350se dies when warm

[rumb]

What not even a tiny sliver?

An AAV that does not close completely will only make the engine perhaps run a bit lean, it is not the worst of things, and the rest of the system will generally overcome all that. Still it is important to systematically approach all of this. The entire system is a bit of a symphony all players need to be working together.

The AAV is relative easy to clean and adjust. There are videos on USA youtube that do a fine job explaining. We can also help here. The main points are to cleaning it well so that the piston moves freely and then adjusting the temperature bulb to make it close completely.

You can take off and place in a pan of hot water and watch it operate.

[milo]

Hi Rab and co.
Hopefully attachments visible... can you tell me more about the vacuum side of the WUR please, I never looked at that part.

[milo]

The brass part visible is fixed and seems to have a spring element inside, looking into the fuel return port there is a small chrome piston that cant be accessed from the Primary pressure reg orifice , the replacement reg is alongside the old one that was fitted to the car when it came to me.[hadn't run for 20 years] the rubber parts on the nose of the new reg is just a bit larger than the hole in the brass fitting, there is no piston there.

[revilla]

Hello Milo,

At this point we might need the help of other forum members. 

I have never seen that setup. In fact my interpretation of that picture was just to show the content of the kit, which include the o-rings, all those MANY shims, etc.  But honestly I've never seen that.  Ours are identical, but there's a piston, a large spring, there's the green o-ring and another one at the tip of the piston.  I only had to add one 1mm shim to arrive to 5.6 bars.

The only thing K-jet pressures reg I have ever seen is the following.

The 2 o-rings and the washer at the bottom are spares. 

The FD for sure needs a piston and a large spring to hold the pressure.  They aren't shown in your picture.  With all those o-rings and all those shims I understand why it's hard to get the pre reg in.  What's your primary pressure?  I don't see how the pressure can raise to 5.x without a piston/spring.

[Randys01]

I for one am familiar with your type of FPRV.  It is the only one I've ever seen on any fuel distrib including the later all alloy adjustable ala W126. My 6.9 is 1979 and your bus is 1980.  This is getting to the end of production of the steel non adjust FD so I think we can assume they are "late type" .
I cannot confirm or otherwise that FD's for the 6cyls may use a different FPRV. Matters not here and now.
So you have a new replacement for what came out of it but it wont fit. Now I'm a bit rusty but I do not recall all those little O rings on the tip. Others will chime in but one of those O rings belongs "inside" the piston/valve body.
Your old one should give you a clue.
Once you have the O rings sorted, then it's a matter of fitting up using 1 shim and measuring the system pressure.5.6 bar is a nice average on your gauge.
Add a shim if pressure is low. once you have correct syst pressure you can move on.
Now the description of the symptom seems to have changed.? Originally it conked out as it got hot at idle. Now you say it runs fine until you give it a kick in the guts and when it drops back to idle it flames out? Yes?

Forget the AAV.

Get the FPRV and system press sorted [hot and cold] and see if it still arcs up.
If it does I think   we turn to the WUR...  a fiendish little gizmo if ever there was one. The influence of vacuum  is significant when it comes to enrichening the fuel supply. The porting for this was reversed thru production adding to the mystique!

[milo]

Hi Randy
Thanks for response [and Robert] Mmm the plot thickens, all my pressures are good , line pressure , cold pressure and hot are all in spec. with the old Reg and yes when warm give it a boot and it dies.
The reason I turned to the primary Reg in the first place is to my understanding the device maintains fuel pressure and of course if the pressure drops or raises just for a second when I boot the throttle then it could cause the dying maybe?
Im still not sure if I should be using those little rubber bits but you've got to wonder why they are fitted to it and where do they go .
If I could come to a solid conclusion about the rubber bits then I could move on.

Yes the WUR .. Robert said it enriches the mixture when accelerating for kick down etc. and I hav'nt attended to the vacuum side of it at all. I've modified the petrol side to allow adjustment on the fly , removed the gauze filters, cleaned and cleaned again. Even dropping the fuel pressure slightly when the engine comes warm by a few pounds in the hope of avoiding any weakening to the point of dying doesn't work , I monitor the mixture of one cylinder with a glass spark plug
but it all gets a bit haphazard fiddling with pressure ,adjusting mixture and peering at glass plug .
So far the its never failed to disappoint , bollocks. 

