1998 Suzuki DT140 low idle and stalling

robalo12

Recruit
Joined
Feb 1, 2013
Messages
2
Hi all. I'm having an issue with my 1998 fuel injected DT140 losing idle speed and stalling after it warms up. To try and correct this condition, I have replaced my ball, water seperator, spark plugs, fuel injector o-rings, and inspected my fuel injectors for blockage (none found). Compression across all cylinders is 120, and all coils are firing. The initial issue happened on the water. After about a 10min run, the motor stalled wouldn't start again, I took the plugs out and they seemed to be fouled, I attempted to clean them and try to start it again however it wouldn't start. Once we got the boat out of the water, I trimmed the motor down and an excessive amount of raw fuel came out of the exhaust, and the motor started immediately. With the new parts, it will now start with no issue at all when cold, but once it warms up the idle drops and it eventually stalls. After this happens, the throttle has to be feathered to get the motor to start again, it will stay running if I keep the RPMs around 1500, however if they drop below 1000 for more than a few seconds it stalls out, all the time seaming to have good fuel pressure. Also the spark plugs smell like gas when taken out after it stalls. I have removed the throttle body to check for carbon build up but none was found. Vaccum going to the fuel pressure regulator seems to be good. I am stumped. Any information would be greatly appreciated!!! Thanks in advance
 

buler

Cadet
Joined
Jul 2, 2012
Messages
10
Re: 1998 Suzuki DT140 low idle and stalling

i dealt with a similar problem did everything youve done with no improvement. take off the intake manifold and see how many reed valves are broken. i would bet that is your problem. wish someone would have helped me out. it took me months before i got fed up and started ripping the motor apart and found that 4 of mine were broken and missing closest dealer 5 hours away and for some reason nobody in my state will work on it. everyone says Suzuki wants a small fortune to become a dealer. GOOD LUCK!!!
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 1998 Suzuki DT140 low idle and stalling

You need to test fuel pressures not just think they are ok.

And check to see if lift pumps have holes in diaphragms leaking fuel into crankcase
 

robalo12

Recruit
Joined
Feb 1, 2013
Messages
2
Re: 1998 Suzuki DT140 low idle and stalling

Thanks for the input! I got it running fine on the trailor hooked up to the hose. I cleaned the throttle body vacuum ports, ajusted the throttle position sensor and reset the idle. Out of water it purrs like a kitten. Once I put it in the water, that was a different story. It took about 30 seconds in the water to stall, and wouldn't start. I trimmed the motor up, turned her over, and it fired right up. Something else interesting that I found was my #4 plug was already fouledafter being ran for roughly a half an hour. I'll be checking those reed valves, and fuel pressure this weekend for sure! Thank you so much with the help.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 1998 Suzuki DT140 low idle and stalling

You really need a service manual for your motor and follow the steps in it for testing things or take it into a Suzuki dealer to have it checked out.
these EFI motors are not something everyone have the info and knowledge or the equipment to work on properly. If you do not set things to the spec in manual it will not be correct

Motor needs the proper fuel/air mix to run under load.
placing lower unit in water causes more back pressure
 

lakensea

Chief Petty Officer
Joined
Jan 30, 2002
Messages
542
Re: 1998 Suzuki DT140 low idle and stalling

If anyone has touched the throttle position sensor adjustment screw without the proper test harness and factory setting procedure, then there is a good chance you have at least one problem there. How do you knoe the fuell pressure "seems good"? Did you hook up an EFI fuel pressure gauge? "Vacuum to the fuel pressure regulator seems good" - the fuel pressure regulator does not run off of vacuum. Have you checked for proper ignition output with the CD-77 meter? Have you checked for proper ignition timing?
 

buler

Cadet
Joined
Jul 2, 2012
Messages
10
Re: 1998 Suzuki DT140 low idle and stalling

i am willing to bet that you have 2 or more broken reed valves.
 
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