Modern Vespa

The spring weather has finally arrived here, so over the weekend I picked my bike up from the garage where it has been sitting unused for three months. It started up without any problem, and everything seemed fine on the 30 minute ride home.

I parked it, and due to rain it sat unused for the next two days. Yesterday, intending to commute to work, I got on the scoot and started it up without incident, and pulled away. I only made it about 15 meters down the street however, when it stalled out -- a rare but not unprecedented occurrence. What was unprecedented is that the scoot would not restart. I could hear the sound of the engine trying to start, but it would not turn over. After a few minutes I became concerned that I would wear down the battery, and parked it.

I am hoping that there might be a quick and easy fix for this so as to avoid an expensive tow to a Vespa dealer. Are there any user serviceable bits or pieces that I can check or try (especially things that can go wrong after sitting for three months) before I declare defeat and call a tow truck? I should add that previous to this, I have had absolutely no mechanical problems with the bike during the three years I have owned it since new.

Thanks in advance.

Check the vacuum line that opens the fuel tap. If that has come loose or is cracked, the fuel tap won't open. The motor will run until the fuel in the carb bowl is exhausted and then quit.

Oh wait... GTS250 is probably fuel injected. No fuel tap, just a fuel pump. Next thing I'd check would be the spark plug boot. Make sure it is secure on the plug.

-Craig

Does the fuel pump usually whine/prime when the key is first turned on; on the 250s?

I would suspect the fuel pump. You can remove the spark plug and see if it smells like gas(good pump, functioning injector, computer controlled), then check for spark(good coil, computer controlled).

If you have no spark, and no gas, it could be that the computer is not getting the (rotational) pulse signal from the engine.

Agree with checking for a loose spark plug cap as others have had this problem. Replace it if it is loose.
Try rebooting the computer by going to the battery and pull the positive wire off the battery and after about a minute reattach the positive wire...rebooting is done.
You can pull the fuel line at the injector, put it in a jar or can (that can catch the fuel) and try starting the engine...fuel should pump into the jar...if not you are not getting fuel to your engine...might have a plugged fuel filter or bad fuel pump. Good luck.

First, ensure the battery is fully charged using a battery tender - you've made no mention of battery care whilst the scoot was laid up.

Then when turning the ignition on, check that the code LED flashes once then goes off, and that you can hear the fuel pump prime.

Do not twist the throttle when attempting to start.

If it doesn't start, check the condition of the spark plug cap and HT lead. Ensure they are clean, dry, and fully screwed together. Ensure the cap is fully engaged with the spark plug.

If it still won't start, check the condition of the spark plug, and test to check you have a good, strong spark.

If it still won't start, report back and we can move on to testing fuel injection etc.

Many thanks for all of the helpful replies so far.

Yes, the bike is fuel injected, and the battery seems fine (although it was probably not started regularly for about 90 days or so) and the electrics on the dash light up properly when the key is turned and seems alright. Whatever is failing seems to be the next step which fails to complete the ignition process, so spark and fuel seem like the most likely culprits.

I opened and closed the fuel reservoir to make sure its not a vacuum issue, and I also pulled the pet carrier and made sure all of the connections seem tight. I located the plug boot (at least I think I did, green connector?) and it seems tightly screwed into place. Still, no joy.

Could it be the plug itself? Do these things just go bad suddenly. Is it worth trying to unscrew the plug and replace it? If so, does anybody happen to know the part I need?

I will also try rebooting as suggested. I'm afraid that if its a bad fuel pump, I am then already well outside the realm of measures I can take by myself to rectify it, and if its something like that might as well just call for the tow and let the dealer handle it.

Thanks again.

Can you confirm that you hear the fuel pump prime when you switch the ignition on?

With modern capacitor discharge ignition systems and better regulated air fuel ratios, spark plugs (almost) never fail, but they are still a great diagnostic tool.

I wish I could answer that question, but I'm not sure what I should be listening for. I do hear the regular "whine" of the engine that I am used to hearing when I press the ignition button. I'm not proud to tell you that I've got no idea what component or components make that particular sound (or combination of sounds). Is there any distinctive sound that the pump makes that I could listen for?

Thanks.

Yes.

When you turn the ignition on, *without trying to start the engine*, you should hear the 'injection load' relay click and the fuel pump whirr for two seconds as it brings the fuel delivery system up to pressure. If you don't hear the whirr, ensure you can hear the click of the relay - if you can't hear that, chase down a blown fuse. If you can hear the relay, but not the pump it may be either a faulty pump or duff contacts in the relay. A multimeter will help here, as will taking a look at the circuit diagram.

Great, I'll check if I can hear those sounds. Might it be easier just to pop the fuses and eyeball them? Can I tell if one of them has gone bad by visual inspection? Or is there more to it than that?

Thanks again.

Yes, look for the melted down connection thorough the clear portion of the fuse. Do an image search on the web for "blown fuse" to see an example.

Well, thanks to all of the great information above, I was able to diagnose the issue.

I put my ear close to the engine to listen for the relay clicking (and heard it) when I got close enough to see that spark plug boot, although seated on one end, was actually disconnected from the cable on the other (I didn't realize yesterday that there was another piece to it). Sure enough, I saw the other connector dangling unconnected.

With great difficulty, I was able to reach around, and reconnect the cable to the spark boot -- and the bike started. I didn't think it felt like a very secure connection, and I was right, it conked out again before I made it around the block when the connector came unattached again.

It seems to me that part of the connector is missing. I suppose some duct tape might do the trick temporarily, but I think I will have to bring it in to the dealer -- at least now I think I can avoid the expense of the tow.

I should mention also that the bike was in storage at the dealer after they finished a large body work job. I'm wondering if the fact that the spark boot cable fell off 30 minutes of riding later is coincidental, or if it might have been damaged in the course of the body work.

In any case, many thanks for the very helpful information.

The HT cable screws into the spark plug cap - take off the cap, and inspect the screw terminal inside. If OK, cut off 1/4" from the HT cable (to ensure 'fresh meat') and screw the plug cap onto it. Then reinstate the cap onto the plug.

Have you now found out what the fuel pump sounds like at switch-on?

Yes, I did figure out what the fuel pump sounds like, and it is in fact pumping. I never noticed it before. Thanks again for that advice.

I suspect that I have a piece missing from the cable. There is a little rubber thing, but nothing with a screw cap. I have a feeling that it must have broken off. Hopefully I can manage to jury-rig it to drive to the dealer under my own power.

Take detailed close-up pictures - then we can advise better. Well done following so far.

Well, I think I am nearly ready to call this a success. Yesterday, I spent a few minutes reconnecting this, and took it for a few test drives with no issues (except that I had one single occasion of a rough start -- could be related or not).

As can be seen in the picture, I had the wire running from the front of the bike (being held with pliers), and the connector "boot" attached to the spark plug (to its left). Not shown is a rubber nipple that I think was once holding these things all together. Space was very tight and there was no slack, and a long pair of needle nose pliers was necessary to grab the cable, and reattach it to the narrow end of the nipple. I then jammed the larger end of the nipple to the spark plug boot to connect it all -- and the bike started without any issue.

I am worried though that these are not connected as snugly as they should be, and that this will be susceptible to coming apart again. I think from other photos I have seen, that there is a metal crimp connector holding everything together -- I couldn't find anything at Home Depot which was similar. Instead, I reverted to duct tape, which is now wrapped around everything -- not too elegant, but it seems to work while I look for a more permanent solution. Any ideas in this regard?

Many thanks again for your kind assistance. It makes me very happy that I saved a tow to the dealer, and several hundred dollars.