Cold Start issue

[jaa241]

Hey guys,
Thought I'd throw this out there. I am still having some cold start issues. It is a 84' or 85' mercruiser 140 serial number 6920111 and mercarb 1389-8490 which is a rochester I believe. The issue is with a cold start on the trailer in the water. It fires right up, with a throttle prime and throttled about 1/4 way. It takes about 10 to 15 minutes to get the engine warmed up enough to get it into neutal and to put it in gear to get off trailer. Once running, it runs great.

I have pretty much replaced everything. It is not fuel, or spark, and have rebuilt carb.

What I am wondering is about the resistance wire, coil and electronic ignition.

I am use the pertonix ignition for 4cycle. It says to use a 3.0ohm.

I current use a MSD ballaster resister of .8 ohms, and MSD 8222 epoxy coil that is .7 ohm = 1.5 ohm

Do you think this is causing the cold start issue, because it is not 3.0ohm. Also the voltage coming out may not be around 40,000 volts like the flamethrowers coils.

Or - could just use a 3.4 ohm coil that throws out 45,000volts without any other ballaster or wire resister.

Thanks for all the help ahead of time!

 

[alldodge]

Re: Cold Start issue

Hey guys,
Thought I'd throw this out there. I am still having some cold start issues. It is a 84' or 85' mercruiser 140 serial number 6920111 and mercarb 1389-8490 which is a rochester I believe. The issue is with a cold start on the trailer in the water. It fires right up, with a throttle prime and throttled about 1/4 way. It takes about 10 to 15 minutes to get the engine warmed up enough to get it into neutal and to put it in gear to get off trailer. Once running, it runs great.

I have pretty much replaced everything. It is not fuel, or spark, and have rebuilt carb.

What I am wondering is about the resistance wire, coil and electronic ignition.

I am use the pertonix ignition for 4cycle. It says to use a 3.0ohm.

I current use a MSD ballaster resister of .8 ohms, and MSD 8222 epoxy coil that is .7 ohm = 1.5 ohm

Do you think this is causing the cold start issue, because it is not 3.0ohm. Also the voltage coming out may not be around 40,000 volts like the flamethrowers coils.

Or - could just use a 3.4 ohm coil that throws out 45,000volts without any other ballaster or wire resister.

Thanks for all the help ahead of time!

So it starts right up and continues to run so long as you keep the rpm's up, right?

If this is the case then it sounds like a fuel issue and the choke would be my first thought.

 

[MikDee]

Re: Cold Start issue

Is your choke working? Is it even attached to anything? That's what it sounds like to me also.

 

[jaa241]

Re: Cold Start issue

Replaced choke brand new from mercruiser. Took off arrestor to make sure it was working. It open ups over time.

I am thinking it is not getting a good enough spark when it is cold.

I don't think it is the fuel because like i said it runs fine when its warmed up. Seriously, once it warms up there is no issues.

Could it be the voltage from the coil or the resister causing an issue?

 

[jaa241]

Re: Cold Start issue

So it starts right up and continues to run so long as you keep the rpm's up, right?

If this is the case then it sounds like a fuel issue and the choke would be my first thought.

Yes I would keep it up around 900 to 1000 rpms until i can shift it back into neutral and into reverse to back it off trailer.

Not sure how it could be a fuel issue. It runs perfect once it is warm.

 

[alldodge]

Re: Cold Start issue

Yes I would keep it up around 900 to 1000 rpms until i can shift it back into neutral and into reverse to back it off trailer.

Not sure how it could be a fuel issue. It runs perfect once it is warm.

I don't see it to be spark, if it didn't have enough spark it wouldn't run that well when warm. I'm going for fuel, a vacuum leak or low compression. Put a vacuum gauge on it and see what your getting, once you have that, put a tee fitting and measure pump pressure to the carb

 

[jaa241]

Re: Cold Start issue

How would you want me to check vacuum on fuel line. Before or after fuel pump and what psi would I be looking for. Thanks

 

[alldodge]

Re: Cold Start issue

How would you want me to check vacuum on fuel line. Before or after fuel pump and what psi would I be looking for. Thanks

Sorry should have explained further. The standard vacuum gauge is also a low pressure fuel gauge. Put the vacuum gauge line on a intake vacuum port. You may find one with a rubber plug over the end. Measure vacuum at idle and high idle. Note if the gauge is steady or bounces around.

After that, put the gauge between the fuel pump and the carb using a tee fitting. Should read between 4 to 7 psi.

Performance Tool Vacuum and Fuel Pump Tester, Model# W80594 | Automotive Diagnostics| Northern Tool + Equipment

 

[jaa241]

Re: Cold Start issue

Thanks I will get one a check it out. What is idle 650 assuming, what would high idle be 800. Thanks again for all your help.

 

[jaa241]

Re: Cold Start issue

Hey Guys,

Checked out the vacuum and held pretty consistent. I also check the pressue for the fuel like and it was holding at 5.85. Any other suggestions.

Like i said, I replaced choke, new spark plugs and wires, new fuel pump, rebuilt carb, electronic ignition, coil, and new starter.

Still confused as to why it runs perfect when its warm, but has an issue when I try to start it up for the first time.

 

[alldodge]

Re: Cold Start issue

Hey Guys,

Checked out the vacuum and held pretty consistent. I also check the pressue for the fuel like and it was holding at 5.85. Any other suggestions.

Like i said, I replaced choke, new spark plugs and wires, new fuel pump, rebuilt carb, electronic ignition, coil, and new starter.

Still confused as to why it runs perfect when its warm, but has an issue when I try to start it up for the first time.

The idle would be around 650 in gear, so it will be idling a bit higher in netural

What was the vacuum reading, was is above 15?

If the choke is set properly it should keep the engine running when cold, it could need to be set more closed.

It could also be you have the idling jets turned to far in, creating a lean condition.

Look at the plugs are they white?

 

[stonyloam]

Re: Cold Start issue

Are you running a full 12 volts to the Petronix or connecting it to the coil with the resister in line? The Petronix should be connected to a separate wire getting a full 12V from the choke wire. That being said, since it starts and runs it seems like it would be a carb problem.