engine cranks up runs for 5 - 10 sec and stops help!

[vince champion]

Hi, i have a 1994 Johnson 140hp v4 (saltwater) The engine will crank up and start but will run for only a few sec (5 to 10 sec) and shuts of automatically.The motor was sitting in someone yard for almost a year. I was thinking this problem might be cause of the fuel pump. So i told my cousin to pump the primer as i start the motor but the motor still shuts off.

can anyone tell me is it the fuel pump that needs to be replace?
or is it the Carbs need to be redone?
I heard that the floats get stuck after sitting for a while is this true?

Any suggestion will be greatly appreciated. Thanks

Vince.

 

[ezeke]

Re: engine cranks up runs for 5 - 10 sec and stops help!

Make sure the fuel and oil are new.

Try pushing the key in and holding it while you crank the motor. Then keep bumping the key in until the engine smooths out.

The motor has QuikStart to advance the timing which will disengage too quickly if you let the engine run past 1100 RPM initially.

 

[vince champion]

Re: engine cranks up runs for 5 - 10 sec and stops help!

Thanks for the suggestion ezeke. I tried this and the motor still shuts off. I read a post about starting a motor backfiring at start up. When i start mine i hear a loud gun shot sound and the motor stays on for 5 sec and dies out.

Im thinking this is carb problem since its been sitting around for quite some time.

Any other suggestions please?

thanks, vince.

 

[tashasdaddy]

Re: engine cranks up runs for 5 - 10 sec and stops help!

first check compression and spark, 100 psi plus on compression, within 10 % of each other. if all is good do the carbs. see sticky at the top of this forum.

 

[vince champion]

Re: engine cranks up runs for 5 - 10 sec and stops help!

Im sorry this might be a stupid question, but i am new to this. When checking compression dont the motor need to be running? I cant get the motor to idle for more then 5 sec.

 

[ezeke]

Re: engine cranks up runs for 5 - 10 sec and stops help!

Compression is checked using a screw in gauge with all of the spark plugs removed. Crank a few seconds on each hole and record the values by the cylinder number.

 

[vince champion]

Re: engine cranks up runs for 5 - 10 sec and stops help!

I will try to do a compression test this weekend. Thanks and will post updates.

 

[HighTrim]

Re: engine cranks up runs for 5 - 10 sec and stops help!

When i start mine i hear a loud gun shot sound and the motor stays on for 5 sec and dies out.

Any other suggestions please?

thanks, vince.

Backfiring out of the exhaust port is caused by having the ignition system fire a particular cylinder when the exhaust port is open ( ie piston down). This would sound like a shotgun going off..... is this the condition that you're experiencing?

This is usually due to a sheared flywheel key, a flywheel with melted (moved) center sensor magnets if they exist, timer base leads routed incorrectly to the powerpack, or having the leads from the powerpack to the coils reversed to mention a few.

Spitting back, sounding like a mild backfire, indicates a carb slow speed restricted jet..... something causing a lean carburetor scenario.

 

[vince champion]

Re: engine cranks up runs for 5 - 10 sec and stops help!

high trim, The shot gun sound happens only once or twice. The mild gun fire sound sounds more like it. I just bought 4 carb rebuild kit. I will rebuild/clean my carb and see what happens. Also do a compression test after. Thanks again.

 

[tashasdaddy]

Re: engine cranks up runs for 5 - 10 sec and stops help!

do your compression and spark test, first. turn the motor over and equal amount of times for each cylinder. you may have problems that the carb kits could be a waste of time and money. see the sticky at the top of this forum, before you do your carbs.

 

[vince champion]

Re: engine cranks up runs for 5 - 10 sec and stops help!

Well guys since i already have the carb kit i decided to just rebuild the carbs and do a compression test this weekend. What i found out was one of the screw on 1 of the carbs wont come off. It is a white silverish screw kinda of like a big/thick needle with a spring on it. on the other 3 carb that screw came off fine but this one no matter how much i turn it wont come out.
What exactly is this screw for? Can this be the reason why my motor idles only for 5 sec and shuts off?

p.s when i put the screw back on i put it to the exact location and turn. so im sure i didnt mess things up.

Thanks.

 

[vince champion]

Re: engine cranks up runs for 5 - 10 sec and stops help!

Ok i found out the screw that i cant get out is called the "needle valve screw" and need valve spring that goes around the screw. So can this be one of the reason why my motor wont stay running?

thanks in advance vince.

 

[vince champion]

Re: engine cranks up runs for 5 - 10 sec and stops help!

Ok, rebuilt and clean carbs and now it runs fine =). The only thing i need to change is the needle valve that controls the idle. It idles fine but has a hicup every so often. Thanks to all who help me out. Greatly appreciated.

vince.

p.s I love this site!

 

[tashasdaddy]

Re: engine cranks up runs for 5 - 10 sec and stops help!

that needle is set at the factory, it sounds like you still have a dirty slow speed jet or the venturi, in the ports are partially clogged. did you clean the little hole in the top of the main port. where the throttle butterfly is?

 

[vince champion]

Re: engine cranks up runs for 5 - 10 sec and stops help!

Not exactly sure where the venturi is located at. But im pretty sure i cleaned every hole i can in the carb. If it is located on the throttle body then no i didnt clean it. I didnt take out the throttle body only the carbs. I did spray around the throttle body with carb cleaner tho. Should i check that part out?