Modern Vespa

ISSUE RESOLVED:
It turns out it was a faulty Immobilizer Antenna. Purchased a new one ($165 USD) and replaced it.

I started it up with no issue and let it idle for a while until the cooling fans came on, then test drove it.

I then preceded to turn the key off, turn back on and start, no issues apparent. Took it for a further test drive to keep it hot and still no issue after.

UPDATE:

2022 Vespa GTS 300 Super:

After starting and riding with no issues, then turning engine off….

Immobilizer will activate and will not recognize key when engine is hot (immobilizer light blinks twice then stays on happens with all keys)

This can happen when engine is hot or even if left in the sun all day.

Again, you can start it and ride it with no issues, turn the key off, then immediately turn the key back on, and then the immobilizer will light up and not recognize the key. Even the brown programming key after it is warmed up.

Waiting a few hours or the next day when the engine is cold, it will start up with no issue at all 

-

Hey all, first time posting with a heartbreaking issue…

Need help with a peculiar starting issue:

2022 GTS 300 Super, bought used a year ago

At random times after being ridden and the engine is warm, or even if parked in the sun for a while, there is no response at all when trying to start.

Then after even only 15 minutes or longer, it will start right up with no issues. Sometimess just leave it sittinging there, other times after walking it and shamefully pushing it to a quiet corner of a parking lot.

I have changed out to new OEM parts: battery, starter button, kill switch, starter relay. And yes there is power, brake lever held, kill switch off, kickstand up.

Otherwise It starts up and rides fine. The only other odd observation is after riding for a while then shutting it down and parking, there is an interesting sound that sounds like air or fluid going through a struggling pump. Like a whining sound.

So bottom line, after it apparently warms up, it randomly doesn't start at all. Everything seems absolutely normal, but when pushing the starter button there is absolutely no reaction… No clicking, no cranking, NOTHING.

***Again, it can be running for a while, then I can shut off the key, turn it back on, push the starter button and absolutely nothing happens.

If you made it this far thanks for hearing me out. And I welcome any positive thoughts and suggestions from experiences you've had.

The mooing sound after switching off is normal: FAQ: Why does my GTS groan/moan/moo or fart when off?

You'll have to chase where the power is intermittent with a multimeter. Yes, this can be tedious, and it WILL be the last thing you try...

Welcome to MV and congratulations to your first post.

When it is warm and does NOT start, do you hear a quiet whirring noise from the fuel pump when you switch on the ignition? This quiet whirring should always appear when the ignition is switched on.

I note you say 'kickstand up' - does this bike have a kill-switch in the sidestand? If so, that is vulnerable to the elements, and would be the first thing I'd check - by bypassing it.

yes this model does. and it will activate the red kill light on the dash. since they've already investigated the kill switch I assume they would have checked the red light on the dash

There is a hot start service bulletin on that issue for later HPE motor model GTS 300's. I had the identical problem with my 2021 GTS Super 300 model. It took nearly a year for my dealer working with Vespa get to the bottom of my problem. It had to do with excess pressure in the combustion chamber. Like I said, there is a service bulletin issued by Vespa for this hot start issue. I can't at the moment locate the link to the bulletin. Im sure someone will chime in with it shortly. Good luck! Don't despair. It is fixable. My bike runs fine now.

would have thought you'd hear it try if it was that?

I'm suspecting fuel pump like GermanGTSDriver hinted at

The Vespa service bulletin I am referring to is for excess pressure in the combustion chamber. I can't recall the exact fix, but it was not a new fuel pump. The link to the service bulletin and fix has been posted here before. I'm sure someone will repost it in due time.

I found it…..

https://static.nhtsa.gov/odi/tsbs/2020/MC-10178216-0001.pdf

You must've misread me, I wasn't suggesting the solution to your issue was the pump.

Was suggesting that i suspect it's a different issue to what you experienced, namely a fuel pump fail

Ok gotcha. Sorry . I misunderstood. It's late and I have insomnia. I gotta get some sleep!

How good that somewhere in the world the night is already over again...

It's quite simple guys: Does not start when hot, starter motor does not turn (as described by the topic opener) and you cannot hear the fuel pump when the ignition is switched on = thermal problem with the fuel pump. Solution: Replace fuel pump.

However, if the fuel pump performs the usual pre-pumping process when the ignition is switched on, even when the engine is hot, the problem is not a defective fuel pump, but something else.

But we don't need to worry any more: Topic opener changed the initial post after we asked questions, but didn't provide any answers to our questions. So every line here is a waste of time.

