Modern Vespa

Hi everyone. At a point with my GTV where I'd appreciate any suggestions what else to check / do. I have read lots of good comments and ideas here but have exhausted my ideas on what to look for. So thanks for your help in advance.....

My 300 GTV is just over a year old (2017 model year) and has around 3000 miles on it. It ran fine until I shut it off one night and the next morning it would would not start (cranking over fine but not firing).

Here are in random order the details I have looked into:

- Fuses all good
- Reads the key (flashing read light goes off after inserting key)
- Battery voltage: 12.4V (with a charger connected)
- Battery Voltage during cranking: 11.2V (charger still connected)
- Cranking speeds sounds normal.
- No diagnostic codes present (using ScooterWest's MIU diagnostic tool)
- Used the diagnostic tool to reset TPS. Same no start.
- No dealer within about 150 miles.... ;-(

Fuel related:
- I can hear fuel pump as soon as key is turned on
- Disconnected the fuel line from pump at injector. Hit starter button and solid stream of fuel comes out.
- Do not know exact pressure as I have no way to check fuel pressure. Suggestions?
- Reconnected line to injector and removed injector from engine. Aimed the injector into a clear container and hit starter button. Observed consistent spray pattern shh...shh...shh...shh...shh
- Replaced injector just in case. Same no start situation.

Fire related:
- Removed spark plug. Tip looked like normal/expected wear.
- Connected spark plug wire while plug was out, grounded plug threads and hit starter button. Observed consistent bright spark.
- Changed spark plug just in case. Same no start.

Air related:
- Removed elbow hose connecting air filter box to intake. Same no start.

Compression:
- Put my finger on the spark plug hole and hit starter button. Feels like compression is there.


I think you can see why I am asking for help. Any input is truly appreciated.

The only thing that troubles me, is you re-set the TPS. Everything I've read, and been told, is to not mess with that. Only a dealer with the up to date, current software should re-set that. You might be doomed to take it to a dealer to get a new fuel map, and TPS re-set.

Still doesn't explain, or help fix your problem in the first place. It would have been nice to know (before you re-set the TPS) if it would crank (stumble alive) by spraying starter fluid into the spark hole.

You might try taking off the valve cover to watch if the valves are doing their thing correctly. If you could put your hands on a leak down tester (it's a royal PITA to get the hose threaded into the spark plug hole), that might lead you towards any valve train issues that might not be obvious looking under the cover. If all looks good, check your valve lash while you're in there.

None of that valve train mess in the above paragraph will correct a bad TPS setting.

The only thing which is not on your check list is a complete obstruction of the exhaust. Probably easiest to check this by removing the silencer which would also allow you to check that at least air is pumping through the engine. Cold starting is not much of a science, you just dump plenty of fuel in the inlet tract and provided its sparking at about the right time it should fire even if its not going to run very well. Try using an ether cold start spray. This will fire almost anything provided there is a spark. Any prolonged failure to start when fuel is present would result in a fairly strong smell of fuel at the exhaust, also easiest to detect when silencer is removed as the fuel should practically be dribbling out.
I did come across a trick that was played on an unpopular local policeman where diesel was substituted for petrol but I'm sure that one wouldn't fool you because its so easy to smell the difference.

It isn't mentioned but you did check the kill switch is positioned correctly I presume.....

I'm going to suggest a different battery. This may not be the issue. But I just had the same thing happen on my Guzzi. Had been starting fine. Went out the next morning and she wouldn't start. The measured voltage was marginally ok but with these modern systems the electronics require a good battery with all the cels working together.

Worth a shot.

Bill

You want to see 14.4 volts for about an hour, then 13.6V for about four hours (with a decent multi-stage charger) and 12.6 to 12.7V at rest after the surface charge has subsided.

I'm not saying the battery is the problem - but ensure it is fully charged before further diagnosis.

IIRC, the 2017 model can only be started with the throttle closed. So check the idle bypass isn't blocked in the throttle body.

Here's all about it:
https://cheekythoma3.wixsite.com/itsme/idle

And quoting the last bit:

"The next one is more for dealers, on the diagnostic tool there is an option to reset the TPS, why i dont know as it must NEVER be done after the throttle body has left the factory as it gets done when the butterfly valve is positioned correctly, the workshop manual tells you never to do it, the factory training course tells you never to do it, yet the amount of times ive known people to do it as they dont understand and see the word RESET and cant resist pressing it is beyond me... once pressed the bike now thinks 5.7 degrees is 0 degress and youll get haning idle speeds, stalling when slowing down etc... and the only way to cure it is a new ECU @ £350"

So I really hope you knew exactly what you were doing when you reset the TPS - if the ECU doesn't know it's at idle, it won't start...

starreem: Thanks for your input.

Agree, TPS reset perhaps not a good idea.... I had put it fairly early in my list of things I tried. Actually, it was the very last thing I did when I figured a trip to the dealer is likely anyway.... Kind of a 'might as well' thing....

I need to get some starter fluid. Have not tried that yet.

I also will put the valve suggestion on the to-do list for now. A little irritated with the whole thing right now...

roadster: Thanks for suggesting checking the exhaust. Had not thought of that. A quick check by putting my thumb on the silencer while cranking lead to consistent puffs of air pushing my thumb away....

@West Arm Rider: Yes, thanks.

italianmotofest: I will try that, thanks.

jimc:

Thanks for your response and input. I will definitely look into the battery / voltage issue.

re TPS: Yes, I may or may not have scr..... myself. Eventually we'll know, I assume....

Tried starting fluid. Did not fire at all. Just cranking....

