95 SPX revving very fast w/fuel in 'On' position but normal in 'Reserve' position

[ettguy]

Hey guys,
New to the forum and have been searching for this issue but haven't found it discussed quite like I'm experiencing it.

My 95 SPX fires okay out of the water but after a couple minutes, it starts revving extremely high with the fuel selector in normal. I replaced the gray lines yesterday but the problem continues.

So today I tried running it with the selector in Reserve and lo and behold, it runs perfectly normally. Is the problem the fuel selector valve or the carb or something else? Whichever it is, please point me to procedure to remedy the problem. Thanks!

Tom

 

[gsxgtxman]

Probably wouldn't hurt to replace the fuel selector.

 

[ettguy]

Not a fuel selector problem

I pulled the Fuel Selector and it didn't look too bad. I cleaned it up anyway with carb cleaner and blew it out with my air compressor. No flow restriction at all with either selection. Put it back on and still getting the runaway revs in the On position.

Any other suggestions?

 

[Dave_eng]

I would be double checking the fuel line routing to the fuel tank sender. It is easy to mix up the lines and then strange things start happening. If you look closely on the top of the sender the fuel line ports are identified.

Dave p

 

[ettguy]

Good thought, Dave. That sounds like a bone-headed thing I'd do but not this time. I saw where the lines were labeled so I marked them with tape before removing any of the lines so I'm sure I re-routed the black ones correctly.

Again, this problem was occurring before I touched any of the fuel lines so I don't think that is the problem as it ran fine last season.

Is the only difference between the reserve and on position that the reserve bypasses the fuel filter? I seem to remember there was another difference but can't recall what that was.

 

[gsxgtxman]

What's the compression?

 

[ettguy]

Compression?

I don't know. I guess I could borrow a tester from a buddy if you think that matters. Is there an expected compression difference when running on Reserve?

I have another SeaDoo that broke a crankshaft last year so I pulled the fuel probe off of it and replaced the other one thinking that that might be the problem. No joy.

Still runs away in On but runs normal in Reserve.

 

[ettguy]

Bump

Has anyone ever heard of this issue before? I'm stumped.

 

[gsxgtxman]

Usually the runaway symptom is due to either an air leak around the carbs or you're running too lean.

A compression test is the starting point when diagnosing any motor issue. If you know your compression is good we can start to diagnose. Typically you want 150 psi on both cylinders. 120 is okay. What you dont want to see is 150 on MAG and 100 on PTO. I believe +/- 15% is acceptable.

 

[ettguy]

Okay, I'll borrow a tester and check it out. I suspect the compression will be normal since it runs well in the reserve fuel position though. Thanks for your feedback!

 

[wombat1]

I just installed a primer kit on my 97 GTX today. I had to pull the carbs to install the kit. One of my carb gaskets was slightly damaged but I decided to install it any way, since I couldn't get a replacement today.

After starting up the ski on the trailer the revs went sky high and I had to shut it down. Did this three times and decided to look at it tomorrow, since it was getting late. I suspect that I have an air leak from that bad gasket.

 

[ettguy]

Very interesting Wambat1. I'd be curious to hear if it has the same issue if you switch the fuel to reserve before you replace the gasket.

 

[gsxgtxman]

I just went through the same thing on my GTX LTD 951. I tried to save some money and reuse the gasket that I knew was damaged. Started er up and she rev'd to 6200 rpm. It scared the $hit out of me. It wouldn't shut off.:willy_nilly: I pulled the lanyard, battery, turned off the fuel, and finally killed it by pulling the choke. If it happens to one of you, your choke is your best friend.

 

[ettguy]

Wow!

Holy crap! I guess that's how Toyota drivers with stuck accelerators felt. :auto:

 

[ettguy]

Still stumped!!

Well, I'm still baffled by the problem. I pulled the carbs off today and found that the small filters were very clogged so cleaned them up really well. Didn't find any other issues like bad gaskets or crud anywhere so I put it back together.

Again, it purrs like a kitten for as long as I care to run it with the fuel selector in the reserve position but then I switch to the On position and within about 10 seconds, it starts revving up, up and away. Switch back to reserve and it settles right back down again.

Can anyone tell me besides running the fuel through the main filter what is different when running on reserve?

 

[ettguy]

Tried one more thing - FAIL!

I replaced the fuel selector valve and fuel filter assembly too although they looked fine. That didn't help either, unfortunately. Tried it with fuel cap on and off. Tried it with fuel filter cup very loose too. No joy no matter what I try. So, I've replaced everything I can think of at this point including the fuel probe, fuel filter assembly, fuel selector valve, all gray tubing and cleaned the carb.

Any help would be greatly appreciated!