1998 GTX Limited Running on one cylinder

[dfowler]

Have a 1998 GTX Limited. Went out for the 1st time this year and everything was good. Started and ran well. We hit a small wave and lost power. Came back up to speed and ran ok for a little while, but then lost power again. Could only get about 3550 rpm out of it. Changed plugs. One was a little oily, but not too bad. No better. Nursed it a little longer until we could get to a dock and checked/changed plugs again. Still no better. After getting it out of the water and on the trailer, checked it out some more. Only running on one front cylinder. Experimented by moving plug wire from dead cylinder to front cylinder. That cylinder still fired. Have been researching all week. Gather that I should do a pressure check on the cylinders. What pressure should I be looking for? Any other ideas? Starts right up, but only on front cylinder. No messages, or beeps (strangely, I don't even get the two beeps when I put the lanyard on anymore).

Thanks for any help anyone might have.

 

[derek]

compression is ideally 150 psi each. at 100 in both sides you are on the low end of ok, as long as they are close-10 percent diff max. if one is 150 and one is 100 the low one has suffered damade and will continue to drop quikly. if it isn't running because of compression, you probably are around 50 on the bad hole. thyis is a 787 motor. it could also be the RAVE valves, or specifically one of them. they are the 2 round lumps on top of the motor. could also be a plugged up rear carb. the grey fuel lines have this nice silicone lining. ethanol in all pump gas these days eats the inside lining. then it redeposits the gunk inside your carbs and filters. if your fuel lines are grey, and they are, replace them. all of them. you will need 10 to 12 feet of auto parts store black fuel line. then you gotta clean out the filters in the carbs. good luck. keep us posted.

 

[dfowler]

Thanks for the ideas. I'll check compression and fuel lines in the morning. I've seen instructions on the forum for cleaning the RAVE valves. I'll look them up too.

Thanks again. I'll post what I find.

 

[dfowler]

Ok, checked compression on both cylinders. 140 on front cylinder and 130 on back cylinder. Runs on front cylinder, but not back. New plugs, same thing. Does have the grey fuel lines. Not sure if that's the problem though, the back plug is getting wet. It almost fires on the back cylinder, but won't catch. Not quite clear on what the RAVE valves do and how to get them apart. Going to search for that again now.

Thanks for any new ideas.

Oh, checked the id plate on the engine, it's a 947 motor (which agrees with the owners manual).

 

[robin savell lloyd]

This one has me stumped. you say you have 130 psi compression on that cylinder. it is low but I think it should run you say spark plug comes out wet. I do not see a reason it should not run unless you put a new plug in that was bad which hapens very rarely. I sure would like to know myself what the problem is. only thing I can thank of is it is not geting enough gas but you say plug is wet. good luck robin :cheers:

 

[dfowler]

Robin,

Maybe the plug is more oily than wet. Could it be getting oil but not fuel? I've been looking at the carbs and trying to figure out how to get to them. They're buried under part of the exhaust (I think that's what it is). It looks like this has to come out to get to them. Could I try a little starting fluid in that carb intake to see if it runs on that for a short time, or will this cause damage?

Thanks

 

[robin savell lloyd]

Most people are scared of starting fluid. not me. you say you think it may be oil on plug that does sound logical. I would spray a little starting fluid in intake and see if that cylinder fires. I bet it problly will. the gray fuel lines probbly cloged filter in that carb and carb ran lean causing the compression to be lower than the front cylinder. but remember I can allway be wrong so good luck Robin :cheers: