Modern Vespa

I have intermittent starting problem with my Vespa GTS, 8 times out of 10 it works fine, but once in a while, it starts for a brief second and than as soon as I accelerate, it shuts down. I then wait 15 minutes to 30 minutes and it goes away and starts again.

I have changed my battery, my kill switch and my spark plug and the problem was still there. So I went to my Vespa dealer in Montreal and he told me it was my voltage regulator, I had it replace last week. But today after 5 days of riding it normally, the problem came back. My dealer told me, "It could take me couple of hours for troubleshooting it and finding the problem, if I can find it".

Has anyone had similar problems and found a solution?

Thanking you in advance.

I have also recorded the problem, here it is:
What does it sound like? Thank you.

My 2006 does the exact same thing.
The tech at a local Vespa dealer checked the ECU for faults and only found a coil fault that was unrelated. He checked the Vespa database for fuel pump recall and found my scoot' wasn't on the list. I suggest you check the database with a dealer on your scoot'.
I still suspect the fuel pump as the indications are correct for this issue. However, replacement is very expensive, and what if the pump is okay?
My GTS is a 2006 with many new parts and ~4,300 miles on the clock.
It's a Vespa and will be for sale soon.
Just to show that I'm open minded about Piaggio products, I've purchased a new BV350 and, fingers crossed, hope to have many trouble-free hours of fun riding on it!

I have replaced the fuel pump a couple years ago, I hope that's not the problem again.

Good luck with the BV350.

Interesting! Whatever is causing your problem is very likely the problem with my GTS as well. The exact same problem on both scoot's...
Have you replaced the coil? This was suggested as a potential problem because it MAY not work when hot but be okay when cool. Maybe airflow around the coil while riding is enough to keep it cool but when stopped it heatsoaks enough to not work? The same technician that was unable to find the problem suggested carrying a plastic bag of ice on rides and applying it to the coil when the engine wouldn't start to isolate this as a potential problem.

You might want to look at the CDI. When mine (carbed LX) had trouble starting when it was hot it turned out to be a faulty CDI. They do go bad. Is there someone you can swap it out with to see if that's the problem? They do go bad and as the bikes are getting older shops are seeing more CDI'S going bad.

Hi Judy.
Great call!
CDI stands for Capacitive Discharge Ignition and refers to a specific technology used to create high voltages for igniting a spark plug.
Are you talking about the ECU, Engine Control Unit? If so, the tech suggested the ECU but I didn't put that in my message above.
The ECU is yet another expensive potential root cause of our problem...

Thank you for the tips. I will try first cooling the coil, since the problem is mostly after restarting my GTS after a long ride when the coil has probably been heating up. I guess spraying cold water on it, is not recommended, isn't it?

The 'injection loads relay' can be a culprit with dirty contacts. Very cheap and easy to check by substitution.

JimC.
Where is this relay?

Open the seat, take out the pet carrier, and it's on the left hand side of the scoot.

As shown in the workshop manual, 'ELE SYS 13' (page 63 of 317)...

Thanks, I'll have a look!

Where is the CDI located on a GTS 250 ?

It's integral to the ECU in the throttle body. I'm afraid Judy's CDI comments are irrelevant to the GTS's and other fuel injected Piaggio scooters that have all the 'brains' in the throttle body.

I would love to know how things work out for you, as I am having the same problem. The only difference is, I experience this before I go to work in the morning, only. So basically after a period of overnight rest.

Mine always start in the morning, the problem for me is right after riding it. A trick I have found that reduced the problem, is to give at startup a full amount of throttle without releasing the handle, of course you have to insure that the road is clear in front of you.

By the way, I have tried cooling the coil after a failed start, it didn't work. What else should I try now? Thank you for tour suggestions.

My problem only when hot.
Try cooling the ECU.
Try the fuel injection relay that JimC suggested.

Thank you. Is this the fuel injection relay?https://flic.kr/p/KaHkRZ

picture uploaded to MV so anyone can view it easily.

No, that's the starter relay. Look on the other side.

Ok, is it the white relay on this picture?
http://members.modernvespa.net/woodlina/uploads/mainfuselocation_002_177.jpg

Yes. Also as shown in the workshop manual...

JIM so the GTS doesn't have the red blinking light? I refer to that as the CDI or ECU. The immobilizer thingy. That went bad on my LX and i thought all the Vespa models had it. When that goes you will have hard starts and then eventually it won't start.
We swapped mine out when i had to let my scooter cool down when it got hot. Eventually it wouldn't start and when we swapped it out i haven't had any problems with my scooter. So whatever that thing is called ,if you have one, swap it out. Mine was back behind the glove box but i haven't a clue where it's at on a GTS. We only have one GTS over here and i haven't seen the scooter opened up.

Yes, they do. The 'Code LED' is part of the immobiliser, which (unfortunately say I, posts passim London thefts) is part of the throttle body. It's integral with the ECU, which also has capacitor discharge ignition (CDI) built in.

The functions are separate, but linked.

Ok, I changed the injection loads relay and it seems to be more stable, when I start my GTS the injection and throttle rev at a higher RPM. Prior to the relay change, it would have stalled inevitably after a couple of startups, it only stalled once after many startup tests (it didn't restart for 15 minutes). This time, I was letting the engine run for a while without giving it some throttle, which on a normal situation I wouldn't do. Should I still be worried?

All i know is when my LX (yes i know it's carbed and the 250 is IE) we changed out the relay and starter moter. Spent money and they weren't the problem. On a whim, since i had a LT 150, we took the CDI, ECU, immobilizer or whatever you want to call it out of the LT and put it in the LX. Fired right up and has started and acted well ever since. Now that our bikes are getting older, i had a dealer tell me they have seen more of them failing. I'd try that of you keep having problems.

Awaiting the relay and will change it in my GTS. I hope this is the solution as this problem has plagued the scoot' for quite a while.

I have the same year GTS. Try to start and run the Vespa for few days with the Master key.

I've tested the blue key and it's working well.
I was told that the blue key can lose its ability to communicate to the scoot' and use the brown key to test this.

The new relay has not repaired my hot start issue. The scoot' wouldn't start today after the first ride since relay replacement. I removed the pet carrier and waited about 40 minutes and it started up and ran. Frustrating.
I'm up to ~$200.00 in service and parts with no solution. Vespa service said it could be the fuel pump but the scoot is not on the factory pump list and the pump is making all the right sounds, etc. and doesn't seem to be the issue.
Fuel injector?