1993 70HP Johnson Could this be fuel pump.

[James R]

Comps good, sparks test good at 1/2 inch, timing good, sync good, lower unit good, carbs clean, bores good, reeds replaced, all cylinders run on idle and respond to carb adjustment. Revs right up off load.
Back it into the pond set idle at 800 in forward gear. Dies after about 1 min. Will not rev beyond 2500 in gear. Sqeezing bulb makes no difference and remains mostly full. Can refire with throttle opened but reluctant to fire without throttle.
Need help bad.

 

[tashasdaddy]

Re: 1993 70HP Johnson Could this be fuel pump.

i would say carbs, if squeezing the bulb does not effect it. have you check spark right after it quits, could be electronics.

 

[James R]

Re: 1993 70HP Johnson Could this be fuel pump.

TD thank you for the response.
The carbs have been off three times now having been thoroughly cleaned and new kits fitted. all the carbs respond well to idle jet adjustment.
My timing light should show if one or all the sparks are failing so I will try that and monitor at point of shut down and at restart. Good idea. Thanks.

 

[flatheadgrenada]

Re: 1993 70HP Johnson Could this be fuel pump.

I would love to know what you found in resolving your issues. I have the exact symptoms on my 1986 60 HP Johnson.

Thanks !
T.P.

 

[tashasdaddy]

Re: 1993 70HP Johnson Could this be fuel pump.

flatheadgrenada, yours could be ethanol poisoning. http://forums.iboats.com/showthread.php?t=299680

 

[bustermin]

Re: 1993 70HP Johnson Could this be fuel pump.

It sounds to me like a carb issue as well. I would take the carb(s) off and verify the main jet is clear. When you rebuilt the carb did you clear ALL passages with compressed air? I have seen many many carbs be rebuilt and have problems because the mechanic did not take the time to blow it completely out. And they always say "It looked clear to me". Also, verify your float(s) are properly adjusted and are not cracked and letting fuel get inside. And verify the needle valve(s) is not worn out.

 

[divinginn]

Re: 1993 70HP Johnson Could this be fuel pump.

It could also be a sensor shutting down one cylinder. Temperature or oil sensor,something to look at. my Yamaha was doing it when the impeller was getting weak.

 

[tashasdaddy]

Re: 1993 70HP Johnson Could this be fuel pump.

Johnson doesn't shut down just one cylinder, but a coil could heat up and fail.

 

[petryshyn]

Re: 1993 70HP Johnson Could this be fuel pump.

Hi James R

feel the head for overheating. If its overheating, it may be going into "SLOW". It could also be a bad temp sensor causing "SLOW"

Cheers

 

[James R]

Re: 1993 70HP Johnson Could this be fuel pump.

Well I have exhausted all the possible tests including the head off and can find nothing. There is no evidence of leaking CS seals. Carbs good, sparks good and where they should be, lower unit running free, motor running cool,all cylinders idling evenly, comes up on RPM without hesitation off load.This motor has been run hard but appears to be in good shape.
Suspect Blow by but I don't have a way to check it.

 

[James R]

Re: 1993 70HP Johnson Could this be fuel pump.

That was one thing I had not considered, faulty sensor. But it comes up to 2500. Would it not slow to something lower?

 

[HybridMX6]

Re: 1993 70HP Johnson Could this be fuel pump.

SLOW kicks in and drops RPM's to 2500 or less, so it could still be SLOW kicking in. I believe all you have to do to check it is to unplug the sensor and give it a try.

 

[bdsandman]

Re: 1993 70HP Johnson Could this be fuel pump.

James my 95 70hp was doing the same thing. It was running too lean under load. The adjustments were set at 1.75 turns out which is starting factory spec. As suggested by someone here I backed them out to 3 turns and in from there until it would idle again properly. It turned out to be about 2.25 turns out. It ran like a charm after that.

Still having a problem with top end but that's another story.

 

[James R]

Re: 1993 70HP Johnson Could this be fuel pump.

Thanks bsandman. The carbs did set up to around 2.25.