50D2 ignition issues

[lmuss53]

Ok, we need some Nissan help. Model 50D2 3 cylinder carbed 2 stroke 2003 model, It starts and idles fine and is firing on all 3 cylinders, if you put the timing light on it and raise the fast idle it comes up to about 2k and all 3 cylinders commence to miss about half the time. The owner took it back to the selling dealer, who lent him a box full of used and new ignition parts to try. They replaced all 3 coils with new ones, the switchbox with a new one and swapped everything under the flywheel with "good" used stuff. No change. They did not do any DVA tests at all. I entered the picture at this point, and we did the tests per the CDI manual. The results,are posted in a picture. The components under this flywheel are not what I am used to seeing so I called CDI and was told the out of spec coil was the exciter coil and changing it would fix us up. CDI doesn't make one so we called the selling dealer who informed us that you don't use DVA meters on Nissans and he did not have the exciter coil . I ordered one and put it on yesterday. No change. The spark is still erratic, the resistance readings are still off and DVA way out of whack I have not moved trigger wires to see if that changes anything, but the owner did put 3 new coils and a CDI box before. The owner and his brother did a lot of stuff over about the last 3 months. I'm confident it is a spark issue, perhaps linked to a limp mode. Disconnecting the kill circuit and or rectifier changes nothing, flywheel key is square and straight, magnets clean and tight, The trigger outputs are fine on the DVA right up until the miss starts, then they fall off but never get below the 110V minimum. The issue of the alarm circuit resolved itself when we discovered it only works when the boat is in gear, the alarm circuit is powered thru the nuetral safety switch.

What do we chase next?

Carbs are clean, this is not a fuel issue, I am fairly certain. The timing light changes without question and the spark falls off when the miss starts.

 

[pvanv]

You really should have a copy of the Factory service manual. This is covered in detail in section 7.

The CD Unit will limit the engine speed to about half the maximum
RPM when the overheat sensor, water pressure sensor, or oil level
sensor signals an abnormal condition. Depending upon the model
of the engine, one, two or all three sensors are provided.
[h=5]SERVICE MANUAL : 3 & 4 CYLINDER 2-STROKES[/h]

Description

Covers all 3 & 4 cylinder 2-stroke models.

Part #: 003-21036-1
List Price (MSRP): $50.00

 

[lmuss53]

I've got two manuals, the Seloc generic for 3 and 4 cylinders and the factory manual for NS 50D, all sensors have been unhooked one at a time with no impact on how the engine runs, the CDI box has been replaced with a brand new one, also. Overheat alarm works as it should. It has been to two professsional techs, including the dealer who sold it. I have a small shop and am trying to help these guys get it fixed. I am not charging them for all of the time I get in it, because now I want to help them figure it out. The dealer cleaned the carbs and said there is nothing wrong with it (but it won't push the boat) and charged them $400. I am looking for a fresh idea, because I, and all the folks I know in this business, have run out. The manuals and CDI have very similar troubleshooting procedures in them. Although I did not write all the results down, everything on the CDI procedure has been done several times, by different techs, with the same result.

My Nissan manual is for an older model, I am going to try to find the one you listed and see if it has anything fresh. I believe something is prompting it to go into the limp mode when it shouldn't.

 

[lmuss53]

Why is the exciter coil resistance out of whack, but replacing the exciter coil changes nothing? The one guy we should be able to ask (the dealer) doesn't know and doesn't seem interested in helping us find out. We need someone who worked on these somewhere to chime in.

 

[pvanv]

What is the exciter resistance with the new exciter?

From p7-48 of the FSM:
Description of Operation for models 40 / 50 / 60 / 70 / 80 / 90
Engines
In these engines, the water pressure sensor (1) and overheat
sensor (2) control the half-maximum RPM limitation input
[terminal (9)] to the CD Unit (4). When either, or both, of these
sensors detect an abnormal condition (see Section 4), the half-
maximum RPM limitation input goes low and the CD Unit limits the
engine speed to about half its maximum RPM. At the same time,
the abnormal condition also activates the warning horn (6). Note
that the oil level sensor (3) only activates the warning horn and the
oil level light (17) in the tachometer (5) because the diodes (15)
block the signal from CD Unit.

 

[lmuss53]

Exactly the same as it was, it's listed above with the circled numbers. We are not getting an alarm of any sort.

 

[pvanv]

The Seloc manual will be of little help.
If you disconnect the black/yellow jumper on the CD (which is the RPM stagger signal), do you still have the issue?
Can you cause a warning horn by grounding the overheat sensor?
It looks like the pulser (trigger) coils are all in spec. 217, 213, 214 are in spec.

 

[lmuss53]

Issue is still there with black/yellow disconnected.

Yes, you can ground the alarm and sound the warning horn, but only with shifter in gear. I had the controller apart to see why and the alarm circuit is poweded thru the neutral safety switch. Since it would not alarm in neutral, I suspected a pinched wire.

Yes trigger readings are all good, CDI to coils are good, but high, around 250, they drop off significantly when the miss starts but stay around 160..

I had not seen it yet, but the owner states that the issue was only on one coil before he replaced the box. I'm wondering if he could have gotten a bad CDI box.