1996 Force 120 HP Hard to start after running.

[todd.bellamy]

I have a Force 120 HP engine that came with a boat I purchased. Knowing the good and bad history of the FORCE brand I decided to roll the dice. I've done a great deal of work on it so far including, rebuild fuel pump, carb rebuild (both), new starter, new plugs, new fuel filter, replaced water pump, checked compression on all cylinders (good), and scraped/cleaned all electrical connections and grounds.

However I'm left with a nagging problem. The motor runs GREAT in the driveway and I can't reproduce my hard start problem there. When I get the boat to the bay it starts right up on the first turn, but after running around a bit and stopping for 5-20, minutes she will crank over, but doesn't fire. If I let it sit for a 40-60 minutes, starts right up.

This has really caused problems while doing slow drift fishing where we want to drift for 10 minutes then the thing won't start. Again cranking but not fire. I don't think its a vapor lock because even spraying fuel into the carb directly won't get it to start. Again spinning but no fire.

I'm thinking the next step would be to check the CDM modules? How do I do that?
Maybe check the Startor? How do I do that?
Maybe check the Trigger? How do I do that?

Please help guys! You're my only hope!

 

[pnwboat]

Re: 1996 Force 120 HP Hard to start after running.

Have you verified the spark at the plugs when it's acting up? That will determine which direction to go.

Here is a link to troubleshoot the ignition system.

Page 14 - Force outboard ignition troubleshooter

 

[todd.bellamy]

Re: 1996 Force 120 HP Hard to start after running.

Have you verified the spark at the plugs when it's acting up? That will determine which direction to go.

Here is a link to troubleshoot the ignition system.

Page 14 - Force outboard ignition troubleshooter

Thanks!
Also forgot to mention that I replaced the rectifier as well! Not sure what happened to it originally.







I think i'll pick up one of those nice little spark testers like this one:

Not so easy working around the back of the boat when your floating.

 

[pnwboat]

Re: 1996 Force 120 HP Hard to start after running.

Sounds like you may be losing spark, but need to make sure. Don't assume anything. This particular ignition system (Mercury ThunderBolt CDM) is fairly straight forward as far as trouble-shooting.

Make sure the gas tank vent is open and not plugged up. You can test by either blowing through the vent line, or take the gas cap off or just very loosely screwed on. Make sure it doesn't fall off while you're running at speed.

It's also very easy to flood the motor. You shouldn't engage the choke for more that 2 or 3 seconds at the most each time when you try to start. Are you setting the throttle handle in the "neutral fast idle" position when starting?

 

[Frank Acampora]

Re: 1996 Force 120 HP Hard to start after running.

After verifying that you do have spark during the problem: These engines can be a bit fussy. The only time you need to choke (or in your case, enrich) is for the first start of the day or if the engine has been sitting for an extended period of time and is dead cold.

Some of these engines simply will not start unless the control box is put into fast idle/warm-up position.

And, don't forget, hard starting can be a symptom of fouled plugs, so change or clean them on general principles.

 

[roscoe]

Re: 1996 Force 120 HP Hard to start after running.

So, after it sets a while, it won't start and is acting like it is flooded, and then will start after setting for an hour.
Again, acting like it is flooded.

I know you said you rebuilt the fuel pump, but I would look there.
I will bet a bucket of my snow, for a pail of your sunshine, that your fuel pump diaphram is torn, or one of the check valves is bad.
Gas will leak through and seep into the block flooding the crankcase with excess fuel.

 

[Frank Acampora]

Re: 1996 Force 120 HP Hard to start after running.

And check the enrichment valve to see if it is stuck open. Some have a red button on top and some have a red lever. The valve will be mounted on the starter side of the manifold between the two carbs. It will have two small hoses attached to it. When the starting problem begins, If it has the button, use a small clamp or vise-grip to crimp the small hose coming from the carb bowl. then try to start the engine.

If it has a red lever, check to see if the lever is in open position. if this does no good, then crimp the hose

 

[todd.bellamy]

Re: 1996 Force 120 HP Hard to start after running.

Roscoe, I disassembled and re assembled the fuel pump, no issues there, sorry to say the snow stays. Where can I find the check valves?

Frank Acampora, are you talking about the Fuel Primer Solenoid? I've uploaded a video I took of the engine running in my driveway. Pointing to different parts of the engine, can you tell me the time in the video when i point to the enrichment valve?

Thanks Guys!

 

[Frank Acampora]

Re: 1996 Force 120 HP Hard to start after running.

At about 19 seconds you point the camera at the enrichment valve. At the end of the video some ugly dude shows up LOL.

