98 DT115s efi intermittent spark, shuts off at high rpm

[Shortliner]

Hello everyone, new member. I'm stumped at diagnosing this problem. My 3rd year with engine. 1st year ran perfect. Last year problem occurred only occasionally. Would get up on plane, engine would bog down and stall. Start up, take off, maybe not happen again the rest of the day. This season, does it every time I get on plane between 3000-3500 rpm with no alarms. My 1st impression was a fuel issue. Drained tank, all new bulb, lines and filters. New plugs. Compression good, 115psi on all. While on muffs decided to put timing light on plug wires to check coils. Noticed a miss on every plug wire at idle every 3-4 seconds. Started to suspect ecu or stator. Removed stator and inspected. Looked clean, no burns. Cleaned and replaced. Trying to test resistance on everything. Gear counter within specs. Can't figure out how to test the others. My manuals wiring diagram matches the colors on my stator and timing coil but the test instructions use different colors. Says black lead to black ground??? There's no black ground on my harnesses. Tried ground to other things. This is driving me bananas. Haha. I just like know what's wrong before I start replacing parts randomly. Has anyone ever had these symptoms? Any help on proper testing of the electronics? The one fuel test I haven't done is the high pressure fuel pump. I'm picking up a pressure guage soon to test that. Sorry I wrote a book but maybe there's enough info here to help someone smarter than me figure this out. Thanks.

[Shortliner]

May have found a problem. Decided to take apart the fuel vapor separator. Looked good clean And needle was functioning properly. Removed the brass needle seat and saw a blockage. It is a thin, flat piece of clear plastic wedged in the threads blocking at least a 3rd of the passage. It's about as thick as plastic from a water bottle. The only thing between that blockage and the fuel filter are 2 new lines and the round low pressure fuel pump. Can someone tell me if the diaphragms in the pump are this type of material or what it could be?

[Shortliner]

Ok. Disassembled the pump and found that one of the 2 check valves is the culprit. These things are small plastic disks that allow flow one way. I tried to find these check valves for sale but can only find the diaphragm sets. I suppose you have to buy a new pump when a piece of quarter sized plastic fails. Does anyone know if these check valves are sold separately? If I could get this site to upload a pic I could show everyone. I think this was my problem to begin with. But still not sure till pump is repaired. I have been researching some things and found out that timing lights are very unreliable for diagnosing spark issues so I may not even need to worry about that. Where can I buy these plastic check valves?

[Shortliner]

Problem solved. I made my own check valve out of plastic from a toy package lying around. Took the boat out and ran like a raped ape. Bought a used pump from eBay to replace soon. I am a little disappointed, to say the least, that Suzuki does not sell replacement valves for this part. Paying 100$ for a new part because of a faulty dime piece of plastic is plain robbery. Flat out unacceptable. I can only wonder how many people have overspent to fix such a simple problem. Furthermore, no thanks to the experts that never responded to my post. I did a search and found at least 1 other person asking about these little check valves. Like me he got no response. I'm sure if they could be bought they would cost at least 15$ each. Ridiculous!

[Moonlighter]

Thanks for sharing your experience - I am sure that others will benefit as a result.

You should consider that this is a relatively small forum and that people will only respond to your questions if they have something to offer by way of constructive suggestion.

It is a bit harsh to put up one post here, and then complain about lack of assistance after just a couple of days! Some patience is required.

Fortunately you seem good a at problem solving and worked the issue out for yourself in just 2 days.

Perhaps consider coming back on here every week or so to check if there are any issues being raised by other members that YOU Can assist them to solve. We all need to get involved and share knowledge, that is the point of forums like this one.

[Shortliner]

Your right moonlighter. Sorry, I was angry typing over the un buyable check valves. There is tons of good info and ppl on here. Happy boating everybody.

[jlsipe]

Same issue

I have a 2008 DF140 and have same problem. Engine will act like it starved for fuel above 3500 RPM on and off. Some times it runs fine and others times it misses. Trying to figure it out. Ran great for the first three years.

[Moonlighter]

Might be best to start a new thread - this one was dealing with a 2 stroke motor, yours is an EFi 4 stroke, totally different.