Has anyone replaced their fuel pressure regulator?

ballcock said:

I don't honestly know how you'd go about checking this , though there was suggestion on RL that you can disconnect lines by the regulator and judge if it was working by whether fuel comes flowing out or not.

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Considering that fuel injection systems work under high pressure (5 bar?) that sounds like a recipe for a potential disaster.
I was thinking more in terms of fitting a suitable pressure gauge to the fuel rail and running the engine to see if the regulator is still capable of keeping the system pressure at a constant level as it is intended to. Best left to a workshop familiar with trouble-shooting FI systems.

PS: Just noticed that geolab has posted in the meantime, confirming that replacing a suspect pressure regulator is cheaper than testing it and detailing the replacement procedure. :thumb:

Just did a quick Google search and found this:

http://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

As I thought, it would be usual practice to check the rail pressure with a fuel resistant manometer.

However, where the 993 engine is concerned I suspect that access to the rail to fit the gauge is not ideal, so swapping the regulator as geolab suggests may be the more painless fix. The regulator is probably a generic Bosch part anyway, and available at reasonable cost.

dw911 said:

ballcock said:

I've also read that diagnostics won't show up a faulty CHT unless there's a break in the wiring , so it could be faulty but go unchecked for some time.

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Thats not strictly true, with the right diagnostics you can measure the temperature/resistance readings of the cht sensor.
you can also check it with a multi meter, I have a graph with the readings vs temperature you should see if its working correctly, I'll try & find it and post it up for you, so you can if you want check it before you go to the trouble of changing it, just in case its something other than the cht sensor

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Did not show up on mine and nothing else was changed and the car now starts perfect :thumb:

All good stuff this, I hope it helps MR B
:worship:

Red993C4 said:

ballcock said:

I don't honestly know how you'd go about checking this , though there was suggestion on RL that you can disconnect lines by the regulator and judge if it was working by whether fuel comes flowing out or not.

Click to expand...

Considering that fuel injection systems work under high pressure (5 bar?) that sounds like a recipe for a potential disaster.
I was thinking more in terms of fitting a suitable pressure gauge to the fuel rail and running the engine to see if the regulator is still capable of keeping the system pressure at a constant level as it is intended to. Best left to a workshop familiar with trouble-shooting FI systems.

Click to expand...

I think what they mean is to take off just the vacuum pipe from the fuel pressure regulator, if the membrane inside the fuel pressure regulator is split,fuel will leak out of the vacuum side.

As you say though if your working on the pressurised fuel side do take care

dw911 said:

Red993C4 said:

ballcock said:

I don't honestly know how you'd go about checking this , though there was suggestion on RL that you can disconnect lines by the regulator and judge if it was working by whether fuel comes flowing out or not.

Click to expand...

Considering that fuel injection systems work under high pressure (5 bar?) that sounds like a recipe for a potential disaster.
I was thinking more in terms of fitting a suitable pressure gauge to the fuel rail and running the engine to see if the regulator is still capable of keeping the system pressure at a constant level as it is intended to. Best left to a workshop familiar with trouble-shooting FI systems.

Click to expand...

I think what they mean is to take off just the vacuum pipe, if the membrane inside the fuel pressure garage is split,fuel will leak out of the vacuum side.

Click to expand...

That would only test for one failure mode for the regulator though: failed diaphragm.
I could imagine a regulator might also not function properly due to a weakened spring, a worn valve seat or debris keeping it partly open? :dont know:

As a side, if it turns out to be the cht sensor, which seems likely.
I came across a thread sometime back where someone had made a special tool from a chopped about spark plug spanner for removing the cht sensor,made the job much easier.
I cant find the thread now, but you maybe able too, could be useful if your going to change it yourself

dw911 said:

As a side, if it turns out to be the cht sensor, which seems likely.
I came across a thread sometime back where someone had made a special tool from a chopped about spark plug spanner for removing the cht sensor,made the job much easier.
I cant find the thread now, but you maybe able too, could be useful if your going to change it yourself

Click to expand...

Or Snap-on do one for £40 ish

Some really useful info here folks , thanks a mil .. Good to see the old 911UK back !
Goe , you might remember we talked about this last year , unfortunately a thorough iSV clean didn't solve the problem. But thanks again for the time you spent diagnosing.

In terms of testing the reg, I should have been a bit clearer , sorry. It' s the vacuum line that is supposed to be pulled. Any fuel here will suggest a broken diaphragm , apparently the most likely culprit, though I'd imagine the spring would be a close second.
I believe our stock regs keep to 3.8 bar not 5, but that's still good solid pressure!


A question on CHT.. Could it be that the sensor is only failing in the lukewarm condition? Good for cold and hot readings?
Having said that , last Summer , my car did the same hesitant start from cold for the first time, this maybe pointing at a CHT gong south?
It wasn't a warm day so I couldn't imagine fuel evaporation at the rail to be the problem.

I've seen thread where the chopped spark plug does the job thanks. I think I'd be inclined to leave CHT replacement to my indie, looks like a PITA to remove.

Interesting point made re FPR, in that you'd expect throttle hesitancy too , I'm not getting this, so maybe I AM being pointed towards CHT.
Just for the record, my vacuum system seems to be working fine , actuators are holding the vacuum and working on start up, vario actuators also doing their thing.

My car is off the road for the salty season , so I won't have anything definitive back for a while , but when she's back on the road I will try and set the key to second position (dash lights on) for 15 seconds before starting to see if this makes a difference.

Thanks for all info and suggestions so far.
All further ideas gratefully received!

[/quote] That would only test for one failure mode for the regulator though: failed diaphragm.
I could imagine a regulator might also not function properly due to a weakened spring, a worn valve seat or debris keeping it partly open? :dont know:[/quote]

Yes your right, would only test one failure, was just another thought from the description of pulling of the line & looking to see if fuel leaked out, could not see what would be gained from pulling off a fuel line to see if it was leaking fuel as the car runs , so guessed maybe they ment the vacuum line.
Although I initially thought, as you did, that they ment testing with a fuel pressure gauge

[/quote] That would only test for one failure mode for the regulator though: failed diaphragm.
I could imagine a regulator might also not function properly due to a weakened spring, a worn valve seat or debris keeping it partly open? :dont know:[/quote]

Yes your right, would only test one failure, was just another thought from the description of pulling of the line & looking to see if fuel leaked out, could not see what would be gained from pulling off a fuel line to see if it was leaking fuel as the car runs , so guessed maybe they ment the vacuum line.
Although I initially thought, as you did, that they ment testing with a fuel pressure gauge

ballcock said:

I believe our stock regs keep to 3.8 bar not 5, but that's still good solid

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I was thinking of a racing engine I'd been involved with in my misspent youth when I wrote 5 bar, and added the "?" because I didn't know offhand whether series production engines had caught up in the meantime.
3.8 bar would correspond to the 55 psi mentioned as one of two possible road car values on the American web site I linked to, so quite feasible.

PS: Checked the PET list for the 993 fuel rail in the meantime and saw that Porsche in fact installed a valve on it to enable the easy connection of a fuel pressure gauge. That must be the screw thread that geolab referred to when he said that it was a bit "iffy".