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Discussion Starter #1 (Edited)
Im having problems with vacuum generation on my t4 which ive just done a TDi conversion on.

It holds vacuum fine(no leaks) but does not generate enough vacuum to keep up with the demand on the system under 1800rpm. soon as im moving the pedal softens up but in stop start traffic my pedal is solid in a few presses.

any ideas why? i stupidly removed both lids from the two pumps i had (my old abl one and the new ahu one) both same part numbers so i thought id disturbed the internals from generating vacuum correctly. tried fitting a new internal seal to one but make no difference

Grabbed another vacuum pump from the scrappers (same part no) and didnt remove lid but this one is exactly the same.

Any ideas?

the one way valve in the lid operates correctly,

the one way valve in the vacuum line also operates correctly.

there is no leak on the servo rubber plug.


This is the cylindrical pump (not all t4's use this design.)


How can i have a problem at low revs? the pump is obviously driving from the intermediate shaft otherwise it wouldnt generate any vacuum. it is also correctly engages with the oil pickup drive shaft internally else it wouldnt sit into the block correctly. what can it be?

regards

andy
 

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Discussion Starter #3
tried yet another pump and a different vacuum pipe and still no difference,

the intermediate shaft is driving it ok,


only thing i can think of is mabe upon fitting the pickup from my abl into the TDi motor something is overtight and is sticking and takes approx 1800rpm to overcome?

any ideas?
 

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Discussion Starter #5
its not the servo buddy,

a) servo was fine prior to engine swap, didnt touch it during swap.

b) vacuum pump should be sucking on tickover, with pipe completely removed and finger on the end.... nothing

c) tried point b on a 1y powered polo (same pump) and this will suck your finger easily to the pump. so its definately something to do with the engagement of my pump inside the block i think.


Its definitely engaging as it wouldnt generate any vacuum if this wasnt the case, the pump also drives the pickup, maybe something isnt quite right in there.

all i did during engine swap was remove old ahu pickup and fit my old abl pickup (standard process as tdi engine in golf sits at different angle to t4's) no other TDi converts have had this problem
 

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Discussion Starter #7
I cant believe you are still getting grief with this mate :eek: Hope you get it sorted soon!
between playing with it ive learnt to live with it, i drive a beetle during the summer months so used to no servo assistance!

luckily the minute i rev over 1800rpm it generates vacuum and brakes are fine, its just four of five presses in stop start traffic and my pedal goes hard.

its not a servo leak either as i can park up (with vacuum) leave it 24hrs, hop in and still has vacuum
 

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Discussion Starter #8
comparing these two assemblies

ABL (1.9TD)

http://www.wagenstad.com/index.php?modid=581&page=1-115-20


AHU (TDi)

http://www.wagenstad.com/index.php?modid=187&page=1-115-20http://www.wagenstad.com/index.php?modid=187&page=1-115-20


what i did was to swap part 13 from the ABL motor, and fitted it to the AHU engine along with the sump (this is because of the angle of the engine when fitted to a t4.)



Parts 14 and 21 are common to both and are the same part number but part 22(gear for driveshaft) is common to the TDi engine but is 'not a spare part for the abl model'.

My question is how are items 14 and 21 held in place? does the vacuum pump engage directly with the intermediate shaft (part 1) of is it driven from part 22? It has to be something in here that is causing my vacuum problems at low revs.
 

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Discussion Starter #12
UPDATE:

Stripped the engine down today, bit the bullet (removed the sump) which involved removing the power steering pump, pulley and bracket.

Here is what i found inside, The picture below shows my abl pump next to the ahu pump (interestingly these are both the same part number!) its just the pickup that are different.

Circled is the problem. Gas exhausted by the vacuum pump enters the oil pump shaft where the arrow is at the top and exits through the hole in the step in the shaft. The hole in the pump i removed was almost completely blocked as you can see!



Here is what i removed from the hole



Lesson to all you engine building guys and the paramount importance of cleanliness when rebuilding the engine, i was extremely careful as well, i have no idea how whatever that is got in there!


Havent had chance to rerun yet as my powersteering pump has gone and the golf one didnt fit, (outolet pipe is in the wrong direction :(
 

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lookin at your lifelile you gunna live long and prosper but theres a black spot somwhere in the middleI:
well sorted matey
 
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