omc 240 misfiring with new engine

[Bryan_S]

its a 351w and its brand spanikin new.

I seem to have a misfire. it wont idle, sounds like hell.... not like a new engine.

Seems to be gettin spark

lost

~Bryan S

 

[bruceb58]

Re: omc 240 misfiring with new engine

Double check your firing order. How is timing and dwell?

I know its new but you still may want to check the compression.

What is the history of the carb that is on it?

 

[Bryan_S]

Re: omc 240 misfiring with new engine

the carb was rebuilt last week... ive done some more testing.....

thinking maybe the cap was cracked so i moved the wires over one and still misses on the same cyl.

i pulled the plug, and i have spark.... whether its good spark or not i dunno.

firing order i used is 1-3-7-2-6-5-4-8

im beginning to think i have a weak coil.

not sure though any suggestions would be greatly appreciated

thank you for the response

~Bryan S

 

[bruceb58]

Re: omc 240 misfiring with new engine

Just checking. You also realize the distributor rotates counterclockwide right?

What is your dwell at?

What is your timing at?

thinking maybe the cap was cracked so i moved the wires over one and still misses on the same cyl.

If you are thinking the cap is cracked, why aren't you changing the cap? Rotating the wires over one is not going to help that. While we are on the subject of ignition components, you should be starting out with brand new cap, rotor, wires and plugs...new points as well if so equipped.

 

[proxyx]

Re: omc 240 misfiring with new engine

firing order is embossed on the engine block (intake cover), got to follow it.
Who installed the engine/harness? Make sure you have the right firing order.
Don't know if this is right, but here: 1 8 4 5 6 2 7 3 ... I got diff. one from Googling your engine... this is what I have I believe.
So many issues with your NEW engine...? gotta be a firing order. Check and doublecheck.

 

[bruceb58]

Re: omc 240 misfiring with new engine

Don't know if this is right, but here: 1 8 4 5 6 2 7 3 .

That is not correct...that is for a reverse rotation engine.

Be aware that on a Ford, cylinders 1,2,3 and 4 are all on the same side of the engine...unlike a GM engine. Also, #1 is on the opposite side compared to a GM engine.

 

[proxyx]

Re: omc 240 misfiring with new engine

That is not correct...that is for a reverse rotation engine.

Be aware that on a Ford, cylinders 1,2,3 and 4 are all on the same side of the engine...unlike a GM engine. Also, #1 is on the opposite side compared to a GM engine.

not saying to use it, LOL. just pointing out that's it's easy to get confused.
Funny, the setup is he same, I was saying clockwise, you pictured ccw.
The point is: ignition is where I would look. Order and timing.

 

[bruceb58]

Re: omc 240 misfiring with new engine

not saying to use it, LOL. just pointing out that's it's easy to get confused.

Hmmm...glad you cleared that up. Seems to me that it would confuse the OP even more...guess that's just me.

 

[proxyx]

Re: omc 240 misfiring with new engine

Hmmm...glad you cleared that up. Seems to me that it would confuse the OP even more...guess that's just me.

There was nothing to clear! Everyone uses firing order not from the book or internet but block/intake only. Period. I said that unequivocally. Point was to doublecheck it!!! VERIFY.

 

[Bryan_S]

Re: omc 240 misfiring with new engine

heh no confusion...

i do realize that the rotor runs ccw, and have installed the wires in the correct firing order..

the cap is NOT cracked. well it might have been but ive replaced it, and the misfire is still present.

timing is not set yet, cuz i cant shake the misfire


gonna try replacing the coil.

thanks for the replies

 

[proxyx]

Re: omc 240 misfiring with new engine

before you replace it check the coil with spark tester, spark should jump 1/2 inch min.
then all idiv. wires with the same tester, see if you can come up with something

 

[Bryan_S]

Re: omc 240 misfiring with new engine

new coil 16.99

lol

its old, the motor is new, even if it isnt the coil, its 16.99 ...........

~Bryan S

 

[bruceb58]

Re: omc 240 misfiring with new engine

timing is not set yet, cuz i cant shake the misfire

You need to check it and the dwell. Either one can be causing your misfire!

 

[Bryan_S]

Re: omc 240 misfiring with new engine

well got a new coil, and....... DAMN IT!

it was NOT the coil, but oh well a new coil on a new engine..... 20 bux... big deal.

I did however find ( i believe) the culprit of the misfire.

I had the engine assembled by a "professional"...... LOL

ok so after the coil didnt fix it...

I figured it had to be an intake leak.. and it was

my professional engine assembler apparently goofed when installing the carb/plate or plate to manifold gasket.... or something.... there is a HUUUUGE intake leak on both sides of the carb.

Thanks for the responses, i do believe this is the problem

will let everyone know asap

~Bryan S

 

[proxyx]

Re: omc 240 misfiring with new engine

well, we all know that "professionals" are not saints that's why so many look for self help sources, looks like a cheap fix in your case

 

[Bryan_S]

Re: omc 240 misfiring with new engine

ok hmm another issue, im sure you all can give me the right advice =]

ok here is the deal.

the stock intake was so caked with rust, i chose to get an aluminum edelbrock 351w performer intake.

this intake has the egr hole on the carb mount area.

My professional, installed a paper gasket over this to a hollow carb base plate.

so when i took the carb off, i noticed the gasket was burnt in that area.

My question is.....

can i just put a solid spacer over this?

here is the intake i have http://www.edelbrock.com/automotive_new/mc/manifolds/images/3781.jpg

notice the hole on the carb mount surface..... this is what im talking about.

being there is no egr involved here, would a solid spacer be the answer here?

thank you for your replies

~Bryan S

 

[proxyx]

Re: omc 240 misfiring with new engine

egr gaskets from what I've seen are fire resistant (brown, steel enforced material), solid spacer with temp resistant gasket would work if paper burns.
Or plug it (tap, die) or better yet weld it permanently...

but you wrote:
"its a 351w and its brand spankin new"... then "the stock intake was so caked with rust" ...(??)

 

[bruceb58]

Re: omc 240 misfiring with new engine

You ever use this boat in saltwater? An aluminum intake is not going to last long.

 

[Bryan_S]

Re: omc 240 misfiring with new engine

its has a freshwater cooling system.

the new engine was a long block, not a complete engine.

the intake was off of the old engine.

gonna try to find me a spacer plate and gasket in the morning.

thanks

~Bryan S

 

[Bryan_S]

Re: omc 240 misfiring with new engine

ok, got her all fixed up, new carb base plate, new gasket, and she purr's like a kitten. FREAKIN FINALLY!

so i changed all the gear oil in the outdrive and intermediate.

got the reg stickers on, and a date with a pick up truck at 10 am tomorrow morning!

everything seems great.

I wanna Thank all of you for your help.

This site is great, and the people are curtious, and very patient with us newbs.

Keep up the good work iboats!

~Bryan S

thanks again!