Modern Vespa

I just bought this scoot used last week from a Vespa dealer and have put 400 miles on it. It did not come with a manual and has 3800 miles.

I noticed today that sometimes the yellow engine light comes on when I come to a stop. Any ideas? Temp is fine and running fine. I had a new fuel pump installed before taking delivery since I knew several were recalled.

Any help greatly appreciated.

If it hasn't been used in a while and the fuel is stale that will make the light come on occasionally as the poor burning fuel causes a fault with the oxygen sensor.

Mine has done it after sitting for a long winter, (even with stabilizer in the fuel) running the tank right down to get as much of the crud out of the system as possible and then filling a fresh tank of gas was the cure.

The check engine light can come on for a variety of reasons. I hope that you received some sort of warranty with the scooter from the dealer because they will need to hook up their diagnostic computer to the onboard plug to determine exactly what the problem is.

I have ran three tanks of gas through it in the last five days so I don't think it would be that. This morning I filled up with 90 octane ethanol free so that should be a plus, not an issue.

As to the warranty situation, in Florida all vehicles are sold "as-is" unless they are a "certified pre-owned" car from a dealer with that program.

The light doesn't come on and stay on, it just comes on briefly then goes back off. It also only seems to do this when I'm coming to a stop, usually from a higher speed.

Thanks -

If the light is coming on while the engine is revving and goes out as you stop when the engine returns to idle, it's highly possible that your voltage regulator is bad. Those are the symptoms.

If that's what your scooter is doing, check the battery voltage at idle and again while you're revving the engine. If it exceeds 14.9 volts while it's revving, the VR is bad. A new one is around $175 plus installation.

It is actually the opposite. It is off while I am revving, then comes on as I come to a stop, but it only stays on for about 2 or 3 seconds.

Well, at least you've eliminated the VR as the culprit. It's hard to say since your only symptom is the intermittent light. If it were doing some other odd behavior with the light, we'd at least have something to build on. Sorry, but I can't point you anywhere except where Fritz pointed you.............to the oxygen sensor

Is it possible that it is just vapor lock? When I had my 200GT the tank used to "fart" when I was done riding it for a long period of time. I just went back out to this one and it was making some of the same noises. I unscrewed the gas cap and it had a huge air release. She started right up, and I shut it off after about 15 seconds. I then unscrewed the gas cap and same thing. Maybe I just need to ride with the cap loose like I did on my GT???

Download owners and shop manuals here.

http://www.scootermanuals.us/manuals/Vespa/GTS250/index.htm

My guess that it is one of the following...

Lambda probe

Voltage regulator

Stator

Get it checked, easy stuff for the dealer.

Best,
SDG

You don't need to ride with the cap loose. Simply drill a small (like 1/64") hole through the "O" in your gas cap where it says "GASOLINE." Worked for me.

You, on the other hand, obviously had a problem with your fuel evaporation/venting system. Why didn't you either fix it or disconnect it rather than just riding around with the cap off the fuel tank.

You shouldn't have air release when removing the gas cap. This is a classic symptom of the gas tank having been over filled and you're building pressure in the tank because the evaporative canister is saturated.. It will eventually dry out but many people disconnect or completely remove the evaporative canister system since it's been the source of many problems for many riders (not only on Vespas but on a lot of motorcycle brands)
Here's the instructions for disconnecting or removing the system.

How to remove or disconnect the Evap Sys. from GTS/GTV

I've had my engine light come on and had the engine racing,
Took it in and found the harness had melted,
But it was still allowing current through.
They also found the voltage regulator was toast.

Although getting at the voltage regulator is a bitch,
It's behind a lot of panels that have to come off.

It cost me quite a bit in labour to get it fixed,
It wasn't under warranty.

Did not know this was an option. Thanks for the heads up!

Thanks for the link. If it can be removed then why is it there? Is this the appendix of the scooter?

The state of CA requires it to stop gas fumes from entering the air in case of an overfill. Most manufacturers do not want to build one model for CA and another for the rest of North America so they put it on all of them. It's a worthless addition to the scooter and causes problems (like the one you're having) for many people. Some report no problems but since you have pressure in the tank, this is the cause. You can let it dry out for a few days if it's not too saturated but if I were you, I would disconnect or remove it. It's very simple to do.

Admittedly I do overfill my tank trying to get the maximum mileage out of a tank and I did do exactly that today. I'm thinking I may let it dry out for a day or two, stop filling it too high, and see if that fixes the problem.

Thanks for all the help. Us old vintage guys just don't understand this modern stuff!

If you start experiencing any hard starting, stuttering or stalling, this will be due to the gas in the canister.............so don't panic. If it stalls, just remove the gas cap to relieve the pressure and then put it back on. What it's doing is inhibiting the engine from getting the air that normally passes through the canister. It will probably dry out enough to stop the light from coming on in a few days unless it's really doused with gas. The way you will know when it's dried out is that you'll stop having the pressure release when you remove the gas cap.

