testing fuel pressure regulator?

[fla 9]

Is there any way to test the fuel pressure regulator? On my car, from cold once it has fired up it will take a few seconds to idle properly, starting from low revs then building up to the normal 800 or so rpm. Also, when you open the throttle from low speed it will buck a little so I ease back and then press is more gradually. The leads seem to be ok and the coilpack doesn't appear to be arcing. Does this point to the fpr?

[Sean_Jaymo 0]

Turn the engine on and get it running for a minute or 2 to eliminate any cold start or battery problems. Turn it off and leave it 30 seconds. If the engine fires immediately then the fpr is holding fuel pressure and is ok, if it take a few cranks to fire into life, then the fpr is on its way out and you are relying on the fuel pump to build sufficient pressure to start.

 

Either the fpr is on its way or the vacuum line controlling it is beyond its best.

 

A good fpr should hold its pressure for a few days.

 

---------- Post added at 11:22 PM ---------- Previous post was at 11:19 PM ----------

 

It does sound like an ignition problem to me, are the spark plugs ok and gapped properly, how old are the leads? They break down with age and loose their 'fizz' a bit.

[fla 9]

thanks Sean will check and see today. Changed the spark plugs around 5,000 miles back, leads have 70,000 miles on them.

[Sean_Jaymo 0]

That's quite some time for leads. Maybe worth looking at replacing them if the FPR comes back as being good. I think leads are a 40 or 60k item? Can't tell you for certain though.

[Stonejag 10]

Turn the engine on and get it running for a minute or 2 to eliminate any cold start or battery problems. Turn it off and leave it 30 seconds. If the engine fires immediately then the fpr is holding fuel pressure and is ok, if it take a few cranks to fire into life, then the fpr is on its way out and you are relying on the fuel pump to build sufficient pressure to start.

 

Either the fpr is on its way or the vacuum line controlling it is beyond its best.

Thanks for sharing that, now I know why mine is so hard to hot-start! :) Doing exactly as you describe. Luckily I just had a new rail and injector set turn up!

 

Stone

[Roger Blassberg 0]

That's useful information for me too!! It starts very well from cold, come Hell or high water, and settles to a very nice even idle, no missing or stuttering.

 

But try to start from hot and it can take 5 seconds of cranking. I'll have a good look at the small bore hose and clips, then may need a pressure regulator. No doubt it is silly money............

 

Best wishes

 

RB

[Stonejag 10]

Same here: starts first time, every time from cold but when warmed up, if it decides it's not going to start then it just won't! I'd noticed it improved the odds if I turned the key and then waited for the fuel gauge to level off before trying to start it, which also makes perfect sense.

 

Also looks fairly easy to remove:

 

11: 078133534C pressure regulator

 

12: 037198031 gasket set for pressure regulator

 

13: 037133047A retaining clip

 

Stone

[edit: just tried it on my spare fuel rail. It's not fairly easy to remove! Maybe there's a trick to it, but pulling straight out isn't shifting it...]

Edited June 7, 2013 by Stonejag

[Sean_Jaymo 0]

If it starts and fires without chugging for a few seconds when cold, then your fpr is holding its pressure and is ok. With full pressure, the engine should fire pretty much instantly. As long as everything else is working well that is.

 

It's another issue if it doesn't start straight away when warm but it does when it's cold. I only say start the car from cold and leave it a few mins to run before trying to restart to eliminate potential battery drain and cold start problems.

[fla 9]

Also looks fairly easy to remove:

 

 

 

Is anything 'fairly easy' on the Corrado??!! Might come out with some penetrating oil and then a drop of normal lube. I guess it will have got seized slightly onto the steel fuel rail.

[Sean_Jaymo 0]

Breaking the Corrado is 'fairly easy'!

[Roger Blassberg 0]

OK, having laid that one to rest, what ARE the causes of hot starting problems? Weak fuel pump, fuel filter, ?? I know that it's not injectors because they have just been cleaned. Maybe the temperature sensor giving too rich a mixture, but it runs really well and gives very acceptable consumption figures.

 

Best wishes

 

RB

[Mawrick 0]

Currently looking into this problem mysekf with my corrado, have started to think about cam position sensor and/or engine speed sensor, but would have thought vag-com would show some errors on those ?.....

[Sean_Jaymo 0]

Hot starting is rarely fuel related on injection engined cars. If however you have your foot on the accelerator, you can flood the engine if you have a bit of a weak ignition system.

 

Air on a cold start is a little bit denser due to the cold environment of the engine and if you pump the accelerator a bit on a cold start, the the extra fuel will be compensated by the denser air and beneficial to the weaker spark. When the air temperature rises in a warm engine, you loose this extra density and you essentially flood the engine.

 

When you have too high an air/fuel mix, the mixture won't ignite and you potentially end up with a vapour lock which is when you have the fuel in the combustion chamber evaporating into the inlet manifold (as well as the exhaust but that's not the problem).

 

This excess fuel can then either recondense in the inlet manifold or stay a vapour which will enrich the fresh air coming in to the combustion chamber with fuel causing a rich air/fuel mixture again which puts the whole cycle into a vicious circle!

 

To help cure this, leave the ignition off for a few moments and hold the accelerator open fully to allow the vapour to evaporate before starting again. When you restart, try not to touch the accelerator.

 

So in essence, you potentially have;

 

A tired maf feeding the wrong air flow data to the ecu for it to fuel the injectors (not likely if it's good on fuel otherwise)

 

A split vacuum hose somewhere allowing in too much air (usually noticed with a lumpy idle with the severity of the idle being governed by the size of the split). This is likely if you don't pump the pedal a bit on startup.

 

A weak ignition system (hesitation under load with the severity being governed by the weakness)

 

Essentially, you need fuel, oxygen and ignition. Too much of anything in there and you get a mixture which is too rich or lean to start.

[Mawrick 0]

Could it be caused by a cam shaft sensor ? (or should these show up in VAG-COM)?.

 

I'm also thinking maybe it might be bacause of the cone filter that sits on the MAF - and was thinking about trying to go back to OEM filter.

 

I'v got no errors on vag-com, and the fuel consumption seem to be ok, idle seem to be ok, and everything but this small annoyance that I have to crank it for a while before it fires.....1-2-3 sec cranking.

[Sean_Jaymo 0]

How old is your ignition system? Years and mileage wise?

[Mawrick 0]

The car is a 1995 VR6, just turned 130 000km today (roughly 81 000 miles), AFAIK the ignition leads where quite new when I got the car - and it's only been driven 6-7000 in my ownership.....but this problem have always been there...

 

it will always start, but sometimes need to crank for a little while...

 

also this one have coilpack

[Sean_Jaymo 0]

Is the coilpack in good condition? They don't always live for ever.

Edited June 11, 2013 by Sean_Jaymo

[Mawrick 0]

Is the coilpack in good condition? They don't always live for ever.

 

Can't see any damages to it, doesn't seem to be cracked or anything - and I actually think it have been replaced just a little while before I bought it.

 

So should only have done roughly 7-8000km