what is purpose of part throttle enrichment valve, when, in what time of staging. what is positive effect of this element and what is negative if not working or something.
To quote almost exactly from Haynes Carb manual... Part-load enrichment (power valve) Fuel flows from the float chamber into the enrichment chamber (the lump on the LHS just above the throttle actuator of the 3PU) through a fuel channel. An air passage is taken from under the throttle plate to the cover of the chamber. At idle, and light throttle operation, manifold vac draws the diaphragm back against spring pressure to close off the valve, and fuel outlet channel. Under acceleration, and wide-open throttle operation, the manifold vac is depleted. The diaphragm returns under spring pressure and opens the fuel channel. This allows fuel to flow through a calibrated bushing (a hole!) to supplement the fuel in the upper part of the main well. Fuel level rises and mixture is enriched. If this is leaking, you'll get unnecessary fuel enrichment. If the diaphragm has failed, this will be even worse, I think. My fuel economy improved a good bit after I reconditioned this gadget. Funny thing was, I never got to check the condition of the old power valve (having reconditioned the one off my spare carb), 'cos I dropped it down the back of the engine bay and have not found it to this day! Pete
Presumably then, the accelerator pump is for more "instant" power rather than just gradual acceleration?
Spot-on fella, The accelerator pump has no vacuum-operated component, just a mechanical thrust of extra fuel through the pump jet. It just gets the ball rolling, cos all the other acceleration mechanisms rely on changes in airflow through the venturis, which only happens with increased revs or change of throttle angle, so kinda catch 22. Pete
how can that affect on fuel economy or passing fuel or blocking fuel i mean how can affect at perfomanse. does it needs to be replace after 19 years.
I can't remember exactly how it works at this time on a Friday night, but I would say at 19 years old it is very likely to be working badly, or not at all. May well affect performance and economy if it's not working right.. I'll try to have a look/think over the weekend.
do you have this part divided in pieces, can you make a photos for me. i dont have spare so i cannot test it how it works and which part are bad. thx
No, I lost it! What happened was that I used the valve off my spare carb to recondition with new diaphragm/seals etc, then when I did the swap, one lunchtime in the carpark at work, I dropped the old one as I unscrewed it from the side of the carb. I never found it. Went down the back of the engine bay, and may still be there, more likely it fell out on the road somewhere. Doh . Anyway, looking at the fuel entry/exit passages on my spare carb, it looks like it does approximately what the Haynes manual says, when the load is low, it hangs on to a certain volume of fuel in the 'bump' bit on the side of the carb, then at higher load it releases this fuel directly into the downstream side of the primary main jet, i.e. bypassing the jet, going straight to the fuel outlet in the centre of the venturi. Edit: This isn't quite right, I realised later. The 'bump' bit doesn't 'hang on' to any fuel, it's just a volume of space that the diaphragm can move in and out of. All that really happens is that when vacuum levels are high, at idle and other times when the throttles are almost shut, the passage for fuel to get to the primary main outlet is closed, by this diaphragm pulling the valve shut. When the vacuum on the diaphragm is lower, at wider throttle openings, the channel is opened, allowing enrichment flow of fuel. If the diaphragm was split, it could never do anything much, except maybe leak fuel all the time through the vacuum feed?! If the o-ring seal was leaking (but the diaphragm was OK), it would probably still work, but not as well, and would leak 'extra' fuel that wasn't required at low loads, all the time, hurting your economy. Judging by what I saw while refurbishing the 'spare' one , the diaphragm is most likely to have just aged, and stiffened, rather than split, reducing its ability to move on demand. The tiny o-ring on the outlet valve was also quite hard and probably not sealing well at all. Can you get hold of a refurbishment kit where you are? If not we could sort something out postally? Somewhere, I have a Pierburg part number for a refurb kit for just that valve, I think; I'll see if I can find the piece of paper...
i think i can find i have already saw it but i did not buy it. i dont believe in that repair kit proably they are not original probably someehere from turkey
has anyone made some tests or checks about this element on carb? does anyone has some pics or parts. how can this element directly degrade economy or perfomanse, which part of it is badly, and what are the simpthoms when this element is broken.
