rebuild entire fuel system an cranks but wont stay running

[flboy0638]

1995 force 40hp serial oe109561

When I got the engine last month it would fire off but never crank. The primer bulb would not get hard so i suspected carb needle not seating or stuck. new fuel hose, rebuilt carb, rebuilt fuel pump, new spark plugs, new non ethanol gas with sea foam in it, new hose, and i bypassed the fuel connector an my tank line is right on the back of the fuel pump. I get a good stiff primer bulb an the engine will crank an run. 1st time for 3 minutes but now will not crank for long sometime very hard to crank. when it cranks i manually go to the throlle arm an try my best to keep it running with a variety of positions... more throttle, less, none, excttt. all this in a effort to try an get a feel for the motor. Can not keep it running. I can walk away for a half a day come back an itll crank but cuts out an hard to crank after that

 

[flboy0638]

Just tested compression an i have 130psi on top an 129 on bottom.

tested spark on both an a nice blue spark on both grounded to engine block.

 

[Jiggz]

First, we need to clarify terminologies. The word "crank" when used with gas engines mean the starter engages the flywheel and turns it over. In the old days before the electric starter, automobiles uses a long handled steel "crank" to crank or turn over the engine to get it started, hence the term "crank". As soon as the engine starts, meaning the spark plugs are firing or sparking and combustion is taking place, then the engine is "firing", that does not mean it is running. It just fires. Now if the firing continues, then the engine is "running".

Terms aside, it sounds like your problem is fuel starvation. Install a Fram G2 (Walmart has them for less than $5) clear fuel filter between the fuel pump outlet and the carb's inlet. This is more for troubleshooting than a filter (although it can serve as a secondary fuel filter). Now prime the fuel system with the primer bulb. The clear fuel filter should be at least 3/4 full (or could be initially less due to air in the system but should stay full after first use). Make sure the carb's idle mixture screw is set to at least 1 ~ 1 1/2 turn out from slightly seated. Place the control lever in fast idle position. Remove cowl to observe motor and filter. Engage the choke and start the motor (make sure cooling water is connected). If motor starts, let it idle while watching the clear fuel filter. If motor will not idle try raising the idle to about 1000 RPM with the idle screw located at the bottom of the timing/control tower (NOT WITH THE IDLE MIXTURE SCREW LOCATED ON THE CARB). If it still would not stay idling, the motor is likely misfiring and only running on one cylinder.

If motor idles but eventually dies, and the clear fuel filter stays full, you most likely have carb problem, reeds or electrical problem. However, since you mentioned there is good blue spark in all cylinders then it could just be the carb settings or the reeds or it could also be a timing issue.

However, if the motor dies and the clear fuel filter is empty, then you have fuel delivery problem. It could be leaky fuel hoses, faulty fuel pump, faulty check valve on primer bulb, restricted tank vent or pick up tube, etc.

 

[flboy0638]

Understand your post completely and will do! Will report back...Thanks

 

[flboy0638]

I have done a few of the things you asked me too.

************Task 1*************************Terms aside, it sounds like your problem is fuel starvation. Install a Fram G2 (Walmart has them for less than $5) clear fuel filter between the fuel pump outlet and the carb's inlet. This is more for troubleshooting than a filter (although it can serve as a secondary fuel filter). Now prime the fuel system with the primer bulb. The clear fuel filter should be at least 3/4 full (or could be initially less due to air in the system but should stay full after first use).

===============RESULT============ Id say it stays about 3/4 the w ay full. I get a good hard bulb quickly like the needle is doing its job. I never need to choke the engine as It fires right up instantly every first time. Note I say first because after it cuts off its hard to start after that.

************Task 2*************************Make sure the carb's idle mixture screw is set to at least 1 ~ 1 1/2 turn out from slightly seated.

===============RESULT============complete, set screw like you asked but, did not try an adjust as I heard do this while your driving under a load. Did not need to anyways ran smooth

************Task 3************************Place the control lever in fast idle position.

===============RESULT=========== complete, barely need to give any gas at all , it fires right up but i did give it a lil to follow your directions.

