Johnson 40hp fuel pump

[basstracker1970]

Hello and thank you in advance, I have a 1993 johnson tracker 40hp that I removed the vro system on and installed a new fuel pump. The motor runs great from mid way to wide open but doesnt seem to want to idle very good. The carbs have been cleaned several times compression is 125,129 spark is awesome big blue flames. I checked the fuel pump pressure and at idle its showing 3 PSI of perssure. My manual says it should be 1 at 600 rpm. The engine seems to be running rich at idle. Seems to me that the fuel pump for some reason is putting out to much fuel pressure. Please if anyone can shed some light here please do.

 

[spingley]

Re: Johnson 40hp fuel pump

When you say you cleaned the carbs several times do you removed them and rebuilt them?

 

[kenmyfam]

Re: Johnson 40hp fuel pump

I'm with that one.
Define "cleaned carb's" please.

 

[basstracker1970]

Re: Johnson 40hp fuel pump

Hello, Yes I removed both carbs cleaned blew out with air and installed new kits in both. I ordered the seirra Part # 18-7352 fuel pump on it. The pump just seems to be putting out to much pressure. What is normal for this pump? My manual says 1 psi at 60 rpm and 1.5 psi at 24-3500 rpm. Im getting 3 psi at idle from this pump. That seems way to high. Could something be wrong with the pump causing the high pressure? Thanks for any help you can give.....

 

[kenmyfam]

Re: Johnson 40hp fuel pump

Did you put a "single wire" through the jets ??? air may not be enough.

 

[basstracker1970]

Re: Johnson 40hp fuel pump

Yes all jets are clean. My question here is about the fuel pump. What is the correct pressure it should be putting out. Mine seems to be putting out to much at idle.

 

[tx1961whaler]

Re: Johnson 40hp fuel pump

Yes all jets are clean. My question here is about the fuel pump. What is the correct pressure it should be putting out. Mine seems to be putting out to much at idle.

3 psi is fine; the carb floats/needle will handle it.
The pump is most likely not your problem.

Did it idle well before the new fuel pump?
What are the cylinder compression readings?
What kind of spark plugs are in it, and how old are they?
On the carb, was the #5 welch plug removed and the tiny passages under it cleaned?

 

[basstracker1970]

Re: Johnson 40hp fuel pump

I didnt remove the welch plugs but i sprayed carb cleaner in them and blew them out with air. The deal is I bought this boat back in feb at a boat shop and the motor ran and idled fine. My first time out the motor started up fine idled great. Took off ran a little up the lake shut it off for about 30 min started it back up and went about 20 seconds wide open then it started to surge at top end and wouldnt idle very good. I brought it home cleaned carbs put in new kits and I found a hose that wasnt tight so i fixed that and the surging is gone. The motor will run great now wide open but the idleing isnt right still. It seems like no matter what you do at ideling it is running rich. The air/fuel screws dont seem to have much effect on the motor when adj them. This motor is driving me nutz....

 

[basstracker1970]

Re: Johnson 40hp fuel pump

I forgot the plugs are NGK BR8HS new plugs Gapped at .035 . I removed the vro pump first thing because i dont trust them. I bought this fuel pump here. Seirra 18-7352 pump. Compression is 124 top and 129 bottom cold reading.

 

[Dhadley]

Re: Johnson 40hp fuel pump

Job 1 is to get rid of the KGB plugs and get Champions in there.

Then get the carbs apart and soak them in good carb cleaner. Sometimes a spray just won't cut it. Yes, pun intended.

 

[Al-53]

Re: Johnson 40hp fuel pump

Basstrackr ..I will make a suggestion and it may help you....When I got my 35 I could not get the idle right....I read here and also made some calls..I was told check the plugs..I did... also seen they were NGK's....I was told to replace them with Champions....I believe they were QL77JC4's..probally the same ones for your motor also...but any ways I changed them out...Motor ran much better and I got my idle adjustment also...I was told OMC were desighned to run champs...all I use now....

Al

 

[kenmyfam]

Re: Johnson 40hp fuel pump

Job 1 is to get rid of the KGB plugs and get Champions in there.

Then get the carbs apart and soak them in good carb cleaner. Sometimes a spray just won't cut it. Yes, pun intended.

KGB plugs LOL funny but true.
Get the champ's back in there !!!!

 

[basstracker1970]

Re: Johnson 40hp fuel pump

I know one thing for sure dont use autolite plugs. When i got my boat it had them in there so I changed them to NGK plugs. Since i have been having so much idleing problems I thought what the heck and tried them. It ran like crap. The NGK plugs run alot better but I will get the champion plugs and see how that works.

 

[Dhadley]

Re: Johnson 40hp fuel pump

Your motor was designed to run Champion plugs. Running another brand may or may not hurt it but we've seen burned pistons and the only thing wrong was the spark plugs. There's nothing wrong with NGK's, Mercs and Yamahas are designed to run them. We find that in a lot of cases in a "direct crossover" the NGK runs a bit hotter than the Champions. That's fine if your fuel delivery system was set up for a hotter plug. You're better off to run what the motor was designed for.

 

[basstracker1970]

Re: Johnson 40hp fuel pump

OK guys I went and got me a set of champion QL78Yc plugs and did a decarb with the OMC tuner cleaner ( THat stuff rocks) . I Did the decarb with the old ngk plugs then installed the new champions and ran engine a little at idle. I dont know why but it sounds different now. I rechecked the compression after the decarb and both were 130 PSI. I pull the champion plugs to see how they were burning and they looked good so far. The plugs wasnt wet at all like the ngk's always were. Im going to the lake tomorrow evening and will see how she runs. I will let you know....

 

[kenmyfam]

Re: Johnson 40hp fuel pump

OK guys I went and got me a set of champion QL78Yc plugs and did a decarb with the OMC tuner cleaner ( THat stuff rocks) . I Did the decarb with the old ngk plugs then installed the new champions and ran engine a little at idle. I dont know why but it sounds different now. I rechecked the compression after the decarb and both were 130 PSI. I pull the champion plugs to see how they were burning and they looked good so far. The plugs wasnt wet at all like the ngk's always were. Im going to the lake tomorrow evening and will see how she runs. I will let you know....

Sounds promising so far. Be sure to post back how you go on.

 

[Scottycat]

Re: Johnson 40hp fuel pump

Yes, please check back.
I am having problems with my 50 hp johnson, sounds like a similar deal.

 

[basstracker1970]

Re: Johnson 40hp fuel pump

Ok I didnt make it out the other day but im getting ready to head to the lake here in a few hours. I will let you know how it does asap.

 

[basstracker1970]

Re: Johnson 40hp fuel pump

Ok went to lake yesterday evening. Motor started right up as usual. Seemed to idle a little better with the champion plugs but still has a kinda jerk at idle its not smooth. It's still not idleing smooth as it should. Kinda acts like it is strugling to idle a bit. I dont know what else to try myself. I have been from one end of this motor to the other. Im going to get me a mercury and forget about this nightmare......

 

[Leglav8s10]

Re: Johnson 40hp fuel pump

Ok went to lake yesterday evening. Motor started right up as usual. Seemed to idle a little better with the champion plugs but still has a kinda jerk at idle its not smooth. It's still not idleing smooth as it should. Kinda acts like it is strugling to idle a bit. I dont know what else to try myself. I have been from one end of this motor to the other. Im going to get me a mercury and forget about this nightmare......

One thing you might want to look into is if your stator is moving smoothly and if the idle timing is right on. If the stator is sticking, it may be retarding or advancing your idle timing and giving you a rough idle.

Does the engine misfire or backfire at all?