Modern Vespa

It happened twice, about 300 miles apart. 2007 GTV 250ie, runs a few miles OK, then coughs a little (a few seconds) as if running out of gas, then the engine stops and does not start again. The first time, about four hours later with the engine cool, I wiggled the spark plug cable a little, the engine started and everything was OK for about a month. Now it happened again, and I just changed the spark plug and I know it works - I can see it firing merrily when operating the ignition with the spark plug touching the engine block. Cleaned the air filter recently, and there surely is enough gas in the tank. But the engine won't start again. Any suggestions as to what I may try next would be greatly appreciated.

Do a search on "fuel pump."

You have lots of company.

Currently, is your GTV not starting at all (even from cold), or is it stalling?

If it's stalling try this-
Next time you do a long run undo the gas cap & see if the tank's under pressure/vacuum. If it is you have an evap system problem:
EVAP Hose Removal
How to remove or disconnect the Evap Sys. from GTS/GTV

Do you have a engine management light on? Have you tried to run a tank of fuel with Seafoam? I know every once in a while my GTS will sputter at Idle and in my case I believe is was a injector problem. Perhaps not spraying correctly. A tank of gas with cleaner in it fixed the problem.

PS what mine did at a stop was at first it would idle ok. Then the idle would drop and then bounce back up near correct idle speed. Then thru a few of these cycles the idle would get so low it would stall.

It is not starting at all, even from cold.

The "check engine" did mysteriously come on about a month ago while riding, but then it went away after I turned the engine off and on. I am not sure that was connected with the current problem.

OK, I'll search the fuel pump discussions and let you know how things turn out.

That's harder to troubleshoot, but here's the workshop manual's take on it: You can find links to the workshop manuals in the Modern Vespa wiki.

I finally figured out the problem. The fuel injector was broken. If I knew at the beginning what I know now, this is what I would have done. First, I would have disconnected the fuel injector connector (the red arrow points to it on the bottom image below). There is a metal clip that needs to be pulled out to take off the connector. Second, I would have measured the resistance between the two fuel injector contacts. I would have noticed that the resistance was not even close to the prescribed 14.5 ohms, but closer to infinity. Also, I would have noticed some obvious cracks between the plastic connector and the injector body (red arrow on the top picture below).

I just installed a new injector and the engine started purring for the first time since it left me stranded.

Thanks again for your help.

Have the O2 sensor checked.

Why? Is there a reason to suspect the oxygen sensor if the injector broke down?

Scratch that, my mistake, I typed this after too many beers and not enough reading.