Author Topic: Mercruiser 140 difficult to start when cold [FINALLY, SOLVED!] (Read 49918 times)

Neutron68 · « **Reply #60 on:** June 06, 2016, 06:30:03 PM »

Quote

Also (mentioned before) check that your Pertonix is connected to your ignition source BEFORE your ballast resistor or resistance wire and not at the coil or else it could be underpowered.

What's the easiest way to determine if there is a resistor (or resistor wire) feeding the + terminal of the coil?
To measure resistance, I need to have 2 points for the meter probes. One point is the + terminal of the coil. Where is the other point?
Or can I just measure the Voltage at the + terminal of the coil, and if it's less than 12V, I know there's a resistor in the wire feeding it?

What I can tell you, is that this Petronix ignition module was initially mounted in the pervious 120 engine and moved to this 140 engine.
There were no problems with throttle-kill on the 120 engine.

Eric

Rich_V174SS · « **Reply #61 on:** June 06, 2016, 06:33:17 PM »

Where are the Pertronix wires connected to on the engine?

Neutron68 · « **Reply #62 on:** June 06, 2016, 06:41:15 PM »

Quote from: Rich_V174SS on June 06, 2016, 06:33:17 PM

Where are the Pertronix wires connected to on the engine?

They are connected to the + and - terminals of the ignition coil.

Rich_V174SS · « **Reply #63 on:** June 06, 2016, 06:48:28 PM »

The red wire should go before the resistor/ballast. Does your carburetor have and electric choke heater? If 'yes' then tap power there for the red Pertronix wire. If not then you have to find your ballast resistor, white ceramic looking blocks with wires, probably mounted on the rear of the engine near the harness plug. Pictures of your engine and the wiring could help.

Neutron68 · « **Reply #64 on:** June 06, 2016, 10:08:02 PM »

Rich,

The choke is not electric, so wiring to that 12V point is not an option.

Attached are the best photos I have showing the coil side of the engine.

I have not seen any sign of resistors - just wire bundles, wrapped in black tape.
That is why I asked if there was a way to determine if there is resistor wire or inline resistors using a multi-meter.

The boat is a 1978. If Greg kept the original boat wiring harness, it's a 1978.
This replacement engine serial number resolves to a 1973 model.
I don't know if Greg changed wiring harnesses or not.

The Pertronix manual shows connecting the ignition module direct to the ignition coil, if there is no ballast resistor.
Right now, we don't know if it has a ballast resistor or not, so it may already be correctly connected.

We know the 120 engine ran fine (no acceleration kill) with this ignition module, wired to the ignition coil terminals.
If Greg used the same wiring harness, then this 140 engine should run fine with the Pertronix module wired to the coil terminals.

Eric

Plugcheck · « **Reply #65 on:** June 07, 2016, 07:37:38 AM »

I doubt the issue is with the electronic ignition, not that I wouldn't check it. The ballast resistor, if located or if it exists, will be close to the coil. Check running voltage at the coil while running from B+ to ground. If its less than charging voltage you have a drop. The ballast resistor is not required when running the later pertronix igniters since they use adaptive dwell. As for your slump off idle, you have a lean condition as the throttle plates open. This can be caused by many things, but all pointing to the same carburetor. Air horn could be warped, throttle shaft is worn, progression ports are clogged, accelerator pump/discharge is not supplying correct volume, fuel level is incorrect, vacuum leak, main jet/emulsion issue, or possibly several other possibilities. Try a different carb, or just break down and buy a new one.

Neutron68 · « **Reply #66 on:** June 07, 2016, 10:12:33 AM »

I did a google search for pictures of marine ballast resistor and found a couple of ceramic packages - definitely nothing like that mounted anywhere on the engine. And, it looks like the ballast resistors are in the range of 3 Ohms.
see http://www.wholesalemarine.com/cdi-ballast-resistor-3-0-ohm-for-i-o-engines.html?gclid=CjwKEAjw4dm6BRCQhtzl6Z6N4i0SJADFPu1nTkpXqvfRM25rGcg5PaS7z8Voi_3TogvNGm7aUTm9sBoCgqDw_wcB

To be sure there isn't a resistance wire, I'll measure voltage at the coil and see if it's less than the battery voltage.

From the symptoms, is the carb I currently have not beyond repair/refurb?
Should I remove it and buy a new or refurbished carb with a warranty?

In regard to buying a replacement carburetor,

1. do I need to stay with the same vintage of Rochester 2 barrel carb?
This 1973 engine originally had a part number 7040084, which has a non-electric choke on it.
Do I need to replace it with the same vintage carb, with a non-electric choke?

2. any recommended sources of new or refurbished carburetors?

3. what price range is reasonable? $300?

