Fuel pressure regulators (internal) - Suzuki GSX-R Motorcycle Forums Gixxer.com
 
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post #1 of 12 (permalink) Old 07-16-2016, 04:53 PM Thread Starter
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Fuel pressure regulators (internal)

Hey guys, does anyone know a source for fuel pressure regulators for the K1-K2 era pumps?
Mines blown out (bleeds all pressure out instantly through the diaphragm end) and I can't find dick all for a new one short of ~$400 for a filter with regulator or worse.
It looks like the Burgman uses a similar regulator, but at ~$130 and no idea the pressure rating, it isn't a gamble I'm feeling right now.
Has anyone found anything reasonable that will work, or modified the system any? I'm OK with eliminating the filter and using an external filter if necessary to use some sort of generic regulator, I just don't see an immediately obvious way to do so.
Thanks for any thoughts.
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post #2 of 12 (permalink) Old 07-18-2016, 06:17 PM Thread Starter
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Apparently there isn't shit out there. I ended up ordering an 02 filter/regulator assembly from partszilla. It's $100+ cheaper, just needs a modification for the different fuel light thermistor setup, I can handle that. Still $245 for a $20 regulator though, sucks.
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post #3 of 12 (permalink) Old 07-19-2016, 12:14 PM
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Re: Fuel pressure regulators (internal)

I knew that the K2 had one thermistor vs two on the K1. But the fiche suggests that there's a lot more to it than that. There's a fair chance that you can remove the regulator and sell the actual filter to someone with a K2 for $100+.

It used to be possible to buy used complete pumps for $50 or less. But not any more. I was going to suggest that you buy a K3-K6 pump as the cutaways in the service manuals suggest that they have the same regulator. But you may have made the best choice.
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post #4 of 12 (permalink) Old 07-19-2016, 04:46 PM Thread Starter
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Re: Fuel pressure regulators (internal)

Quote:
Originally Posted by BillV View Post
I knew that the K2 had one thermistor vs two on the K1. But the fiche suggests that there's a lot more to it than that. There's a fair chance that you can remove the regulator and sell the actual filter to someone with a K2 for $100+.

It used to be possible to buy used complete pumps for $50 or less. But not any more. I was going to suggest that you buy a K3-K6 pump as the cutaways in the service manuals suggest that they have the same regulator. But you may have made the best choice.

Thanks, I did look into K3-K4 that looked pretty usable too... The K2 just came up closest from what I could tell and by comparison "cheapest" considering risk. The new one showed up today, I'll snap some pictures in a bit assuming things go well with it of course.
It is pretty friggin awful that they want that kind of money for pumps and for filters that is just criminal. Hell its BS that they don't sell the regulator itself for that matter. More than anything I'm just ticked as this bike is more or less showroom condition and has never had anything fail on me, of all the things to crap out the regulator seems to be pretty unheard of as far as failure goes on this model. Weird stuff.
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post #5 of 12 (permalink) Old 07-19-2016, 06:42 PM Thread Starter
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Re: Fuel pressure regulators (internal)

Yeah that went pretty smoothly. The shape is a little different (less contact around the pump motor), but effectively the same principle. The sending unit "hole" the mast slides into at the bottom is also missing (didn't suspect that, I only figured the top anchor would be in the wrong place). The top anchor instead of a snap-in situation is a full circle that is slides into, sort of the reverse of the 01 setup. Of course the bolt hole is in the same location anyway, so calibration is not an issue. Then I just ran some zip tie action through the 02 top anchor hole to keep it secure (though it only moved a few mm anyway with the bolt tight).

Pressure is much better now... instead of 20 psi and bleeding to zero in 1-2 seconds I have 45 psi and rock solid after prime, so that's a huge improvement. Didn't start right away, but the plugs could be pretty fouled from the low pressure operation before (I was able to run it just really poorly before). I'm going to pull the intake and give it a shot of induction cleaner to prime it and see if it stays running/runs normally or if I need to check injector flow again now that I have good pressure.


edit: Yep, quick shot in the throttles and it fired right up, no problems restarting either. Runs great
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Last edited by superbovine; 07-19-2016 at 07:10 PM. Reason: update
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post #6 of 12 (permalink) Old 07-20-2016, 10:44 AM
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Re: Fuel pressure regulators (internal)

"of all the things to crap out the regulator seems to be pretty unheard of as far as failure goes on this model"

Agreed. Makes me wonder if you're letting water or something else get into the tank.
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post #7 of 12 (permalink) Old 07-20-2016, 12:20 PM Thread Starter
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Re: Fuel pressure regulators (internal)

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Originally Posted by BillV View Post
"of all the things to crap out the regulator seems to be pretty unheard of as far as failure goes on this model"

Agreed. Makes me wonder if you're letting water or something else get into the tank.