Yes, I hear the sound from the fuel pump. Next time I get it hot and it happens I'll pay attention to see if it does or does not.

Thanks! Great info

Sounds like the exact same problem I had with my 2021 model. She starts fine now. Hot or cold. Good luck!

Bollocks. If the fuel pump is duff, that doesn't stop the starter motor turning over.

If the starter motor can only do half a turn, then extreme compression or a duff battery can be the cause.

If the starter motor does nothing at all, with no sound from the relay, it's a different problem altogether. Bad connection in the kill-switch circuitry perhaps - all sorts of possibilities.

My money would be on a dry joint inside the ECU, so neither the 'fuel injection loads' relay nor the first relay before the main starter relay get grounded by the ECU.

Does the brake light come on when the bike is failing to start? ie, the switch in the brake lever could be moody

As far as I know, if the fuel pump does not build up sufficient pressure when the ignition is switched on, the starter motor will not turn when the engine is started. Possibly/probably the ECU interrupts the starting process if there is insufficient fuel pressure.

Let's wait until the problem occurs again with the OP and see whether the fuel pump whirs when the ignition is switched on or not...

After it happened a few times I now noticed the immobilizer light on

the immo light comes on and strays on? yeah well that ain't any fuel pump or kill switch or anything else. the 'once it's warmed up might be an unrelated coincidence. The antenna might be dying or bad position (fallen off the back of the keyswitch).

It only happens when it's hot. That's what's confusing. Otherwise there's zero issues with starting and operating. I can run it on the highway for miles and then once I turn it off and try to start it, the immobilizer light stays on and I can't start it until it cools down.

So It only happens when it's hot. That's what's confusing. Otherwise there's zero issues with starting and operating. I can run it on the highway for miles and then once I turn it off and try to start it, the immobilizer light stays on and I can't start it until it cools down.

I've narrowed it down to the immobilizer. It only happens when it's hot. That's what's confusing. Otherwise there's zero issues with starting and operating. I can run it on the highway for miles and then once I turn it off and try to start it, the immobilizer light stays on and I can't start it until it cools down.

No need to post the same thing three times...
Especially as SteelBytes gave you the tip about the immobilizer ring antenna around the lock.

I can't remember any case of a temperature-dependent cause of error with the antenna. Nevertheless, I would start with the antenna if the transponder in the key is occasionally not recognized.

Dodgy connection that's temperature sensitive. Could even be a dry joint inside the ECU.

First thing to try - break and re-make all plug and socket connections in the kill-switch path.

Please explain how a bad connection around the killswitch leads to an error code in the immobilizer. Thank you!

Error on my part! I had meant to mean all connections that eventually lead to the ECU (confused this with another thread... - I blame old age. ).

Late to the conversation, but my 2012 GTV had a similar issue with less than 1K miles on the bike. The immobilizer antenna would not read the key but only when the bike was at operating temperature, like after stopping for gas or a quick run into the store. I can't for the life of me think of why it would be heat related other than the proximity to the coolant system, but new antenna was the fix. I took it as on opportunity to replace the cheap plastic bag hook with a fancy aluminum one since the inner cover had to come off!

I've already upgraded the bag hook to an aluminum one too, but that's a great idea.

It looks like replacing the antenna is the next step so I'm considering buying a new one

Good Morning - I have a 2022 GTS300. At 600 miles my bike was experiencing the same sort of thing......when hot after riding a bit it died......but then wait 15-20 mins it would start up again. It turned out I needed a new fuel pump......Sadly, the same thing happened again at 5000 miles......fuel pump. I am happy to report now that since my 5000 mark I am at 13,500 miles with zero issues. If you not hear the whirr sound you turn your ignition it may be your fuel pump. It was super frustrating for me!!

Good point. I was worried about the pump as others were mentioning the same thing, but there would never be any issues with it turning over when the start was actually engaged on mine.

When mine doesn't start, it's completely unresponsive and the immobilizer light is on.

Glad you solved your issue and I'll keep it in mind if mine starts acting that way

It turns out it was a faulty immobilizer antenna.

It turns out it was a faulty immobilizer antenna. No issue after replacing with new one.

It turns out it was a faulty immobilizer antenna.

It turns out it was a faulty immobilizer antenna.

It turns out it was a faulty immobilizer antenna. When changing it out, the connection appeared fine and it was secure to the ignition. Once replaced there was no issue after.

Congratulations on solving the problem and thanks for the feedback!

Tip: It would be easier if you just write one post and mark the people you want to address with an "@" followed by the name (i.e. Echo5Victor)