleaned. He said the two from the '98 are "working perfectly". (Side bar... when I removed the injectors this time, one of the injectors fell out of the fuel rail. The circlip was half broken off. I don't know if this would have affected it being seated properly or anything like that, but I doubt it. When I originally removed the '99s injectors and rail, the circlips were pretty much rusted away, but the ski was still running fine.)

I ordered new circlips. When they arrive, I will have my injectors back, along with a spare pair of injectors and fuel rail to try. If I try both, and the ski still runs, poorly, what's my next step? Fuel pump? Coil? Something else?

 

[Mickirig1]

Make sure you have spring tension on the oil pump bell crank. It's real easy to install it wrong and have the pump flowing too much oil. The spring may of broken too. Check the adjustment marks are lined up and return to them after full throttle movement. Try the trim the spark plug wire back and re-install on the boot procedure. Put Dielectric tune up grease in the boots to seal off moisture and voltage leakage. Maybe even the coil is getting weak, low voltage or intermittent failure. Clean the plugs and re-gap. My plugs have 50 hours on them and still run strong.

 

[dperkinstx]

I got my fuel injectors back, along with new circlips. I installed them and tried again. The ski still runs bad. It won't even idle. I revved it up and it seems to run better, but I noticed the motor "pulsating". I held the throttle about half open. The motor would speed up and slow down a couple hundred RPMs. I removed the spark plugs, then put them back on the plug wires. I cranked to make sure I got spark. The spark was bright white.

What else could my issue be? Bad fuel pump? Could the injectors not be getting a good signal? Something else?

Any input would be greatly appreciated

 

[racerxxx]

Just to make sure nothing is wrong, put the set up from the good running ski into the bad running ski and the bad into the good. That will get you whether your working on an injector problem or something else.

Sent from my SGH-T889 using Tapatalk

 

[- BiRkS_]

+ 1 with racerxx said. Also You need to determine what is fouling the cylinders. Is it fuel, oil, or water? I had an rfi that would only run on one cylinder and the plug was always perfectly clean. Tore down the head and had a bad o-ring on the head...

Another possibility is the fuel pressure regulator is going bad and over pressurizing the system. On any RFI ski i have worked on, I've always removed the fuel baffle and cleaned/replaced the filter screen and inspected fuel pump and reg.

 

[ranga97]

How do you inspect the fuel reg?

 

[dperkinstx]

Update:

Today I brought the skis from the boat shed to the house. My intent was to swap stuff with my good running GTX RFI until I found exactly what was failing. Just for grins, I did a compression test first. I'm only getting 30 PSI from the front (mag) cylinder. The rear (PTO) cylinder is 148.

The ski runs, but poorly. At idle, the motor shakes hard.

I've installed the injectors and fuel rail a couple times already. I used the same method on the good running ski. Therefore, I don't think I'm losing vacuum around the hole where the injector is seated, but I'm wishing that's the issue.

I'm at a loss. How can fouling plugs turn into no compression and not being able to idle?

 

[crundell73]

I was having missing troubles on my 787 and tested it with a timing light and found out I have no good spark on the first plug and not getting any spark from my back plug wire , but I think I had my stator shorting out from metal shavings .

 

[Mickirig1]

Sounds like top end is toast. Maybe too much gas not enough oil. Wore out the rings or a popped gasket.