Blown Ignition Fuse

[SquatchTech]

91 Vmax

Bought the bike about a month ago installed COPs using Crown Vic coils no resistor, then I replaced the pickup coil, shot gun cleaned the carbs. Now the Ignition fuse keeps blowing.

I've noticed that this thing has an aftermarket fuel pump the wiring seems a little weird to me.... Well, that didn't change anything, ignoring the fuel pump now.

Now the fuse blows immediately when I put a new one in.

 

[SquatchTech]

Interesting the bike doesn't need to be running to blow the Ignition fuse.

 

[Fire-medic]

Trace all the ignition wires back from the switch, one at a time. Look for skinned wires shorting to the frame or another exposed metal part of the bike. That's a start. The hot wire to the switch sounds like that's the issue.

You should have the newer ignition module, 1990-2007. Was your pick-up coil a two-wire?

https://www.vmaxforum.net/attachments/yamaha-v-max-custom-wiring-diagrams-4-compressed-pdf.28837/

 

[SquatchTech]

Ok after looking at a wiring diagram in the service manual, I'm not supposed to be able to crank the motor over with the key across the country (metaphorically speaking)!

 

[SquatchTech]

You should have the newer ignition module, 1990-2007. Was your pick-up coil a two-wire?

Yes, it's a 2 wire single sensor.

 

[SquatchTech]

Well I found the culprit, it's a coil. Yes one of the Crown Vic coils. However, the coil failed via an internal short. Now I thought, having worked on a fleet of Crown Vics for 4 years, that is an unusual failure. Oh well, put another coil in ride like 5 blocks down the road boom blown fuse put another fuse in instantly boom, get home found that the front throttle side coil had failed same location as last time. This one decided to spill it's guts and was burning hot and again internally shorted.

What's up with this location and it's desire to burn up coils??? LoL

I know I know this is the out come of DIY mods, but I'm determined to get this bike running with these coils, I'm SOOO close. I understand that buying a pre-made kit is an option I'm just not there yet.

I'd be willing to buy the unterminated harness first B4 the kit.

 

[Fire-medic]

How many times do you need to get hit in the head before you decide that whoever is next-to you, isn't a good person, and that he doesn't have your best-interests at-heart? C'mon, two coils fail, almost immediately? In the same location? I'd be skinning-back the wiring to that coil to expose the dead short to another wire, or to the chassis, or whatever point the wire is grounding-out. Remember that three seem to be doing the job, but the fourth is 'that guy standing next-to you.'

I presume that you're using used coils. What is the impedance spec on that coil stick, and what does it measure? What do the other coil sticks measure for impedance? The chances that two coils fail, almost immediately, or as you said, 'immediately,' being thought-of as otherwise in good operational condition, is what in statistics is called a "rare event." There's another cause you've overlooked, besides two bad coil sticks. Something-else is causing them to-fail. You haven't determined what that is, start tracing the wires to find the dead-short. It's a two-wire connection to the coil stick, so that greatly-reduces where you have-to look.

 

[SquatchTech]

I presume that you're using used coils.

Yes

What is the impedance spec on that coil stick, and what does it measure? What do the other coil sticks measure for impedance?

Spec 0.3ohm - 1.0 ohm
The others B4 install .5 - .6ohm (including first casualty)
First casualty .1ohm
Second casualty B4 install .5ohm
After getting home .2ohm

 

[Fire-medic]

Did you look to-see what a stock VMax primary coil impedance is?



Call it 3 ohms. What are the Ford coils?

You are probably lucky you haven't fried your CDI box yet.

VMX12- Service-Manual.pdf (vmoa.net)
Look under the forum VMOA section for this. And thank the people who get things like this posted, to ease trouble-shooting.

The pick-up coil range is 94-127 ohms (+- 110 ohms)

 

[SquatchTech]

The white wire going to cylinder 4 is continuous to ground the other 3 are not. I stripped the tape all the way so that the white wire is completely exposed to the CDI it looks healthy.

 

[Parminio]

How many times do you need to get hit in the head before you decide that whoever is next-to you, isn't a good person, and that he doesn't have your best-interests at-heart? C'mon, two coils fail, almost immediately? In the same location? I'd be skinning-back the wiring to that coil to expose the dead short to another wire, or to the chassis, or whatever point the wire is grounding-out. Remember that three seem to be doing the job, but the fourth is 'that guy standing next-to you.'

I'd bite the bullet, find someone parting out a max and just replace the entire harness.

Or go "the other route".

 

[SquatchTech]

I'd bite the bullet, find someone parting out a max and just replace the entire harness.

Or go "the other route".

No guarantee that will fix the issue, I'm the type of person where I need to know why this is bad and why I need this part... In other words, I don't replace things untill I diagnose the actual problem.

What ever the bike needs I'll do it, but I'm not giving up.

The only thing I'm questioning @ this point is "how does the CDI work?" If I knew that I think I'd be able to diagnose if the CDI is bad or not... Definitely faster if I knew.

 

[Parminio]

Yes, it's guaranteed.

That's the best part of the Cops system: it makes the entire factory system redundant.

That's primarily why people use it.

 

[SquatchTech]

White wire coming from CDI to cylinder 4 is continuous to BOTH ground AND battery positive with the key off, that is not a good sign this is obvious to me.

