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BV350 died the other day when I was going to get gas. Started missing while I was riding, pulled up to the pump and it stalled. Thought I had run out of gas till it only took 2.2 Gal.
Finely got it to start and gone about 1/4 mile and it died again.

Started by checking battery connections then looking at the spark plug cap, swapped it out to be sure, looked fine. Still no start, called tow truck too hot to work on it on the side of the road.
Got it home and it fired right up, Son of a Bitch. So grabbed a few more tools and took off once the sun went down. After about 30 minutes of riding it started running bad, missing at less than half throttle. Opened throttle up and she took off running fine. Then pulled up to a long light and it dies again.
Pushed it half way home till it finely started.
Had good spark, squirt of starting fluid and it ran for a few secs, so it is a fuel issue.
Next day started doing research and find it takes the same fuel injector as the MP3 500, so what the hell, there is a small chance it could be the fuel injector and not the ECU.
Threw in the injector from my parts MP3 500 and it fired right up and ran great. Headed to the parents house for dinner no problems on the way there, but on the way home it started acting up again, made it home.
From reading and testing, all I can determine it that my ECU is failing at temp.
Luckily found a new one on Ebay for $324.00 so saved $200 over the dealer.

We'll see next week how good my diagnostic skills are.

Now to start reading up on how to program the ECU to my key.
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Bummer. Sorry to hear about your trouble. Hope you get it sorted out. Thanks for sharing! 8)
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Sounds a bit too much like my diagnosis methods --- tossing parts at it -- see if anything sticks to the wall?
I suspect you're already wondering the same.
Here's hoping you found the part that sticks!
Do you have a scooter specific manual - with trouble shooting section?
O.S.
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Had a customer with a similar problem on a Beverly 300 Tourer. Narrowed it down to the RUN/OFF pin on the ECU. Gave him two options. New ECU or trying something that might work or not. Warmed the pin with a soldering iron. Three years now, he only comes for regural maintenance...
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OldSchooot wrote:
Sounds a bit too much like my diagnosis methods --- tossing parts at it -- see if anything sticks to the wall?
I suspect you're already wondering the same.
Here's hoping you found the part that sticks!
Do you have a scooter specific manual - with trouble shooting section?
O.S.
Yes, used the BV350 manual. From everything I could determine, it points to the ECU. I don't throw a $325 part at anything. I tested with what I had and with process of elimination it has to be the ECU.
Got spark and know I have compression, fuel injector is good. If it's not getting gas and the fuel injector is good it has to be an ECU heat issue. Tried putting my heat gun on the ECU but was afraid I was going to melt something if I got it any hotter than I did.
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Ugh, I dislike hearing stories where someone's bike leaves them stranded, but I hope that you've got this one sorted out - and that my BV 350 doesn't feel the need to share the experence...
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Throttle body gets here tomorrow, may not have time to install till Wednesday though. Unless I can get out of work early today and get the old one off. Hum, may have to "Work from home" for a few hours today, it's dead at work today, the internet seems to be working fine so I am not needed.
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Smells a lot like a GTS fuel pump problem.

w.
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Bald Wasp wrote:
Smells a lot like a GTS fuel pump problem.

w.
Fuel pump is running. Thought about that sitting at the gas station, so I listened for it.
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sounds like a fuel tank vent issue to me. a blocked vent line will cause fuel starvation as this is because of the vacuum effect. once the scoot sits for a minute pressure equalizes and fuel can flow again but only till the vacuum effect takes over again. loosen you gas cap and see how it runs.
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old as dirt wrote:
sounds like a fuel tank vent issue to me. a blocked vent line will cause fuel starvation as this is because of the vacuum effect. once the scoot sits for a minute pressure equalizes and fuel can flow again but only till the vacuum effect takes over again. loosen you gas cap and see how it runs.
Evap removed and can blow in the tank and it comes out the vent hose.
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The way to check a fuel pump is not by sound alone. Fuel flow to the point of injection is the question?
While I've never had the Vespa fuel pump out ethanol plays havoc . Many PTW's use fuel pumps that can be sourced outside of OE assemblies and replaced as a stand alone pump far less $$$. Ebay & Amazon have many of them-getting the right physical size in high quality is the solution.
Try the ECU thing too?
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I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
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Bueller wrote:
I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
Do you have a method to test the ECU output?
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Kantuckid wrote:
The way to check a fuel pump is not by sound alone. Fuel flow to the point of injection is the question?
While I've never had the Vespa fuel pump out ethanol plays havoc . Many PTW's use fuel pumps that can be sourced outside of OE assemblies and replaced as a stand alone pump far less $$$. Ebay & Amazon have many of them-getting the right physical size in high quality is the solution.
Try the ECU thing too?
No past history of Vespa fuel pumps be affected by ethanol, not one report of that here.
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JKJ-FZ6 wrote:
Bueller wrote:
I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
Do you have a method to test the ECU output?
Nothing in the manual to test ECU without a PADS.
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Bueller wrote:
I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
you gave me an idea, I am going to take another break down ride and take the spare injector with me. When it dies, I'll pull wire off injector, hook up the spare see if I get gas when cranking