[rumb]

I am assuming the Robert you are referring to is me. IF so, Regarding WUR, That is not what I was trying to say at all.  The WUR only attends the the warm up cycle by allowing more air in which raises the idle.  As it warms up and shuts the valve then the  idle drops. Once it drops the idle speed is adjusted with the big white plastic screw on the IAV - Idle Air Valve.  Of course he first thing to get correct is the timing if you have not attended to already.  I had said the WUR valve being open would very small make the mix leaner as there would be a bit more air added. But the WUR is exactly what it says Warm Up Regulator. Again it is one of bits of the system and one that is easily repaired and then not any concern after that. Certainly not the most important part but it does have it's job to do.

[milo]

Hi Rumb
No I meant revilla when referring to Robert, that's the name at the bottom of his posts.
I believe both by cam timing and ignition timing are good , my concern still revolves round the primary fuel pressure valve , im thinking those tiny rubber doughnuts supplied with the valve are very relevant and hope someone can give definite  instruction on them.
thanks.

[Randys01]

Err Rumb with all due respect I think you are referring to the AAV not the WUR.

Milo
The FPRV.  The 2 little O rings on the tip do not belong. They are spares.  If you look at the FPRV you took out and dismantle it you will find the little O ring inside. Your new one should  have the little O ring fitted up.
I suspect there is nothing wrong with your orig FPRV.
The test here is to read the control pressure when the engine is hot and you rev it. Normal hot control press should be about 3.6 bar.
do you have that?
when you rev it, the CP will drop a tad as the vacuum enrichment lowers the seat of the control valve in the WUR.  It will be a blip on the radar b4 resuming to 3.6bar.
I'm wondering that if and when you do this action that the control pressure is actually rising thus cutting the fuel supply off and stalling the motor or at least causing it to run ratty before it recovers.
Accordingly if you see the CP rise momentarily say to 4.2 bar then you have your vacuum lines muddled up.
This is so frustrating.  If I had the damn car in front of me I'd have it sorted in 20 minutes!

[revilla]

Good morning everyone,

Right, the needle moves a couple of marks under acceleration but then comes back to 3.6 quickly at idle. 

What's still HARD for me to understand is how in that FPRV setup (no piston) the shims supplied in the new kit would increase/decrease the System Pressure ()...

Adding shims for example won't physically change any axial forces against the copper fuel return orifice. Other than the volume the extra shims will occupy in the chamber (and that won't change anything under fluid equilibrium) I can't see how the System Pressure can be adjusted by adding and removing them.  I just can't see it.
On the other setup which has a piston and a spring inside it pressing against the return orifice, adding shims will proportionally increase the force thus increasing the System Pressure once equilibrium is stablished.

Yes, WUR is important, vacuum, etc. We can help you with that. One little test you can do is to remove/reattach a few times while engine running warm the larger vacuum hose on top of the WUR and check for changes in CP. It should have the effect of lowering the CP (richer mixture) a bit. If not, your WUR is not doing what it should. I'm assuming you have the WUR with WOT side vacuum hose. Please confirm.

I believe I read though you have checked for vacuum leaks, right? That is key and "could" be causing the condition you described.  Also, your mixture screw in the FD has been adjusted  while warm I remember reading.  That's touchy and can also cause that  symptoms.

Cheers.

[rumb]

Err Rumb with all due respect I think you are referring to the AAV not the WUR.  

Yes, thanks for correcting. I fear all this sitting about has addled my brain😷.....

[milo]

Hi all
Like I was saying earlier there is a small piston visible in the return port which the nose of the valve pushes on, the rubber doughnuts play a part or they wouldn't be supplied , if they were 'spares' then spares for what?

[Randys01]

The old FPRV.  In the bolt head of the FPRV you will see  a  threaded insert with  a small hex socket.  Undo this and the inner piston and baby O ring should reveal themselves. If the O ring is not present, repeat the procedure with the new FPRV. If this has the O ring [as it should ] then you know your old one is dodgey.
let's just get to this point.

[milo]

Hi sir
thanks for response.
Old one no baby o ring.
New one no baby o ring, im looking at the first o ring which has a tapered edge , the others are slightly less snug and are just ordinary

[milo]

Same pic twice, I meant to show old one too but its just a dirty version of the new one.
Are you suggesting I put the tapered doughnut and o rings in where I should have found them in the end of the valve?
Other pic showing small clip holding spring in place so I can remove and dismantle if need be, Im just wondering why Bosch didn't put them where they should be in the first place