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Might seem an odd question, but....does this thing have a programmer on it? None of this makes any sense, unless there is a problem with the controller. Just another thought, because I can't see the bike: You wires the coils correctly? The twin plug system DOES NOT control one cylinder per coil, but rather one front and one rear. It should run on one coil, as long as it's splitting the spark between the cylinders. Decades ago, I dual plugged my 98 inch SuperGlide. Initially, I used two coils, one for the right side and one for the left. I replaced the ignition controller with a "single fire" system with 2 pickup coils. That let me run one coil for the rear cylinder, and one for the front. That allowed me to set the ign. timing separately for each cylinder, and use the full voltage from the coils to fire the plugs. The Drifter does not have a single fire system.

It does not have a programmer on it. The spark issue appears to be fully fixed, but now the fuel injectors are spraying too much fuel.

I think it may be the water temp sensor, it doesn't appear to have a vaccuum hooked up to the connection. 

ECU test results?

No codes. 

Yep, so everything's working, bikes cranking great.. but it's still spraying too much fuel for the bike to start. Plugs are still dripping wet... we followed the vacuum diagram.

It feels like every time we fix one issue, another one comes right around the corner. 

Good news, we have spark but now no fuel spray.

Does anyone have a vaccuum hose diagram? Of so, please post it here.

Thanks!

So, good and bad news.

Map sensor vaccuum wasn't hooked up at all, got all new vaccuum lining and that fixed the fuel problem for the most part.

Now, I no longer have any spark. This is bizzare. Went from having strong consistent spark to none.

Will add, anytime I apply slight throttle while cranking it, the starter relay will click.

Anyone have any new ideas?

Fuel pressure regulator works to reduce the line pressure only after the engine starts. It's vacuum controlled. Stuck injectors spray fuel as soon as they have pressure applied to them Injector pulse width is controlled by the fuel map in the ecm, and the cell addresses vary by the coolant temperature reading.

Makes me think it has to do with my throttle position sensor... I'll test that according to manual specs 

Update: still figuring out the injector issue.

They do not appear to be leaky or stuck open, but when I try to start the bike they fire an unreasonable amount of gas. And there is a lot of pressure in the return line to the tank, could it be the pressure regulator?

So, I suppose I did a combination of things and now I have strong consistent spark.

Now, everytime I try and start it it'll gunshot or pop but won't full on start. I can see fuel mist leaving the pipes.

Plugs end up dripping wet, what do I do now?

Maybe my injectors are stuck open? Sure seems like it

I'm sure you've tried this, but did the ecu fault code flash anything up?

Only in the past, and it was the fuel pump which I ended up replacing. 

Just thinking outside the box.... assuming you have the plugs contacting cylinders, maybe they spark once when you hit the starter but then due to the cranking vibration they lose contact and don't spark?

Good thought, but I have my buddy holding up the bike and pulling in clutch and holding the start button for me. I'm definitely making contact so that isn't it.

Such a weird issue.

Just to clarify, the motorcycle 'ground' is 'floating' with respect to a dual fire coil output and is not strictly required for the plugs to fire (except in that it provides an electrical path for a pair of plugs in the same cylinder).  The plugs don't fire from coil to ground, rather the complete fire path is from : coil > wire > plug 1 > motor > plug2 > wire > coil (the same coil) - interrupt any part of that path and neither plug fires.
If you have both plugs out, you need to connect them somehow in order for them to complete the circuit and spark.

I'd think that's part of my issue (having all the plugs out, or 2 at a time out) but that still does not really explain why it only sparks ONCE when I press the starter button.

It makes me think something is telling the ECU "hey, shut off spark." 

Here is the ign system wiring diagram. I still think you have flooded the engine. The waste spark system relies on at least one clean plug per coil in order to work. If there is no path to ground through an ionized air gap, the spark will not happen.  Keep in mind, the spark jumps from the ground electrode to the positive electrode on one plug and from positive to ground on the other plug. All waste spark systems are like this, whether it's a Honda, a Harley, or a Chevrolet. It may be hard to visualize, but that's how it works.

I am not flooding it... because the spark plugs are outside of the engine.

Its a super weird issue, especially now that it's acting different with the new VDS.

Got the new VDS in, it changed the behavior of everything. The bike wouldn't spark at all with the kickstand down, etc as soon as I replaced the VDS. it would try to start before even with kickstand down and the clutch out.

Still have that spark issue. Clutch sensor works, neutral switch illuminates, kill switch works, fuel pump was working. Ignition switch working.

To reiterate, it will only spark ONCE when holding down the starter. If you keep holding down the starter button, it will not continue sparking.

Any ideas?

Try the basics first.

VDS sensor, as you say
Side stand switch wires OK?
Neutral switch illuminating?
Clutch switch, under lever, not disintegrated?
Engine kill switch, they look fine but fall apart inside housing
Fuel pump connection, does it sound with ignition on?
Ignition switch?
Starter relay/fuse?
Is the motor spinning if you jump the starter solenoid?
(ECU's rarely give problems)

Process of elimination, you'll find it.

Yes,
I have already gone through that entire list. The motor will spin over via the starter motor, it just has the spark issue.

VDS has no continuity, so that's a problem in the first place. Should be here tonight or tomorrow and then we will find out.

Thanks for the suggestions! 

Vehicle down sensor.

It has no continuity, so I went ahead and ordered a used but allegedly operational one on ebay. It was also half apart when I found it so...

Update 2: Put VDS back together, no continuity in any situation. Bike will engage starter without it, but won't spark at all without it obviously.

Perhaps, this could be my issue? 

Battery tested good after a load test, also I found the VDS not together properly. Even with it messed up, it still tries to start. Could this be preventing spark? I thought a bad VDS would also prevent starter motor.

Did you load test the battery?

Will do so Monday, will report my findings. 

It is a 1999 model, so no clock that I know of.

So it sounds like the battery isn't my issue, what other things could it be? Super weird thay it only sparks once. I had hope that the circular relay was the issue... but apparently it's not even connected to the ignition system.

When I mean external power, I am referencing a jump pack. Could a bad battery cause no spark even with the jump pack connected? 

That's what I would think too... but even with a fully charged battery and even going as far as providing external power.. no change. I've also disabled the fuel system because yes, it kept flooding. 

Update: I can see a spark only when I first tap the start button. If I hold it down, no spark. But if I tap it quickly it will spark once. Thoughts?

Thanks! I don't see that relay I was talking about on there... perhaps that an entirely different issue in itself. Any ideas on why it wouldn't have spark? It did have spark at one point when I first got it.

Hi all, I just got this VN1500 Drifter from my friend, whose brother was recently deceased in a motorcycle accident due to an intoxicated driver. This was his baby, and his project. So I am honored to continue his work and hopefully get this thing going!

It had spark when I first got it, but now it does not. I just found that my ignition relay (The circular one to the right of the battery) has an ohms resistance at 10. Would this probably be a safe bet that this is my issue?

Thanks!