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MGB More Weber help needed

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Coastalman

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I posted awhile ago about buying a B with a Weber. With the advice of forum members, I rebuilt the Weber with a Redline kit after soaking it in cleaner for two days, cleaned out the fuel line, installed two new fuel filters and put clean non ethanol gas in the tank. The fuel getting to the Weber 32/36 down draft is clean. My problem is that the car will crank just fine with the manual choke pulled out. It will not idle. I have a Weber manual and set the idle adjustments as suggested and still the car stops running as I try to push the choke in to a running position.
What should I try next? It is frustrating to go through so many steps and then no idle.
Thanks,
Charlie
 
It's frustrating when you're in the middle of checking and re-checking, but it will be very rewarding once you have it sorted.

First, you can't set the idle adjustments if the car is running on the choke. If you set the idle speed with the choke engaged, then the idle speed adjustment screw would be bearing against the fast idle cam. Once you disengage the choke, the idle speed would be much too low. Also, setting the idle mixture with the choke engaged would result in a mixture that's much too lean when the choke is disengaged. (Or did you mean that you followed the bench setup instructions? There's another round of idle adjustments to be done with the engine running...)

Just to clarify, the car cranks with the choke pulled out -- but does it start and idle with the choke out, and then die when you try to push the choke back in? Or is it refusing to start and idle at all?

If you take off the air cleaner and look down the throats while cycling the throttle once quickly (engine off), do you get a squirt of fuel down one throat? If not, you have a fuel delivery issue. Either something is clogged, the fuel pump isn't cooperating, or a fuel line may be loose and drawing in more air than fuel.

One more tedious but necessary cleaning step: Check each of the jets (particularly the idle jets) and make sure they are clean inside. Don't use a piece of wire to scrape them out or you may alter the jet size. If something is stuck inside one or more jets, that will interfere with fuel flow. I would not be surprised if an idle jet is clogged. The reduced amount of fuel would be a good match for the reduced amount of air from a closed choke, but when you open the choke it would go dead lean.
 
The engine does start with the choke pulled out. The accelerator is very responsive with quick throttle RPMs. When I try to move the choke inward it starts "coughing/sputtering a bit and then dies completely if the choke is pushed all the way in. I did take the Weber apart to put the rebuild kit in it. I soaked the whole thing in a can of NAPA's parts cleaner and checked the jets. Maybe I missed something, but I thought I did a good job. I did set the adjusting screws without the engine running. Bench/manual instructions.
Thanks for the reply. I really want to get this straightened out. I have owned the B for several weeks and have not been able to drive it yet. It is all waxed, buffed and cleaned up so that it looks good in the garage.
Charlie
 
Then the idle speed screw is probably set correctly and the idle mixture screw should be at the "usually ideal (if everything else is correct)" point. The good news is, that was the hard part. The bad news is that now you're at the tedious part.

Three things to check next. Each of these could make the carb run very lean, and engaging the choke would tend to compensate.

1. Float level (if you didn't already set it during the rebuild, but it wouldn't hurt to double-check) -- too low makes the carb run lean
2. Idle jet sizes and condition, as well as the condition of the O-rings on the idle jet holders (leaking air will make the carb run lean)
2b. Is there a shut-off solenoid in the primary idle jet? If it's stuck in the half-engaged position, it would be like having a smaller idle jet (leaner mixture)
3. Try turning the idle mixture screw out 1/2 turn at a time, counting each half turn. If it gets closer to being able to run without the choke, that indicates the need to bump up the idle jet size(s).

OTOH, if you get to the point where the mixture screw is about to fall out and it's still not running right, then there's something else either blocking fuel flow or else allowing too much air flow. Unless the previous owner changed jets without fully understanding, the conversion kit should have been jetted very close from the factory. I'd be surprised if you had to go up more than one jet size.
 
