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Robert Dustone
Visitor
| | Posted on Friday, December 16, 2005 - 11:44 pm: | 
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Hi my name is Todd and I have a P55 installed in a 16 foot clinker, it will not start.
1. The engine was rebuilt with new rings by a marine engineer not too long ago and has plenty of compression.
2. I have had the magneto checked by an auto electrician, the points are fine, the plugs are fine, I have tried every plug gap possible. The dogged gears on the magneto and engine have a faint notches etched into them, I lined both these up when I reinstalled the magneto. The bakelite or fibre disk between the two gears has about 3mm of slack between the notches and I have tried taking this slop up with spacers but it made no difference.
3. I have completely cleaned the carby which seems to be fine, however the plugs never seem to become wet or flood although there is fuel vapour in the cylinders.
4. I have tried every choke and throttle setting, which makes no difference.
5. This motor has always been cantankerous sometimes backfiring and being difficult to start both when it is both hot and cold. Normally I use Aero-start if it doesn't fire after a couple of minutes, however the Aero-start is not making any difference now.
6. The last time I ran the boat successfully was a long all day cruise with just myself aboard at full throttle most of the time, the boat used a lot of fuel about 20 litres. Between then when the engine was going and now when it is definitely not the engine was very hard to start, I adjusted the throttle linkage a lot and set the idle very high to get the engine going, because of this I only ran the engine for a few minutes at a time, hoping to get it running and to bring the idle back to normal speed.
7. I think it must be the timing, but how can I adjust this to make the engine start, the distributor can't be rotated like in a car? A previous owner has left white timing marks on the pulleys connected to the magneto though, so it must be possible.
Any help is greatly appreciated.
Thanks Todd |
J.B. Castagnos
Senior Member
Username: jb_castagnos
Post Number: 274
Registered: 07-2002
| | Posted on Saturday, December 17, 2005 - 07:07 am: |
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Todd, I'm not familiar with your particular engine but it sounds like an ignition problem. Have you tied a new sparkplug? Does the mag jump a 1/4"+ gap consistantly? Timing is critical for performance, but close shoud get you running. Is it an impulse mag? If so it should fire with the piston at or near top center, anywhere close should get a pop or sneeze. No impulse should fire before top center, guessing 20 or 30 degrees before, but as I said, for starting if it's firing near the top something should happen. With impulse you can watch the piston coming up and listen for the mag to snap. Without you'll have to watch the points, mag should fire when the points open. A new plug with a close gap will allow you to cheat a little with a weak mag. |
Peter Ogborne
Senior Member
Username: peterogborne
Post Number: 274
Registered: 09-2002
| | Posted on Sunday, December 18, 2005 - 06:25 am: |
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I agree with JB . Sounds like ignition as JB suggests try a new spark plug.
Many the time i have tried to start an engine and then put in a new plug........instant success.
Also double check you fuel system.
Let us all know if you have success. |
Robert Dunstone
Visitor
| | Posted on Tuesday, December 20, 2005 - 08:17 pm: |
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Thanks for your replies. How do I adjust the timing? The cogs that connect the magneto to the engine have several marks and notches on them, what is the correct way for the magneto to be refitted? The engine will not flood even with me trying my hardest by choking the carby, using the tickler and pumping in heaps of expensive Aero-start, so I'm wondering if the inlet manifold or ports could be blocked, does this ever happen. I have drained the crankcases and no fuel comes out just a little engine oil trickles out.
Thanks for your help Todd |
Peter Ogborne
Senior Member
Username: peterogborne
Post Number: 277
Registered: 09-2002
| | Posted on Wednesday, December 21, 2005 - 07:39 am: |
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Robert.....ignition timing.There is TDC stamped on the Flywheel rim. This indicates when the piston for each cylinder is at the top of the stroke. There is an M stamped on the flywheel rim 2 inches before the TDC mark . The M is the position that the magneto points should break.
So you line up the M at the centre of the engine.Use number 1 cylinder[ the one next to the flywheel].Take off the magneto and slacken off the coupling[so that you can turn it independantly of the magneto rotor,ie with out the points opening]. Replace the magneto so that the points are just opening when the M is at the top of the flywheel. A good way the determine the exact point of opening is to place a piece of thin paper between the open points ,close them and when you can just start to pull the paper that is your opening point.When you have done this and I repeat, the points should just be opening when the M is at the top. If this is OK remove the magneto with out moving the setting and tighten up the coupling.Now replace the magneto .....just check again that the timing has not altered.
You will now see that it is not required to have marks on the chain sprockets or the gear drive . The latter is the drive to the water pump.
It most unlikely that the ports are blocked but you can take off the expansion chamber cover and inspect the condition within.
Holding the carb tickler down should produce a flood of fuel from the small hole at the top side of the float chamber.If the plugs remain dry during your attempts to start the engine it indicates lack of fuel. You said the the engine when it was running was backfiring .Sometimes this does indicate a too lean mixture[not enough fuel] but this is more likely to be shown as spitting back through the carb ....keep trying ,they are a simple engine .
