Modern Vespa

I have been going crazy for the past week trying to figure out why my Vespa doesn't have spark and won't start. Ive worked on plenty of scooters before but never had an issue like this and I'm hoping you guys can help me out. I have an identical running Vespa for testing parts and trying to isolate the problem part by part.


I did find a wire that was rubbing that goes from the harness to the coil pack. SEE PHOTO. I repaired the wire with a crimper and the connection is solid now. STILL NO SPARK

Here's the run down of the trouble shooting I've done:

Battery: brand new and fully charged. Connections are tight

Fuses: glove box, and left side and front fuses under the storage are all good.

Fuel pump: I just replaced it to eliminate any issue of no fuel delivery. It does turn on and it does produce pressure when the key is turned to the on position

Spark plug: works. I tested it on the running Vespa. Does not produce spark on this Vespa

Coil pack, boot, and HT wire: works on running Vespa, does not produce spark on this vespa

Kill switch: I didn't take it out as the bike starter does crank. If the kill switch was faulty, the starter wouldn't crank

Voltage regulator: tested and works fine on the other Vespa

Stator: coils are in good condition. Checked ohms and it reads around. 03 to 05 on all three phases at the connector with the three yellow wires. Unless I'm mistaken, I don't believe the stator controls spark to the coil pack. I've never had an issue with the charging system so I'm going to rule the stator out.


I put the bike back together minus the plastic panels and rear wheel. So then I decided to try and start it with the brown key AND I GOT SPARK FROM THE PLUG! I was jumping and celebrating because finally I had spark. then I figured maybe the blue key was bad so I put the blue key in AND NO SPARK. so then I put the brown key back in to test for spark again. SPARK IS GONE! I've almost run out of patience. I can't get the spark back. Could it be the ECU? I haven't heard of these going bad.

Please help!

You have a faulty immobiliser,
I would first check the wires and if ok,then replace the round anttenna thats clipped into the rear of the ign lock barrel.
Not uncommon but quite rare.
Cheers andy
Ps you can have your keys checked by a code reader at a fiat garage.

Andy,
I appreciate your response. I tested the antenna that's clips around the ignition on another running Vespa 250. It had no issues starting that bike.

So now I'm looking at the codes showing up on the leds in the speedo.

The red led constantly blinks when the key is off as normal to show that the ECU is working.

I turn the key to the on position and the red light blinks once for a second then twice quickly for half a second and then goes away.

At the same time, the amber check engine light comes on for 4 seconds off for 4 seconds then stays on.

You deffo need to get it on the piaggio fault code reader, there will be stored codes, because from now on buying and swapping parts becomes very expensive on a guessing game.
Sorry i cannot be of anymore help, but you have youself explored all the other avenues first
And the last bit of advice is where i would be at now.
Dealer then part with 50 bucks come out with diagnostic piece of paper.
Cheers Andy
.

Andy, I've pretty much taken every electronic component apart and tested resistance and continuity. I ordered the diagnostic software from scooter West for the gts. Hopefully, I can finally get to a solution. I've spent close to 27 hours diagnosing this scooter. My friends and family are worried. LolLol. I'll get back with my findings

From page 30 of the GTS workshop manual: From page 31: It would seem your immobilizer recognizes your Red/brown key, tells you two other keys are programmed, and enables the ignition.

I've circled exactly what is happening with the red led. The led goes off after the quick two flashes. Now that amber check engine light.... I have no clue about.

But what you have circled indicates the red LED stays "on". You previously stated it went out, after the two short flashes.

Your description more closely looks like item #4 below ( the amber LED is a totally different problem, and likely the reason it will not start, not the immobiliser)

Which key are you using? Do you get a different red LED sequence when you use the other key?

Starreem, crap I read it wrong. You're right. All I have left is that the amber light comes on, then off 4 seconds then back on and I can't start the bike because there's no Spark. So according to the ECU it should be ready to start. It does crank no problem every time but no luck on spark for combustion

I used the master key and the blue key. Same sequences for both

So, if the immobiliser checks out, it's looking like an ignition fault.

How does the ignition determine it needs to fire? There must be some sort of crankshaft position sensor, surely?

At this point, you will need to wait for the scan tool you ordered to determine the fault codes stored as indicated by the amber LED that stays on. Curious though that you get the same red LED sequence with both of your keys. I just went out and tried mine, and I get the three blinks with my red/brown master key, but only one blink with my blue service key.