why the hell didn't I think of this before Facepalm emoticon
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JKJ-FZ6 wrote:
Bueller wrote:
I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
Do you have a method to test the ECU output?
Quick responding DVOM or better yet a noid light, but I doubt you'll have one of those unless like me you spent a couple of decades turning wrenches in the car biz.
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WEB-Tech wrote:
Bueller wrote:
I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
you gave me an idea, I am going to take another break down ride and take the spare injector with me. When it dies, I'll pull wire off injector, hook up the spare see if I get gas when cranking

why the hell didn't I think of this before Facepalm emoticon
It can be done, but it will be difficult to detect the small amount of fuel that comes out of an injector for such a small engine. I once ran a BMW R1150 on one cylinder with the other cylinder's injector removed to see if it was working, and it was difficult to see even at 1500 RPM. It is a very small amount of fuel.
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Bueller wrote:
JKJ-FZ6 wrote:
Bueller wrote:
I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
Do you have a method to test the ECU output?
Quick responding DVOM or better yet a noid light, but I doubt you'll have one of those unless like me you spent a couple of decades turning wrenches in the car biz.
I have an oscilloscope from a few decades in electronics. Nerd emoticon I suppose I could see pulses to the injector with that. Rather hoping that won't ever be necessary, however! 8)

Now, I'm getting curious...are there ways to test an ECU without a specialized tool, other than swapping?
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Bueller wrote:
JKJ-FZ6 wrote:
Bueller wrote:
I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
Do you have a method to test the ECU output?
Quick responding DVOM or better yet a noid light, but I doubt you'll have one of those unless like me you spent a couple of decades turning wrenches in the car biz.
I have a DVOM, Fluke 77 from my Field Engineering days.
Advice please.
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JKJ-FZ6 wrote:
Now, I'm getting curious...are there ways to test an ECU without a specialized tool, other than swapping?
Only option I can think is the B.O.B. sold by Piaggio...
Piaggio B.O.B.
Piaggio B.O.B.
250 - 500 ECUs adapter
250 - 500 ECUs adapter
Pinout
Pinout
2T 50cc Purejet adapter
2T 50cc Purejet adapter
MP3 RL ECU adapter
MP3 RL ECU adapter
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JKJ-FZ6 wrote:
Bueller wrote:
JKJ-FZ6 wrote:
Bueller wrote:
I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
Do you have a method to test the ECU output?
Quick responding DVOM or better yet a noid light, but I doubt you'll have one of those unless like me you spent a couple of decades turning wrenches in the car biz.
I have an oscilloscope from a few decades in electronics. Nerd emoticon I suppose I could see pulses to the injector with that. Rather hoping that won't ever be necessary, however! 8)

Now, I'm getting curious...are there ways to test an ECU without a specialized tool, other than swapping?
There should be, all the PADS does is look at voltages.
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WEB-Tech wrote:
JKJ-FZ6 wrote:
Bueller wrote:
I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
Do you have a method to test the ECU output?
Nothing in the manual to test ECU without a PADS.
Bugger the manual - they're written for the shop mechs, not us owners. You can check that it's pulsing with an LED test probe. The newer "auto electrics" 12V testers are LED and will work for this. Double check your circuit diagram to check if the ECU pulses the 12V or the ground side - or put the tester across the connector terminals directly.

Or as you say further down, use a 'scope.
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WEB-Tech wrote:
Bueller wrote:
JKJ-FZ6 wrote:
Bueller wrote:
I'd check to see if the injector is being pulsed by the ECU during cranking. If it is (and since you already said you have spark during the malfunction) I'd recommend checking actual fuel pressure next to make sure it is in spec. You may very well be on the right track with the ECU, but I'd want to know for sure before buying replacement parts
Do you have a method to test the ECU output?
Quick responding DVOM or better yet a noid light, but I doubt you'll have one of those unless like me you spent a couple of decades turning wrenches in the car biz.
I have a DVOM, Fluke 77 from my Field Engineering days.
Advice please.
I've never tested an injector driver in the ECU this way, but I'd start with the continuity function. As JimC said you need to verify how the ECU controls the injector. It likely controls the ground side, and the injector has a constant 12v feed any time the key is on. Most manufacturers do it this way because electronic components take less abuse if they switch the ground side instead of the power side. If this is the case you should be able to see/hear continuity to ground pulsing on the return wire to the ECU. If you can't get the continuity function to work, try the dc voltage setting and use the bar readout below the numbers. I assume your 77 has that feature - my 78 does. I would think a Fluke is high quality and fast enough to show you something at engine cranking speed.