There may be too much air flow or air getting into the intake manifold. After checking your suggestions I started looking at areas where air might be getting in. there is a fitting on the intake manifold that connects to the brake booster via a hose. It appears that where that hose attaches to the booster the fitting is loose or can wobble from side to side a bit. That is where I'll be checking next. I'll take the hose off at the fitting on the manifold and plug that hole. Maybe that is my problem. I'll let you know.
Charlie
 
(y)

MG boosters being outside my experience... hopefully there's a nut inside that you can tighten to get the fitting to seal again?
 
Coastalman said:
There may be too much air flow or air getting into the intake manifold. After checking your suggestions I started looking at areas where air might be getting in. there is a fitting on the intake manifold that connects to the brake booster via a hose. It appears that where that hose attaches to the booster the fitting is loose or can wobble from side to side a bit. That is where I'll be checking next. I'll take the hose off at the fitting on the manifold and plug that hole. Maybe that is my problem. I'll let you know.
Charlie
Click to expand...

That one way valve at the servo should not move around or wobble like you describe. That is possibly causing a vacuum leak and leaning out the mixture. You fatten up the mixture with the choke and it runs, push in the choke and it dies, that is a classic symptom of a vacuum leak. Odds are it is not the one way valve itself but the seal where it is plugged in to the servo. But as a just in case, here are part numbers with the assumption that it is a BL servo fitted and not an aftermarket servo:

One Way Valve 37H4896 (old BMC/BL part number) which has been superseded to 606030A at Rimmer Brothers (shows in stock) out of the UK and Moss Europe (shows not in stock). Moss USA part number is 182-195, no indication of stock status. British Parts Northwest 18G8953R, aftermarket servos only, call them for details.

Sealing Grommet Servo to One Way Valve BAU1019 (BMC/BL part number) Rimmer Brothers (shows in stock) out of the UK and Moss Europe (shows not in stock). Moss USA part number is 182-196, no indication of stock status.
 
I have thrown in the towel for working on the car myself. I'm taking it to Raleigh on Monday to put it in the hands of an excellent British car repair person who has been working on these cars for over 50 years. Maybe now the idle will be corrected and I can enjoy driving my B during the fall season. In the meantime I'll just have to suffer by driving my MGA.
Charlie
 
Coastalman said:
I have thrown in the towel for working on the car myself. I'm taking it to Raleigh on Monday to put it in the hands of an excellent British car repair person who has been working on these cars for over 50 years. Maybe now the idle will be corrected and I can enjoy driving my B during the fall season. In the meantime I'll just have to suffer by driving my MGA.
Charlie
Click to expand...
Sometimes your best tool is a credit card - get it done and get out to drive! Keep us posted
 
The mechanic has checked out the Weber on my B and determined that a previous owner has, at some point, taken it apart and not put everything back in. His recommendation is to buy a new Weber. With that said, I have seen that Redline in California sells, what they say, is an original Weber from Spain. Does anyone have any recommendations for another supplier who may have good quality Webers and not Chinese knockoffs?

Charlie
 
Go with Redline. Make sure and ask them if they have any suggested jetting changes based on your application (MGB) and being at what is essentially sea level.
 
I know literally nothing about webers - except to say that other than needing a manifold, there is likewise no reason not to go back to an SU at this point. OK just took a peek - they are about twice the price (new) on ebay.

good luck!
 
JP, nominally I would agree with you on the SUs but it's not so straight forward as that in this case. In another thread "Which Weber DGV is the right one.", the OP indicates that he has a 1977 MGB that is already fitted with a DGV. In this thread where he has pulled out the "plastic wrench" the mechanic looking at the car has basically said this one is toast, replace it. That means either going back to the Zenith-Stromberg CD-175, swapping out inlet and exhaust manifolds and running either HS4 or HIF4 SUs or the really radical solution would be do all the manifold swapping and fit it with a single 45 DCOE Weber or similar type from Dellorto, etc but to take advantage of the performance potential associated with the carburetor, engine work and modifications would have to be made and it is a whole pricier to get all bits (different types and sizes of various jets, different size venturi, etc) and a lot more work to properly dial those carburetors in then the relatively minor changes that might need to be made to a DGV.

