Modern Vespa

Hi all, 1st post for me on Modern Vespa. Great site that I've used a bunch already. I just recently inherited a 2001 ET4 150 (w/317mi) and a 2009 MP3 500ie (w/107mi). Both scoots have been sitting for at least 10 years. I was able to get the ET4 road worthy, but the MP3 is proving to be a much more temperamental beast. I have read sooo much on this thing and much of it has helped but I am at a scratch-your-head stand still with this project unless someone can recommend a next step that makes a difference.

The issue: Starts but will not stay running for more than 10-30 sec. Just dies/stalls out.

Originally would not start.

What I have done:

New battery, ytx14.
New premium gas.
New oil.
New oil filter.
Determined that the fuel pump was dead (at 107 miles). Dropped tank and replaced with Kesmo 13001 FP. Was able to blow through existing fuel filter. Reassembled.
Checked all fuses, ok. However the one at the coil(?) needed cleaning.
Tested relays as in the service guide, ok. Also swapped them around to see if that would make a difference, nope.
Burped gas line of air by disconnecting the gas line at the injector.
Cleaned throttle body with tb cleaner. Looked pretty clean to begin with.

Thinking spark plugs are the next to replace, even though they are virtually brand new(?).

Steering/suspension lock is not working, but is off. If I try to turn it on it just beeps at me and flashes a red light on dash. Immobilizer system is working fine but turns off as it's supposed to when key is turned to on.

Is there another system that isn't passing some diagnostic test and cutting the bike off?

Any advice on how to proceed, other than taking it to a shop, from here would be most appreciated.

That sounds like the throttle body bypass is clogged - old gas residue? See:
https://cheekythoma3.wixsite.com/itsme/idle

Thank you. Good read. Will pursue cleaning the throttle body again this time I'm going to pull it off the bike like I would a carb.
It did go from running rough and blubbering to much smoother and even through this process.
I'll post the results later.

and a ytx14 is to light its 12 amps it needs to be a ytx16bs 14amp or better a Mtx16bs motbatt 16amp 19amph

I cleaned it out quite thoroughly. The bypass plunger doesn't seem to want to move. Not sure if in closed or open position here.

View from front of tb:


View from back of tb:

Could that really be the reason for poor idle or stalling? You would think that once started the system would draw power from a stator-like thing rather than the battery. I could not find the oem requirements so I went what the battery mfg. said was supported.
That said, if I need to get a 16 to get it to run right then a 16 it is.

I think there was a slow speed stalling issue with that era MP3 500. I had a 2008 and the ECU needed a reflash at the dealer, for the same reason. Mine started and ran, but it would stall at every stop unless I revved it against the brakes. They charged me a King's ransom for it, but afterwards it started and ran MUCH better.

Ok, new MBTX16U motobatt battery installed.

Same issue.

Starts and runs at 2k rpm then idle starts to drop and shortly after cuts out/stalls.

I plan on getting the ECU flash at a dealer, but my closest is in Portland. I need to touch base with them.

If there any other things I should do or check that haven't been suggested so far please let me know.

Have you disconnected the fuel injector to see if it is producing a good spray of fuel, or have you tried adding fuel injector cleaner to the fuel tank?

I have disconnected the hose that goes to the injector to "burp" the line. Got good flow when I turned the key to on.
No cleaner or cleaning done to the injector itself. I think it's getting gas just fine at this point. The issue happens when the bike revs down to a normal operating idle.

I'm wondering if it is safe to disassemble the throttle body assembly to make sure all parts are moving as intended. I think that the bypass might be stuck closed, but I am unfamiliar with what the thing is supposed to look like to begin with. I was hoping that someone with that granular knowledge might be on here.

Vid of it in "action".
https://www.youtube.com/watch?v=tf7vK7cW_oE

It sounds like an ECU update is going to be your fix. I have a GTS with an intermittent stalling issue when slowing down to a stop. I've been told an ECU update should fix it, but I'm going to wait until I return back to the UK in a couple of months time as I don't know anyone with a PADS diagnostics in Cyprus.

Can you post the URL for the video clip? Many Web browsers (including mine) will only play the clips unless there is a link to click on. I think if you amend your post by clicking the 'URL' tab, cut and paste the video link address, then click the 'URL' tab again, we will all be able to see it.

Yes!
https://www.youtube.com/watch?v=tf7vK7cW_oE

When you talk to the Portland dealership ask them to check the history of your scooter. If you give them the VIN number they may be able to tell whether the updates have all been done or not. No point in making the ride up there and paying money for something that's already been done.

Thanks for fixing the video link.

You haven't mentioned the air filter. Have you checked it for debris or for over oiling?

Air filter was checked and was clear and not over oiled. Also same symptoms with stalling at idle without air filter hooked up.

Good point, will do.

When I had this problem on my 400 (twice) it was the throttle body, which needed cleaning.