Please come back and report what the problem was.

OK so I finally got my diagnostic tool from scooter West. However, when I plugged it in it wasn't working. I called up techno research and they said they had a bad Vespa software out and sent me a new update. It wouldn't receive a signal from the diagnostic port though.

When I looked at the pins on the port and the diagnostic tool, they didn't line up so I took them out of the connector and connected them individually to each prong.

Anyway, I finally got a code to the mysterious no Spark issue.

P0335 crankshaft sensor error.

Anyone know where it is and where I can get one?

I found out from the service manual that the crankshaft sensor is referred to as REVOLUTION TIMING SENSOR. Can't track the part down on the engine itself or online.

Hi buddy,
The sensor that its refering to is the pick up on the side of the caseing where the flywheel and stator plate are
Good luck
Andy

andy, thanks for your response. is it on the wire connected to the stator that screws into the case with two screws?? a photo would be more helpful.

Hi 86,
As Andy points out, That sensor is screwed inside the the same cover as the the stator coil. The manual shows it above the coil. Maybe it got jostled out of place or disconnected when you pulled the cover off?

Bill

Here is the inside of where the stator goes. Can someone point to me where the crank sensor is?

That's the only sensor I see that screws on to the casing

I am in now way someone that has any mechanical prowess... But I've read your posts over and over and it sure reminds me of when the fuel injector went belly up on my bike, also a 2007. Luckily, I only paid for a tow and a new battery I really didn't need before it was diagnosed and fixed.

Sure sounds like a lot of the same symptoms... to me.

Yes, that looks like a typical crank sensor. As the rotor turns there will be 'something' that triggers the sensor. Normal (car) practice is a toothed wheel with a 'missing' tooth. But it could be a groove machined in a smooth surface..

Unless the ECU gets a 'signal' from the CPS it can't trigger either spark or injection. In fact, it doesn't even recognise that the engine is turning.

This is the 'phonic wheel' arrangement on a Paton racer. You can clearly see how the system works..

Piaggio doesn't sell that sensor separately apparently. I'm going to order a new stator and hopefully it can finally fix the no Spark issue. Thanks for your help. I'll report my findings next week.

did you ohm it out? when you get the new one please measure the cranking voltage ac?
On some the space/gap to the rotor can be a problem.

John

John, the stator checks out, but the pickup sensor i'm not sure how to measure. I never had a charging issue so I didn't think anything of the stator. Come to find out, the pickup sensor with the magnet is also the crankshaft sensor or "revolution timing sensor" as the piaggio service manual calls it.

Looking at the sensor and how it's a part of the wiring harness for the stator, i don't even know how to test it for ohms. But anyway, I should be getting the new part some time mid next week.

I have absolutely no experience of the Piaggio system. Zero.

But, as a general rule, a CPS is tested like this..

Identify the two wires that come from the unit. Using a multimeter, set to the 'resistance' scale, measure the resistance through the unit by placing the two probes from your meter on the two wires. You need a resistance. Exactly how much is not actually important, but it needs to be there.

Next, keeping the probes connected across the unit, switch to 'AC Volts' scale on the meter and crank the engine. You're looking for a 'rising' AC (the figure increasing as the engine turns). Again the actual figure isn't important.

If you have a resistance and a rising AC then the CPS is presumed good. If you are missing either (or both) then it isn't.

Without a signal from the CPS the ECU doesn't recognise that it needs to trigger either spark or injection. You have tested (or swooped) just about every component apart from the CPS, so, logic dictates that's where you need to look.

I would actually look there first (having had lots of trouble with them over the years in the course of my work). Symptoms often include intermittent spark and losing the spark when the engine is hot. Like all modern electrics they are very reliable right up to the point where they're not..

I just wanted to add to this (what you call CPS I call a pulse coil/pick up) some use two wire type and others one wire. The ones that use one wire ground to where they mount. I also have a 2007 GTS and would like to know the voltage from the pulse coil.

John

John, I think we're both right. It's probably a 'pulse coil acting as a crank position sensor' (and I don't want to type that more than once ).

I'm not familiar with the single wire type but, as I said, I'm not a scooter expert. Presumably the tests I mentioned would be done between the single wire and earth (ground)?