Plugcheck · « **Reply #67 on:** June 07, 2016, 10:27:46 AM »

Four cylinder engines used 3 ohm resistors, 6-8 cylinder engines used 1.5 to 2 ohm units. Dwell period is why they are different. At idle, dwell period is high, if current was not limited by the resistor, the ignition coil would overheat. Another test would be current to the coil while running. Put your meter in series, let the engine idle, check the current. Then do the same with a direct wire to the battery. If the current is different, then a current limiter is in place, if nearly identical, then no ballast resistor. As for carbs, I'd opt for one with electric choke. No way for me to tell if your current carb is toast without seeing it. Could you borrow one to test? The 140 is common, should not be hard to find a marine carb for it.

Neutron68 · « **Reply #68 on:** June 07, 2016, 10:49:57 AM »

Is there any advantage in buying one of the Pertronix Flamethrower ignition coils?

Their marketing language implies benefits.
"While it's the perfect coil to go with the PerTronix Ignitor breakerless ignition, our 40,000 volt Flame-Thrower canister coil can benefit virtually any distributor type inductive system. Its higher voltage allows larger spark plug gaps for added power, smoother response and better fuel economy. These coils are internally resisted so they are compatible with many ignition systems."

Plugcheck · « **Reply #69 on:** June 07, 2016, 10:53:09 AM »

OK, I may be biased, but I always change the coil when I convert from points. The Flamethrower is well matched to the Igniter having adaptive dwell. Made my 140 run like new.

Neutron68 · « **Reply #70 on:** June 07, 2016, 11:01:39 AM »

Quote from: Plugcheck on June 07, 2016, 10:53:09 AM

The Flamethrower is well matched to the Igniter having adaptive dwell. Made my 140 run like new.

I like the sound of that! Any need to gap the spark plugs wider?

Plugcheck · « **Reply #71 on:** June 07, 2016, 03:03:08 PM »

I would check/gap the plugs. Prob was .030-.035, could go up to .045 did the pertronix instructions recommend a gap setting?

Neutron68 · « **Reply #72 on:** June 07, 2016, 03:18:21 PM »

Quote from: Plugcheck on June 07, 2016, 03:03:08 PM

I would check/gap the plugs. Prob was .030-.035, could go up to .045 did the pertronix instructions recommend a gap setting?

The paper instructions in the box didn't say anything about changing the spark gap, but their marketing text implies it:
"Its higher voltage allows larger spark plug gaps for added power, smoother response and better fuel economy."

And their support page says that it might improve engine performance.
from http://www.pertronix.com/support/tips/
What should I gap the spark plugs to?
The Ignitor has no set specification in which the spark plugs should be gaped at. Every engine responds differently to spark plug setting. In most cases increasing the factory recommended gap by .005 improves the engine performance.

Neutron68 · « **Reply #73 on:** June 08, 2016, 09:38:03 PM »

I contacted The Carburetor Shop today and they said there was a 99.5% chance they could refurbish my carb and get it running right.
So, I'm going to pull it this weekend and take it to Maplewood next week!

Before I pull it, I'll check for evidence of a resistance wire feeding the ignition coil.

Eric

Jason · « **Reply #74 on:** June 09, 2016, 06:41:38 AM »

Quote from: Neutron68 on June 08, 2016, 09:38:03 PM

I contacted The Carburetor Show today and they said there was a 99.5% chance they could refurbish my carb and get it running right.
So, I'm going to pull it this weekend and take it to Maplewood next week!

Before I pull it, I'll check for evidence of the resistance wire feeding the ignition coil.

Eric

The Carb Shop rebuild my 140 carb too. Been happy with it.

Plugcheck · « **Reply #75 on:** June 09, 2016, 07:21:11 AM »

With a name like "The Carburetor shop" I would guess they can go through it and do a good job. Not many carb specialists around any more, kind of a lost art. Let us know how it turns out.

Neutron68 · « **Reply #76 on:** June 09, 2016, 08:27:16 AM »

On the resistance wire topic:
If there is a resistance wire in my wiring harness, how long is that section of wire?
Does it only run between the circular connector near the back of the engine and the ignition coil, or does it run from the ignition coil all the way up to the ignition key switch on the instrument panel?

Eric

75starflight · « **Reply #77 on:** June 09, 2016, 09:41:33 AM »

Eric, I have my old 120 in my shop at home, it has the same harness as the 140. I will strip back where the resistance wire is located and post a picture for you.

On The Carb Shop. They were able to rebuild my very gunked up 140 carb and it runs and idles like a dream now. I recommend them.

Neutron68 · « **Reply #78 on:** June 09, 2016, 05:50:40 PM »

The guy I talked to at The Carb Shop said it would likely cost about $200 to refurb it and he'd have it done in 3-4 days.
Given that most of the refurbed carbs I have seen for sale are around $300, there is some savings here and guaranteed compatibility with this 1973 engine.

I wonder how much is done during a refurb? Ultrasonic cleaning? Jet or venturi replacement? Repainting?

Eric

75starflight · « **Reply #79 on:** June 09, 2016, 06:44:01 PM »

He does a really good job! I had alot of build up in the bowl and some damaged parts on mine. He replaced all the parts and cleaned the carb thoroughly. He also calls if he runs into a problem and let's you know what the extra costs will be.