Weber carb problem

[gouldsborough7]

Back in May 2007 I started up a discussion on the probelms I was experiencing with my carb, which I believed was off a 3 litre Grannie and my Berli is a 2 litre Pinto.

Anyway, after a bit of fettling, including a manual choke conversion, I managed to resolve the problems, i.e. getting the engine to run smoothly at low revs, and general starting snags.

Yesterday on the dreaded M25 motorway, in a really grotty half-hour traffic jam, the engine conked out! The temp gauge was showing Normal, so I assume the engine was not over-heating. I managed to get the car well off the road beyond the hardshoulder. I checked condition of the sparking plugs, and they were only slightly sooty (normal for this car). Anyway, I changed the plugs for another set, and waited about half-an-hour to let things cool down and the traffic to get moving.

The engine was OK cruising at speed, but was not a happy bunny for the rest of the journey if in slow traffic, and would stall if the tickover was allowed to drop to less than 1000rpm. Trying to accelerate from low revs in top or 4th gear was impossible, and I had to rev it in lower gears to stop it jerking.

So before I consider a rebuild or replacement of the carb, has anybody had similar experiences, with ideas on how to resolve them, please?
Cheers
Mike

[macdonald.dm]

Re: Weber carb problem

Hi Mike.

If your car suddenly won't run smoothly below around 2,000 rpm, and behaves strangely below that speed, then it could be an air leak on the inlet manifold.

There should be a post about this very thing on this forum, but darned if I can find it. I had a similar problem - happened very suddenly, and meant the car would run ok above 2k-ish rpm, but let it fall below that level and it would start to rev and fall, rev and fall - exactly as if I was 'blipping' the throttle!

Dip the clutch, and the engine would stall. The throttle needed a fair press to keep the revs up and the engine running.

Danny (and others, I think) immediately diagnosed an air leak on the inlet manifold.

I was doubting of this as I couldn't believe a tiny leak would cause such strange behaviour, but had to swallow large amounts of humble pie after removing the manifold and finding the teeniest, tiniest amount of corrosion on the manifold face which I guessed had lifted the mating surface and allowed air through. The surface immediately around this little lump was 'oily', whereas the rest of the proper mating surfaces were perfectly smooth and clean.

I still didn't believe it until I cleaned it up, applied a thin smear of gasket stuff on both sides of the actual proper gasket, and re-bolted. Cured.

Other will be along to confirm/advise of alternatives, I'm sure!

[macdonald.dm]

Re: Weber carb problem

Possibly, the leak (if it IS a leak!) could be between the carb and manifold, instead of manifold/head.

[dogoncrazy]

Re: Weber carb problem

Had a similair problem with a 32/34dmtl weber on my pinto. remove idle jets and after putting them under 50x magnification microscope revealed a VERY small sliver of metal in one of them almost like swarf you get from a drill but much finer.Removed with fine tweezers[again under microscope] refitted jets and all was well! Webers don't tolerate any crap the way an SU carb will

[gouldsborough7]

Re: Weber carb problem

Hi Donnie
The problem when queuing on the M25 started with the tickover becoming merely erratic. I have experienced this once in the past, and on that occasion once I got moving again the problem went away. Yesterday, the tickover became so bad that I had to keep the choke knob pulled out 5mm or so, just to maintain reve in excess of 1000rpm. When we got moving, the problem did not recur for about 20 miles, but I was still being careful to keep the revs higher than the usual 750rpm.

When I eventually got off the M25 and took a chance by pushing in the choke knob, the engine died on tickover. On this occasion, and previously on M25, the engine was extremely difficult to re-start, and often misfired through the carb with smoke, and the engine sounding like it was running backwards.

I consulted a carb specialist "Fast Road Cars" with the intention of buying a brand-new Weber. By this time, I had convinced myself that the problem was the jumbo Grannie Weber carb, of unknown age and history. The rep sounded very kit-car sympathetic and said that Grannie carb was really only suited to very high speeds and was unnecessary for normal road use. He recommended a 32/36 DGV for my Berli, which I took the plunge and purchased. It comes with manual choke fittings already, and apparently should be ready to run without any significant adjustments on slow-running mixture. Only one screw on this model, plus one for the tickover. He thought that with a kit-car, I might not notice any reduction in power, and the new carb should be slightly more economical and smoother-running.

He was willing to answer subsequent telephone enquiries if I had any snags in fitting the carb. New cost with carriage was around £170, which I thought was not bad. I remember spending this sort of money years ago in getting the weber on my Robin Hood reconned.

I'll take on board the comments about air leakages (thanks), and will re-do the the engine-manifold joint with a new gasket.

The joint between carb and manifold will have a new insulation block and gasket materials. A smear of blue Hermitite wont go amiss either at both locations. I'll let you know the outome.
Cheers
Mike

[danny_nelson]

Re: Weber carb problem

I cannot add any more than what has been said above I am sure the answer is there for you.
Regards
Danny.

[ROBERT.JACKSON]

Re: Weber carb problem

I once had the same issue, but it was the brake servo piston seal failure allowing air loss as the servo pipe fits on the inlet manifold.Just blank of the servo pipe and test.Check your points and timing has not slipped, is the vacum pipe from dizzy to carb ok ?.

[gouldsborough7]

Re: Weber carb problem

Thanks Bob
I'll take on board your ideas, and check them out. I've got electronic ignition with no points, so that is eliminated. However, it begs the question about my electronic box of tricks!

