Where to look for Zenith manual?

ViR2 · 08-08-2009, 02:00 PM

I'm totaly new to carbs. I need to get my car to the shop to have it's carbs adjusted properly, but problem is that, driver side cylinders are the only ones working properly, passenger side does not have fuel flowing enough and is running very lean. Can some one point out which pins are for adjusting fuel flow?

Carbs are Zenith 40TIN

James Brown · James Brown's Garage

just entered the Zenith fray myself. there is no manual that l can find for these. there is a exploded parts diagram in the PET.
several causes for no fuel on one card like blocked fuel lines, cloged fuel filter (if you have 2), floats not set correctly or clogged float needle valve, tons of other things...
Best to just pull them off and rebuild them. You get a good diagram when you get the gasket set from our host. Not that hard to do just CLEAN everything you can on them and use new filters, one per carb, when you put it back togeather.
is this on your 912? or what model car/year/engine/miles/pictures!!! good luck

ViR2 · 08-08-2009, 02:56 PM

yes it in my 912, thou with 2.4T engine. These will be rebuilt, but first I need to get the car to the shop

) thing is that fuel is flowing, just not enough to work normally when rev's are low. Thank's for a tip

LakeCleElum · 08-08-2009, 03:05 PM

The was a great web site posted here for the Zenith, but I see it is no longer up.

My experience, the nozzles for fuel thru the accel. pump are really tiny. They plug easily which leads to hard starting and hesitation. These are not hard to pull apart. Clean all jets, nozzles and passages with carb cleaner and compressed air......Gasket kits are available. G'luck

tswaney · tswaney's Garage

send me an email to tswaney at sbcglobal dot net

I may have a document that may be helpful.

911Tfan · 08-10-2009, 05:19 AM

even though there are differences i am figuring from looking at them that there is similarity between the zenith and weber carbs. 3 chokes, 2 float bowls, emulsion tubes, etc... i read a weber book to gain a basic understanding .

Christien · Christien's Garage

There was a great website that had a great explanation, along with scans from a Zenith manual. I can't find it now on a google search, maybe it's been taken down, but I archived the entire site in case that happened. If anyone wants it, pm me your email address. It's a fantastic resource that anyone with Zenith carbs must have.

Hawkeye's-911T · Hawkeye's-911T's Garage

Hi Christien
I think you may get swamped by your kind offer. Will PM you shortly
Cheers
JB

Christien · Christien's Garage

No worries. It's the best resource for Zeniths out there, though still not exactly a "for dummies" guide. It's really too bad it's disappeared. Come to think of it, if someone has server space and wants to host it, pm me and I'll email it to you. The zip file is small, only about 3.5 MB, and retains the original folder structure of the site, complete with all html files and images.

levdeb · levdeb's Garage

I will host it for everyone! Once I get it from you, I will post it at:

http://www.BillLeVasseur.com/zenith

(don't have it yet guys, so be patient! lol)

Will bump when I do.

Thanks Christien!

Porsche-O-Phile · Porsche-O-Phile's Garage

Thanks for hosting that - it's great information (I got it already courtesy of Christien).

levdeb · levdeb's Garage

Its hosted. Thanks to Christien and Porsche-O-Phile.

Zenith 40 TIN Carburettor Manual

Enjoy!

levdeb · levdeb's Garage

Geez, now that I am reading this manual, do I NEED the "Auxiliary Enrichment System"?? Would it be better (or even an upgrade) to block it off like this guy did??

Porsche-O-Phile · Porsche-O-Phile's Garage

From what I've read, it seems like it's better from an emissions standpoint, but to simplify operation and make the Zenith setup reliable, it's probably better to disable it. Not sure which way I'm going to go yet. Knowing me I'll probably try to have it operating - I'm a sucker for punishment sometimes (dammit - I just KNOW I can make this work!)

James Brown · James Brown's Garage

I took mine off and rtv'd the port closed, vacuum plugs in the ports-good to go.

nilknarf · nilknarf's Garage

Bringing back an old thread to update everyone's bookmarks... I found what I think is the manual information on a different site: Porsche Leather Work and Zenith Carburettor Manual

Cheers!

Curt

69BahamaYellow · 09-20-2010, 04:58 PM

I can tell you that without the aux. enrichment circuit, the car will backfire a lot when you get off the throttle and coast above 2000 RPM or so. With an over rich mixture, you can eliminate this somewhat, but you won't entirely get rid of it.

Make sure you can identify the following pieces, as they are all required, and must be adjusted correctly for the system to work. The Zenith manual in one of the above links tells you how, but I would troubleshoot in this order:

1) Aux. Enrichment device - one per carb. Take this apart first as each contains a flimsy rubber diaphram, which probably has a hole burned in it. (that's the main reason it's not working. Fix the diaphram and you're 75% done with the repair.

2) RPM switch. - This is on the engine fuse box, and looks like a voltage regulator. If this is missing, you may want to consider just plugging the enrichment tubes and live with the backfire.

3) microswitch - This is the little button below the throttle stop on the driver side carb. The RPM switch turns power on to this switch, so long as engine RPM is above about 1500 RPM, and the microswitch makes sure that power is supplied to a small solenoid valve in the passenger side carb, only when the throttle is closed. If either the RPM or the microswitch is not working, this will cause the burned holes in the diaphrams in step one above. I had to repair mine twice to find this out, because apparantly the diaphrams need to have at least occasional fuel flowing past them to keep from overheating. It only takes about 3 short drives around town to burn up a new diaphram if the switches arent working. This probably explains why so many people scrap the enrichment circuit. Very frustrating......

4) Solenoid valve - just one, and if it's there, you can almost assume it's working, as these things are pretty reliable (that's also why it's last on my troubleshooting list.

The last step is to adjust the mixture and flow needle valves on the enrichment devises. This is complicated and you will need a flow meeter to balance left & right side flow. Technically, you also need a CO meeter, but you can do it by sound and a little trial and error if your good w/ carbs. Once you have these things set right, The circuit works really well; that is until the ethanol in your gas starts eating all the rubber components. I live in TX, so ethanol has only been mandated for about a year now. So far, mine are still holding, but time will tell. So long as Pellican keeps carrying the rebuild kits, I suppose we're all still OK to run with these things......

Christien · Christien's Garage

Curt, thanks for posting that link. That looks to be exactly what I've been emailing out to everyone - I'm glad someone's re-hosted that site. If it ever goes down, feel free to pm me for a copy - I backed it up years ago, complete with directory structure, so if you unzip it and retain the structure, all the links will work, like a regular website.

James Brown · James Brown's Garage

I have that on file also, very good info. alot of it is available no where else.

nilknarf · nilknarf's Garage

I had actually found the link after I had sent you my plea for enlightenment Christien, but I genuinely appreciate you sending me the files- I'll be adding them to the Porsche "toy box" on my computer!

I noticed there are a few broken img links in the website I found- I haven't had time to extract the site you sent, but I'm hoping a few of those broken images are just bad links in his directory structure.

I'm sure Wayne has a "helpful links" page on the PP site- it'd be great to have this one added to his resources list.

Curt