Fuel Pressure

[Toystoretom]

Hello Ladies and Germs,

I'm chasing an off idle stumble (while I'm riding) and thought I would check my fuel pressure. I figured it might be low. It showed up at 45 PSI (about 3 bar) and it is supposed to be 2.5 bar (about 35 psi). I used a brand new MAC gauge and a Snap on gauge I've used for years, both read the same. Bad fuel pressure regulator? Does this do bad mojo things on a 2001 California Special? Where does one get a Moto Guzzi fuel pressure regulator?

Thank you for your time and finish your leftovers.

Tom

[CalVin2007]

 Tom, all the specs I have found say 3 bar for 1993-2003 Guzzi external fuel pumps. Could your spec source be incorrect?

  Terry

[Wayne Orwig]

From the fuel injection manual for the earlier P8.



But the 2001 Cal Special is a 15M isn't it? I don't have that pressure.

[Kiwi_Roy]

I think 3 bar is correct
Even if it's supposed to be 2.5 the extra half a bar would make very little difference, to double the flow you have to square the pressure drop.

[Toystoretom]

The 2001 Cali I think is the 15M. You may be right about my specs being wrong. When I bought this bike it came with a shop manual that has been reproduced from an original and it is missing pages. It has no index page or front cover. After looking at it I do believe it is for a 2003. It is talking about lambda sensors which my bike doesn't have and I think that's where I got the 2.5 bar spec.

So assuming my bike should be at 3.0 bar... The fuel pressure looks to be OK.

I'll check that off of my list.

You guys are great! Thanks for your help!

Tom

[oldbike54]

 Yes , 15 m .

  Dusty

[Wayne Orwig]

Found it for the 15M


Text cut from the manual
Finally, from a hydraulic point of view, upon a fuel compression of  3±0,2 bar, the jet brakes down as soon as it comes out from the nozzle (atomizing), thereby forming a cone of about 30°.
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The pressure adjuster is a differential type with diaphragm, and is pre-set during assembly at 3±0,2 bar.

[LaMojo]

The Bosch FPR that mounts to the frame is 2.5 bars (as per Bosch's specs).  I think this applies to 1999 and earlier bikes. 

[creaky99]

This may or may not be related to your problem, but here goes anyway.  My 98 EV was suffering from a slight stumble off idle, sight stumble opening the throttle a bit at cruising speed along with a slightly erratic idle speed.  I gave it a tune up, valve adjust, new plugs, new fuel filter, checked the TPS voltage, synced the throttle bodies. No help, still had the stumble(s). After scratching my head for a while, it occurred to me (as it should have much earlier) that there might be a vacuum leak somewhere. Turned out there were several vacuum leaks. The hoses to the canister were all brittle and cracking causing the problem. I pulled all the hoses and plugged the ports. Bike now runs perfectly. 

[Toystoretom]

This bike has no canister. I sprayed ether around and nothing. I've been checking the hoses and can't find anything.

I've ordered the cables for the GuzziDiag, I might have a bad sensor somewhere.

I have to bring my compression tester home and check that.

I did find one sticky deal, the throttle shaft on the left throttle body was very worn and allowed the butterfly to move about at will, tons of slop. I bought a nice set of throttle bodies off of a bike that only had 7000 miles, put those on... same thing (but it does hold an idle now).

I've got the valves a little loose to make sure they are seating. I have new: plugs, air filter, fuel filter and changed all the fluids.

I'll find it   

Thanks for your ideas, if you have more... let me know.

[pauldaytona]

well did it allways do it?

With 15m you can adjust CO, that might solve it.