johnson 4 HP idle problems

[floflodr]

i have a johnson J4RSSM 4HP with not more then 40hours on it.

i have used it for about 20 hours since i bought it and now all of a sudden the engine isnt running properly anymore,

To get it to start i need to pull the chocke, make a few attempts, push the choke in and it will start but only in high revolutions, as soon i take down the revs the engine dies, approx. above 3500-4000 revs. the engine does not run in idle speed.

i have the feeling it is not getting enough gas, but when i pull off the hose that leads to the carburator i do get a lot of gas.

i have already checked and cleaned the carburator, replaced the gasoline filter, checked the start plugs and start plug cables.

please help me out guys, im in the Dominican rep and mechanics here will only break more then they will fix.

thanks a lot for any help and have a happy new year everyone

 

[tashasdaddy]

Re: johnson 4 HP idle problems

check compression, and spark with a spark tester, besure you have good spark on both plugs, also check the float level in the carb. i can determine the year of the motor. what year is it.

this may help. http://forums.iboats.com/showthread.php?t=167352

 

[floflodr]

Re: johnson 4 HP idle problems

its a 1989 4 HP J4RSSM johnson

i had already read the thread, what i dont understand is that i just recently used the engine approx. 2 weeks ago for approx. 7 hours on one day, later that day i started it in fresh water to clean and all worked fine, 2 weeks later the problem appread, without doing any modifications, all i did was spray
WD-40 all over it as i always do to prevent corrosion

thanks again for any help

 

[JB]

Re: johnson 4 HP idle problems

The low speed (idle) circuit in that carb has at least one very tiny orifice, floflodr. It is where the fuel is introduced into the carb throat just about where the throttle butterfly touches. Sometimes routine cleaning doesn't get that orifice clean and it requires direct air pressure or a physical probe to open it up.

A fine wire bent into an "L" can usually get it. If not, you need to remove the welch plug opposite it to get a fine probe into it.

Good luck, and welcome to iboats.

 

[DJ]

Re: johnson 4 HP idle problems

Low speed idle circuit, as JB mentioned. Also, classic symptoms of a misadjusted/sinking float.

 

[floflodr]

Re: johnson 4 HP idle problems

i will checkout the misadjusted/sinking float tomorrow again, thanks a lot.

in my johnson owners manual it tells you to always let the engine run dry after usage, i have now read that this may not be such a good idea, can anyone tell me more about that, and if it may have caused this problem

also can anyone tell me if i can disclose the fuel pump as the problem factos as the engine does run at high revs ?

 

[DJ]

Re: johnson 4 HP idle problems

i will checkout the misadjusted/sinking float tomorrow again, thanks a lot.

in my johnson owners manual it tells you to always let the engine run dry after usage, i have now read that this may not be such a good idea, can anyone tell me more about that, and if it may have caused this problem

also can anyone tell me if i can disclose the fuel pump as the problem factos as the engine does run at high revs ?

You can do it either way. I ALWAYS have some type of treatment in my fuel whether it be Sta Bil or Sea Foam.

If you DO NOT run it out, your fuel must be treated.

 

[floflodr]

Re: johnson 4 HP idle problems

what can you please tell me about discarding the fuel pump as the cause of my problem stated above ?

 

[JB]

Re: johnson 4 HP idle problems

If your fuel pump is failing it usually affects high speed operation first, floflodr.

The fact that your engine runs fine at higher speeds suggests that the fuel pump is working fine.

I don't think running the carb dry when taking out has anything to do with your problems.

I think the carb and maybe the link 'n' synch are at the root of your problem.

 

[floflodr]

Re: johnson 4 HP idle problems

the problem has been solved, thanks to everyone.

i just bought a 17footer with a 1990 90HP johnson, so im sure i will have to make a lot more questions in the next few days.

 

[JB]

Re: johnson 4 HP idle problems

Please tell us what the problem was, floflodr, and how it was solved.

 

[HighTrim]

Re: johnson 4 HP idle problems

I agree JB. I for one am usually interested in how alot of these stories play out. Sadly it is rare to get feedback after the fact.

 

[samo_ott]

Re: johnson 4 HP idle problems

Dang it, I want to know what happened also! It's like missing the end of a movie!