496 hard start

[Snprhed]

So I recently got a 90 234 Edge that has a 496 Mag. I replaced the plugs on sat but it still cranks and cranks. Itll light off and run good. it doesnt try and stall or anything. Shut it off and it is difficult to restart.

The breather seems super loud. I was running it with the engine cover off, but it seems way louder than any other 496 ive seen. The boat ran down the lake well, and didnt seem to be choking off from lack of air.

 

[Singleton]

ECU or fuel pump

 

[Snprhed]

So it doesnt have a lanyard. Ive tried pushing it, or not pushing it. Neither seems to change anything

 

[dribble]

Check your fuel pressure.

 

[Moneypit]

Check the spark quality.. Stick a phillips screw driver into a plug wire socket. Hold the shank about 1/2" from a good ground.. MAKING SURE THERE ARE NO FUEL VAPORS HANGING AROUND, crank it.. The spark should jump the gap easily, and be blue in color...New plugs and old wires can make even the best brand spark plugs weak... Fuel pressure could be an issue, but low F/pres will usually show up at WOT before it is an issue while cranking. Your problem sounds to me like a weak spark... A static compression test might be in order as well if the spark looks good..
Ray

 

[FreeBird236]

Someone posted a few weeks ago about a 496 making a loud whistling kind of sound at the breather, someone knew what it was, sorry I don't remember. Didn't say anything about hard starting, just the whistle.

 

[GRADS]

Someone posted a few weeks ago about a 496 making a loud whistling kind of sound at the breather, someone knew what it was, sorry I don't remember. Didn't say anything about hard starting, just the whistle.

That was me. It was the IAC muffler in the throttle body. Now I'm wondering if it's a problem with his IAC. Hmmm.

 

[Snprhed]

Check the spark quality.. Stick a phillips screw driver into a plug wire socket. Hold the shank about 1/2" from a good ground.. MAKING SURE THERE ARE NO FUEL VAPORS HANGING AROUND, crank it.. The spark should jump the gap easily, and be blue in color...New plugs and old wires can make even the best brand spark plugs weak... Fuel pressure could be an issue, but low F/pres will usually show up at WOT before it is an issue while cranking. Your problem sounds to me like a weak spark... A static compression test might be in order as well if the spark looks good..
Ray

my dad owns a marine repair shop (semi retired and he only does outboards) so I have access to a spark checker. That was my thought about the fuel side as well. If there is an issues it should show up in the upper rpm range as well. It has not been run much since the 496 was put in (a couple of years) dont know if that would change anything.

 

[Shrub Lurker]

Have it scanned.

 

[guest hs]

Make sure you have a good 1000 cranking amp battery. The engine needs to crank at a minimum of 300 RPM for the ECM to turn on. Also check and see if you have an IAC muffler installed to quote down the intake sucking air in.

 

[Shlbyntro]

I'm leaning more towards a bad iac/iac filter but fuel pump pressure could also still be an issue. Fuel pressure tester and scan and see what happens.

Also, 496s are highly sensitive to old/bad fuel and fouled spark plugs. Would be wise to change out the spark plugs and make sure you have good fuel in that girl as well. If the fuel is 2 years old, its gotta go.

 

[Fun Times]

So I recently got a 90 234 Edge that has a 496 Mag.

What year model do you believe the engine to be?
Do you know if the engine serial number is handy?

Though there are a number of items that could affect engine starting times, It would be a good idea to clean the Throttle Body and Idle Air Control Valve system while you're in there checking things over along with cleaning the flame arrestor to see if starting time improves any.

In some cases a quick check to see if you have an air issue during engine cranking (starting) is to open the throttle handle about a quarter of the way to see if the engine starts quicker/more normal to you by introducing more air over what the IAC valve is allowing.

