Fuel Pressure Regulator - faulty?

[mikseymono]

Hi everyone...

In tracking down my poor performance issues.....just trying to eliminate possible faulty parts.

So, my fuel pressure checks out as per Clarks under the various conditions. The only thing I have not done it physically drive it with it stuck to windscreen......anyhows, I don't have a non start issue but when I pulled the small vac hose from the FPR it smelled of petrol. There where no drips of petrol coming out and checked for about 5 mins with engine running and vac hose off and still no drips. However, it really does smell of petrol when you take it off.

Is this normal? If not, any way to test it?

Thanks,

M

[Jfrahm]

If it were leaking enough fuel to cause poor running the plugs would show signs and it should also produce black smoke or at least smell rich when sitting at idle. At idle your vacuum should be quite high and that'd be when the most fuel would get sucked through the failing regulator into the vacuum system.

You could use a hand pump and the vacuum brake bleeder can that often comes with it to see if you can pull some fuel out, try it with the system under pressure for maximum pressure delta to vacuum.

I'll smell-test my regulator in a bit. -Joel.

[Jfrahm]

OK just checked and I can not-really smell fuel at the regulator vacuum line. One sniff produced a very faint fuel smell but really it was insignificant. Of course the other end of this hose is connected to the intake which can smell of fuel a bit. This was a vague suggestion of a fuel smell and of no concern.

If you have a stronger smell it might be coming from elsewhere, a dripping injector or maybe just bad luck with an injector firing after the ignition was shut down at key-off.

If you disconnect one injector does it run better?

[djnolan]

The damper diaphragm could be bad and cause fuel to get pulled in through the vacuum line into the throttle body.

[944 S2]

Originally Posted by djnolan

The damper diaphragm could be bad and cause fuel to get pulled in through the vacuum line into the throttle body.

Easy check. Pull the vacuum line of the damper and see if it leaks fuel. If it does it’s bad which means it’s dumping raw fuel directly into the intake!
Look closely you can see a drip of gas from the vacuum line. This was on my S2.

[Waz951]

^^ This is good advice. Had the same problem with my 944T and its FPD. Some other symptoms are slow loss of fuel pressure and lazy/slow starts. Also wrote up a little except about it on my blog. Bad news for the 944 crowd is that OEM FPD is currently NLA jacking the prices through the roof of any left around.

[Jfrahm]

as the OP said "There where no drips of petrol coming out and checked for about 5 mins with engine running and vac hose off and still no drips. However, it really does smell of petrol when you take it off. "

[DannoXYZ]

M, you need to measure actual fuel pressure in rail.

One reading at idle with vacuum hose connected.
Another reading with it disconnected.

Also measure voltage output of AFM as you manually move flapper door through its entire range of motion. What is minimum voltage with door closed. What is max voltage with door fully open? Does voltage increase smoothly with no dropouts along way?

Disassemble entire intake from AFM to intake-valves and replace all gaskets and clamps

[mikseymono]

Just a mini thread resurection...mine....

Pulled my Vac pipe off the FPR and it smelled of gas/petrol. Not stinking but definitely there. There is no gas coming out when it runs and no drips after I shut it down.

Before I start chasing this down, should there be NO smell at all of gas in the vac lines? Or is a little normal?

Thanks in advance.

M

[djnolan]

It would be better to check the FPR or FPD with a "vacuum diaphragm tester" if you can't do a proper fuel system pressure test per Clarkes.

[mikseymono]

Thanks for reply....tried today with a brake bleeder vacuum...but it didn't want to work!
Is the fuel smell normal in the vac line? I can get a FPR fairly cheap...but just asking.

Thanks,

M

[Jfrahm]

My experience is that a faint fuel smell is normal. It's a tube connected to an intake that is going to have residual fuel in it. A strong fuel smell is not normal IMO.

But you can just put some scrap line on the unit to a small container and see if it drips or shoots fuel out with the DME relay jumper wire in place to force the fuel pump on.

[944 S2]

Another tip would be to simply plug the vacuum line and see if she runs better. When I did that the car started right away (was having a hard to start issue) and ran smoothly.