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Vespa GTS 125ie
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Location: Poland
 
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Vespa GTS 125ie
Joined: UTC
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Location: Poland
UTC quote
Hi all,

I've scrolled these forums up and down for some months now, tried all the fixes from people with similar issues, yet my issue still seems to persist.

As the title says my Vespa has intermittent starting issues with no apparent reason (not something I could figure out) but mostly when starting from cold sitting in the garage at room temperature, regardless if it was ridden for long or short before.

2012 Vespa GTS 125ie, 17800 kms

Issue:
Immobilizer LED blinks one long on ignition
Starter cranks fine
After engine cranks it sounds like the engine starts for like 2 revolutions then it cuts out
Cycling the key on/off then trying again does the same thing, until it cranks long enough that I can give it a bit of throttle that keeps it alive. After this all is perfectly fine.
Sometimes it starts straight away with no issues.

Troubleshooting done(I'm not a mechanic but i'm pretty handy with tools):
- Battery checked, all good (tightened connections as well)
- Fuel pump tested and primes well on ignition
- Injector cleaned
- Valves adjusted
- cleaned idle bypass
- Spark plug changed (spark plug lead looks in good condition)

What did I miss? What else to check?
⚠️ Last edited by lorantis on UTC; edited 1 time
@steelbytes avatar
UTC

Veni, Vidi, Posti
2019 GTS300 Supertech E3 60,000km
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Location: Batmania aka Melbourne, Australia
 
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@steelbytes avatar
2019 GTS300 Supertech E3 60,000km
Joined: UTC
Posts: 5558
Location: Batmania aka Melbourne, Australia
UTC quote
Cleaned the idle bypass? (Not sure if the 125 has one?)
OP
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Member
Vespa GTS 125ie
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Location: Poland
 
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Vespa GTS 125ie
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Yup, did that too. (added to the list)
@jakem avatar
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Vespa Sprint Sport S 125cc
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@jakem avatar
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Earth leads can cause some strange issues and are easy to check / replace.

Is the coolant level stable? Is there any coolant in the oil?

Have you changed the air filter, and can you see if the exhaust is clear - sometimes mice have a habit of making nests in the exhaust if the Vespa has been left for awhile.

At some point, you might have to consider going back through your list again - are the valves definitely adjusted to the correct value?

Is it worth pulling the spark plug and seeing the new colour?

EDIT: The brake light has to be illuminated for the Vespa to start. When you are trying to start the Vespa, is the brake light on? No flickering?
@gtdespatchcourier avatar
UTC

Molto Verboso
GTS 300ie
Joined: UTC
Posts: 1655
Location: Sunshine Coast, Australia
 
Molto Verboso
@gtdespatchcourier avatar
GTS 300ie
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UTC quote
Dodgy kill switch?
@steelbytes avatar
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Veni, Vidi, Posti
2019 GTS300 Supertech E3 60,000km
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Location: Batmania aka Melbourne, Australia
 
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@steelbytes avatar
2019 GTS300 Supertech E3 60,000km
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GTdespatchcourier wrote:
Dodgy kill switch?
he said it cranks so not kill switch problem
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Coolant level is stable. It was a bit under minimum so i topped it up. No coolant in the oil.

I feel it's a fueling issue, but with the pump and injector working fine I'm not sure what else to look into.

No idea what would cause such a random intermittent issue, once in a week, or every 2 weeks.
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Molto Verboso
GTS 300ie
Joined: UTC
Posts: 1655
Location: Sunshine Coast, Australia
 
Molto Verboso
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GTS 300ie
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UTC quote
Dodgy kill switch might let you crank and then the vibrations screw with the dodgy contact. I had a dodgy kill switch that would cause a stall just after starting if you went over a bump.
@steelbytes avatar
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Veni, Vidi, Posti
2019 GTS300 Supertech E3 60,000km
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Location: Batmania aka Melbourne, Australia
 
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@steelbytes avatar
2019 GTS300 Supertech E3 60,000km
Joined: UTC
Posts: 5558
Location: Batmania aka Melbourne, Australia
UTC quote
GTdespatchcourier wrote:
Dodgy kill switch might let you crank and then the vibrations screw with the dodgy contact. I had a dodgy kill switch that would cause a stall just after starting if you went over a bump.
Fair point
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Vespa GTS 125ie
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I tried jiggling the kill switch while the engine is running to see if I can notice any sign of it being dodgy, but it seems to be solid in the ON position (I would expect if it would be dodgy, it would try to cut out at least a bit while moving it around)