Notes for Part Number 863829
(Not used on all applications)
If used on your engine model/serial number..., Item # 5, 35-863829 MUFFLER, Intake Air Control is typically part of the sudden loud air sounds you hear, https://www.mercruiserparts.com/bam/subassembly/31816/11414/70

https://www.perfprotech.com/blog/articles/mercruiser-serial-numbers

 

[02HoWaRd26]

Check your kill switch/lanyard. It's happened to all of us at one point or another.

Did you bother reading the whole post or just the thread name???

He said it cranks and cranks then starts, hard start, not doesn’t start!

 

[Snprhed]

What year model do you believe the engine to be?
Do you know if the engine serial number is handy?

Though there are a number of items that could affect engine starting times, It would be a good idea to clean the Throttle Body and Idle Air Control Valve system while you're in there checking things over along with cleaning the flame arrestor to see if starting time improves any.

In some cases a quick check to see if you have an air issue during engine cranking (starting) is to open the throttle handle about a quarter of the way to see if the engine starts quicker/more normal to you by introducing more air over what the IAC valve is allowing.

Notes for Part Number 863829
(Not used on all applications)
If used on your engine model/serial number..., Item # 5, 35-863829 MUFFLER, Intake Air Control is typically part of the sudden loud air sounds you hear

If I recall correctly you can see the tag and its an 2003. Yes you have to bump the throttle to get it to light.

 

[Snprhed]

I'm leaning more towards a bad iac/iac filter but fuel pump pressure could also still be an issue. Fuel pressure tester and scan and see what happens.

Also, 496s are highly sensitive to old/bad fuel and fouled spark plugs. Would be wise to change out the spark plugs and make sure you have good fuel in that girl as well. If the fuel is 2 years old, its gotta go.

Yep I just changed the plugs, it had a 1/4 tank so I filled it and added 2 cans of sea foam. Previous owner ran it once or twice last year so im pretty sure its not super old gas. After I filled it I dropped it in the lake and ran it. It started pretty quick at the ramp. I ran it for 6-10 min (ran pretty well) but the gimble ring is worn out and when you trim it down it has an unsettling step out in the rear end.

I really just wanted to see if the ride was as good as people say, to see if I wanted to drop the money in this to get it back to where it should be. The flat turning is weird (Ive only owned V-hull boats) It ran 66 or so without pushing it. Ive already got a stainless steel replacement gimble ring that I will put on now that Ive determined I want to proceed.

 

[Snprhed]

Just an update. We checked fuel rail pressure (40PSI). We thought it would be helpful to see if it had any fault codes so I had it scanned. It shows a crank position sensor fault.

Merc wants $330 for the sensor. So I ordered a GM one for $70. It will be in monday and will update after installed.

On a side note the guy I bought it from said the guy he bought it from said it had about 50 hours on it. I was skeptical, but it looked like it was in good shape. The scan showed 70 hours 28 of which were at 1500-2999 and 19 was at 0-749

 

[lbhsbz]

The scan showed 70 hours 28 of which were at 1500-2999 and 19 was at 0-749

Change the crank sensor, put fresh gas, and give it an Italian tune up.

 

[Snprhed]

I hate to ask, but what is an "Italian tune up"

 

[4Waters]

I hate to ask, but what is an "Italian tune up"

I had to look it up, here is what I found.



An Italian tuneup usually refers to a process whereby a motor vehicle engine is run at full load for extended periods in order to burn carbon buildup from the combustion chambers, spark plugs, and exhaust system.

 

[rrrr]

Did you bother reading the whole post or just the thread name???

He said it cranks and cranks then starts, hard start, not doesn’t start!

The lanyard is the limit of Grad's mechanical knowledge. If it's not a lanyard problem, he's reached the end of his diagnostic tree.

 

[Carlson-jet]

I had to look it up, here is what I found.



An Italian tuneup usually refers to a process whereby a motor vehicle engine is run at full load for extended periods in order to burn carbon buildup from the combustion chambers, spark plugs, and exhaust system.

Actually it is a little further. The valves must be floating.

 

[Snprhed]

Alright, crank position sensor fixed it. Boat ran like a top.

 

[Snprhed]