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MG MGF Technical - Faulty PBV ?


My F makes a strange noise which is coming from the PBV. The care has not been in use for 4 weeks or so and now that today streets are dry I had a quick ride. The strange whistle type of noise definetly comes from the PBV. Initially I thought it could have something to do with the low temperatures but even with a warm engine it is still there but not as noisy as in cold condition. The car also stays in the garage when it is not in use. What could it be? In summer when the car had been in use after a week or two starting the ignition you could also hear the PBV as if it would build up pressure. Any suggestions?


Oliver G.

Bruce Caldwell


PBV = Power boost Valve

Thanks Stu
Bruce Caldwell

Hi all,
it is not uncommon that regulator valves like the PBV (and similare types used in the industry for pressure regulation of air / fluids ) do make noises... If it isnt a leak on the vakuum hose from the mainfold it is the regulating membrame that emmits the noise! A slight tweak on the adjusting screw will probably be enough to get it silent again.
When on the subject of fuelling etc. I hope Dieter has got the E-mail about Lotus type of securing the fuellines from me and will add it to his Tech- site. It is a simple thing to do for ALL F-ers to ensure that those "quick-release" fuel-connections stay together !

BR, Carl.
Carl Blom

It's better to agree in advance on how works this technology ?

Can't recall all details about what's inside the BPV.
From memory it's just a spring, one seal (ball?) and the valve body with some holes.

PVB is nothing different then a standard Fuel Pressure Valve controlling the fuel pressure in front of the injectors.
The only difference between the standard and a PBV is that at the PBV the pressure or better said the spring pre-tension is adustable.

Looks simplified ia a diagram like a none return valve.

(Fuel tank side)

injector1 ....I
injector2 ....I
injector3 ....I
injector4 ....I

Regarding above ASCII diagram:
the row ........ Pump
should be the fuel tank with the pump

The column (I) on the left should be the flow back line to the fuel tank

The I on the right is also a column, but the BBS would eat blanks, so just imagine it is the fuel line from out of the tank .. T-joint to the FPV (PBV) and to the injectors.

Function is IMO:
fuel pump builds the pressure
FPV (Fuel Pressure Valve) opens when the fuel pressure from the fuel pump gets above the force built up by the spring/seal/hole sytem and that fuel amount flows over and back into the fuel tank.

Is this right ?
Confirmation by anyone ?

If so then the noise could be the rattling spring or ball.
Dieter K.

oops, seldom parallel post ;)
Carl, yes I got the email. Inquired at the for a picture yesterday.

Dieter K.


The statement that a PBV is no more than an adjustable FPR (Fuel Pressure Regulator) is incorrect.

A PBV is also designed to *increase* fuel pressure when manifold vacuum is low, I.E. when the throttle is opened, this can help to iron out flat spots caused by conservative mapping of transients.

Dave Andrews

Hi Dave,

Am I correct in assuming that fitting a PBV is not desirable/necessary when using a programmable ECU ? Does the acceleration enrichment function achieves the same effect ?

Russell Morgan

yeah the ecu can perform the same function except raise the actual fuel pressure!
which could be useful.
if thats all you want it for id suggest a Weber made regulator as they are better than Glenco (FSE).

if the 'FSE' PBV whistles/whines there is usually something wrong with it.
when did you buy the PBV? cos id contact the supplier and tell them you need another.

Drew Spalding

Hi all

thanks for the comments. It is strange but after leaving the car for one hour and shortening the vakuum hose the constent noise was gone although there is still a 3-4 second "whistle" when turning on the ignition. This happens someimes but not permanently.

Drew: I bought it from a german Lotus and MG tuner about one year ago.

Lets hope it remains silent 'cause it's really a pain. Next time I try Carl's advice but if it doesn't help I contact the seller.


Oliver G.


Acceleration fuelling in the ECU will normally give enrichment over transients and if the engine is properly mapped then you dont need or want the extra fuel in response to low manifold vacuum, in fact its a nuisance. Its best to use a regular FPR then your fuelling will be as the mapper intended.

Dave Andrews

I had the whistling too (using PBV from the same Reseller as Oliver, same PBV as Brown and Gammons) , I adjusted the pressure by adjusting the nuts swapped from 95 to 98 octan at the same time, no more whistling.

Exactly the same problem as Oliver stated, when pressing throttle and then *releasing* it, it emitted that whistling/ringing sound.

I am no expert, just stating my experience with above mentioned problem.


@ Dave, thanks for correction, looked up now,
*g, the failure in my above 'diagram' is a missing vakuum connection from inlet manifild and the membrane.



injector1 ....I
injector2 ....I
injector3 ....I
injector4 ....I

- PBV pressure range is up to 5 bar, bigger regulator membrane
(old standard shown on top right)

- FPV standard is only up to 3 bar

PBV 'reaction' (response) under load is much quicker by up to 70 percent then at the standard FPV.

@ Oliver,
suggest to speak direct with Felix M. Arnet from M-C. I think he should be able to help.
Dieter K.

This thread was discussed between 04/01/2003 and 05/01/2003

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