Modern Vespa

On the way home along a motorway, I had been belting it along at about 120 kph when the engine faltered and then cut out. Fortunately I was in the left lane (we drive on the left in Australia), so was able to pull over onto the verge.

After a brief stop, I tried starting the engine again. It started, but as I tried to pull off, it misfired and cut out again. So I phoned for roadside assistance.

After the scooter and I had been dropped off at my home, I tried starting it again, and it started perfectly. So now I have the hassle of locating an intermittent fault. First thing I checked was the spark plug lead, but that felt fine. There was plenty of petrol in the tank, according to the gauge.

Does this sound like fuel pump? My GTS250 is a 2007 model. I have a spare pump in the shed, but I understand it is a real hassle to replace one. Can one test it easily by disconnecting the hoses on the injector and switching on the engine to see if petrol is pumped out? (after it has cut out again and won't start).

I have left the battery on trickle-charge overnight, as it got hammered a bit trying to start the engine.

Mike

Edit: I suppose I can just switch on the engine/ignition and listen for the pump!

Mike, although you said you checked your spark plug lead, your problem sounds exactly like a loose connection, or short along the HT wire. I have had this happen to me more than once. The first time it happened it was because the lead had somehow become unclipped and was dangling on the exhaust header and the insulation burnt through causing it to short out. The next time it was the screw cap on the spark plug that had unscrewed. Your lead could also be coming loose at the coil side, or at the spark plug cap. I hope you get it sorted out one way or the other, intermittent problems are no fun!

Cheers,

Bob

Thanks, Bob. All I did was reach down there and tug the cord and cap gently to ensure they weren't loose. More detailed examination tomorrow (it is midnight here).

Just been Googling pump failures, and my symptoms don't fit the usual pattern, which is just hard (or no) starting when the engine is hot, not misfiring and cutout at speed.

See what the morrow holds.

Mike

It may, or may not be the fuel pump but the 2007 model year is not subject to the recall.

Ask me how I know.

I had a similar issue with mine summer before last, but it wouldn't restart without replacing a fuse. It wound up being a chaffed wire in the front of the engine bay ahead/above of the cylinder head. After taping and installing shrink tubing I haven't had an issue since. I was told this problem isn't uncommon for the GTS scoots and several have completely flamed out from this issue. The wire that was chaffed supplied power from the fuse block on the left side of the scooter over to the fuel pump and ECU. Hope this helps.

I saw this. Somewhere in the middle of the video robot talks about the spark plug cap. In addition to looseness he talks about checking the resistance of the cap. Sounds like an easy check for you just to be sure...



Bill

I just had my spark plug wire fail on my 2007 GTS. Pulled out from the boot. Luckily it's a very easy fix. Good luck mate.

-John

Thanks. My spark plug wire and boot all seem fine.

I started the scooter this morning, and it seemed fine. Then I jiggled some of the wires above the engine, and it cut out. The wires implicated were some for the Malossi ForceMaster 2. So I removed the ForceMaster and tried again.

The engine will idle, but won't rev above 3000 rpm. As it gets to 3000 it goes VROOmoomVROOooum, revving and then cutting back.

I realize the CPU has to reprogram itself to not having the ForceMaster, but I had the battery disconnected for about an hour while I was fiddling, so it should have more-or-less reset itself. Anyway, I have played with Lambda Emulators, the ForceMaster, and the PM gadget, and never had this before.

Time to do some Googling, but I hope someone on this forum will come up with an answer.

Mike

Do you have a way of checking the pressure the fuel pump is putting out?

Low fuel pressure would cause the symptoms you describe. Maybe worth checking before you pull the tank.

When the fuel pump relay went bad/intermittent in my bike it felt like it 'ran out of gas', which was different than the sensation of the plug wire going. Cheap to change out that relay.

Do you have access to a Digitek/navigator tester? Wonder what codes, if any are stored.

Good luck with it.

R

Because you own one...

Yes, funny how that colour only came out in that one year. I bought mine in 2008, but I had to hunt all over for the previous year's model to get that colour.

I don't have any method of testing the fuel pump. I do have a spare one, but it is a bugger to drop the engine and get to the tank. In the meanwhile I shall check the injector for blockage and make sure all the electrical connectors are clean. I expect I will be calling a scooter workshop to come and collect my scooter. Times like this I wish I still had my PX - they are so simple!

Anyway, I am stuck with a scooter that won't go, and I will miss the club ride on Sunday.

Mike

If you have a spare fuel pump, you can rig it with any fuel container instead of the existing tank for testing purposes, can you not?

First thing this morning I removed the injector and installed a spare one. Voila! Problem solved. Took the scooter for a ride around the block and all was fine.

Next problem - how to clean out the blocked injector and know that it will be useable again. Start with a look under a microscope to see whether I can see the blockage from the outside. Unfortunately one can't get to the inside to check there. Then shake it in petrol and try it in the scooter again, I guess.

Mike

OK, I was wrong. Scooter was fine going around the block, but as soon as I got out of the suburban speed limits and opened the throttle, the engine cut out. Wouldn't start again, until I had let it cool down, and then it would only idle.

Managed to get home, but I think it was running on pure gravity fuel feed. My neighbour, who is a car mechanic, and races motorbikes, has lent me a fuel pressure gauge, but I have to figure out how to connect it in line with the injector. He suggested checking the fuel pump relay. I didn't know there was one, so will have to consult my manuals and the web to learn a bit

Anyway, the main symptom is that the fuel flow fails when the engine is hot, and then the engine won't restart until it has cooled down. Sounds like the traditional fuel pump problem, except for the backfiring and cutting out at speed.

Mike

Have you got another cdi/coil you can try? My GT200 died on the way to work last week and luckily I found the issue straight away, it was a split HT lead and I had the same thing happen on my ET4 a few years previous.

I know you've already checked the cdi/lead but there still might be something funky going on with it!

Here's where mine split...

Mine turned out to be a faulty emergency cut off switch - the one above the starter button. Replaced, fine.

I've had this too. I usually turn the engine off with the key so I hardly use the kill-switch. The engine started faltering one morning on an uphill 80kmh stretch. I built an Alfasud many years ago so I have a well-placed mistrust of Italian electron plumbing, sure enough, I flicked the kill-switch a few times and the problem went away.

I should have returned to this topic with the resolution. I took my scooter to a local workshop, and they found it was a faulty spark plug. I had not checked the plug because I could not get the cap off to pull it out. But with 50 years of scootering, mostly on two-strokes, I have never had this sort of problem from a sparkplug. Anyway, all resolved and I am enjoying my riding again.

Thanks again to all those who responded with their suggestions.

Mike

I had the fuel pump issue too on '09 250 GTS. Then, it started cutting out again. Turned out to be a faulty kill switch. Only way to check it was to replace it. Have heard others with spark plug cap and wire issues on high mileage scoots.

Some 2007 were subject to the recall - from personal experience.