Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

[Herbiedog]

Can someone please help, I have just rebuilt my 1990 4.3 LX after I discovered #1 piston had a hole threw the centre??

Anyway was it has been rebored +0.30 and all new bearings rings pistons ect. I have assembled and put it back into the boat. However she will not start, I have checked the following;
Fuel, yes clean and fresh on the plugs
Spark, yes at Cap and Plug strong
Compression, yes 135 all round however manual states 180 so not sure if this is an issue.
Timing, yes set at TDC, rotor pointing towards #1 cylinder valves opening in sequence
Battery yes brand new 110amp turns over fine.

When I am turning her over, it seems that # 2,4, and 6 are trying to fire however the port side is not.

Any help would be great

 

[Don S]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

When you installed the distributor, did you have the crank set on #1 TDC on the compression stroke or the exhaust stroke?
Have a look at this thread.

http://forums.iboats.com/showthread.php?t=427081

 

[Herbiedog]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

On the crank I aligned the white dot with white dot on the cam sprocket. I then rotated the crank to align the 0 TDC on the harmonic damper to the mark on the timing cover. If that makes sense

 

[Don S]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

Did you read the link I posted?

 

[Herbiedog]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

Yes I read the link, and I have checked the TDC both valves are closed

 

[Don S]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

Do you have the rotor pointing to #1 spark plug wire when the engine is at #1 TDC on the compression stroke? and are the wires installed in the proper direction of rotation for the rotor?

 

[Herbiedog]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

Yes the rotor points to #1 at TDC on compression, the leads are in correct firing order 165432 and in sink with the rotor.

 

[dingdongs]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

double check all valves are set correctly making sure also that the timing is set too.you could try increasing the compression for its initial start by pooring a little oil into each cylinder to seal compression bypassing the rings but sounds as if you have something amiss.are all leads to correct pot?

 

[Bondo]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

Yes the rotor points to #1 at TDC on compression, the leads are in correct firing order 165432 and in sink with the rotor.

Ayuh,... Are ya turning the distributer, as you're cranking the motor,..??
Are changes noticed when ya do,..??
Does it fire on those cylinders consistently,..??
Are the plugs on the other side of the motor Wet,..??

 

[kewlkatdady]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

fuel?
Spark?...

 

[Herbiedog]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

All leads are going to the correct pot; as previously mentioned I started from scratch, the block came back from the with the crank and pistons fitted. I inserted the cam, aligned the two white dots on the cam and crank sprockests. I have checked the valves 3 times now just to be sure and they are all opening closing when they should be. I have swapped the carb, put a new disi cap and wires and changed the thunderbolt IV plus coil. It seems that the starboard side is trying to fire but not the port. When I check the spark at the individual plugs it is strong.

 

[JWebber]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

Got your lanyard switch to the on postion, if it's hooked up??

 

[Herbiedog]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

The plugs are wet with fuel, I have even used a fresh can of fuel as the fuel in the tank is about 6 months old. I have used engine start down the carb but it still won't fire.

 

[Herbiedog]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

Yes checked the lanyard switch.

 

[Bondo]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

as previously mentioned I started from scratch,

Ayuh,... Then Check, 'n recheck,....

Ya missed something, somewhere...

 

[Herbiedog]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

OK, Thank you all for the advice, I am now off to the boat and will again check TDC and valve timing as per the thread link above. Standby for further updates...

 

[Joshua Nichols]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

HMMMMMMM? Baffled... Wet plugs... Maybe its just flooded real bad..

Kinda weird you cant get her to fire off on starting dope..

I am following this one.. Interested to see what the problem was

 

[rickryder]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

Sounds like its out of time,while cranking turn distributor advanced and retard slowly like Bond-o said. I would start from basics again. Pull #1 plug,wad up a piece of paper and plug #1 plug hole,tap motor around with a bump started button until paper pops out,Now your coming up on TDC compression stroke,insert a wood dowel into plug hole and bring piston to top, check your timing mark on crank,check rotor position on cap,make sure wires are correct in firing order.

 

[saywhat]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

I cant remember if the 4.3 Merc has a removable harmonic balancer with a woodruff key, etc, but I had a machine shop install the harmonic balancer 180 degrees off on an old 4.2 Jag engine once. Took me 2 solid days of head scratching before I figured that one out....almost identical symptoms to what you are experiencing. Either way, my vote is some sort of timing problem - it should fire even with low compression.

 

[Herbiedog]

Re: Mercruiser 4.3 LX 1990 Alpha 1 Gen 1 won't start

Update...TDC is exactly where it should be, inlet and exhaust valves closed however it appears that inlet valve is still open when coming up to compression this works out to be about 60 deg out. Now about to remove the Harmonic damper and timing cover to re check alignment of timing chain sprocket.