Engine dies - Honda BF9.9a - just serviced Grrrrrr - any ideas on diagnosis?

[Durcott]

Hi Forum folks - hope you had a great weekend.

Mine was a mixture of frustration and embaressment ( - plus I had some trouble on the boat )

Long story short - old Honda BF9.9a has had a comprehensive service, and was pronounced 'good to go' on the test tank. (Trustworthy motor guru.)

Then - a boat sale opportunity that fell through meant the motor sitting in its stern 'locker well' installation for three months on the hard, during the winter .

Boat launched last week - engine no worky. Fresh fuel etc etc. Suspected water in carb, so drained the bowl, and initially things were good.

Tried a 'motor' test - managed the length of the River Axe - about 5 - 10 mins - with no problem. As soon as I got confident, and found open water in Weston Bay - motor died. So did the wind, hence embarresment.

It's certainly running OK, but it keeps cutting out, and then won't start. Cut out is sudden and fast - an instantly dead motor.

Have tried gravity feed by raising tank well above motor. No difference. Have tried nipping the fuel tube upstream of the primer pump - when I do this there is pressure in the bulb, so I 'know' there is fuel.

There is a reasonably healthy spark. There is something that looks suspicially like moisture droplets on the spark plug surfaces .

My suspects at the moment are dodgy fuel pump, or water elsewhere in the system - in-line fuel filter perhaps? But why did I get a reasonably long test run before the cut out?

Has anyone got any sure-fire diagnostic processes for 'water in fuel' or dodgy fuel pump?

Any other suggestions welcome, before I throw the damned thing over the side. (Last service cost a fortune compared to value of motor.)

Kindest regards

Jeff

 

[mtb]

sounds more like electrical to me
if it were fuel it wouldn't simply cut out dead it would die slowly just to wind you up
look at all the connections check connectors are good
why don't you take it back if they charged you for a main service then that's what you should expect

cheers
mick

 

[NickRobinson]

Taking it back is good if practical.

If not, remove plugs (the 10hp is a twin I think) and with the plug holes up, pour in a tablespoon of petrol into each.

Place upright in water and gently pull the rope to ensure no hydraulic lock, it'll turn in the end. Then pull in earnest like a normal start.
If the cyl/pistons/valves/timing/spark are all ok, it'll fire, directing you to a blocked carb. If you are quick and choke it before it dies, you may clear minor blockages with the suction ....

(This is where you tell me it's injected!)

Nick

 

[VicS]

I agree with ntb

The fact that it drops dead would make me look at the ignition system.

Stop button, condition of coils, HT leads etc But if it really has a good strong spark , from the end of the lead not just a weeny one on the plug, but wont start then it pretty much rules out ignition faults. CDI unit is always a bit of an unknown quantity though esp if it has developed an intermittent fault.


However dropplets of water on the plug would make me look at the fuel system for signs of water. Flush out tank, fuel lines, pump and carb. If the carb has sat with water in it it could well need a very thorough clean.. poking a soft wire through all jets.


Any chance that there was water in the engine that has frozen during the winter and done some damage ? There should not have been if it was upright.

 

[Durcott]

Thanks for all the ideas.

When I tell you what actually happened, you'll laugh. I'm still trying to see the funny side though!

I visited the boat tonight, and the engine immediately burst into life. So - I ran it in gear for a while, and the same thing happened. I checked fuel pump, fuel filter, sparks, and cleaned the gunk off the ignition coil.

It ran very well, and then cut out, just the same. It dawned on me I had disconnected the fuel pipe 'temporarily' while messing with the fuel filter. So the 'symptom' of immediate cut out could be simulated by pulling the fuel feed eh?? Hmmmm.

Well - to put an end to this, eventually I found that the 'flow direction' marking on the new ****** primer pump was back to front. So it was able to slowly prime the system under gravity/syphon when the engine was stopped, but unable to keep the fuel pump supplied when running.

2 minutes to swap the pump around, and all was well. Runs sweet as you'd like now.

I was also totally convinced it was an ignition fault. Well - the fuel WAS there wasn't it????

Live and learn.

Thanks again

Jeff

 

[VicS]

The primer bulb was back to front .... thats all there was to it

 

[Durcott]

Yep - I was gutted.

'Cost' me the bank holiday.