AQ171C Starting Problems

"Hope you can help please.
Ha

"Hope you can help please.
Had a really great day out but whilst practising slow speed manoeuvres one of the engines just stopped whilst in neutral. It will stubbornly refuse to start there was no adverse noise or misfiring beforehand but I did notice the charge voltage suddenly stopped charging a little while before. I thought this was in initially a loose V Belt but this was not the case and battery is fully charged.
I am going through the Seloc manual for testing the Renix Ignition and so far all looks good but I cannot remove the coil yet because of rust and so I have sprayed penetrating oil on the screws and will have to wait next weekend to continue further.
But … hoping for some clues. I have a set of spark testers and I am getting a good spark at the coil but it looks like only no.1 cylinder has spark.
My guess is distributor cap and or rotor arm, but would welcome any views."

"I would run a compression tes

"I would run a compression test first to make sure the timing belt has not slipped. If the compression is too low in all cylinders, the timing belt may be the problem. Keep in mind that yours is an "interference" engine and if the timing belt is wrongly installed damage to valves and pistons may occur."

"Hi – thank you for responding

"Hi – thank you for responding.
You are right of course... I may be able to borrow a tester, I was kind of hoping that may not be the problem, I guess it was the loss of charging voltage a while before the engine stopping that led me to believe it was an ignition problem."

"Ignition is one thing, chargi

"Ignition is one thing, charging is a completely different one. If you are getting spark (even if at one spark plug) then there is voltage reaching the coil. Charging is alternator related.

The problem could be due to a number of things, but you have to start troubleshooting somewhere."

If your timing belt has slippe

If your timing belt has slipped you will still get spark at all plug wires. You will only get spark at a single cylinder if the rotor is under that cylinder and not turning. A broken timing belt could cause this. Best to remove the cap and watch the rotor while someone cranks the engine. Unplug the power wires to the coil first to avoid stray spark.

"Update:-
Ben was correct – T

"Update:-
Ben was correct – The timing wheels and the rotor arm are not turning.
The belt has not fully broken and is in situ, but on closer inspection I noticed a couple of timing belt teeth in the bilges.
Looks like a major problem now so I will arrange for a lift out at try to get it repaired for next season."

Aq171c Timing belt installation.

I am now replacing the timing belt but when you first install the belt you line up all the marks on the cam gears to those on the crank as shown in the manual.
The belt I had did not have 2 yellow marks just writing which you can line up between the 2 cam gears After turning the engine clockwise by hand using the crank nut for a number of complete revolutions, should the marks on the belt be way off from those on the cam gears?
The Timing marks on the Crank pulley and the Cam Gears still line up however.
I thought I may have been 180 deg out so I re-installed the belt but still the marks do not line up.
Am I being dumb, missing something or just carry on to do further test? I have both the Seloc manual and the Volvo Penta manual and all looks o/k as far as they go.

Since the cam runs at 1/2 the engine crank speed, the marks on the belt won't line up after you turn the engine. There is no need for the belt to have any specific timing relationship to either the crank or the cam gears. What is key, is the relationship between the crank and the cam.

Hi – Just an update.
I suspected valve train damage so I removed the head and I was correct, the valves have hit 2 of the pistons. Now the damage to the piston crowns is very slight and it has made slight marks in the edge of the valve reliefs. So much so that it is no longer smooth. How important is this damage and can it be filed smooth with a small file or emery paper without future valve problems.
I can send the head away to be overhauled but I am not keen on having to remove the engine to replace the pistons.
Any thoughts would be appreciated.
It may be the engine is beyond economical repair but as this is a twin engine boat then I may have to persevere.

If it were my engine, I'd just very very gently remove any raised burrs where the valves "dinged" the pistons. I'd make no attempt to smooth out the dings themselves.

Hello,
Sorry for the late reply as I have been away for awhile. Believe it or not there can be a relationship to why the alternator stopped charging prior to the timing belt failure in your particular case. The way that your timing belt failed can be caused by a leaking seawater pump. the water drips in between the belt and the crankshaft pully and literally rips the teeth from the belt due to "hydraulic lock". Which means there isn't enough room between the the teeth for both the belt and the water. The clue that this may be the case is that the alternator belt may have gotten wet and the belt slipped. I had this very problem as well and broke 2 belts this very way. (Of course bent many valves as well). Good luck and let me know how things turned out.