#2 Cylinder dead on 454

[jbare]

Hello, here goes... My #2 cylinder will not fire on my 7.4 litre MPI. I have checked compression on all cylinders (110 - 120) on all. Spark plug is sparking. Fuel injector is working. I also went ahead and replaced distributor cap and rotor, wires and spark plugs. As well as cleaned all the fuel injectors. I pulled and inspected exhaust header and risers to check for water leaking into the cylinder, their is none. The only thing that I know for sure is that the spark plug for the #2 cylinder is black and smells of fuel. The boat was running fine on the lake, then the cylinder stopped working at a cruising speed and what I thought sounded like a back fire or two occurred. Engine has 275 hours on it. Also if I pull the #2 spark plug out and turn over the engine it will arc off a spark. Any ideas?? I am out.

 

[Don S]

Re: #2 Cylinder dead on 454

First thing I would ask, is what year, who's engine Mercruiser, Volvo, year, full serial numbers and/or FULL model numbers help 7.4MPI doesn't say much as to what MPI system you have.

How did you "clean the injectors"?

 

[jbare]

Re: #2 Cylinder dead on 454

Mercruiser engine in 2001 Baja islander 232, as soon as I can find it I will get the serial number off the engine. As far as the injectors go I actually pulled them out and soaked them in seafoam overnight. Afterwards I lightly tapped out some small amounts of debris. I then placed two wire leads from the boats batteries on each injector long enough to fire each injector until I had a fine equal spray from all eight injectors. The small amount of debris was rust colored so I replaced the fuel water separator and flushed the line from it to the fuel injector rail.

 

[Don S]

Re: #2 Cylinder dead on 454

As far as the injectors go I actually pulled them out and soaked them in seafoam overnight.

That's not going to work. Maybe for a minute or so. You need to send them out and have them professionally cleaned and checked.

You might get lucky, if you remove the filter in the end of the injector, and energize it with a 9V battery (NOT the boats battery) and back flush it with some Mercruy Power Tuner. Then install new filter. But with rust comming out of it, I wouldn't expect too much.

 

[jbare]

Re: #2 Cylinder dead on 454

Ok will do tommorrow and see what happens. Thanks.

 

[jbare]

Re: #2 Cylinder dead on 454

Ok, installed new fuel injectors and purged air from the system. The boat starts but it still misfires on the #2 cylinder. The spark plug is wet with fuel. I am confused at this point.

 

[dakine]

Re: #2 Cylinder dead on 454

Swap the #2 injector with another one.
If the problem moves with the injector, then it is the injector.

 

[dakine]

Re: #2 Cylinder dead on 454

Ooops!
Our posts overlapped.
Next, I'd move the plug wires around to make sure it isn't crossfire or misfire.

 

[ghettoyacht]

Re: #2 Cylinder dead on 454

i'm thinking bent pushrod, broken rocker, bad lifter. have you pulled the valve cover and watched the operation of the valve train? you could still have good compression even with a non-operational valve. anyone else feel this way?

 

[joey maneri]

Re: #2 Cylinder dead on 454

You could still have compresion with an exhaust valve not working, pos bent push rod, broken rocker arm. An intake valve not working would show low compresion. Popping through the intake could be caused by a valve train problem. Pull the valve cover, Theres not much more it could be.

 

[jbare]

Re: #2 Cylinder dead on 454

Fireing order is fine and swapped injectors...nothing. I guess next option would be to remove valve cover and see whats going on in their.

 

[dakine]

Re: #2 Cylinder dead on 454

Have you checked the wire on the injector all over?
The injector fires when one side of the wiring goes to ground in the ECU.
An intermittent ground through chafed insulation could be causing random injector firing.

 

[havasuboatman]

Re: #2 Cylinder dead on 454

Valve operation is the first thing you should have checked. My guess is your injector fouled, went lean and backfired slaming your exhaust valve and bending the pushrod. Now you aren't exhausting so you are flooding.

 

[ENSIGN]

Re: #2 Cylinder dead on 454

A cylinder leak down test might be a good idea It doesn't cost anything !!!