The rules ...failure to start and run properly can be put down to these five causes,
1..choked exhaust
2..chocked pump system ,indicated by over heating
3..carburation incorrect
4..ignition defective
5..wear |
J.B. Castagnos
Senior Member
Username: jb_castagnos
Post Number: 277
Registered: 07-2002
| | Posted on Wednesday, December 21, 2005 - 08:25 am: |
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Does this engine have poppet valves? They are known to stick. A broken reed valve? Is it a three port, they are very snsitive to cylinder scoring, but you said you have good compression. Peter mentioned plugged exhaust. Turning it over you should feel suction on the carb as the piston goes up. |
David Stott
Member
Username: david_stott
Post Number: 4
Registered: 06-2005
| | Posted on Wednesday, December 21, 2005 - 05:25 pm: |
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If you cannot get fuel at the carby then you have a fuel supply problem. On my P55, I have had trouble with air locks in the fuel lines. Check that you have a consistent fall from the tank then only one rise to the carby. Then bleed the lines to get any air out. I have also found that modern car paper canister fuel filters do not cope with gravity feed and cause their own air lock. I have resorted to a mesh filter from a ride on lawn mower and have had no further problems. |
Peter Ogborne
Senior Member
Username: peterogborne
Post Number: 278
Registered: 09-2002
| | Posted on Wednesday, December 21, 2005 - 07:50 pm: |
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Good thinking David .....air lock could be the trouble. |
Robert Dunstone
Visitor
| | Posted on Tuesday, December 27, 2005 - 11:17 pm: |
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Hi, Thanks again for the replies.
I have fitted new plugs gapped at 22thou. I have adjusted the timing as suggested. I have cleaned the carby and fuel lines and replaced the fuel with a new mix at 32 to 1. I have removed the expansion chamber and drained the water that was contained in there, I have checked the exhaust and it is not blocked. The motor will just not start. There is still plenty of cylinder compression, however the motor just does not seem to draw through the carby and when the crankcase drain bolts are removed there seems to be no pressure in the crankcase as the motor is turned over. The spark plugs are always dry and never have any traces of fuel on them and only a small amount of vapour is pushed out of the cylinders even with heaps of aero-start being used. How much cylinder compression do these motors normally have? Did these motors ever have reed valves, I didn't think they did? I'm wondering if the crancase is leaking hence the low pressure and no fuel reaching the cylinders, what is the easiest way to check?
Thanks again, Todd |
Peter Ogborne
Senior Member
Username: peterogborne
Post Number: 281
Registered: 09-2002
| | Posted on Wednesday, December 28, 2005 - 06:42 am: |
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Todd ...the P55 nor for that matter any of the engines ever had reed valves. They are a simple crankcase compression engine with cylinder ports.
The only thing that I can start to think about are the seals. If as you say the engine was rebuilt ask the person who did the job what he did about the crankcase seals.If he replaced the original Stuart Turner seals the problem may be there. These seals are ok when they work but they do wear . I prefer to replace these with a modern synthetic rubber seal . A repacement can be obtained at any bearing supplier....I can give you the exact dimensions I you want them just means me measuring the bearing housings.If the original seals are leaking you will not get sufficient transfer of fuel mix to the combustion chamber.Also on the P55 there is a center bush on the crankshaft it is a split bronze bush that acts as a sleeve valve diecting the induction gas from the carb to each of the crankcases. There are two things to look for here ....the clearance between the bush and the crankshaft should not be more than .008 of an inch.The bush can also with some difficulty be put in incorrectly restricting the gas flow.
I dont know if the rebuilder was experienced in the Stuart Turner P55 engines.Another thing to look for is if the piston has been fitted in the opposite position. The crown of the piston has a deflector ,this directs the gas flow up and not straight out of the exhaust port. I am sorry to throw all this at you but an inexperienced person when fitting the cylinder to the crankcase may have fitted a crankcase to cylinder gasket that covers or partly covers the port.The latter is something that we have all been guilty of. These are all '' Last resorts''.
Hope you have success.Keep posting and I hope we can solve the problem. |
Peter Ogborne
Senior Member
Username: peterogborne
Post Number: 282
Registered: 09-2002
| | Posted on Wednesday, December 28, 2005 - 06:50 am: |
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Todd ......I forgot to say you can check if the piston is in the correct way by removing the expansion chamber cover and viewing the piston through the cylinder port . The correct fitting is with the deflector crown ,ie the vertical face towards the carb side . |
Kim Siddorn
Visitor
| | Posted on Tuesday, February 21, 2006 - 09:03 pm: |
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I had a P55 industrial unit, identical to the marine engine, but sans gearbox & fitted with a governor. It too was a swine to start & in fact, I never did start it using the handle - same problem no fuel getting to the plugs. I solved it by cutting a notch in the edge of the pulley and wrapping a rope around it. This enabled me to get a good pull at it and when thus spun at a decent speed, it would start every time, hot or cold. Dunno if this helps ;o)) |
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