Author Topic: Mercruiser 140 difficult to start when cold [FINALLY, SOLVED!] (Read 51177 times)

75starflight · « **Reply #80 on:** June 09, 2016, 07:15:36 PM »

Here is a picture of the part of the harness that connects to the coil posts. The light brown wires are the positive side of the coil one wire if you strip the black tape background will have a solder joint where the resistance wire is connected to the main harness.

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Plugcheck · « **Reply #81 on:** June 09, 2016, 11:05:15 PM »

There is another way to check, but it involves actually adding a ballast or resistor. This applies equally to just about systems. Take a 3 ohm ballast or another power resistor and tie one side to the wire you removed from the plus side of the coil. Tie the other side of the resistor to ground. Apply power to the circuit. If you read battery across the resistor, there is no other resistance in the circuit. If another ballast or resistance wire is in the boat then you will read much less than battery voltage. Basically your creating a voltage divider in this test. Might save you some time if a resistance wire is buried somewhere in the harness.

Neutron68 · « **Reply #82 on:** June 10, 2016, 09:48:31 AM »

Quote from: 75starflight on June 09, 2016, 07:15:36 PM

Here is a picture of the part of the harness that connects to the coil posts. The light brown wires are the positive side of the coil one wire if you strip the black tape background will have a solder joint where the resistance wire is connected to the main harness.

From most of the wiring diagrams I've seen in the online Mercruiser manual, the ignition wire that the resistance wire should be connected to is purple?
see the pages around: http://boatinfo.no/lib/mercruiser/manuals/mercruiser3.html#/368

75starflight · « **Reply #83 on:** June 10, 2016, 11:58:20 AM »

Yes, there will be a different color wire connected at the soldier connection to the resistance wire. Remove the black tape on that part of the harness and you will see where the resistance wire and feed wire connect.

Also, if you want, you could clip the eye ring off and check the voltage on each wire to see which one is the resistance wire. One wire with the key switch in the cranking position will carry a full 12 volts and the other wire will be dead. Then with the key switch in the run position you should see the dead wire come to life with less than 12 volts. Then the wire that was hot in the cranking position will now be dead.

Plugcheck · « **Reply #84 on:** June 10, 2016, 10:21:48 PM »

Just got a new Summit magazine and noticed Pertronix is offering a bypass relay to eliminate the ballast resistor. Likely they use the ballast in line to drive the relay coil. Might be a simpler way to insure full power to ignition system without changing the original harness or running long wires to keyswitch.

Neutron68 · « **Reply #85 on:** June 11, 2016, 10:55:59 AM »

http://www.pertronix.com/prod/new/details.aspx?id=138
Sounds useful. Too bad we didn't know about it earlier this week. I could have ordered one with the Flamethrower coil.

Neutron68 · « **Reply #86 on:** June 11, 2016, 12:22:31 PM »

New Information:

1. There is evidence of a resistance wire. With the ground lead of the meter to a good ground point, the battery measures 13.8V and the Voltage at the + terminal of the coil was 6V. And the wire bundle that runs to the coil + terminal got slightly warm after the key was in the ignition position for a couple of minutes.

2. The resistance of the old ignition coil (from + to - terminal) is 1.5 Ohms! WRONG IGNITION COIL?

Pertronix shows that you should have a 3 Ohm coil on a 4 cylindar engine.
http://www.pertronix.com/prod/ig/flame/coils/chart.aspx

What effect would having the wrong ignition coil be?

75starflight · « **Reply #87 on:** June 11, 2016, 04:03:24 PM »

It would cause the coil to overheat and cause starting issues. You may have just found the problem. I have a spare OEM mercruiser coil. I will go check the resistance on it.

Edit: my spare coil does omg out around 3.0

Neutron68 · « **Reply #88 on:** June 11, 2016, 05:10:32 PM »

I swapped in the Flamethrower 3 Ohm coil this afternoon. I have not put in a resistance wire bypass yet. I plan to try that next. I found an exposed spot where I can tap into the purple ignition-switched 12V wire.