(emphasis added)

You had the winning idea on my very recent evap issue, but the above looks like it can't be so. In every evap removal instruction I have seen it is advised to block the brass nipple or the hose that is on it. So it is inhibiting the engine from getting the air that normally passes through the canister. But that doesn't stall the engine.

You block the nipple on an FI engine.
You leave it open on a carb'd engine.

Arno, when the evap system is hooked up and working, air passes through the charcoal canister (although the amount of air is greatly restricted by the canister) and the fumes are pulled into the engine through the hose that you would block off if you removed the evap canister. So, NO....a large amount of air doesn't pass through but enough so that when the canister gets saturated, it can cause the engine to stall or stumble............or become very hard to start. When the evap is unhooked the overflow line that normally goes into the canister is now open to the air and this stops the build up of pressure in the tank that would occur if you just plugged the hose going into the throttle body without leaving the overflow hose open to the air so the tank can breathe.
i.e., the inlet that you would block off if you removed the evap system normally serves as a vent for the gas tank and a place for the fumes from the canister to be burned off in the ignited mixture. It normally would prevent pressure from building in the tank so if you remove the canister and open the overfill line to the air, the inlet would then need to be closed since no fumes would be injected to the throttle body and the tank can now vent through the overflow line.

(emphasis added)

If Jim's comment on the difference between FI'd and carb'd engines is the answer, than my point ends here.

If it is not, then I still do not see a difference between an (intently) blocked hose and a clogged canister that results in an equally blocked hose. In both scenarios, there is no or less air being breathed into the engine via that hose. So why would one scenario cause the engine to stall or start hard and the other would not? That is my question.

The other hose from the filler neck is not an issue, I fully understand its function.

Arno............I'll try again: Because when the canister is clogged, the overflow hose which also serves as a vent for the gas tank can no longer vent.............therefore pressure can build in the tank when the canister is clogged. When you remove the overflow hose from the canister and leave it open, it replaces the vent function that it served. That same hose also served the purpose of draining gas fumes from the tank. That takes us to the other hose that goes into the throttle body. Since the fumes will no longer be fed into the throttle body because the evap system has been removed, it should be plugged because you're no longer feeding it gas fumes. Once the evap system is removed, if you leave that hose unplugged, it will draw more air than it would have when the canister was hooked between the overfill line and this hose. It is my understanding that the carb models do require that this hose be left open. Since I have never owned a carburetor equipped scooter or motorcycle that was equipped with an evap system, I have never bothered to study why the hose arrangements are different. I've removed these systems from over a half dozen motorcycles and five scooters that I've owned (all fuel injected) and I've looked at the evap systems on several other brands (fuel injected) that others have owned and have had trouble with........... and talked with quite a few people (professional motorcycle mechanics included). Evap systems on motorcycles and scooters are widely viewed by many mechanics and riders as a huge pain in the butt due to the fact that they have caused many problems for many a rider. What you do with yours is entirely your business. I can't explain it any better than I have.

That is the part I did not see linked to the issue of the engine stalling/not starting. Instead, I saw a restricted air intake into the throttle body claimed to be the culprit ("What [the clogged canister is] doing is inhibiting the engine from getting the air that normally passes through the canister. ")

Now it is all clear again. Thanks for bearing with me, XLR8.

What curious timing? I have noticed that my engine light has been coming on during revs but off at idle. I wonder if this is a VR issue that XLR8 mentions. I have to set up an appt with SDG's shop to have it check it out...

Just check the voltage at the battery with the engine idling and then again with it revving. You'll know quickly if the VR is bad because the meter will jump to well over 15 volts when you're revving the engine. BTW: If it's your VR, then it's cooking your battery every time you ride it and you'll need a new one if you ride it too much with a bad VR.

ronin, it is unlikely, but I would check it anyway: see if the hose from the evap to the brass ellbow on the cylinder is connected. Let me know if you are not sure where to look.

Mine had come off there and I had a CEL with high RPMs. Once reconnected, the CEL stayed off.

Checked the voltage at the battery terminals. Around 14.5V at idle and it spiked above 16V when I revved the engine and the CEL came on. Bad VR undoubtedly...

I want to replace it myself. I found a replacement part on eBay.
http://www.ebay.com/itm/Ducati-OEM-regulator-54040191A-fits-many-models-NEW-/160797542927?pt=Motorcycles_Parts_Accessories&hash=item257047ca0f&vxp=mtr

I believe this is the correct part. Before I purchase it, should I be looking elsewhere? Thanks...

RoninRacer: Yep, your VR is defective. The link that you posted to the new VR looks like the one that I replaced three years ago and I bought it from a Ducati dealer (and it came in a new Ducati parts box). It appears that you have the correct one. Here's a thread with that same part number on Modern Vespa: GTS Voltage Regulator / Rectifier Replacement Info HERE

Thanks for your help...Appreciate it...

I'm glad that I could help you.

I'm at 16 volts when at idle an up to 18.5 revving.

I could not find a link here showing how to replace one. Can anyone offer any guidance?

Thanks!