Also as mentioned, an LED test light should be able to keep up at cranking speeds too. Lastly, you can always check with the local Autozone to see if they have a loaner noid light set.

Good luck, and please post the result for the rest of us BV350 owners.
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Will keep you updated.
Throttle body arrived at my house, I may just through it on, can't return it anyway Clown emoticon
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Ok, decided to do more testing first.
Went back and looked at the ebay auction details for the throttle body, and I can return it if I don't need it.

Fluke 77 don't pick up injector pulse. Will get a Noid light if needed.

Went for a ride with the injector from the MP3 500 still installed and got it to die again.
Pulled injector and cracked motor, no fuel spray.
Pulled fuel hose off injector, turned on ignition got fuel.
Went and ate thinking it would start by the time I got back, it didn't.

Now here is where it gets odd.
For the hell of it, I connected the original injector back up to the fuel line and plugged in the cable, tested for fuel spray by cranking motor, got a nice spray pattern, bolted the original injector back in, it started and road home.

Getting ready to see if I can duplicate the fix by replacing injector when it died. not sure what it will prove but at least might give JimC or someone an idea.

Off for another test ride.

May go up to Advanced Auto too to see if their fuel gauge has an adaptor that will fit the fuel line. Too test fuel pressure when it dies.
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The only idea I've got is that it was more about the time elapsed than anything else - something had cooled down enough to work again. An electrical connection somewhere no doubt. I'm reminded of a fault in a TV monitor many moons ago - one transistor had a temperature bug where it was fine except within a 2° range. A bugger to find... Colder or hotter, just fine. Worked out in the end one leg had come detached inside.

Similar to folk who keep cleaning their carbs because the bike stalls 100yds from home at the traffic lights - when actually it's the valves that need adjusting. By the time the carb's been cleaned (done in 5 minutes once you're used to it) the engine has warmed more evenly from the short time its been sitting and the engine will start again and run perfectly. BTDTGGTS...

So keep carrying that spare injector until you nail the actual fault!
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Is fuel pressure bleeding off?
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I'd almost guarantee you have a temperature-sensitive issue. That could be a driver or other electronic item in the ECU, but it could also be a poor connection at a terminal or a wire broken inside of its insulation. My bet is on the ECU, but a noid light shouldn't be too hard to come by. If you can't find one I can always loan you my kit, though it will take a couple of days to get there.
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Forgot to add that when it is in failure mode you can watch for a pulse at the noid light while doing a wiggle test on the injector harness and ECU connector. You can even (lightly!) tap on the ECU and see if that makes the circuit start working. All of those things would be considerably more difficult to do with the voltmeter, even if it was fast enough to keep up.
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Check your spark plug cap.
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From his first post:

Started by checking battery connections then looking at the spark plug cap, swapped it out to be sure, looked fine. Still no start
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Dry solder joint
SaFiS wrote:
Had a customer with a similar problem on a Beverly 300 Tourer. Narrowed it down to the RUN/OFF pin on the ECU. Gave him two options. New ECU or trying something that might work or not. Warmed the pin with a soldering iron. Three years now, he only comes for regural maintenance...
I think SaFis and Bueller are on to something and it may be a dry solder joint in the ECU. It most often times takes a magnifying glass to spot the separation. Don't use a heat gun, just re-warm the pin as suggested.
Hope you get it sorted soon.
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My vote is for the fuel pump.
After all I've done to nail down a hard cold start the fuel pump is the only place I haven't gone. I'm going to install a one way check valve in the fuel line to see if the fuel pump has one and it's failed. If I'm correct, then I'll look into replacing the pump.
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Abner_Bjorn wrote:
Check your spark plug cap.
Checked/changed, more than once.
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breaknwind wrote:
My vote is for the fuel pump.
After all I've done to nail down a hard cold start the fuel pump is the only place I haven't gone. I'm going to install a one way check valve in the fuel line to see if the fuel pump has one and it's failed. If I'm correct, then I'll look into replacing the pump.
Have fuel pressure, can't hold it back with my thumb, checked by pulling fuel hose.
And I have an ECU in my hand, so that will be the first part to be added.
Everything is pointing the ECU

And before adding a check valve just cycle the key three or four times, that will prime the system if it is draining back into the tank.
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WEB-Tech wrote:
And before adding a check valve just cycle the key three or four times, that will prime the system if it is draining back into the tank.
Nope, tried it 10 times, still doesn't push the air out. It would be nice if the online manual had more info about the fuel pump.
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Ok, swapped out the Throttle body/ECU.
That was easy to program. Going for a ride once traffic dyes down some.
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Replacing the throttle body / ECU may have fixed it. I've been riding for the past hour. Not even a hiccup.
Eating dinner and going for a longer ride.

Haven't made it more than 30 minutes before.
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