1993 Johnson 70HP 2stroke: won't start when WARM

[ondarvr]

Well guys, I think my warm start problem might be solved I was talking to a mechanic at our new marina and he told me that pushing in and *holding* the ignition key on this type engine actually injects a small amount of fuel into the engine. Holding it in does not do anything further - you get just one squirt of gas while it's held in. On a warm engine, where the gas has probably evaporated, you need multiple shots of gas. Simply push in the key multiple times to prime engine, then try to start it. I had mistakenly been under the assumption that when key was pushed in I was choking the engine using good old butterfly valves (I think that's what you call the plate, right?). Maybe some engines work that way, but this one injects fuel. I wonder how many other folks are fooled by this?

Your mechanic is only partially correct, and doesn't really understand the primer valve. It is not a pump that squirts fuel, it's just a valve that opens, the only pressure is supplied by squeezing the bulb. Once you push the key in you get one squirt of fuel until pressure builds again from either squeezing the primer bulb, or from the motor turning over and the fuel pump supplying pressure. That's why I explained a couple of methods on how to start it in my prior post, these methods will force fuel into the motor itself.

 

[ReedMikel]

Thanks for the further explanation! I guess that's why it's called a "primer solenoid" instead of a "pump". I can't tell you how many mechanics and other boat owners asked if I was "choking" it. Because they used the word choke I just assumed it meant the old butterfly valve on a carb. Learn something new every day

 

[racerone]

These primers have been used since 1980 or so.

 

[Fed]

I have to say I think this fuel evaporation and vapor locks are internet myths.

Take fuel evaporation, empty a carb bowl in 30 minutes? I don't think so.
Take vapor locks, vapor magically forming in a fuel line which causes a motor not to start? I don't think so.

It all sounds as silly as pushing the key in 10 times to give it 10 squirts then cranking the motor over.

 

[ondarvr]

I don't claim to know the exact reason why a carb'd 2 stroke outboard won't start after a warm soak (this was the term used here and elsewhere years ago for this issue), all I can say is that holding the key in and squeezing the bulb can help get most of them restarted. You may believe or not believe whatever you wish.

 

[Fed]

I don't know either ondarvr but I'd like to.
I think it's mainly a problem with people not knowing how to start 2 stroke outboards due to not knowing how they work.
I often see people proudly announce they can cold start their motor with no fast idle & no choke, straight away I think well there's something wrong with that motor.

Heat soak is one you don't hear much about now, wasn't it a Mercruiser problem they put out a bulletin on?

 

[ondarvr]

I know I've had a couple motors that would occasionally not start easily after about a thirty minute rest, if they didn't start instantly it would take a little work, so I started using this method. Just recently a friend of mine that's a guide had this exact issue with his 200hp carb'd Merc, I was with him one time when it wouldn't start and he said this would happen after stopping for 20-30 minutes, and if it didn't start instantly it may not start until it cooled off. I told him to use the hold the key and pump the bulb method, it started instantly, he never had a problem getting it running after that when he used this method.

I can't say exactly what goes wrong or why this works, but evaporation is a reason that would fit the scenario.

 

[Fed]

I give mine a little fast idle & if it doesn't fire within the first few seconds I push the key in so the end result is much the same as what you do except I use the fuel pump to pressure the system & you use the bulb.
It leads me to think that after 30 minutes the motor cools and the fuel condenses out of the fuel/air mix in the crankcase.
I simply can't believe a carb bowl could evaporate in 30 minutes.

Do you have any thoughts on vapor locks?

 

[jakedaawg]

Well guys, I think my warm start problem might be solved I was talking to a mechanic at our new marina and he told me that pushing in and *holding* the ignition key on this type engine actually injects a small amount of fuel into the engine. Holding it in does not do anything further - you get just one squirt of gas while it's held in. On a warm engine, where the gas has probably evaporated, you need multiple shots of gas. Simply push in the key multiple times to prime engine, then try to start it. I had mistakenly been under the assumption that when key was pushed in I was choking the engine using good old butterfly valves (I think that's what you call the plate, right?). Maybe some engines work that way, but this one injects fuel. I wonder how many other folks are fooled by this?

This is not quite right. Pushing in on the key activates the primer solenoid. It allows a small amount of fuel to be pushed in to the manifold behind the throttle plates. It squires this fuel as long as the key is held in AND the motor is cranking. Right hand, true story.

 

[ReedMikel]

I guess lots of folks don't understand this breed of engine, as several marina mechanics and other boat owners always suggested *holding in* the key to choke the engine. Nobody ever suggested repeated pushing in of the key to *prime* engine. I'll find out over the next few weeks if this truly has resolved my warm start issue. My intuition says yes Thanks to all that have contributed to this thread!

