Carb woes.

[siii8873]

No matter what I do I cannot get my rover to rus as good as I would like. I nned to always choke the carb (Zenith) a little to get it to run good. I bought a rebuild kit and replaced all the internal parts, lapped the mating faces, cleaned it. No matter what adjustments I make I cannot get it to idle well. It seems to run ok except at idle. I have also done a full ignition system tune up (plugs, wires, rotor, condenser, cap, points, timing). Do these carbs just wear out at some time or is there something I'm missing. I am definitly not the best with carbs so there could be something I'm missing.

[ArlowCT]

We went through 2 Zenith's on my dads rover and never got them to run right. Both were new and taken apart to warp them and lap them smooth again and again and again. Nothing seemed to work. Eventually we put a weber on and never looked back. I wish I had a solution but I do know many other people have had these problems, someone must have found the answer.

[Nic900]

Hi
I have had the same issue with rebuilding my Zenith, I also went the route of a Weber but am not happy with, espesially as it had to be replaced as it leaked stright from the box and now the replacement is leaking and thi started not 6 months into it's service life. I have just purchased a used Zenith from Ebay and will have another go at a rebuild. I know they can be done but much time and care must be taken to get a good result. I'll let you know how it goes.

Cheers
Nic

[sayers]

did you see my post in "slop in the linkage " on the forum. I had the same problem.

[Rineheitzgabot]

Very happy with my Weber.

[Bertha]

1 word---WEBER-its worth the money.

[sven]

Before you write off the carb, hows the rest of the engine? Have you done a compression test?

[Jeff Aronson]

Zenith

I assume you've seen the link on the Forum page concerning the Zenith carbs?

Oddly, the problem with them is usually running to rich, not too lean. Usually when you have to pull on the choke cable to get it to run better, you're running lean. That's controlled by a mixture screw; I assume you've adjusted it.

A leak at the intake manifold gasket will also make the carb require more choke, even when warm. When the gasket is split, you're taking in additional air into the cylinder without going through the carb. There's no way that the adjustments in the carb can accommodate that problem. While the car is running, spray some WD-40 or PB Blaster around the intake manifold. Do the rpm change? If so, there's your problem.

Timing that is too advanced will also make the engine run lean. If it's running very lean, it's also running hot. If you've had the plugs in there for a while you might want to pull the plugs and see if they're white at the tips. That's a sure sign of hot running from either advanced timing or lean mixture.

Have you checked the points to be certain of their gap?

Have you replaced the inline fuel filter? You might have water in the tank. Have you looked at the fuel pump bowl? Is there water in there?

If you've not checked compression and/or cannot, start the car, warm it up, and then pull each plug wire, one by one. The engine speed should change quite dramatically. If it does not, or the change is slight, you have a problem at that cylinder. Check the plug wire and/or replace it with a working one. Still running poorly? Pull the plug and/or replace it. Still a problem? Look at that plug and compare it with other ones. It's probably different in appearance - too black or wet. That tells you about a compression problem in that cylinder. That would cause you to need to push more gas in the engine, and thus, use the choke.

Those are some additional ways to diagnose the problem. I doubt it's the carb itself. BTW, I've been very lucky and very happy with the Webers I've had on my Series II-A. I get about 100,000 miles between carbs.

Good luck,

Jeff

[ybt502r]

I started with a Weber but it never ran well. Replaced the Weber with a new Zenith and the truck ran fine for a while (I'd at least fixed the carb problems). Warped the Zenith on a long drive across the high plains (Colorado to Canada), then broke off the mixture screw tip on the rebuild. Fitted a 'new' (actually rebuilt and sold as rebuilt) Zenith, replaced the jet with a high altitude one (for Calgary) and went to electronic ignition...and the S3 has never run better.

The Weber had poor mileage and poor acceleration, the original Zenith was good and solid but not outstanding, and this final combination (rebuilt non-warped Zenith with correct jet for the altitude) with the electronic ignition (Pertronix) is just right. Everything seems to work as intended, and it even starts first time even in the real cold.

Don't know if I've helped, but previous issues I had with my old carbs and idling I found were due to bad condensors...went through a couple before moving to the Pertronix. Now I know why everyone likes them.

[mechman]

The big problem I had with the Zeniths was the accelerator pump sticking. Sometimes it was a corroded check valve ball sticking as well. I've rebuilt dozens of these, when I worked at a local Rover shop a few years back.

To fix it, you have to gently polish the surface of the piston and bore with a piece of crocus cloth, then clean the heck out of the check ball (I fill the chamber with a good carb cleaner and let it soak). Try to get rid of the scratches on the surface of the piston. Make sure the check ball rattles around a bit, that it's not stuck to the bottom. If it's really stuck, nudge it loose with a pin (but don't remove the retaining clip!) then resoak it.

When the accelerator pump sticks, the truck will not idle worth spit and will stumble when you begin to accelerate.

One other thing - the threads on the mixture screw are DIFFERENT between a Zenith and a Solex-Zenith. The Solex threads are much finer than the older Zeniths, even though most of the other parts (top, linkages, etc.) are interchangeable. The rebuild kits come with the newer style fine thread screws. DON'T USE THEM ON THE OLD CARBS!!! Polish the needle on your old screw and reuse it. The fine thread screws will ruin your old carb.

Mech