Operation of the enrichment valve is this: A fuel line comes from the bottom of one carb bowl (usually the top carb. When you push in the key to choke the engine, the valve opens. Fuel pressure from the pump pushes fuel through the valve to the hoses leading to the carb flanges. fuel enters the manifold through these barbed fittings on the flanges and richens the engine so there is enough fuel vapors to ignite. When you release the key, the valve closes and fuel level in the top carb is controlled by the float.

If the valve fails in closed position due to electrical or other problems, you push in and hold the red button on top. If the valve fails in the open position, crimp the supply hose and later replace the valve.

If the rubber grommet for mounting the valve is missing or compressed to tightly, the valve will vibrate during running and richen the engine.

 

[todd.bellamy]

Re: 1996 Force 120 HP Hard to start after running.

Sounds good! Just so I'm 100% sure, In the attached schematic it is H, the Fuel Primer Solenoid you are referring to, correct? Also, I see a fair about of overflow in the carb covers after running, probably related?

Thanks Again,
Todd

 

[roscoe]

Re: 1996 Force 120 HP Hard to start after running.

Sounds good! Just so I'm 100% sure, In the attached schematic it is H, the Fuel Primer Solenoid you are referring to, correct? Also, I see a fair about of overflow in the carb covers after running, probably related?

Thanks Again,
Todd

View attachment 220727

yes

 

[Big Fish Billy]

Re: 1996 Force 120 HP Hard to start after running.

Some of these engines simply will not start unless the control box is put into fast idle/warm-up position.

And, don't forget, hard starting can be a symptom of fouled plugs, so change or clean them on general principles.

My 1997 Force 40 will not start warm unless the control is in this fast idle/warm-up position.

 

[todd.bellamy]

Re: 1996 Force 120 HP Hard to start after running.

Roscoe and Fran, I went out after work today and looked at the enrichment valve, the push button on top has very little play in it and seems stiff, however I did not have the key in it. I will try to do some more testing this weekend with the fuel on.

Billy, when you say the fast idle/warm-up position, do you mean having the choke wide open?

When I've had this problem in the past, to get it started, taking quite a few tries, I would have to open the choke up all the way and do quick key turns to get it to fire, at least 10 quick key turns. Then I get boom...............boom..........boom.....boom...boom then idle. (Boom being the engine firing)

 

[pnwboat]

Re: 1996 Force 120 HP Hard to start after running.

The throttle handle has a neutral fast idle position, fast idle/warm up, what ever you want to call it. As mentioned several times above, it's often difficult to get the motor to fire up if the throttle is not set to this position. To engage the neutral fast idle position, the whole throttle handle must be pulled out to the left towards the center of the boat. You may have to push a button on the center of the pivot point of the throttle to get it to release. Depends on which model throttle you have. It only moves out about a quarter of an inch. Once in this position, you can advance the throttle forward without engaging the gears. Try starting it in this position. To return to normal operation, simply move the throttle handle back to the straight up and down neutral position and the handle should "pop" back in.

 

[todd.bellamy]

Re: 1996 Force 120 HP Hard to start after running.

So I feel like an idiot now, all last summer ( when I bought the boat) there is a switch on the controls just in front (actually under) where the key goes, for what I think I the fast idle or choke. I was taking pictures to show you guys when I noticed it. Looks like that is actually my issue. But can you fuys tell me what's what from the photos?

 

[todd.bellamy]

Re: 1996 Force 120 HP Hard to start after running.

 

[todd.bellamy]

Re: 1996 Force 120 HP Hard to start after running.

 

[todd.bellamy]

Re: 1996 Force 120 HP Hard to start after running.

First pic is bottom up, other is top down.

 

[MickLovin]

Re: 1996 Force 120 HP Hard to start after running.

From looking at the wiring diagram and not actually knowing if that is your choke if your switch you are taking pics of has a yellow black wire to it, it should be your choke, but I am pretty sure it is as it would be a spring loaded momentary switch which stays up by holding it, other wise it would be with the key by pushing in. However you could trace the yellow black wire to what on the diagram is indicating a junction connection, but I would say it comes directly from your controls and is not junctioned. Can you hear it engage the primer solenoid when holding the switch up away from off or you maybe able to get someone to listen for a sound when engaging the switch, you probably will need to switch off and on a couple of times to hear it engage and disengage, hope this helps, I am an electrician by trade and know a little about the electrical side but not sure with your outboard.

 

[jerryjerry05]

Re: 1996 Force 120 HP Hard to start after running.

The switch under the key is the emergency shut down.
It should have a lanyard with a connector hooked to it.
It will kill the engine when you fall over(if it's hooked to you).
The fast idle is: The shift handle.
You grab the base of the handle and pull straight out.
It should pull about 1/4-1/2 in and then will go forward or backward.
It allows the motor to rev up while in N
Pull it out and the push it forward and it will rev the motor while in idle.