Double firing

[skynyrdcat]

88 Evinrude 110 HP V-4

I marked TDC for each cyl to check timing and with a light found the #4 is firng 2 times (at right time and at same time as #3)

Any thoughts on what causes this?
Fresh after a rebuild (didn't have engine before so I don't know if it did this before I rebuilt).
I have new plug wires, plugs and power pack but used old charge coil and sensor.

I moved all the wiring around and couldn't find any short, also checked them for grounding with an ohm meter.

 

[tashasdaddy]

Re: Double firing

you might find something in this to help. http://www.boatpartstore.com/page30.asp

 

[CATransplant]

Re: Double firing

88 Evinrude 110 HP V-4

I marked TDC for each cyl to check timing and with a light found the #4 is firng 2 times (at right time and at same time as #3)

Any thoughts on what causes this?
Fresh after a rebuild (didn't have engine before so I don't know if it did this before I rebuilt).
I have new plug wires, plugs and power pack but used old charge coil and sensor.

I moved all the wiring around and couldn't find any short, also checked them for grounding with an ohm meter.

I'm just pulling this out of my head, but it seems to me like that's normal for those engines. The plug firing on the exhaust stroke does no harm, and it simplifies the ignition system.

I could be wrong, but I believe I read that here in a thread some time ago. I hope someone will correct me if I'm mistaken.

 

[Joe Reeves]

Re: Double firing

If the engine runs as it should, I wouldn't be concerned, BUT if it backfires loudly out the exhaust, let us know.

 

[skynyrdcat]

Re: Double firing

Actually it runs a bit rough, and will only get to 42-43000 RPM on WOT

 

[Walker]

Re: Double firing

Internal power pack problems or shorted isolation diodes, if your motor has them, is what is causing the double fire. If the second fire is occuring while the intake ports are even slightly open, and they probably are, you will have problems

 

[skynyrdcat]

Re: Double firing

Internal power pack problems or shorted isolation diodes, if your motor has them, is what is causing the double fire. If the second fire is occuring while the intake ports are even slightly open, and they probably are, you will have problems

Isolation diode????
I don't know where they are or even if I have them, how do I determine?

I just put a new power pack on.

 

[Walker]

Re: Double firing

I don't think your motor has them, but a OMC shop manual specific to your motor would tell.

 

[Joe Reeves]

Re: Double firing

A engine with dual powerpacks would have that diode, and would be checked with an ohm meter between the White wire and the Black/Yellow wire, that is a good diode would have a reading in one direction and not the other.

However, your engine has but one powerpack and to my knowledge would have no need for that diode BUT.......... I don't have that manual.

What is the compression on that engine?

 

[skynyrdcat]

Re: Double firing

A engine with dual powerpacks would have that diode, and would be checked with an ohm meter between the White wire and the Black/Yellow wire, that is a good diode would have a reading in one direction and not the other.

However, your engine has but one powerpack and to my knowledge would have no need for that diode BUT.......... I don't have that manual.

What is the compression on that engine?

I do have the single power pack.

Compression is 95 on all cyl

 

[skynyrdcat]

Re: Double firing

OK, I went through the SELOC manual and it tells me how to check the sensor coil but it calls out the tests on a "4 wire connector" (from the timer base to the power pack). My engine has a 5 wire conncetor but the manual doesn't reference a 5 wire connector.
So, I haven't been able to get past the sensor coil.

Anyone else care to take a stab at this one?


Thanks in advance.

 

[Dennisanoka]

Re: Double firing

The connector is labelled a,b,c,d,e. e is the common. Measure between e and the other 4. Each reading should be 40 ohms +/- 10 ohms. Then measure between each pin and ground, there should be no continuity between any of them and ground.

 

[Dennisanoka]

Re: Double firing

Can someone post a message addressing if the coil sensor output can be measured with a standard voltmeter?

 

[skynyrdcat]

Re: Double firing

Can someone post a message addressing if the coil sensor output can be measured with a standard voltmeter?

I think the book states otherwise, supposed to have a special tester, (i'll confirm later tonight when I get home), but my meter reads high enough to check it, II just need longer arms to crank the engine while I'm looking at the meter


By the way, thanks for the input. I'll check it later the way you described.