Hard to start after warm-up

[eltonb]

I am experiencing a nerve racking problem on my 1998 90HP Johnson outboard. The issue only happens when I am on the lake, I cant reproduce it at home.

After running the boat out to my fishing spot, cut the motor off for 5-10 minutes, the boat absolutely will not start unless I throttle it up a good bit. The first time it happened I had someone with me, and even though the bulb was tight, I pumped the bulb while the other guy tried to start and I believe at that time it would sputter a little but but not start. I then decided to throttle it up and try to start and then it started right up. It experienced the same behavior the rest of the day and did it the last time I took it out. As long as throttle it up, it will always start.

It seems like when I first bought the boat the bulb would stay tight for weeks, but now it leaks down after a few hours, I assume that could be one of my problems.

Are my assumptions correct that it could be the fuel pump, air in the fuel line, or bad bulb?

Why cant I reproduce the problem at home?

Could it be heat related? Could something ignition related be happening after it gets good and warmed up? My intuition tells me no, since it seems to be fuel related since it starts after I throttle it up.

How can I troubleshoot?

 

[jtexas]

Re: Hard to start after warm-up

Relax, that's not unusual, and it's not a sign of impending doom. Fuel pressure should hold all day, but I'm guessing that's a symptom, not the cause of your hard start, since pumping it up doesn't immediately cure it. My theory is a leaky carb float valve (is that a carb or injection motor?) or maybe primer valve, just slightly flooding the engine. At home on the muffs, engine is much easier to start without backpressure on the exhaust. On the water, lifting the hi-idle lever advances the timing, let's it start right up. Time for a carb rebuild.

Any other symptoms? Any recently completed maintenance? What's your idle RPMs, in the water in neutral and in gear?

If your primer bulb & fuel fittings are all original, this might be a good time to replace 'em anyway - they do wear out eventually - I usually keep an old one onboard for spares.

and welcome to iboats!

 

[tashasdaddy]

Re: Hard to start after warm-up

or it could be that the idle just needs to be set up a little faster.

 

[eltonb]

Re: Hard to start after warm-up

Working on auto engines is nothing new to me, but this outboard looks like hieroglyphics to me. Its definately carb and not injection.

If I have never rebuild a carb on a outboard, shall I just let a reputable shop do it? Is there anything simple I can do first?

Where is this primer valve?

How many carb float valves are there on my motor? I assume that because I have 4 intake ports and 4 butterfly valves that there are 4 carbs? Would 1 bad float cause this? How does one isolate which one it is?

Also, I dont see a fuel filter inline, is it somewhere else?

Oh, I always read about carb balancing with a vaccuum kit - what is that all about? What is being balanced? The butterfly valves?

Thanks for all your help.

 

[HighTrim]

Re: Hard to start after warm-up

Here is a diagram of your carb to help with all the terminology. You have 2 carbs on your outboard.

"http://www.crowleymarine.com/brp_parts/diagrams/12667.cfm"

Here is your fuel filter, right before your pump.

"http://www.crowleymarine.com/brp_parts/diagrams/6747.cfm"


Carb rebuild is not a bad job, with the help of a manual and this forum. This video may help for your first time. Good luck.

"http://www.meegsonline.com/tmd/TMDsVideoChronicle2.wmv"

 

[HighTrim]

Re: Hard to start after warm-up

Also, regarding carb balancing that is mainly done on bikes with a four column mechanical (mercury-free) manometer. It gives four simultaneous vacuum readings so you can balance the fuel/air flow through each of the carburetor throats simultaneously. It uses stainless steel rods in close-fitting guides to indicate vacuum in cmHg (centimeters of mercury) on the scale.

On outboards you rebuild the carbs sometimes followed by a link n sync. As you advance the throttle control the ignition timing advances while at the same time the carb butterflies open. It is critical that the two are in sync or in phase. The advance must track the butterflies exactly and at the right time.

(Fuel Primer Solenoid Function)
(J. Reeves)

The RED lever...... The normal operating/running position is to have that red lever positioned over top of the solenoid and aimed at the other end of the solenoid, gently turned to its stop. This is the normal/automatic mode position. Pushing the key in opens the valve within the solenoid allowing fuel to pass thru it in order to prime and start the engine. Looking upon this solenoid as an electric choke results in a better understanding of it.

Having that red lever turned in the opposite direction, facing away from the solenoid, allows fuel to flow thru it to the crankcase area. One would only turn the red lever to this position in a case where the battery might go dead and the engine had to be started via the rope pull method. Look upon putting the red lever in this position as moving a choke lever on a choke equipped engine to the full closed position. Either one would supply fuel to the crankcase/engine for starting purposes BUT if left in that position while running would flood the engine.

The later model primer solenoids are equipped with a schrader valve, used for attaching a pressurized can of fogging oil etc, available at your local dealership with complete instructions.

Pumping the fuel primer bulb up hard fills the carburetor float chambers of course, but that process also applies fuel pressure to the primer solenoid.

The two small hoses leading from the primer solenoid branch off via tees to each fuel manifold section that would feed fuel to the individual cylinders.

Pushing the key in activates the primer solenoid to allow fuel to flow thru it to the intake manifold passageways. Cranking the engine over causes the fuel pump to engage which in turn sends fuel pulses to the primer solenoid via the 3/8" fuel hose.

Some engines incorporates the "Fast Start" feature which automatically advances the spark electronically so no advance of the throttle is required for starting.
Engines that do not have the "Fast Start" feature will be required to have the throttle advanced slightly.

Starting procedure: pump fuel bulb up hard, crank engine and push the key in at the same time. When the engine fires/starts, release the key so that it falls back to the run position.

Bottom line..... Look upon the primer solenoid as an electric choke.

 

[jtexas]

Re: Hard to start after warm-up

2 carbs, 2 floats. no point doing just one. outboard carbs are remarkably simple devices - you can do it. a factory shop manual will more than pay for itself with your first carb rebuild or impeller replacement. www.johnson.com choose parts & accessories / literature. Get your carb kits on iboats.

 

[rufusj]

Re: Hard to start after warm-up

I am having almost the exact same problem on an 83 75hp except that warm or cold makes no difference. The answers in this thread have been very helpful but perhaps jtexas or one of the other experts could clarify for all of us reading this thread how to narrow down between a bad primer solenoid or a leaky float. I am prepared to rebuild my carbs as instructed but would prefer to just pop in a new primer valve/solenoid if that is what it is. Is it possible/probable that the primer valve is stuck open - flooding the engine? My plugs are wet when I check them. Interestingly, when I switch the red lever to manual, turn the engine over a few times and then switch back to auto, it is easier to start.

 

[HighTrim]

Re: Hard to start after warm-up

Rufusj,

Start your own new thread so that this one doesnt get confusing and frustrating. Welcome to iboats. Im sure you will get plenty of help.

 

[plumtothehub]

Re: Hard to start after warm-up

So my 1998 Evinrude 90 HP Outboard Engine Model E90TSLECM is doing exactly like yours. I have changed the water pump, and primer bulb. Did you ever get yours fixed?