Technical dump valve stays open

[beau]

it works but its open all the time, but if i squeeze the vacuum hose it closes again so it can withstand the pressure but the pressure through the vacuum hose is making it stay open all the time? any ideas?

 

[alexGS]

it works but its open all the time, but if i squeeze the vacuum hose it closes again so it can withstand the pressure but the pressure through the vacuum hose is making it stay open all the time? any ideas?

Yes - it's stuffed

Is this the original Bosch-type recirculating dump valve? If so, it probably has a split in the diaphragm. I got a genuine replacement from a Bosch specialist and the difference was night and day - the boost drops quickly to 0 during gearchanges, no more nasty jerks or 'hammering' effect where the engine wants to go faster as the throttle's closed.

If it's non-original (external dump valve?) then it probably needs adjusting. I imagine that it's screwing up the engine idling at the moment.

I'm a believer in the recirculating design, since the air is 'retained' in the system and doesn't have to be replaced with more air through the airflow meter (and therefore, more fuel).

-Alex

 

[antsuno2]

Alex i thought the recirculating valve forces it back to the turbo stalling the blades, and when dumped to atmos keeps turbo spooled up, im for dumping lol Ant!

 

[beau]

its an aftermarket one, im not sure if its connected right either tho, it looks wrong but i duno, surely the vacuum pipe shouldnt have pressure going through it enough to open the valve all the time?

and will this be why my revs go up and down and it nearly stalls when idling?

 

[custard]

try dismantling it and making sure its not stuck
if the cars not been used it could just need a little lube on the rubber seal(s) and a bit of movement

 

[beau]

try dismantling it and making sure its not stuck
if the cars not been used it could just need a little lube on the rubber seal(s) and a bit of movement

it does close when i turn it off, it moves freely by hand.

 

[Chas Uno]

it could just need a little lube on the rubber seal(s) and a bit of movement

 

[Dunc Uno Turbo]

beau, this is EXACTLY why ur revs will be going up and down!

the UT needs a twin piston dv (ok, it should be for some reason mines always ran mint with a diaphram one lol) so get it swapped over. or, just bung the hole up and take the vaccum pipe off and try it then. it "should" idle fine and therefore u will have deffo found ur cause of dodgy idling

Dunc

 

[triks]

put up a pic of set up. The spring in valve sounds as if it's soft,source a firm one.on the other hand the rubber(diapham) could be worn.

 

[beau]

beau, this is EXACTLY why ur revs will be going up and down!

the UT needs a twin piston dv (ok, it should be for some reason mines always ran mint with a diaphram one lol) so get it swapped over. or, just bung the hole up and take the vaccum pipe off and try it then. it "should" idle fine and therefore u will have deffo found ur cause of dodgy idling

Dunc

it was blocked off when i bought it, i think it was ok then cos my mate said to me has it always idled so ****, and i then realsed too, and no it hadnt.

its a twin piston yeah.

il get some pics of the set up later, it looks wrong to me but i duno anything tbh!

 

[alexGS]

Alex i thought the recirculating valve forces it back to the turbo stalling the blades, and when dumped to atmos keeps turbo spooled up, im for dumping lol Ant!

Ah no - the recirculating valve passes air back to the *inlet* of the turbo, therefore NOT stalling the blades... and on the contrary helps to keep the turbo spooled up for longer

The main concern I have with an external dump valve is that the air 'lost' from the system has to be replaced when the turbocharger boosts up again, and that replacement air has to flow through the airflow meter, and therefore the injection ECU injects more fuel than actually needed.

-Alex

 

[alexGS]

il get some pics of the set up later, it looks wrong to me but i duno anything tbh!

Takes a lot to admit that

But your instinct may be right, it could be hooked up to the wrong places (this has happened before!)

I think the dump valve is supposed to work on a pressure differential which is at a maximum as the throttle closes and the boost pressure is high. With the engine idling, the boost pressure is obviously low, so the pressure differential shouldn't exist and the valve should be closed.


-Alex

 

[beau]

some pictures of the set up.

 

[beau]

any one knows if that is plumbed in right then?

 

[BillyTheKid]

that looks right to me, (same as mine anyway lol) i had probs with my baily dv stayin open so got a blitz style one of the 'bay for like £20 and has been fine since.
p.s that is one loverly lookin engine you have there.:yum::worship:

 

[F R O S T Y]

Looks to be plummed in ok beau i reckon the DV is dead tbh it is quite common for those DVs to fail, and yeh i reckon dunc is right about the idle too.
Out of interest does your boost gauge work correctly? I'm sure one of those vacuume pipes goes into the car to the boost gauge??
On yours i can see 1 blue pipe and 1 black from the t-piece on the injector ecu, what is that black pipe connected to??

F R O $ T Y

 

[beau]

that looks right to me, (same as mine anyway lol) i had probs with my baily dv stayin open so got a blitz style one of the 'bay for like £20 and has been fine since.
p.s that is one loverly lookin engine you have there.:yum::worship:

well iv bought a new baileys one now, will see what that does.

and thats just as i bought it

 

[beau]

Looks to be plummed in ok beau i reckon the DV is dead tbh it is quite common for those DVs to fail, and yeh i reckon dunc is right about the idle too.
Out of interest does your boost gauge work correctly? I'm sure one of those vacuume pipes goes into the car to the boost gauge??
On yours i can see 1 blue pipe and 1 black from the t-piece on the injector ecu, what is that black pipe connected to??

F R O $ T Y

good good, cant do much until i get a new coolant hose anyway, want to get a new one really cant find one tho :bang:

it has an aftermarket boost guage, the standard one seems to read 0.5 bar on idle then when u rev it a bit drops to 0 then shoots upto 1 bar with a little rev but the aftermarket one seems to work ok.

 

[beau]

right iv bought a brand new dump valve now, and it doesnt do anything, presumably because its new and has a stronger spring than the old one, anyone know all the turbo/vaccum hoses and where they should go? theres 1 blocked off on the left hand side of the inlet manifold... but what ever, the dump valve looks correctly plumbed in but does nothing.

 

[beau]

anyone got any ideas then?