What exactly did you mean about the servo piston seal? I have not noticed any deterioration to the brakes. Would the air-loss show in the colour of the sparking plugs?

The whole situation is a bit weird, as the car ran for about 70 miles perfectly well before the jam on the M25. Anyway, I expect very soon to take delivery and fit a new Weber 32/36 DGV carb with the exact spec required for a Pinto. I have never been very happy with the 3-litre Grannie version that always sooted up the plugs, and was dodgy at starting if right foot strayed near the go-pedal, and the 22mpg.

On the issue of starting, has anyone got any thoughts on why the Pinto takes a lot of cranking of the starter if the car has not been used for several days or more? Having been started, a re-start is always instant! My Robin Hood with 1600cc PInto had the same problem, and I have often thought this was due to petrol draining back into the tank or evaporation. This would never have been tolerated by customers of the original Cortinas or Sierras, so what is different about kits in this respect?

I'll come back with a finale on the carb fitting, hopefully in the next few days.
Cheers
Mike

[Dane_Rescueman]

Re: Weber carb problem

Your Granada carb could have been over jetted for your car and depending on the mark may not have progressive chokes. The Pinto may well have struggled with this.

Recently, someone had a similar problem with the car refusing to perform well after a period of driving. Most items for checking have already been mentioned but there is the addition of the old classic car howler. The tank breather. Next time the engine stalls at idle, sprint round to the filler cap and open it. If you get a "gasp" of air the the breather is not working properly or is blocked. Low pressure can cause the fuel pump a lot of extra work. The pump obviously works beter at high rpm - more strokes per minute !

I suppose that the old Cortinas were used almost everyday. The Weber 32/36 does seem to allow it's fuel to evaporate over a fair period of time. The little mechanical pump has a lot of work to do to prime an empty Weber. I had the same results with my old engine which used a 32/36.
I have just fitted fuel injection and have installed a swirl pot with a prime pump. If the car has been left for a long period I can operate this priming pump on its own via a press button switch, flip/flop relay, and the ignition in "Aux" position. The engine then can be started easily. A similar prime pup could be used for the Weber. A similar mechnical fuel pump on my dear old MF35X has an external priming lever on the side of the pump which is worth its weight in gold after a long lay off. Why don't they fit these levers to all mechanical pumps. We could all prime our carbs after a long lay off!

I hope all is well with the new carb.

[macdonald.dm]

Re: Weber carb problem

Good point from Bob above - it came to mind as I was falling asleep last night that leaks can also be gained from the servo pipe, vacuum advance, etc!

(And then, this morning, I forgot all about it again...)

I'm sure going for a 32/36 is a good move anyway - so if the problem still exists, it won't have been a waste!

When my car developed this problem, it was instantaneous - and just the weirdest behaviour.

Yes, I also have that 'cranking' situation if the car's been left for a week or so. I give the pedal a good few pumps to try and squirt something in to make it catch! As you say, if the car is being used after only a day or two, it starts instantly! Strange...

[macdonald.dm]

Re: Weber carb problem

And, are you ABSOLUTELY certain that there isn't a leak around the non-return valve you fitted recently in the brake servo pipe...?!

Oh, the coincidence...

[gaddbrose]

Re: Weber carb problem

Hi Mike. before I went over to injection-type Pinto's I ran a 2100 engine on the 38-38 carb. but I was told that the engine would not perform without rejetting. At that time , there were lots of garages with fitters who had the parts and knew how to use them. That carb. was then rejetted and transformed the performance, what you are buying in the 32/36 category is the standard carb., a version commonly used by Fords. At that time [late 1980] the twin 38 carb. was widely sought by the go-faster youth of the day, who would think nothing about lifting the bonnet of a Capri, taking the carb off and fitting it onto their own 2000, and surprise, surprise, it would'nt go. Hope you get it sorted. Brian.

[gaddbrose]

Re: Weber carb problem

Hi Mike, just something to add to the one above. The twin 38 carb. taken from the 3000 grannie was also fitted to the 3000 Capri, and being built to drive a 3000 engine , the jets were too big for a 2000, it delivered too much fuel through and the engine ran very rich and sooty, and expensive. Correctly tuned it still gave about 30 mpg. and enhanced performance.
Thinking about your "air leak", I think you may be clutching at straws. If your leak is between manifold and head, then you would be drawing in extra air , this would make the engine run weak and show whitish plugs and very poor perf. If it is rich, the perf. is still poor, starting bad and sooty. To end , have you checked the timing, if that slips because the dizzy has moved , the symtoms are virtually the same.

[gouldsborough7]

Re: Weber carb problem

Thanks Brian
Ever since I bought the car I have never been all that happy with the carb. I got rid of the auto choke very early on, and ended up fitting 2 choke knobs: 1 for mixture and the other for revs. This made starting more reliable, but it is quite possible that the jets are too big, and an expert could probably sort this out. However, the carb is quite old, and remembering the improvement I obtained on my Robin Hood with a recon carb I thought I would resolve this area once and for all by buying a new Weber designed for my engine.

As a routine, I will take make sure all joints are well done on re-assembly. Your point about the dizzy timing is a good idea and worth a check. I'll let you know the outcome.
Cheers
Mike

[danny_nelson]

Re: Weber carb problem

Brian it depends on what else that has been done to the engine how the carb is jetted. Mike take into consideration the Spec of your engine, do you know what has been done to it?