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Author: Subject: More flow = rich. Same pressure.
ken555

posted on 9/12/18 at 12:08 PM Reply With Quote
More flow = rich. Same pressure.

I've been chasing a sudden change in the fueling of the engine.

All electrical systems seem ok.

The only mechanical change was removal/regiment of a fuel pressure smoother on the end of the fuel rail.

If it has been damaged and now allows more fuel in, but at the same rail pressure would that cause it.






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daviep

posted on 9/12/18 at 01:44 PM Reply With Quote
I'd say no but I'm not 100% clear on your situation, the amount of fuel injected is only affected by the nozzle size, the opening time and the fuel pressure. Are you 100% sure fuel pressure hasn't changed?

If the "pressure smoother" is the fuel pressure regulator and after fiddling with it your running rich it would suggest something has changed.

Is the return line from the fuel pressure regulator OK? no kinks, or restrictions?

Cheers
Davie





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mark chandler

posted on 9/12/18 at 04:39 PM Reply With Quote
I have never heard of a fuel pressure smoother, if you have replaced the fuel pressure regulator for one that holds more pressure then it will richen up the mixture.

If the problem is at idle make sure the vacuum pipe to it is not split.

[Edited on 9/12/18 by mark chandler]

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ken555

posted on 9/12/18 at 06:48 PM Reply With Quote
Dampener might be a better word.
On the inlet of the fuel rail.

Fuel comes in on the banjo, turns 90 degree up the dampener, then 180 degree down the rail.




The FPR is on the other end of the rail.

The fuel pressure hasn't changed, sits at 40psi with no pipe, drops to 38 ish with vacuum pipe connected, nothing has changed.

Car is running so rich that the plugs soot up after a few minutes.

All the sensors seem to be reading fine, TPS is smooth reading from 0.5v to 4.5v
Map reacts to vacuum, both air and coolant temp sensors follow the correct curve.

Timing is spot on, and new plugs didn't cure the problem.

There is no lambda sensor this engine never had one as its the non-cat version.

Injectors seem fine when you apply aerosol carb cleaner and 5v.



Wouldn't a split in the vacuum pipe cause it to run lean ?






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obfripper

posted on 9/12/18 at 08:54 PM Reply With Quote
I would expect approx 10 psi drop with the vac pipe connected if you have a single throttle body, and 6-8 psi with itb's - this amount should equal your idle manifold vacuum.
The pressure damper is to counteract pulsing while the injectors are operating, it's part of the oem design and I'm not sure if it's function affects the operation of the regulator or not.

If your regulator is 3 bar, that should be 43.5 psi without vacuum and 33.5 psi with vacuum connected, suggesting your regulator is not functioning correctly.
With your pressure readings, it would indicate approx 25% overfueling at idle and 16% underfueling at full throttle assuming your gauge is accurate.

A spilt in the vac hose would cause rich running, as it would not be reducing the fuel pressure by the amount required.

Dave

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coyoteboy

posted on 10/12/18 at 01:52 AM Reply With Quote
Fuel Damper.

Won't affect the fuel pressure, but will drastically improve fuel flow at higher revs depending on your fuel line and pump config.
If you had very restrictive pipework or were batch firing all injectors, a damper will run you more rich.





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rusty nuts

posted on 10/12/18 at 08:17 AM Reply With Quote
Why did you change the damper? Might be worth refitting the old one just to check if it eliminates the problem?
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daviep

posted on 10/12/18 at 05:38 PM Reply With Quote
Have you checked the air filter / inlet, rich running could also be a lack of air.





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