Smoking Rover

[Kiloengineer]

My Series IIA 2.25 petrol has me baffled. It smokes like there is no tomorrow. Sometimes its a light gray smoke and then it turns a really dark gray smoke - it varies. The car used to run pretty well but then I let it sit without running for about a year. To get her running again I replaced all the ignition parts (coil, points, plugs, cap, wires etc) although I think I need a new distributor since the shaft has radial play. I changed the oil - level looks right and no water in the oil. I rebuilt the zenith carb with a Proline kit from our hosts, although some of the kit parts were really poor and unservicable and I sent them back (and received very good support from our hosts). Most of the proline kit is still in the carb including the jets. I also installed the EGR valve which was not installed previously and replaced the diaphragm.

When I got the car running it runs pretty smooth although it stalls sometimes. I ran a compression test - 135 to 145 in all cylinders, the low cylinder at 135 came up to 145 with some oil but that difference doesn't seem too bad. I have tried to adjusting the mixture control screw and that changes how the car runs a little bit but it does not stop the smoking.

I would really appreciate any ideas. Has anybody successfully rebuilt the Zenith with a Proline kit? Thanks.
Jason.

[SafeAirOne]

What are the spark plugs telling you about the fuel/air mixture? I suspect a fuel/air ratio (mixture) problem based on the dark gray/black smoke you report. Is there any obstruction in the intake air system (collapsed hose, obstructed filter assembly, etc.)?

[Kiloengineer]

The plugs are quite black and wet so I agree the mixture is a strong symptom. I disconnected the intake hose at the carb to make sure there was nothing coming from the intake filter or the valve cover breather and when disconnected the car still smoked. I am suspect of the zenith rebuild since some of the parts were bad but I used the jets etc. I adjusted the mixture screw per the book (1.5 turns) so I hope I am starting off with a close to correct mixture. I also see that the choke plate is fully open so that is not causing it to run rich.
Thanks again.

[albersj51]

Could it be related the EGR valve you put in, since that want there before?

[TeriAnn]

The plugs are quite black and wet so I agree the mixture is a strong symptom. <<SNIP>>

I adjusted the mixture screw per the book (1.5 turns) so I hope I am starting off with a close to correct mixture. I also see that the choke plate is fully open so that is not causing it to run rich.


You didn't say, but I'm assuming that exhaust smoke you are referring to happens while driving.

The idle mixture screw only affects the idle circuit. It does not affect the cruise circuit. The 1.5 turns in the book is a rough starting point to get the engine started after a rebuild. From there you need to adjust it with the engine running for best idle.

If I were to pick a cause out of the hat, I'd guess the fuel level in the float chamber is too high. Could be that you have the float valve set too high. That's assuming that your float valve is closing correctly and that you have not accidentally swapped in a larger main jet.

You are running the stock fuel pump and not an electric pump right? Your carb likes a low pressure high volume pump and doesn't want to see more than about 3 lbs at the float valve inlet. Many electric fuel pumps pump about 7 lbs pressure which can overwhelm your float valve and cause your symptoms.

Since your distributor has side to side wobble either get it properly rebuilt or buy a new one. It won't solve your immediate problem but it will solve the one you will notice afterwords.

Good luck

[Kiloengineer]

The exhaust smokes a little when idling but then can be really bad when driving, so that is a good point about the idle mixture. When driving it varies as to how thick the smoke is, sometimes just a little and then sometimes a huge cloud. So maybe the float is sticking. I adjusted the float level when rebuilding the carb and I thought I had it spot on. I ended up using the old float needle because the new one in the Proline kit was completely wrong - the ground tip was not concentric and it was too long. So now I have a new needle seat and the old needle - might not be a good combo. I will try to check the float level again and make sure it is not sticking, not sure if I can do this with the carb installed.

Yes I am running a stock fuel pump, replaced a few years ago. I will have to buy a new distributor - is the Lucas 45D unit that is available the best option there? Just hoping not to have to buy a new carb also!

As to the EGR point from alberj51, I did disconnect the vacuum line that goes to the oil filler tube to make sure it wasn't sucking oil from the tube, and I still got smoke. I was surprised how strong the vacuum was. Also, I am not sure I have the diaphragm the right way up - I wonder if that can make a difference?

Thanks all for the ideas.

[TeriAnn]

I ended up using the old float needle because the new one in the Proline kit was completely wrong - the ground tip was not concentric and it was too long. So now I have a new needle seat and the old needle - might not be a good combo.

Your problem could well be a miss matched needle and seat that does not seal the fuel allowing the fuel level to be too high in the float valve. If you are like me you have probably already tossed the old valve seat and can not reinstall it.

See if RN is willing to tell you the brand of rebuild kit they sell under the Proline name then go shopping for a different brand rebuild kit.

It seems like aftermarket offerings is just getting junkier and junkier.

If worse comes to worse you can switch to an early B series Rochester or a Weber 34ICH. You can get decent rebuild kits for both. The Rochester is the simplest to work on.

[Kiloengineer]

You are definitely on the right track Teriann with the float level. When I ran the car this morning I notice that the top cover gasket was wet and there was some fuel on the outside of the carb toward the rear. So I took the cover off and replaced the needle seat with the old one (yes I saved it!), checked the float level again (exactly 33mm) and started her up again. At first it seamed much better, I took it around the block and by the time I got back it was smoking again, this time noticably when I went downhill :confused:.

There is again fuel on the outside of the carb toward the rear. Could this be the classic warped top cover? I looks flat to me but I am not sure how to check it. Unless that sounds likely then I will try to find a better rebuild kit, because I don't know if the jets or other parts I used are any good. I wish I could find a genuine kit.