I just started the engine with the Pertronix Igniter wired directly to the Flamethrower. The engine starts starts and runs. It still has the throttle-up-kill problem.
As someone in this thread mentioned, the engine might be slightly quieter with the Flamethrower coil...less clacky maybe? More smooth and resonant?

Because the resistance of the Flamethrower coil is higher, I see more Voltage at the + terminal of the coil...7V now rather than 6V. That makes sense...it's a Voltage divider and the "lower leg" of the divider is now a higher resistance, thus a higher Voltage.

Eric

Neutron68 · « **Reply #89 on:** June 11, 2016, 08:52:57 PM »

I swapped the ignition coil with the Flamethrower and added a bypass wire for the resistance wire.
I did these changes one at a time and could notice an improvement with each.

With the addition of the resistance wire bypass, the Voltage at the + terminal of the coil came up to about 12V, and when I tried the final combination of Flamethrower and bypasswire, the engine doesn't totally kill when I hit the throttle, but still has a dead spot in the acceleration. You can hear it gasp and then take off.

I'm still planning on pulling the carb off tomorrow for transport back to The Carburetor Shop.
I want to KNOW it's as good as it can be.

https://www.youtube.com/watch?v=785XfqspKrg

Neutron68 · « **Reply #90 on:** June 13, 2016, 10:01:15 AM »

Carb is off and on the way to The Carb Shop.

I was surprised how easy it was to get the carb off: 1 nut on the throttle cable and 4 nuts on the base!

This problem is playing out to be caused by a lot of little problems, adding up to a bigger problem!

Neutron68 · « **Reply #91 on:** June 15, 2016, 05:13:00 PM »

What is that turnbuckle adjustment in the throttle linkage, on the back side of the carb?

What happens if you turn the turnbuckle so that section of the throttle linkage is shorter?
What happens if you turn the turnbuckle so that section of the throttle linkage is longer?

Plugcheck · « **Reply #92 on:** June 15, 2016, 10:31:27 PM »

It is an adjustment related to the throttle position on the controls. Correct adjust allows shift into F/R before rpm comes up. Another check is to insure WOT position when control is all the way forward.

Jason · « **Reply #93 on:** June 16, 2016, 06:47:57 AM »

It's basically your idle speed adjustment.

Neutron68 · « **Reply #94 on:** June 16, 2016, 03:21:13 PM »

The idle set screw is on the carburetor.

Neutron68 · « **Reply #95 on:** June 17, 2016, 11:13:30 PM »

I got the carb at The Carburetor Shop this afternoon.

They said the accelerator pump channel was nearly plugged and it wasn't squirting much gas (some but not much).

I plan to bolt it back on the engine Saturday morning!

75starflight · « **Reply #96 on:** June 18, 2016, 09:14:39 AM »

When you set the idle screws, hook up a vacuum gauge to the manifold. It makes really was o get the carb set correctly. The plug is located towards the rear of the manifold.

Neutron68 · « **Reply #97 on:** June 18, 2016, 10:52:15 AM »

Quote from: 75starflight on June 18, 2016, 09:14:39 AM

When you set the idle screws, hook up a vacuum gauge to the manifold. It makes really was o get the carb set correctly. The plug is located towards the rear of the manifold.

This connection on the side of the carb?

Jason · « **Reply #98 on:** June 18, 2016, 12:11:25 PM »

Quote from: Neutron68 on June 17, 2016, 11:13:30 PM

They said the accelerator pump channel was nearly plugged and it wasn't squirting much gas (some but not much).

BINGO!

Neutron68 · « **Reply #99 on:** June 18, 2016, 01:07:54 PM »

Cleaned carburetor reinstalled...throttle-up problems GONE!

https://www.youtube.com/watch?v=u140RcxUlRE

Postscript:
Every mechanic that touched the carburetor on this engine made an error of some kind!
It took me MONTHS to figure out what each one had done wrong!
Thankfully, the carb is easy to get off and take to an expert!

In the end, I learned a lot more about this engine than I ever intended.

THANK YOU TO ALL TO HAVE CONTRIBUTED TO MY EFFORTS!

Eric