Mind you the white wire is not damaged in any way going to the CDI and my other test lead is connected directly to the batt in both tests.

I think I did fry my CDI, can someone confirm?

Thank you FM & Parminio, I appreciate your responses!!!

 

[MaxMidnight]

The coil is fed with a permanent live and it will fire when the ICU interrupts the ground to that coil.
My guess is that quibble foo valve (or whatever it is, diode?) that controls this is allowing the feed to go strait to earth and the circuit isn't closing.
That would explain why you have a feed and a ground.

What I don't know is how the circuit that controls this works...sorry.

 

[SquatchTech]

My guess is that quibble foo valve (or whatever it is, diode?) that controls this is allowing the feed to go strait to earth and the circuit isn't closing.
That would explain why you have a feed and a ground.

I don't understand what you mean here.

 

[SquatchTech]

I'm getting confused the more I work on this bike.

So here is what I found -

cylinder # 4

key off
white - red/white = continuous
white - ground = continuous
white - batt+ = open
red/white - ground = continuous
red/white - batt+ = open

key on
white - red/white = open
white - ground = continuous
white - batt+ = open
red/white - ground =continuous
red/white - batt+ = open

Disconnect right hand controls key off
white - red/white = open
white - ground = continuous
white - batt+ = open
red/white - ground = open
red/white - batt+ = open

Disconnect right hand controls key on
white - red/white = open
white - ground = continuous
white - batt+ = open
red/white - ground = continuous
red/white - batt+ = open

For reference cylinder # 2

key off
yellow - red/white = open
yellow - ground = open
yellow - batt+ = open
red/white - ground = continuous
red/white - batt+ = open

key on
yellow - red/white = open
yellow - ground = open
yellow - batt+ = open
red/white - ground = continuous
red/white - batt+ = open

Disconnect right hand controls key off
yellow - red/white = open
yellow - ground = open
yellow - batt+ = open
red/white - ground = open
red/white - batt+ = open

Disconnect right hand controls key on
yellow - red/white = open
yellow - ground = open
yellow - batt+ = open
red/white - ground = continuous
red/white - batt+ = open

The circuit that changes things on the right hand controls is the headlight circuit through the starter button when it is in its resting position.

I have not found any damaged wires, yet.

Should I continue stripping the harness back or is my TCI bad?

 

[MaxMidnight]

Sorry, got it arse about face in my previous post, now corrected.
Let me try to explain.

There is a permanent live to and from the coil and it is this that is interrupted by the ICU to create the spark.
Unless there is something else going on in the ICU that I don't know about then I would expect you to to read +12v on the white wire into the ICU and (speculation) the same coming out on the ICU earth wire.

On that basis there will always be a +12v feed in the white wire.
Only when the circuit is interrupted will you loose the earth.

I suspect what you are reading may be normal?

 

[02GF74]

What do you mean by continuous?

If you are using a voltmeter on the resistance setting, you will get a meaningful result only when there are no other voltage sources in the circuit you are measuring. You are doing these tests with battery positive lead disconnected?

FYI The basic idea is that the multimeter places a voltage at the two probes and this will cause a current to flow in the item for which the resistance is being measured

 

[SquatchTech]

What do you mean by continuous?

Wow that is a wake up call, thank you. You're right I should have been using resistance from the beginning instead of continuity testing the harness, I've redone my tests.

cylinder # 4

key off
white - red/white = 1.2 ohm
white - ground = .5 ohm
white - batt+ = 31.36 k ohm
red/white - ground = 1.0 ohm
red/white - batt+ = 31.36 k ohm

key on
white - red/white = 1.3 ohm
white - ground = .6 ohm
white - batt+ = 2.8 ohm
red/white - ground = 1.0 ohm
red/white - batt+ = 1.9 ohm

Disconnect right hand controls key off
white - red/white = 2.93 k ohm
white - ground = .4 ohm
white - batt+ = 31.26 k ohm
red/white - ground = 2.91 k ohm
red/white - batt+ = 34.18 k ohm

Disconnect right hand controls key on
white - red/white = 2.666 k ohm
white - ground = .5 ohm
white - batt+ = 2.68 k ohm
red/white - ground = 2.666 k ohm
red/white - batt+ = 3.6 ohm

For reference cylinder # 2

key off
yellow - red/white = 1.8 M ohm
yellow - ground = 1.8 M ohm
yellow - batt+ = 1.8 M ohm
red/white - ground = 1.1 ohm
red/white - batt+ = 31.37 k ohm

key on
yellow - red/white = 1.8 M ohm
yellow - ground = 1.8M ohm
yellow - batt+ = 1.8 M ohm
red/white - ground = 1.1 ohm
red/white - batt+ = 3.2 ohm

Disconnect right hand controls key off
yellow - red/white = 1.8 M ohm
yellow - ground = 1.8 M ohm
yellow - batt+ = 1.8 M ohm
red/white - ground = OL
red/white - batt+ = OL

Disconnect right hand controls key on
yellow - red/white = 1.8 M ohm
yellow - ground = 1.8 M ohm
yellow - batt+ = 1.8 M ohm
red/white - ground = 2.66 k ohm
red/white - batt+ = 3.0 ohm

Wow that makes a huge difference this is more understandable.