SUMMARY:

I quote.........
"If it still would not stay idling, the motor is likely misfiring and only running on one cylinder."
end quote......

It does sound like it misfires but ONLY when its ready to shut off. For example, Every subsequent time I crank the motor it runs for a little longer each time. Smooth an nice, perhaps maybe misfiring but I dont hear it. This morning it ran smooth for almost five minutes. When it gets ready to cut off, an forgive my descriptions, but it warn you its coming for lack of a better term. It will hesitate once, twice, run a lil, one more hesitate then shut off. Or perhaps like you say "misfire"

I hear you on the carb an reeds thing. Before I go that route I want to crank again tommorow an closely look at the clear fuel filter again at the time it shuts off cause quite frankly, it doesnt look empty or full at the time it shuts off. Mostly though I want to analyze more because I do not understand why it runs fine for a while then starts misfiring and shuts off. This behavior lends itself to fuel problem because why would electricity be time specific like this?

Note to self.........................................................................
fuel filter empty when motor cuts off equals rebuild fuel pump
fuel filter full when motor cuts out rebuild carb, electical issue, or troubleshoot reeds

 

[Jiggz]

The reason it is hard to re-start after it shuts down on the first run, is probably due to low fuel in the carb's bowl, which probably cause it to start "coughing" like it is running out of gas and eventually dies down. And there are two reasons for this, float not set correctly on carb or fuel pump not delivering the proper amount of fuel. The latter can be monitored with the clear fuel filter by at least staying 3/4 full. If it does stay at least 3/4 full, then it will have to be the carb float. No need to dismount the carb for now. Instead, just remove bowl, check the operation of the float using a spare fuel hose connected to the inlet nipple. Blow into the hose with the float down and there should be no restrictions. With the otherhand, raise the float and it should stop you from blowing. Don't blow too hard just enough to hear or feel the air going through to simulate fuel flow.

If the carb's float is working perfect, put it back together and test again. If the problem persists, as soon as the motor dies and is very hard to re-start, try the spray test. Put some fuel oil mix in a spray bottle and spray it directly into the carb (when the motor is hard to start - do not re-prime the bulb). If motor starts immediately thereafter, fuel starvation is still the problem. However, if still will not start or very hard to start with the spray test, then something else is wrong and it is not fuel related.

 

[flboy0638]

Thanks. Will look ar those tommorow. I did fool with the float a while back when i revuilt carb last week. I tweeked the setting with float so the needle would fully close an stop gas when bowl was full. i put a mityvac on the carb with 10psi an the needle was working good releasing and closing but I could have messed the float up.

does the float suppose to sit "even steven" when in the closed position? even steven with the carb?

anyways, before fooling with float ill do the spray test tommorow thanks....

 

[Jiggz]

Let's see what the results of the spray test is and we'll take it from there.

 

[MickLovin]

If the primer gets hard and stays hard your fuel pump diaphragm is ok, if your primer bulb doesn't get hard it could possibly be your fuel pump diaphragm which would eventually starve the engine, as would a badly set float or a sticking needle.

 

[flboy0638]

I rebuild the carb and the fuel pump again. Motor fired up quickly an ran smooth for about a minute. I listened real close to see if running on one cyclinder. I do not think it is. Sounds good. Motor ran a while an started with the warning signs its about to shut off. I shot gas in the throat of the carb but everything was at idle so the butterfiles were close. The engine shut off as It usually does. Shall I try the squirting gas in the engine at about 1/4 throttle?

 

[Jiggz]

You should try squirting the gas with the throttle at least half open. If you are doing this at the driveway on muffs, you will need to use the tie bar or linkage rod to hold the throttles open without getting it into gear. But if you are doing this on the water then you should try doing it at WOT. Just make sure you are away from traffic and a distance from shore. Squirting fuel mix could increase the rpm but it will only last a second or two unless you continually do so. You still need to monitor the clear fuel if it is staying at least 3/4 full.