Simple fuel pressure test?

[paultv]

In the absence of a fuel pressure gauge:

If I drive the car, then park up and release the fuel input hose to the fuel pressure regulator, what would I expect to happen? Should fuel be ejected under pressure, or a dribble or nothing?

Should it do any of these the next morning?

Paul

[DanThe]

When you can buy a basic test kit with hose for £12 there is no point guessing

http://www.ebay.co.uk/itm/Car-Fuel-Pump ... Sw5cNYY3aA

[paultv]

OK so here's my fuel pressure test result:

http://whitewatermedia.net/media/2500rpm.JPG
http://whitewatermedia.net/media/Idle.JPG
http://whitewatermedia.net/media/Vacuum%20off.JPG

So idle gives me 2.5 bar, 2500 revs not under load gives about 2.3 bar and vacuum hose off and plugged gives me 3 bar.

any observations?

Paul

[Brianmoooore]

That is all exactly as it should be, but that is only one of the tests you can do with a fuel pressure gauge, and not the important one for diagnosing your problems.
What you need to know is what happens to the fuel pressure in the hours after you stop the engine.

[paultv]

I've left it for 3 hours, the pressure is almost 3 bar...

Today I also cleaned the ICV, not been done for a couple of years I guess, also tested the AFM track resistance which varied wildly around 3rd way up the track, so I reset the height slightly to run on new tracks, better readings, continuous and smooth increase in resistance.

Took the car out, running as it should - lets see how it goes.

Paul

[paultv]

So leaving overnight, about 18 hours, I have 3 psi left in the system. There is no petrol smell anywhere, the Injectors are new from Injectortune. The fuel filter is 3 months old, there is no leakage from the outlet side of the FPR that I can detect as the pressure slowly falls - but maybe it's so slow the fuel simply evaporates.

The pressure slowly drops with the vacuum side of the FPR plugged as well.

So is this slow loss normal or could the pump be suspect?

The car starts without problem when left overnight, perhaps I don't really have a problem with fuel supply at all.

The engine randomly miss-fires between 3.5K and 4K then roars off like a mad thing at higher revs, tick-over is smooth and unwavering, no hesitation.

It really feels "electrical" as if one plug is missing sparks for a short rev band then picks up, its a very sharp hesitation, you can hear and feel it, no backfire or anything, just as though you pull the plag cable for a moment.

CPS is new and correctly positioned - swapping has no effect - it did this with the injectors before they were cleaned.

I have a Speedtouch mild chip fitted - Motronic 1.3

any thoughts?

Paul

[reggid]

what problem do you have?

[paultv]

"The engine randomly miss-fires between 3.5K and 4K then roars off like a mad thing at higher revs, tick-over is smooth and unwavering, no hesitation. "

It's just that.

Paul

[paultv]

Problem sorted out.

Testing all the plug leads revealed open circuit on cylinder 4 lead. The resistor in the plug cap had burnt out, allowing the spark to jump and run No.4 pot normally except during 3.5K and 4K revs, but performed fine at other revs, pretty odd behavior, I've read so many threads on this sort of intermittent miss fire - no one ever suggested checking the plug leads - everything but!

Paul