1988dt140 idles for 10-12 sec then dies

[grouperbob]

carbs rebuilt,all 4 cyls running, using portable tank with premix(oil inj also hooked up) starts and idles for around 10 seconds then dies. starts right back up idles and dies after 10 secs. if throtle brought up to high speeds it does not die but when brought back to idle it dies right away. new diaphrams in fuel pump. pulled connecting rod off to test each carb while in idle, each carb brings up rpms. disconnected all harnesses and same thing happens

 

[rodbolt]

Re: 1988dt140 idles for 10-12 sec then dies

keep chasing the carb issue. make sure your adjusting the air fuel screws the correct direction, those screw in to make it richer.

 

[grouperbob]

Re: 1988dt140 idles for 10-12 sec then dies

mechanic told me 1 and 1/4 out so thats where they are set. i did try other settings both in and out, same dies after 10 or 12 seconds. do u think idle mixture would cause a smooth running motor to die after 10 secs(all 4 cyls)? hmm i;m thinking maybe electrical now. any thoughts on cdi? have no manual and not real familiar with suzuki but is there a low speed trigger under flywheel. really reaching now. tx

 

[rodbolt]

Re: 1988dt140 idles for 10-12 sec then dies

replace the entire ign system for about 900 or so, or chase your fuel issue.
what your describing is typical of a lean or several lean cylinders.
try tapping the choke just before it dies and see if you can keep it from dying by momentarily chokeing it. if you can you will be assured your chasing carb issues.

anything can fail, however suzuki electrical failures were incredibly rare.

 

[grouperbob]

Re: 1988dt140 idles for 10-12 sec then dies

pulled carbs and sending them to a pro at checkmate marine. he says it could be idle mixture and that he has some kind of washing machine to clean carbs. thanks for advice. will post results. but hurricane looks like its on the way so things might be delayed.

 

[deejaycee_2000]

Re: 1988dt140 idles for 10-12 sec then dies

you said you are running it on a portable tank .... make sure your ventilation screw is open at the tank .....

 

[grouperbob]

Re: 1988dt140 idles for 10-12 sec then dies

mech said it looked like a couple of floats were out of adjustment as well as a torn gasket under one needle valve. he set floats and replaced gasket. have carbs back now and will install after storm. mech asked me to come by with boat so he can sync carbs.

 

[grouperbob]

Re: 1988dt140 idles for 10-12 sec then dies

well, well, well. another mystery solved. after reinstalling carbs i took it over to mechanic. he started it up and it died after 10 sec. he took ignition cover off and started disconnecting things till it kept running(tho rough). seems like throttle valve sensor he says. hmm. who would have guest something electronic? so i bought another one($50) and installed (stalled being the key word). yep it died after 10 secinds. but this time i loosened the adjustment screws and started moving it to where engine ran best and tightened screws. now it will idle fine with idle switch on high. ran into another mech and he says voltage is critical on colored leads. must be 45-55volts with engine running. mine is only 19.8 on one and 18.5 on other. rain has delayed further testing

 

[rodbolt]

Re: 1988dt140 idles for 10-12 sec then dies

ign timing on that motor is controled by a set of resistors on the idle speed switch and the TVS. its possible the ign tining is retarding to far.
there are a lot of colored wires on a suzuki.
most run something under 8Vpeak and some need as much as 150 vpeak.
dont confuse ign controlling components with ign producing components.

sometimes coprrosion takes the idle speed swtch out,in those cases I wire in the correct resistor to give me the idle speed I desire and let it ride.
I have no clue where your mechanic got his voltage ranges, I am looking at the service specs and find nothing close to his specs.
at engine start the CDI bypasses the timing switch and sets the ign timing at 7*BTDC for 12 seconds then the ign timing switch takes over, if the switch fails timing may retard beyond acceptable limits.
carefully test the outputs of the gear counter coil and the TVS as well as testing the ign timing(idle speed) switch. the TVS also has a deacceleration function that when closed the switch forces the idle speed control(ign timing) back through the idle speed switch.
lookint at the idle speed switch we will call full clockwise rotation pos A and full CCW positionE. with a multimeter test resistance between the blk/white wires from the switch.
A 0 ohms,B 2.5-3.6Kohms,C 7-10 K ohms,D 21-32Kohms and E should read infinity.
the factory service manual actually has quite a bit of information on how the ign system works and is controled.