I've seen it topic154345 and topic68491 that it can cause issues similar to what I'm experiencing so might as well order a new one and see if it fixes my problem.
@gtdespatchcourier avatar
UTC

Molto Verboso
GTS 300ie
Joined: UTC
Posts: 1655
Location: Sunshine Coast, Australia
 
Molto Verboso
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GTS 300ie
Joined: UTC
Posts: 1655
Location: Sunshine Coast, Australia
UTC quote
Cheaper to cut the wires and join them together. I do it on all my bikes.
OP
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Member
Vespa GTS 125ie
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Location: Poland
 
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Vespa GTS 125ie
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UTC quote
Hi all,

While waiting for the kill switch to arrive I managed to get the starting issue on camera.

https://youtube.com/shorts/2APb4IS5jUM?si=PRqAKW3CuVF6y1kj

Any idea what it could be?
@steelbytes avatar
UTC

Veni, Vidi, Posti
2019 GTS300 Supertech E3 60,000km
Joined: UTC
Posts: 5558
Location: Batmania aka Melbourne, Australia
 
Veni, Vidi, Posti
@steelbytes avatar
2019 GTS300 Supertech E3 60,000km
Joined: UTC
Posts: 5558
Location: Batmania aka Melbourne, Australia
UTC quote
As JakeM asked, have you checked the air filter?
OP
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Member
Vespa GTS 125ie
Joined: UTC
Posts: 8
Location: Poland
 
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Vespa GTS 125ie
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UTC quote
I cleaned the filter last year(had a bit of oil on one of the corners but not dirty otherwise). The starting issue was the same before and after.

I've ordered a new malossi filter together with the kill switch. Once they arrive I'll pop them in see if it would make any difference.
@gtdespatchcourier avatar
UTC

Molto Verboso
GTS 300ie
Joined: UTC
Posts: 1655
Location: Sunshine Coast, Australia
 
Molto Verboso
@gtdespatchcourier avatar
GTS 300ie
Joined: UTC
Posts: 1655
Location: Sunshine Coast, Australia
UTC quote
Maybe check the spark plug lead connection at the other end.
OP
UTC

Member
Vespa GTS 125ie
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Posts: 8
Location: Poland
 
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UTC quote
Checked the cable as well. Took it out cleaned it. Checked for cracks.

All looks good, contact to the coil is solid.
OP
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Vespa GTS 125ie
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Location: Poland
 
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Vespa GTS 125ie
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Location: Poland
UTC quote
While still waiting for the kill switch and air filter, another issue seemed to have come up.(intermittent starting issue still there )

After riding a bit and the engine warms up, while pulling up to a light the idle stays very high (having to hold the break not to move). It almost feels like the throttle getting stuck slightly open. Turning off by the key and restarting brings the idle back to normal (if i shut it off from the kill switch and restart it afterwards the high idle stays)

Is there some sensor (O2, temperature, etc.) that might have gone bad, causing the starting issues, and now the high idle?

LE: Seems the exhaust gasket is failing, it's leaking a lot, if I plug the end, the engine speed barely changes. -could this cause any of the issues?
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The failling exhaust gasket could cause issues, when your GTS has a lambda sensor, but I don't think the 2012 models already have such a sensor. And even with a sensor, the system would think there is too much oxigen in the exhaust, and therefore enrich the mixture.
Another possible cause, as you mentionned, is a defective temperature sensor. Do you have the same problems sometimes with the engine warm or hot? And if not, does your GTS has a temp gauge? If your sensor doesn't tell the ECU the engine is cold, then the brain will not add extra fuel, and the mixture will be too lean (works the same way the choke on a carb engine does).
The stepper motor in the throttle body can also be failling, but that would be subject of diagnose with special software and tools.
And has somebody in the recent past tried to change the idle rpm by fiddling with the idle screw on the throttle body? Because if they did, you will need the same diagnostic tool as mentioned above.
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