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2010 Suzuki DF70A issue

Old 05-17-2020, 01:01 PM
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Default 2010 Suzuki DF70A issue

Going out on a limb here since Iíve scoured google for any answer related to my problem. Which Iíve found doesnít exist. So here goes.

I can pump the bulb up tight. Rock hard. It will crank like a brand new motor. Itíll take off down the lake like a brand new motor. Runs like a shot cat. No issues at all. However, my wife likes to cruise and this motor has developed an issue where after idling around a bit it will cut off. Seems to only happen below 1500rpms, and itís not immediately. Itís like it burns up the fuel thatís in the engine and fuel line (which takes a bit cause theyíre so good on gas) and after that it cuts off. If I try and crank it without pumping the bulb it wonít start. If I pump the bulb itís like it never happened. Starts right up.

Hereís the work Iíve had done on it lately.

High pressure fuel pump went out in 2018. Had it replaced. Seems that this problem started after that.

First boat trip of this year, Got to where it wouldnít idle at all, only at fast idle and would die immediately upon idle. Took it to mechanic, they checked and cleaned my high pressure fuel pump and VST, changed the idle control valve and that seemed to fix the no idle problem. I was thinking it would fix the problem referred to above but it didnít.

I carried it back to the shop told them what was happening, waited another 2 weeks and of course typical mechanic fashion, ďwe couldnít duplicate the problemĒ ďmaybe you just had a hiccupĒ. Well buddy let me tell you. Iím no fool. Needless to say I wonít be going back there.

ive thought maybe the tank wasnít venting correctly. So Iíve tried loosening up the gas cap. Still happens.

Iíve Replaced the fuel hose and primer bulb. Still happens.

Any thoughts from the experts?


Thanks
Caleb
Old 05-17-2020, 02:32 PM
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I know a guy that has the same symptoms on a 09 df90.cleaned the vst and all filters,replaced fuel line and bulb.his cuts off after idling for long periods when he throttles up it dies won't start without pumping bulb.hes going to throw a few dollars at it and change the low pressure pump that supplies the vst because his mechanic says it will take alot of hrs to duplicate the problem at the shop.keep u posted.
Old 05-18-2020, 09:22 AM
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Thanks dude. I've contemplated replacing that pump as well. I asked this mechanic to check it and possibly replace it but they said since I didnt have gas in my oil that it was probably fine. I'm wary of replacing it myself because from what I've read you have to rotate the crankshaft to bring No.1 Top cylinder to Top Dead center on compression stroke. Not sure how i'd know it was in position?
Old 05-18-2020, 09:50 AM
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It sounds like you could have an issue with the VST overflowing because of a bad needle valve. Take the cowling off and run it at idle until is starts to die. If you have some gas coming out of the plastic air intake or a strong smell of gas there then your VST is overflowing. It will run great above idle but it will slowly stall at idle. Just went through this over the weekend. Was about to start looking for a cause of fuel starvation until I saw the gas dripping down. When I got to the VST it was pristine. But the needle valve has some slight corrosion which caused the leak.

Doug
Old 05-18-2020, 09:55 AM
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I had the same motor with a similar problem. Would not idle. I found a crack in the fuel pickup tube. Itís easy enough to check and a cheap fix.
Old 05-18-2020, 09:58 AM
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I've noticed a gas smell after it shuts off while on the water. and I know that you are not supposed to small gas with these engines. So I;ve wonders about that. I just text the mechanic and apparently they replaced that needle valve.
Old 05-18-2020, 10:01 AM
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If you are taking advice from non-experts, I believe you are dealing with vapor lock. Earlier Suzukiís 90-140ís had that issue. You said it does not use much fuel, so the fuel under the cowling is slow moving. Under the cowling is hot, and I expect boiling the slow moving fuel at some point, since you are using so little. When you are running faster, the fuel does not stay under the cowling as long as does not get as hot. When you have vapor lock, pumping the ball will increase the pressure to turn the vapor back to liquid and also add cool fuel to the lines. If you can replicate the issue, see if you can prevent it by slowing pumping the fuel ball when it is about to happen. People were fixing the 90-140 issue by adding a low pressure electrical fuel pump.
Old 05-18-2020, 10:01 AM
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Originally Posted by Dougfish View Post
It sounds like you could have an issue with the VST overflowing because of a bad needle valve. Take the cowling off and run it at idle until is starts to die. If you have some gas coming out of the plastic air intake or a strong smell of gas there then your VST is overflowing. It will run great above idle but it will slowly stall at idle. Just went through this over the weekend. Was about to start looking for a cause of fuel starvation until I saw the gas dripping down. When I got to the VST it was pristine. But the needle valve has some slight corrosion which caused the leak.

Doug
This is where the measured fuel flow system can be used to trouble shoot the system. If fuel is being dumped out of the VST into the intake then it will show up as an increase in abnormal fuel flow.
Old 07-14-2020, 08:13 AM
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Just bringing this thread back to the top. Anyone else have any ideas?
Old 07-14-2020, 08:57 AM
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Did you ever bust the VST open to look at the needle valve? Any other symptoms? Did you let it idle until it starts to die and take a look at the hose that comes from the VST to the top of the plastic intake. Disconnect it and watch it run at idle for 10 minutes or so. If gas starts pouring out you can say itís the needle valve in the VST. If not then thatís one less thing to look at.

Doug

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