I think its just a combination of lots of sitting (it is a 2001 afterall, and only has 15k on it) and just plain old bad luck.
It had given me some problems a month or so back but eventually started and ran OK, I figured the gas was starting to turn. So when it wouldn't start last week I immediately pumped the fuel out.... no contamination/water, and still good too (ran it out in another vehicle without issue). On top, the filter sock was clean as a whistle when I took it apart too. This bike was pretty much babied since new so none of the typical tank debris, rust etc.
With the regulator not failing based on spring pressure but actually losing pressure out the vents, I'm betting the diaphragm rubber just rotted from old age. Still really weird though... in searching for some solution that didn't involve buying a filter assembly I found basically no one with regulator failures... at most a person or two thinking it might be it then it ended up being bad injectors or something else entirely.

Whatever, it runs like a raped ape now... I'm thinking it may have been running at 30-35 psi for a long time too, as I swear it feels far more responsive.
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post #8 of 12 (permalink) Old 07-20-2016, 11:10 PM
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Re: Fuel pressure regulators (internal)

It will be more responsive. Correct fuel pressure a the injectors gives better fuel atomisation.
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post #9 of 12 (permalink) Old 07-21-2016, 06:50 AM
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Re: Fuel pressure regulators (internal)

Wouldn't it be dangerously lean with such a low fuel pressure? The ECU measures out fuel by varying the injector-on time, assuming a constant pressure. If the pressure is too low, it doesn't have a way of knowing it and compensating. With a pressure of 75% of the regulated value, the AFR could be as much as 30% higher than the intended target. That would explain the sluggishness for sure, but I'd also expect other signs of trouble, such as pinging or even engine damage.
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post #10 of 12 (permalink) Old 07-21-2016, 08:12 AM Thread Starter
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Re: Fuel pressure regulators (internal)

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Originally Posted by dpapavas View Post
Wouldn't it be dangerously lean with such a low fuel pressure? The ECU measures out fuel by varying the injector-on time, assuming a constant pressure. If the pressure is too low, it doesn't have a way of knowing it and compensating. With a pressure of 75% of the regulated value, the AFR could be as much as 30% higher than the intended target. That would explain the sluggishness for sure, but I'd also expect other signs of trouble, such as pinging or even engine damage.

No, that is a pretty common misconception. When the fuel pressure drops you generally go rich on most circumstances. This is because as the pressure drops the fuel stops atomizing on delivery and more fuel gets through just at lower pressure.
Think of it like a garden hose... if you put your thumb over the end of it the pressure ramps up and less water comes out, you take your thumb off and it pours out in huge volume. Same thing on a FI system, when the pressure drops volume increases. There are exceptions I've run into over the years (tech by trade), but few.

Generally when you see a pressure issue resulting in lean conditions it is an over-run condition where the pump/pressure is fine, but at high demand condition (accelerating at 5k+ etc) the pump can not keep up and pressure drops, engine leans out. The leaning out is not a result of actual low pressure though, they are both just symptoms of a pump not able to keep up with demand.

This is not the case in a situation like mine where the regulator fails... if you can't maintain pressure at zero load, its going to run pig rich.
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post #11 of 12 (permalink) Old 07-23-2016, 05:25 PM
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Re: Fuel pressure regulators (internal)

Dpapavas is right. The garden hose analogy isn't appropriate because of the presence of the pressure regulator. Flow through the injectors is roughly proportional to the pressure in the rail and the time that they're open. When the regulator fails in a manner that the pressure to the injector drops, there will be less flow through the injectors. If flow increased when blocked by a thumb, then the flow would be at a maximum when the flow is totally blocked, which it obviously isn't.

I've just noticed that every service manual from K1 to K9 states that "the fuel pressure ... is always kept at absolute fuel pressure of 300 kPa (3.0 kgf/cm˛, 43 psi)". That's baloney. It's kept at 300 kPa gauge pressure (15 psi difference). In fact, the Suzuki recommended fuel pressure gauge reads gauge not absolute pressure.
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post #12 of 12 (permalink) Old 07-23-2016, 05:34 PM Thread Starter
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Re: Fuel pressure regulators (internal)

At upper RPM absolutely hes 100% right. In a carberation application, 100% right. An FI system with base supply pressure being low like here, not the case.
If the garden hose analogy doesn't work for you, keep in mind that the lower the pressure and in turn lower atomization means inability to properly combust and in turn running rich again.
This is 20+ years of professional experience with ongoing training from multiple manufacturers. We can agree to disagree, doesn't matter to me. Not sure why it was even brought up, as it has literally zero to do with the topic.
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