It's a two year old bike. You shouldn't need to do any of these things. . Get it to a dealership, and give them a complete rundown of everything you've already fixed, so they can unfix anything they need to before figuring out what's wrong with it. Everything it sounds like it might be shouldn't happen on a two year old scooter, and you are following the advice of anyone and everyone who offers it. Not the best approach.

Motovista: Agree, and it will probably end up at a dealer.

Dropping it off and picking it up again another day will be a total of around 600miles and 12hours in the truck. Was hoping to be able to avoid that....

If starting fluid ( ether) didn't even fire then you either have no spark or no compression. I'm not sure if you have checked but are the valves actually opening and closing? Decompressor mechanism stuck?

Agreed with everything already said . That battery info you supplied is terrible. You don't start an engine with the charger still connected. But to have such low readings I'd try another battery or boost from your car battery but under no circumstances do you have car engine running just connect the batteries together.
The kill switch is always an issue and should be toggled periodically through the year at least 10 times each time.horrible things.
The air by pass is a very common issue with all piaggio injection engines and yours has the no throttle at start up. Just remove the throttle body it's just a 5 minute job and see if any wd40 comes out of the bypass hole when sprayed.
If it had low compression wouldn't it turn over super fast?

Sounds a bit like the problem I had with my 2015 GTS300, but mine was erratic non-starting. I tried everything to fix the problem, and when all else failed I replaced the ECU/throttle body. An expensive fix, but it did the trick. Scooter has been perfect since. It seems the ECU was flooding the engine at start-up. There were no diagnostics for this problem.

Hope you find a cheaper solution.

There's something really odd if you've got fuel, compression, and spark with still no ignition turning the engine over. Please update this thread if/when you finally get this solved. I'm quite curious...

Cheers.

In the 2010 Cannonball one of the riders, Bagel, had a no start problem which caused him to be shuffled in to a dealer on a support truck. Long story short, the mechanic, who was left handed, grabbed the rear brake lever and the bike started immediately. Bagel, who was right handed, grabbed the front brake lever to start normally and the cut out switch on that side was broken, causing a no start.... ?

Lol that's nasty, when I was younger I couldn't get my gs125 to start so I pushed it 3 miles home. Someone had flicked the kill switch.

We know it's not the kill switch or a brake light switch BECAUSE THE STARTER TURNS.

Changed battery. Same result. Still cranking fine but not starting.....

Is there even the remotest chance that the fuel in the tank was tampered with overnight?

Or... is there any chance the bike was inadvertently refueled with diesel?

How about valve timing?

Maybe the timing chain jumped a tooth or two. I know he said it had compression but maybe not enough to run.

David Masse: It was in my garage the night the 'mystery' happened. So not likely anyone messed with my tank. And I fuel up all my bikes from the same gas canister. So the same fuel is in my LX150 and it starts fine. Appreciate the thought though.....

If the timing chain has jumped a tooth, then the timing is off. No amount of fuel and air will ignite when the spark is happening at the wrong time. You can check this by aligning up the timing mark on the cam sprocket under the valve cover, then removing a monster sized torx (a 45 I think) plug on the right side to see if the timing mark is lining up in that plug window... at least that's how I used to check it on my (RIP)2007 GTS

Just another wild-ass guess -- this came to mind:

What is this on the sprocket?

Could something about the compression release be broken?

It will still run if it's off a tooth.

The only reason I mention this is because it's something I've seen a couple of times recently, and it doesn't involve taking the engine apart.

First off, take that big rubber boot off the spark plug cap and put the cap on the plug. Make sure you hear it click on.
Try to start it.
If it doesn't start, try a Denso plug, or any other plug that's not one of the ones NGK makes specifically for Vespas (CR8EB, CR8EKB). If you can't get a Denso, get an NGK CR7E or CR8E and stick one of the terminal caps on the end. I've seen three bikes recently where the plug wouldn't fire under compression. It's a stretch, but possible.

And the brake switch also causes the motor not to turn over which to OPs seems to be doing fine or he would not know he had spark, fuel and compression.
This is not a not crack issue, it is a no start issue.

Motovista: Thanks. I will pick up a CR7E locally today and try it as well as make sure I have a good connection from the wire to the plug.

Motovista: 👏👏👏👏👏👏👏👏👏

Pulled the plug wire off, removed the grey rubber boot and stuck the plug wire back onto the spark plug (paying attention to the noticeable click as you suggested).

Started right up......! 🛵🛵🛵🛵🛵🛵🛵

Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you! Thank you!
I think you get the idea..... 😉

I love happy endings. Especially when they don't involve $400+ ECU/throttle body assemblies.

And now for the bad news...

It seems that Piaggio has had problems with spark plug caps since they got more complicated than sticking a wire on the end of a spark plug. The cap they use in the Vespa appears to be something they came up with on their own, without consulting people who make spark plug caps for a living. Because of it's unique design, it tends to break and then pop off the plug. So their solution to the badly designed spark plug cap was that silicone boot.
If you want to use the boot, you can cut off about a quarter inch of the tip and try to stick the cap back on the plug. Otherwise, get another plug cap and carry it with you.
As someone who has slowly coasted down a long 60 mph bridge at night because my spark plug cap fell off, I have been looking for a "fix it once," solution for quite a while. I have tried just about every spark plug cap out there, and finally found one that doesn't break or come off. What I use now is a spark plug cap like the ones Malossi uses in their racing series, but with a resistor.
https://scooterpartsco.com/ricambi/021-vespa/spark-plug-resister-cap

When I say it doesn't come off, I mean that once you put it on, it is almost impossible to remove. So it is best with an iridium plug.