I wish I could find more info or pics on a healthy throttle body.

Probably you need to clean the throttle body, in addition to the throttle valve there is a little duct where the air necessary to regulate the minumum level of rpm is regulated by a little step by step motor, if this duct is dirty by oil or sludge deposit it's necessary to clean the duct, in this way after it was clean the level of minimum is too high

I cleaned the throttle body twice including the bypass duct, thoroughly. It was practically spotless to begin with. The scoot has just over 100 miles on it. The pictures above in the thread are of that duct. Either the duct is being mechanically blocked because it's frozen or the step motor is not working correctly or both. But as I've said I have no basis for comparison and that's conjecture. I've thought about taking the throttle body completely apart to make sure things can move, but I'm not sure if that's a good idea.

I need a TB specialist.

So before attempting to take the TB apart I filmed what is happening.

https://youtu.be/aIW__mbsAH0

So, yeah after this I started disassembly and of course one of the throttle flap screws stripped.
I've already drilled through the screw. Now I get to buy a screw extractor and a new screw to add to the this project!


I normally just jump into taking things apart and putting them back together...and it works out 95% of the time. Sometimes I get curve balls.

What a pain in the

It sounds like you got a leak some where air is leaking at the manifold (black rubber pipe) or injector

Wouldn't that cause uneven/irregular engine running?

Edit: Let me say that I really appreciate all the tips and help here, seriously.

I checked the injector like you suggested. I had pulled it early on in this project before I replaced the fuel pump. You know, don't think that I had it seated all the way down. It took some doing.

So, thank you Maksor! Now I just have to repair the throttle body that I buggered up the other day.

Probably you need to control the fuel pressure, you have changed the fuel pump? Sometimes the problem is in the fuel pipes, if you don't have the minimum pressure the engine stops, you must control the pressure generates in the circuit

Amazingly I was able to put the throttle body back together and install it. Also reseated the injector.

Exact.same.issue.

It starts fine and runs smooth. A few seconds later as the idle drops to a normal set idle the engine cuts out.

A suggestion was made to adjust the fuel pressure. How is that accomplished?

Today I flushed out the injector with cleaner.

It ran a little longer but still is having the same result of the engine just cutting out.

This time I paid more attention to the rpms. It starts at around 2000 then goes back down to around 1200 and 1100 before cutting out.

Anyone?

It's doing exactly what my 2008 did, and that completely went away with a computer firmware update. I also went through all the stuff you've been doing. With mine I couldn't come to a stop and use the lock to hold it upright because I had to run the engine too fast to keep it from stalling.

Thanks wentwest! Looks like my next step is a trip to the dealer up in Portland.

thanks for the info, I have an issue and need to replace the battery, it is good to know there is an option,
the link to the issue is:
MP3 400ie, 2009 model: when starting up first time...

thanks again,

you never posted a resolution to the issue. I have a same problem with my GTS250. looking for tips

hi, is that addressed to me?
I recommend in future to use the quote which is top right side of the comment,
cheers,

I have an appointment to take this lemon to the vespa dealership in Portland on June 10th. Will let you know what happens. The first thing we try is going to be an update since a couple different people have stated that it was a successful fix. Stay tuned.

Was that one of your bikes at Vespa Portland Thursday? There were two of them which is a very rare sighting these days. If it is you not to worry. There mechanic is an MP3 specialist and will hopefully figure it out quickly. He's the only person servicing my 2009 to date with zero complaints. Good luck, hope to see you on the Portland streets soon!!

Hi, yes it was!
Tom and everyone up there were great. They updated the ecu and were able to diagnose that the issue is with the fuel pump. That means either I did something wrong when installing it or the fuel pump itself is a pos. Getting into it this week. Then tires and break-in time. I'm in Eugene, cheers!

Awesome! Sorry you had to eventually take it to the shop but at least you brought it to the right people. Hopefully you'll be able to finally get on the road. I have complete faith in Pablo's mechanic skills, wouldn't bring it to anyone else.

I have no doubt in their mechanical skills. For me it's the money involved. I just don't have it.

Solved!!!!

Turns out it was cracked plastics inside of the fuel pump assembly between the pressure regulator and the fuel filter. Unamused by the potential $550+ purchase of a new one (640315) I decided to do a bit of plastic welding with my cheapo Harbor Freight soldering iron. I mean it was hosed already. But it worked! No more idle issues. It just purrs and runs as it should. No more engine dying!

AWESOME find and great fix. Congrats

If you know anyone with a 3D printer it might make for a fun challenge if they would be up for printing you a replacement part. There are materials that can be fed into the 3D printer that would hold up well when immersed in fuel.

Also, congratulations on a successful fix !!! Double thank you for sharing the solution with the community. Someone somewhere may have a similar issue and this will help solve it.

not all plastics are the same though, so using a 3d printer you would have to ensure your using gas resistant plastics.