 

[GA_Boater]

I give mine a little fast idle & if it doesn't fire within the first few seconds I push the key in so the end result is much the same as what you do except I use the fuel pump to pressure the system & you use the bulb.
It leads me to think that after 30 minutes the motor cools and the fuel condenses out of the fuel/air mix in the crankcase.
I simply can't believe a carb bowl could evaporate in 30 minutes.

Do you have any thoughts on vapor locks?

You're probably more right on this than the vapor lock or carb evaporation stuff, Fed. It's possible the fuel condenses in the crankcase. Given how 2 strokes work with the porting and piston timing, it could evaporate in the crankcase and exit through the exhaust ports, too.

With little or no fuel in the crankcase, a warm start becomes more like a cold start when bulb squeezing and or choking/priming is needed to fill the crankcase with a fresh load of fuel.

My old Merc sometimes is harder to start when warm. Cold or hot is almost instant. But sometimes she takes a squeeze or choke after sitting awhile. I don't even think about it anymore, just do it.

 

[oldboat1]

^^Strikes me that's right. If the carb or crankcase goes dry for whatever reasons, it's a tough pull for an outboard fuel pump -- makes some sense that using both the bulb and choke or primer would get fuel to the engine (Ondarvr's fix). The function is pretty much like a cold start -- hand pump and choke/primer.

I'm thinking vapor lock occurs on a carbureted car between the tank and fuel pump. Fuel hits the line around a hot engine and is said to vaporize before getting to the pump and carb? I'm trying to recall when my old Chevy would "vapor lock" (and also whether that was probably an excuse for bad starting procedure, or for some other failure on my part or the Chevy's).

Interesting.

 

[oldboat1]

Thanks for the list of E0 stations! I found one only a few miles away from my lake house in NY. Like BobU, I don't have a spare tank either to do the test. So I'll run my tank dry too and add the E0 mix...

BTW, have ethanol free marina gas available here on Keuka, as well as at two or three area stations. I buy at the marina, but more interested in making sure it's fresh -- in Spring, like to wait for a delivery to fill up.

 

[ReedMikel]

This is not quite right. Pushing in on the key activates the primer solenoid. It allows a small amount of fuel to be pushed in to the manifold behind the throttle plates. It squires this fuel as long as the key is held in AND the motor is cranking. Right hand, true story.

Hmmm, I was under the impression that *holding* in the key only did one squirt. I'm also under the impression that the key does not have to be turned to the crank position. But I'm just a newbie and hearing conflicting stories from experienced mechanics, owners and folks on this forum. Nothing is ever easy

 

[jakedaawg]

@ReedMikel
You can prove it too yourself if you want. On the primer there are two tiny little hoses that come off and go to the manifold. Take one off and have someone operate the switch in a variety of ways. Just saying.

 

[jakedaawg]

also, if you have your motor all warmed up and running well and you bump the key in once the motor stumbles. It has just gotten a shot of fuel. If you hold the key in it will kill it. It has gotten quite a bit and flooded out. This is assuming that the system is correct, maintained, and working properly. I.e hoses that are open and good, good fuel pump and working solenoid and cover assembly.

 

[interalian]

Hmmm, I was under the impression that *holding* in the key only did one squirt. I'm also under the impression that the key does not have to be turned to the crank position. But I'm just a newbie and hearing conflicting stories from experienced mechanics, owners and folks on this forum. Nothing is ever easy

The primer solenoid is just a valve that's fed directly from the fuel line after the pump. When it's open (key pressed), you will get a pulse of fuel to the carb base nipples with every single rotation of the engine, as long as you hold the key in.

 

[ReedMikel]

The primer solenoid is just a valve that's fed directly from the fuel line after the pump. When it's open (key pressed), you will get a pulse of fuel to the carb base nipples with every single rotation of the engine, as long as you hold the key in.

I guess I'll have to do a physical test like jakedaawg said, as my mechanic is saying it only squirts once when you hold it in. He says you have to release it, then push in again for another squirt. There's also the question (in my mind) of whether the primer solenoid is energized when the key is pushed in, but not turned? How about when key is turned 1 click - to the accessory/power position and then pushed? I assume it definitely energizes when key is turned to the 2nd position (crank). I wonder why they would make an ignition key switch that allows you to push it in at all 3 positions if it only energizes the solenoid in one or two of the 3 positions? Just to confuse us

 

[BobU]

Good questions ReedMikel - now you have me wondering how my engine works too? You'd think the engine manufs would make it a "plug and play" operation. But I guess, just like in the computer world, it's more like "plug and PRAY"!

 

[jakedaawg]

Listen guys....

When the key is vertical no power goes anywhere.
When the key is turned one click clockwise this is the "run" or on position. The ignition is on and the choke can have power applied to the solenoid if you press in. The second to the clockwise position is start. This is the momentary part of the switch. You have to hold it there while the engine cranks and when you release it snaps back one position to the run or on point. The choke works in either position as you need it to function in both.