Since he already has a 32/36 DGV fitted, it is basically a swap out of the carburetor with the possibility of needing to make a bit of jetting change since Weber has "slimmed down" their line ups and essentially only offer one version of most carburetor models to cover a wide range of cars and displacements. That is why I suggested that when talking with the tech folks at Redline that he ask about any jetting suggestions they may have for his specific application and location. Due to the swap out nature of the task and not knowing what the OP might have stashed away in the garage this is probably the most cost effective means to get him back on the road quickly with a car that runs decently.
 
That is what I am thinking. I'm not going to race the car, I've long past my autocrossing days and I figure that a new Weber is the most cost effective way of getting the car back on the road. I left a message on Redline's phone number and they haven't returned my call yet. I'll try again today. I have to wait until late morning or the afternoon since they are on the west coast.
I will let you know what they suggest and the price to buy the Weber. I do have a pair of SUs in the garage, but not linkage for them so a Weber it is.
Thanks for all the feedback!

Charlie
 
Here's the latest. The very knowledgeable person I talked to at Redline talked me out of buying a new Weber. He said that the wrong jets were in it and strongly suggested that I start with a jet kit and gave me the number on the exactly correct primary and secondary jets. Also, he doesn't sell to the public. I was referred to Carbs Unlimited along with the exact kit part number for a manual choke Weber. I am having it drop shipped to the mechanic working on my car. The kit was just under $60. The kit contains multiple jets and the identifying number is on them. To add to that, if a new Weber is bought, it comes with general jets put in at the factory so I would have to buy the jet kit anyway in order to put the correct jets for a MGB into the Weber. This has turned out to be a way to try the jet replacement at a lesser price than a new carb. If this does not fix my problem then I already have the jets I would need and those can be transferred to the new Weber. The price for a manual choke Weber new from Carbs Unlimited is $290. More to come as this progresses.

Charlie
 
great news - I love experts like this that sell you (or refer you) only what you need
progress!
 
This is why I suggested Redline, they have been in the game for a good while and have knowledgeable people. I was unaware of not selling to the general public though, I had a family owned dealership connection that I had gone through in the past (family is now completely out of the dealership biz now), so that was a bit of a surprise. I thought they did retail as well, but digging a bit deeper can't help but wonder if that is a change that might be tied to Redline becoming part of the WORLDPAC empire many years ago.
 
Coastalman said:
That is what I am thinking. I'm not going to race the car, I've long past my autocrossing days and I figure that a new Weber is the most cost effective way of getting the car back on the road. I left a message on Redline's phone number and they haven't returned my call yet. I'll try again today. I have to wait until late morning or the afternoon since they are on the west coast.
I will let you know what they suggest and the price to buy the Weber. I do have a pair of SUs in the garage, but not linkage for them so a Weber it is.
Thanks for all the feedback!

Charlie
Click to expand...
Charlie,

Good luck with your Weber. I have an 70 B that has a down draft Weber, but I wish it had SUs.

If you aren't going to use the SUs, would you want to sell them?

Bill
 
I did talk to Redline.. The specialist there said I should just go with the jet package. It has six different jets in it, but the ones I should have for the downdraft that is on my car are this: the primary #65 and the secondary is #55. I did order the pack and had it drop shipped to my mechanic in Raleigh. Oh yes, Redline does not sell to the public. The specialist gave me the part number for the pack and referred me to Carbs Unlimited and their online ordering at www.carbs.net. The mechanic has taken apart the Weber and determined that I do need a new Weber. It is alright, and needed, to have ordered the jet pack. The Redline specialist told me that the new Weber carbs come from the factory with a generic set of jets in them and I would need the right ones anyway. This is another delay, but one that is worth the wait to get the car running correctly.
I'll let the forum know how all this pans out. I do want to drive the MGB this winter as we have a usually mild winter where I live.
Charlie
 
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