**UPDATE** Help with Merc 4.3 starting problem please

[neilmw]

***Problem now solved, see my last post, Thanks***




92 4.3l v6 alpha gen ll
Last year I noticed a leak on the port side manifold, Pulled plugs and found 1 of them had got rusty.
Left the boat for some time although i did turn her over to get any water out then sprayed oil into the chambers before refitting the plugs and laying up.
Have just finished refitiing all new manifolds elbows etc and a starter as the other one had given up the ghost.
I now have it all ready to go but just get it to fire, have checked all the electrics, and have a good spark at the plugs, have checked that fuel is going down the carb which it is, but she just wont fire, all the ignition parts were replaced last year so dont really think its that. So thought I would ask the experts.
Oh and thanks in advance for any advice.

 

[firehog6305]

Re: Help with Merc 4.3 starting problem please

Re: Help with Merc 4.3 starting problem please

how old is the gas????

 

[neilmw]

Re: Help with Merc 4.3 starting problem please

Re: Help with Merc 4.3 starting problem please

Sorry forgot to mention that I have it running from a plastic 25 lt tank straight into the filter(also new) as I am going to drain the main tank and refill.

 

[Haut Medoc]

Re: Help with Merc 4.3 starting problem please

Re: Help with Merc 4.3 starting problem please

Have you verified the firing order & wire placement?......
Have you verified that the rotor is turning?.......​

 

[neilmw]

Re: Help with Merc 4.3 starting problem please

Re: Help with Merc 4.3 starting problem please

Have checked the spark plug leads, just assumed the rotor is turning ....

 

[neilmw]

Re: Help with Merc 4.3 starting problem please

Re: Help with Merc 4.3 starting problem please

Ok, have double checked spark leads, rotor is turning, good spark, plenty of fuel. Also took the rocker covers of and the valves seem to be moving fine.
I am now wondering if the problem is lack of compression as I noticed that whilst turning over when i put my hand over the carb there is hardly any suction. If i do have stuck rings is there any way of freeing them without a rebuild ????????

 

[Silvertip]

Re: Help with Merc 4.3 starting problem please

Re: Help with Merc 4.3 starting problem please

Yes --stuck rings and valves can often be freed using a product called Rislone which is available at any auto store. You do and oil change and replace one quart of oil with Rislone. It is a super high detergency and does a masterful job of cleaning up an engine. It's been around for years. If the rings are stuck because of rust, it's questionable as to whether any attempt to free them is worth while. I would limit high speed operation to 4000 RPM since Rislone is a 5W viscosity. I've rebuilt engines that have been destroyed by overheating. Cast aluminum valve covers get a yellowish coating on them that can't be removed with lacquer thinner yet Rislone in 500 miles removes that coating. Depending on how much boating you do, you might do two oil changes at say 30 day intervals.

 

[yam350yfm]

Re: Help with Merc 4.3 starting problem please

Re: Help with Merc 4.3 starting problem please

If it is turning through then the rings are not stuck anymore. The thing to do before turning it over would have been to spray PB Blaster or Sea Foam into the cylinders.

Get a good compression tester, Autozone will let you use one at no cost (you leave a deposit and get it back when you return the tool). Check all the cylinders and they should all be within 10% of each other. If the cylinder in question has low compression it could be a head gasket problem, as that would put water into the motor too. Did the oil have any water in it?

I would also check the timing, if you had to do anything with the distributor. Get the engine to top dead center and check it statically. I believe it should be set at 8 degrees btdc.

 

[neilmw]

Re: Help with Merc 4.3 starting problem please

Re: Help with Merc 4.3 starting problem please

At the moment I cant get the engine to start, have not touched the distributor at all, will have to do a compression test and see which ones are stuck.

 

[neilmw]

Re: Help with Merc 4.3 starting problem please

Re: Help with Merc 4.3 starting problem please

Well went down to the marina and decided that if it didnt go today, i would have the boat lifted and pay to have it sorted.
Turned the engine over a few times with the plugs out to get the penetrating oil out that I had out put down the bores yesterday, Put the plugs back in, a little squirt of easy start and there was a sign of life........a little pump on the throttle and after another 4-5 turns then she fired up, the only thing i did different over the last 2 days was that today I removed the 2 breather pipes off the 2 rocker covers that go into the air filter, when she was running there was what looked like steam coming from the rocker cover breathers, after a few minutes this cleared and left it running for 30 minutes, left the boat at lunch time and returned this evening to find that it started on the button, went for a 45 min run and it ran sweet.
So thanks for all your help, and I am now one happy man