And, yes, it would be good to know an actual figure for both resistance and AC.

You guys were right about that pickup sensor that comes out of the stator. The old stator yellow wires from the brown plug are reading properly on the ohm meter. The other plug for the sensor aren't registering any ohms on any of the wires.

The new part reads. 013 to. 014 on the 20k setting. THIS HAS TO BE IT. I'm going to put the bike back together right after I finish a valve adjustment now that I have the engine dropped. I'll get back to you guys soon!

It's alive! Finally I have spark. it was definitely that stator magnet sensor. What's crazy is that the stator is perfectly fine. I did the valves while the engine was dropped and the stator and 3 screws came out to $109.95 at the dealer.

A little tear came down my cheek as it came to life after weeks of going crazy over this thing.

Thank you everyone for your help. I couldn't have done it without your guidance and advice.

Thanks for the update. Really pleased that you sorted it in the end. Perseverance pays!!

Hi all! glad you sorted your Vespa
i do have a question regarding the stator plate.
i have in program an engine conversion from a gt 125 l to a 250ie engine and carb converted.
i was wondering about the stator plate connection. i know there is two plugs and both of them have 3 wires. the one coming from the stator are the 3 phases and that is clear to me....but what is the other plug doing? the wires are brown (this is the oil pressure sensor i believe) , red and white i believe. i don't know what they are doing
if someone knows please can you share? i can't find any infos regarding it.

thank you

HI. I dont know if it makes any sense for you to get a reply that late after 3 years, but may help others.
The three yellowfins wires are coming from the stator coil to the brown ( on older GTS) or white on the later GTS plug. The other plug IS for the crank position sensor.

Dear all,

very glad I came across this thread. For future troubleshooting:
Had the same issues (intermittent loss of ignition, engine stalls when warm, not starting up until cooling down). Resistance measures through the pickup yielded faulty values (40 kOhm when hot, 120 Ohm when cold).
Replacement of the stator plate was also the solution to me.

All the best
Mo

Failures with the pickup or ignition coil have to do with very small wires in a coil that break. As they warm up the wires heat and move apart, causing the failure. As the component cools down the wires come together and the machine works again.

If one suspects one of these components you can't just ohm the connection because you don't know the value when the part heats up. You can either bring an ohm meter on the test ride and test the value at the plug or isolate the component and heat it with a heat gun and watch the ohm reading. You will normally see the ohm reading change after about 60 celsius. Unfortunately you still have to remove the stator or ignition coil, but that is the only way to bench test things that have small coiled wires. BTW, these internal wires are between 0.5 to 0.7mm!

In some cases you can test in situ, in other cases you have to remove the component and bench test.

Hello!

Thanks a lot for this input.
As for the GTS300, I have the plug easily accessible, as shown by the thread initiator. In cold state, it measures valid values (120 Ohm). When the problem occurred, around 5..10min after engine start, readings became absurd, later jumping to around 190 Ohm for a millisecond only to show no conductivity afterwards.

When disassembled and heated up with a regular hair dryer, values would rapidly rise to around 3..4 kOhm (from initially 120 Ohm). I cannot imagine that this is the proper behaviour.

I'm eager to open the pickup and check the inside. But the case is cast and not easy to open.

Also I noticed, the circumferential surfaces of my stator plate (small rectangular metal faces)
have very suspicious residues, which looks like rust (but could hardly be, since sitting in an oil bath) or very robust oil residues (which is also not likely because the rest of the case looked impeccable). Photos are attached for the curious. Very glad to finally came to replace this part.

Cheers Mo

The "inside" of the pickup, see photo. Additionally there is a rectangular magnet cast in opposite of the flywheel above the coil.

I recently had my Vespa scanned and got the PO335 code. But im able to drive it which obviously means I have spark and fuel. It's been driving fine over a week with code PO335. Also got the code PO130 so I need to replace my oxygen sensor. I'm wondering if the oxygen sensor is throwing off the crank sensor but still no idea why I'm able to drive around fine with code PO335. I'll start with the oxygen sensor and see if the code PO335 goes away. After all if my crank sensor was really bad then I wouldn't be able to start and drive everyday.

Scanned by the dealer with the Piaggio scanner - or using an aftermarket one reporting generic codes?

The codes are the same, only the descriptions will differ.