Jump to content

2012 yzf 450 fuel pressure, fuel pump symptoms bike wont start

Recommended Posts

Hi

I've been having some issues on a 2012 Yamaha yzf450. I just can't get it to start with a kick. It will start with a bump start but the tickover screw on the choke has to be wound all the way out. When it's running it sputters and pops too. 

I've checked the fuel pressure and got a reading of 44-45psi or 303-310 kpa. The manual states 312-328 kpa or 45.25 - 47.5 psi. 

Has anyone got any experience of how the fuel pressure usually checks out? Is it a huge amount down on pressure or just a small amount like this? Also as soon as I stop kicking the bike over the pressure drops. Is that normal or should it hold pressure? 

The valves are in tolerance so I'm thinking it's a fuel problem. When I stick my finger in the throttle body I can't feel any fuel coming out of the injector and the plug is always dry. 

Share this post


Link to post
Share on other sites

Thanks, I checked with a multi meter and there is power going to the injector. 

Could it be an injector fault?

I noticed the vaults shoot up when I kick the bike and then die down gradually. That must be something to do with the capacitor. I've looked in the book but I can't find any information on how to test it, unless it's called something else?

Share this post


Link to post
Share on other sites

45 + is what you need, but you need it for 5 min minimum, for testing the pumps health.

Your symptoms are that of a leaking intake valve, assuming it runs fine once hot......which you said it did not, so that might not be an issue

If you have not been filtering your fuel or treating for contaminates like ethanol, then you injector nozzle will be contaminated. This means the nozzle is not atomizing the fuel enough, and is spitting raw gas instead.

Search 'cleaning a ktm fuel injector'  in youtube for cleaning instructions ( same system as yam's)

Share this post


Link to post
Share on other sites

Thanks KRAN , so the fuel pump should hold pressure for 5 minutes minimum? As in kick the bike over with the gauge connected and then once it reaches 45 it should hold the pressure without any further kicks?

Edited by Be.St.MX
Missing content

Share this post


Link to post
Share on other sites
16 hours ago, Be.St.MX said:

Thanks KRAN , so the fuel pump should hold pressure for 5 minutes minimum? As in kick the bike over with the gauge connected and then once it reaches 45 it should hold the pressure without any further kicks?

No, off the bike using a battery

 

If you have not replaced the stock pump filter it will be clogged shut....

Share this post


Link to post
Share on other sites
On 07/09/2017 at 0:21 AM, THE KRAN said:

No, off the bike using a battery

 

If you have not replaced the stock pump filter it will be clogged shut....

Right so I did a leak down test and was getting a slight leak on the exhaust valves. I got the head ground and all of the valves were replaced. Did a leak down test just to make sure and it's perfect. Compression is high as its also got a new piston. I checked the fuel pump off the bike and I'm getting 46 psi steady pressure. 44 psi when kicking on the bike and will die down to 40psi after a few seconds without power and hold around there. I removed the injector and back washed it, I could hear it clicking in and out and it was flowing when connected to the battery. 

I've not had a chance to bump start the bike as I need a push but before I did the valves the bike would bump start but needed the revs set at the highest position to run and was popping. 

I'm totally out of ideas with this bike now. 

Any suggestions? Thanks for the help so far. 

Share this post


Link to post
Share on other sites

I feel like I'm getting one good spark per kick when I kick it with the plug out. I did a compression test and I'm only getting 55psi. With the auto decompression connected. I might try and remove the auto decompression and see if I can kick it over. I've compression tested bikes. In the past and got high 70's low 80's. I'm wondering if there could be something stopping the head from sitting properly. When I placed the head on the barrel it was sitting about 1mm above the barrel. It was just a little more than hand tight to get the gap to close. I'm wondering if the dowels could be too long and the head is not sitting all the way down. 

Share this post


Link to post
Share on other sites

If you have fuel and air, next are spark and compression.

The capacitors on these things have been known to be finicky.  It's worth getting a spark plug tester light to see if you're getting strong/steady power to it.

Share this post


Link to post
Share on other sites

So I checked compression with a cable tie on the auto decompression and got 110psi. I'm pretty sure I could get that number higher but I couldn't get a good kick on it with the throttle open. So I checked the compression with auto decomp again and put boots on to give it  solid kicks and got 90. So no problem with compression. 

I had tried a plug out of another bike which was running and had no joy getting it running. The plug in the bike looked pretty new so I decided to use that it was a CR8E. So I went out and brought the iridium plug CR8EIX and it went but cut out and did the same thing 3 or 4 times. Then I took it for a little run and it's not cut out since. The bike is running a hotcam so I'm wondering if this could make it stall unless the bike is at perfect operating temperature?

Could the stalling be due to the capacitor not holding charge? What voltage should I get on the capacitor? Is there a good way to test it? I'm not convinced that the plug is the problem but I'll run it and see if it stays running. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×