2800cs Zeniths: Solution sought in the UK

[deQuincey]

When I rebuilt my Zeniths I kept the original float needle valves, the replacements were unacceptable. The float can also get hung on the gasket if not trimmed. There is an old thread describing the procedure of covering the top cover vent hole to see if idle changes, if so there is a leak.

the needle valves that use to come in some of the rebuilding kits are very bad, and i agree on the interference of the float

but IMHO the problems he is facing are different

it is sad to see another pair of zeniths being put in the shelf

 

[bavbob]

I'm no expert, but lack of understanding should not imply replacement. I rebuilt mine, played with them for a while, I got mine running beautifully......and I never rebuilt a carb in my life till then. Read the tech section on these or have your mechanic do so.

 

[JFENG]

Bob, which instructions did you use? BMW blue books, Haynes or ?

 

[deQuincey]

Bob, which instructions did you use? BMW blue books, Haynes or ?

hopefully the bmw usa pages

 

[bavbob]

Yes, I used the Tech Info from this website

 

[dj_efk]

Hi all,

Update: The issue has been narrowed down to the accelerator pump pistons being scored and the seals being bad (there was not any replacement seals in the rebuild kit).

I therefore need new seals and replacement pistons - Any leads on who I could source these from?

Thanks.

 

[deQuincey]

Hi all,

Update: The issue has been narrowed down to the accelerator pump pistons being scored and the seals being bad (there was not any replacement seals in the rebuild kit).

I therefore need new seals and replacement pistons - Any leads on who I could source these from?

Thanks.

there are also many sources for these, quality varies, i would recommend buying at the dealer, very expensive, though

 

[deQuincey]

Hi all,

Update: The issue has been narrowed down to the accelerator pump pistons being scored and the seals being bad (there was not any replacement seals in the rebuild kit).

I therefore need new seals and replacement pistons - Any leads on who I could source these from?

Thanks.

uncertain about what “scored” mean, but surprised that this could be a source of failure

only if the pump seal makes no effective seal i think you might have some fuel drops being irregularly entering the venturis

is that the reason they gave you ?

 

[dj_efk]

there are also many sources for these, quality varies, i would recommend buying at the dealer, very expensive, though

Hi Jesus, do you mean the BMW dealer? I would think these parts are NLA? If not, what dealer do you mean? I do not mind paying a fair amount for such parts.

"scored" means deeply scratched, the workshop is saying they have narrowed down the issue to this and /or the seals.

 

[JFENG]

Is this the workshop that originally rebuilt the carbs and couldn’t tune them?

 

[Stevehose]

There is a mercedes part number for these, I’ll look for it, meanwhile I’ve never seen the seals for sale by themselves, only the entire pump and seal. Be very careful installing them as they tear easily.

 

[dj_efk]

Is this the workshop that originally rebuilt the carbs and couldn’t tune them?

Yes, this is the same carburettor specialist that rebuilt them.

They said that their original comment I mentioned in the original post about scoring in the venturi actually referred to the accelerator pump housing bore (this information is coming to me via the restoration shop that is managing the car's mechanical rebuild, so it may have been them that used the specific word venturi, I realise this is not correct).

They are happy to go back free-of-charge and install new accelerator pump assemblies free of charge if I can source these parts (@Stevehose - noted on your warning, thanks) - however, they are pushing me to swap the carbs out with a Weber conversion kit as these carbs are notoriously unreliable according to the various sources they've tried to use to trouble-shoot. I have tried JPA (Jens Peter Adam) Vergaser Services in Germany and also the carburettor hospital here in the UK, let's see what they come back with, but would appreciate any other leads / thoughts.

Thanks.

 

[deQuincey]

Yes, this is the same carburettor specialist that rebuilt them.

They said that their original comment I mentioned in the original post about scoring in the venturi actually referred to the accelerator pump housing bore (this information is coming to me via the restoration shop that is managing the car's mechanical rebuild, so it may have been them that used the specific word venturi, I realise this is not correct).

They are happy to go back free-of-charge and install new accelerator pump assemblies free of charge if I can source these parts (@Stevehose - noted on your warning, thanks) - however, they are pushing me to swap the carbs out with a Weber conversion kit as these carbs are notoriously unreliable according to the various sources they've tried to use to trouble-shoot. I have tried JPA (Jens Peter Adam) Vergaser Services in Germany and also the carburettor hospital here in the UK, let's see what they come back with, but would appreciate any other leads / thoughts.

Thanks.

almost sure that JPA has them

 

[deQuincey]

There is a mercedes part number for these, I’ll look for it, meanwhile I’ve never seen the seals for sale by themselves, only the entire pump and seal. Be very careful installing them as they tear easily.

seals were for sale at a couple of carb specialists, not sure if at the bmw dealer

 

[deQuincey]

Hi Jesus, do you mean the BMW dealer? I would think these parts are NLA? If not, what dealer do you mean? I do not mind paying a fair amount for such parts.

"scored" means deeply scratched, the workshop is saying they have narrowed down the issue to this and /or the seals.

yes i meant bmw dealer, i think i made my last set rebuilt in 2018 or 2019 and i bought these from bmw for sure

obviously i dont know what is left in bmw warehouses now, so yes they might become nla

 

[bavbob]

I cannot see how any part of the accelerator pump can get "scored". I would not give up on these..........sounds like your shop has had enough and that's why they want the Webers......but do you want the Webers?

 

[deQuincey]

Hi Jesus, do you mean the BMW dealer? I would think these parts are NLA? If not, what dealer do you mean? I do not mind paying a fair amount for such parts.

"scored" means deeply scratched, the workshop is saying they have narrowed down the issue to this and /or the seals.

thank you, if the bore of the accel pump is heavily scored i would be very concerned about this issue

 

[deQuincey]

I cannot see how any part of the accelerator pump can get "scored". I would not give up on these..........sounds like your shop has had enough and that's why they want the Webers......but do you want the Webers?

good point,...do YOU want the webers ?

 

[JFENG]

good point,...do YOU want the webers ?

The good thing about Weber’s are
(1) known good solution
(2) it puts a ceiling in the cost/effort

My concern is getting the Zeniths to work might be a black hole, given the shops which are doing the work. They are relying on the customer to do their job...

So, if the existing shop is used, they are unmotivated to do good work on the Zenith, and this can lead to less good work and more of unnecessary costs.

 

[dj_efk]

@bfeng you have neatly summarised the situation I'm facing.

I have been given the contacts of a lady in Germany that JPA uses to rebuild these carbs and has sufficient know-how/experience/equipment to test them and guarantee they will work correctly once on the car: Annette Hué of IOZ in Muelheim-Kaerlich. Has anyone heard of her previously?

I'm thinking this is my best bet, unless she charges similar to the Weber kit to right the issue of course.