Car broke down, here we go again...

[macaroni]

Thanks.
The carbs are my next port of call (after I've put the fire out...).

Thing is I have twin Dellortos, so its quite a job, but I guess it will have to be jobbed.

[Anders Dinsen]

Thanks.
The carbs are my next port of call (after I've put the fire out...).

LOL!

I tend to think the same... what kind of fuel pump are you running? I ask because I had all kinds of running problems because of a fuel pump that played up with me during autumn. I kept blaming the carbs, but it was just the electrical pump which sometimes stopped spplying fuel. The car would run ok for a while, then start hesitating as the float drained out, finally stopping completely. The confusing part was that when I put ignition on the pump again, it immediately filled the floats.

Side draught Dellortos and Weber's have integral fuel filters, so they seldomly go wrong.

You could also have an air leak. Manifold to head, most likely. The gasket is very thin, and I've seen mine get sucked in around one cylinder.

/Anders

[macaroni]

I am using the standard mechanical fuel pump.
I suspected this weeks ago when it first conked out, but the inline fuel filter seems pretty full and there is plenty of fuel at the carb banjos.
I have heard that fuel pump issues can seem like ignition issues though.

Another variable to think about!

[Anders Dinsen]

I am using the standard mechanical fuel pump.

Well the mechanical pump is very reliable. The earlier ones can develop a leak, but the later ones which are bolted together shouldn't suffer from this problem.

Electrical pumps rely on a little circuit or contact, a solenoid to pump the diaphragm back, and a spring to push it forward. There's a few things that can go wrong there. The mechanical pump simply pumps when the cam turns. It's dead simple. A return line ensures that unconsumed fuel (usually most of it) is fed back to the tank. The electrical pump only supplies the amount of fuel consumed by the carbs and doesn't need a return line.

So the two systems are different, but I don't think it's fair to say one is better than the other. For reliability, the mechanical is probably superior.

I'm running an electrical pump since it's part of my immobilizer circuit.

So I think your problem is on the carbs and that something is blocking a fuel line one or the other - or both.

Before you take them off and apart, you could check the float level when the car is running well, and compare it to when it's failing.

I don't know the Dellortos as such, but I have a book which covers them, and as far as I can see, you should be able to check the float level through the rectangular inspection cover where access is made to the main jets. I think you can see the top of the float and can measure the distance from the top of the float to the top of the carb cover with a vernier caliper. If the float level is very low (further down) when the engine is failing, it could be fuel supply.

/Anders

[macaroni]

Anders,
I think you could be right about it being carb issues.
I sprayed some brake cleaner across each barrel, with the engine running, and as I passed the barrel for cylinder 1 (? - near gearbox), the engine picked up.
The spray was quite localised and the effect was definitely much greater at cylinder 1.
So I am assuming there is a leak between the carb and inlet manifold.
I checked the jets and floats today - all good.

When you fitted your Webers, did you use "cups and rubbers" or "Thackeray washers" to mount the carbs?

[Anders Dinsen]

When you fitted your Webers, did you use "cups and rubbers" or "Thackeray washers" to mount the carbs?

Thackeray washers as they were slightly cheaper. The carbs came with plastic o-ring carriers, but I have converted to MISAB spacers now, as I was not sure about the plastic o-ring carriers' ability to seal.

A piece of water hose is a good tool for finding air leaks - put one end to your ear and move the other end around the carbs until you spot the hissing sound.

Leaks are most likely on the top, since the weight of the carburettors tend to open the gap there.

/Anders

[macaroni]

Well, I fitted my Misab plates and thackeray washers and the car ran much better, but after a few hundred yards (metres..) it would cough and run badly. Each day for several days, it would cough at the same place on my way to work. I'd pull over, fiddle with various things; ignition leads, vacuum pipes, position of air vents, anything, and then it would be OK. After a few days of this I got very cross and put it back into my garage and went to work in my trusty Alfa.
I ordered some new leads from Will, as they were the only part of the ignition system I hadn't changed. Fitted them, took it or a run, after a few minutes it coughed and misfired all the way home. Argh! I then checked the tightness of the carb bolts and while the air filters were off, I checked the balance of the carbs - perfect.
While I was checking the carbs, with the engine running, my hand brushed against the distributor and I got a shock! My feet were off the floor (in time-honoured Murena-mechanic fashion), so that couldn't be right.
I checked the inside of the dizzy cap and it looked perfect, but as I had a spare I tried that.
Result! The car now runs fantastically!

The distributor cap looks fine, and is only a few months old, but is seemingly at fault.
I drove into work today and the car felt wonderful, very strong and pulled very well right up to licence-busting speeds.

I hope I don't speak too soon, but I think my woes are over, for now.

Thanks for listening!

Antony

[Oetker]

There is a simple way to find this kind of problems.
Take a fine watersprayer, for example a can of windowcleaner, and spray some water on ignition and leads to the sparkplugs.
If they have a leak you see blue sparks.
If so, it is time to swap the parts for new.

[Anders Dinsen]

I hope I don't speak too soon, but I think my woes are over, for now.

Hooray! Well done. That was not obvious given the fact that the cap was almost new! It must have had a bad connection from the centre lead to the rotor or something?

There is a simple way to find this kind of problems.

Excellent idea, but why didn't you tell him long ago?

/Anders

[Oetker]

Quote Anders
----------------
Excellent idea, but why didn't you tell him long ago?
=====================================

I have no idea, it just came up again when he told about the shocking moment.
I think it's ok to put it in for the knowledge.
It is perfect for finding out leaky HT cables en rotorcaps.

[macaroni]

Good idea Oetker, I'll do that next time instead of using my hand!

It coughed and spluttered again on the way home tonight, but when I stopped to check it out, one of eth HT leads had come off the dizzy cap. Its all very strange.

[Anders Dinsen]

I have no idea, it just came up again when he told about the shocking moment.
I think it's ok to put it in for the knowledge.
It is perfect for finding out leaky HT cables en rotorcaps.

Indeed, it's a good idea to share it

It coughed and spluttered again on the way home tonight, but when I stopped to check it out, one of eth HT leads had come off the dizzy cap. Its all very strange.

Hmm... I think it's time to give your car a good polish? It's like buying your wife flowers - it sometimes works

/Anders

[macaroni]

Like the Matra, that stopped working a looong time ago!

[Anders Dinsen]

Like the Matra, that stopped working a looong time ago!

Haha, well you are right... I don't know what I was thinking about...

[macaroni]

Well I spoke too soon and last night after an evening of transporting kids around, it started to cough and splutter and this morning it refused to start at all.
I'm thoroughly sick and tired of this car.