Modern Vespa

about 8 months ago, our GTS 250 stopped while riding home (thread here Ugh, GTS 250 stopped. Now fixed! (I hope) ).

After replacing the coil and ECU it still looked like it was not fixed, so transported it to Sydney (120km away) to have a dealer look at it. They 'checked the wiring' and changed the plug and it worked, but they did not really find what the problem was.

It was running fine for some months, but a few weeks ago it stopped on a lonely country road just before sunset. A major PIA! Check with plug held against engine block showed there was no spark.

At home, I started to troubleshoot. Noticed no sound of fuel pump when turning ignition on. Starter motor will turn the engine over, but there is no spark and obviously engine will not start.

A check of the fuses showed that fuse 3, the 10 Amp fuse on the left side of the scooter under the seat feeding the load relay had blown. Replaced the fuse - it blew instantly when ignition turned on.

Remembering Arno's thread with the same fuse blowing (here This mystery appears to be solved. Basta! ) I started investigating with a multimeter. Removed the load relay and probed the socket at terminal 87 (load side of the relay) and the chassis. There was a short. Hmmm, looking at the wiring diagram, it looks like it could be a short of the wiring, or one of the services fed by the load relay - fuel injector, fuel pump, coil, or O2 sensor.

The easiest plan of attack seemed to be to check for obvious chafing of the wiring harness and then start disconnecting services. It was easy to disconnect the fuel injector and O2 probe - still a short. disconnected coil - still a short. Fuel pump is tricky, so uncovered the first 12-18 inches of the wiring harness from the load relay - still a short present.

Bit the bullet and started taking the scooter apart and dropped the tank far enough to disconnect the electrical connection. SUCCESS, no short present when disconnected. Tried connecting and disconnecting a few times to replicate the issue, just in case it was a disturbed wiring harness that was producing he short. Definitely a short when the pump is connected.

So, I am guessing that this is the issue. Also, the pump problem is different from the fuel pump recall, where the impeller was expanding due to high temperatures.

Guess I will now have to order a new pump...

After pump replacement, all appeared well for a day or so. 10 amp fuse that feeds the pump, coil, O2 and injector blew again. Interestingly, it blew after starting the scooter when pushing the scoot off the centre stand. Replaced the fuse and drove home.

After getting it home, the 10 amp fuse was blowing within moments of turning on ignition.

My previous assessment of the fuel pump being shorted was probably erroneous. Looking at the wiring diagram, the pump is connected to ground through the windings of the pump motor, so there will be low resistance measured if it is connected - stupid me.

I unplugged the fuel pump/fuel level wiring harness at the connector at the forward end of the underseat area. turning on ignition still resulted in a blown fuse. I connected the multimeter between the load side of the relay and ground and could see a very low resistance. Left it connected while I started unplugging the O2 sensor. The multimeter started showing the resistance changing as soon as I started to manipulate the wiring attached to the O2 sensor plug. Now, after manipulating that wiring, the short has disappeared. Not sure if the short was in the plug/socket, the wiring in the loom connecting to the plug or the wiring leading from the socket to the oxygen sensor. After pulling and prodding the wiring, I cannot reproduce the short and the scooter starts and runs fine (even with a 7.5 amp fuse in place that I was using during the troubleshooting).

[edit] additional information that may help diagnose problem:

When the shop 'changed the plug' (but could not find any specific cause of the non-starting) - the one they took out was quite carbon-fouled. Also, after thinking it was fixed after pump replacement and it blew a fuse, when I got it home it was idling fast-normal-fast-normal... Would these two symptoms relate to an oxygen sensor issue? [edit]

Advice for the best way to proceed? I have been a bit stupid, throwing parts at the problem to no avail. My thoughts are to strip the harness outer covering at the loom connecting to the plug to the oxygen sensor and look for any obvious problems.

I guess it is (hopefully) good news the the general location of the short has most likely been narrowed down. In frustration I was thinking that I might have to replace the whole wiring harness.

Hi all,

I had my Vespa quit on me twice during the recall crisis a few years ago. The second time was on the highway coming home from the shop after they replaced the pump with a pre-recall model. To be fair to the shop - this was at the time Vespa was still calling it an "upgrade" and not very open about the situation. I finally did get the correct replacement pump and all was well.

Fast forward several years later and about 6,000 miles. No problems to speak of until last week. I was on a 100+ mile trip in Maryland, riding pretty close to full throttle (about 68mph on the GPS) in 95F+ weather. About 45 minutes into the trip the Vespa conked out. Lucky for me, I was able to maneuver to the side of the road without getting run over. Being all too familiar with the symptoms I knew it was the fuel pump and 30 minutes later it started up and ran as though nothing had happened.

I realize I was pushing the bike to the limit but, my friends, this is the third time the bike had quit on me while driving in traffic. As much as I love the bike, and I really do enjoy it, this was the last straw. Each time the bike failed I was traveling at decent speeds in traffic and it could have ended ugly, think about what GM is going through with faulty starter switches today. I simply don't have confidence in the bike anymore so this weekend I went to the dark side and purchased a non-Piaggio scooter replacement.

It was a hard decision. I have a lot of passion for the bike, but I feel I used up all my lucky charms and don't want to re-live going from 55 to 0 on a busy highway, running with the bike in the middle of the road to try to get to safety. That is not the kind of excitement I want to repeat.

With all that said, its time to say goodbye to a great community of people on this forum. The help, the humor, even the snide remarks added to the enjoyment of being a Vespa owner.

Good luck to you all!