Intermittent shuddering

[Lukeh17]

Hi,

I posted about this problem late last year and I thought it was sorted with a coil change but apparently not. When driving at about 50-60 mph and once the engine is warm and I've been driving for 50 or 60 for awhile, the car seems to shudder/jolt and the revs and speed slowly drop - it's like it momentarily gets starved of something. If I go into a lower gear and reduce the speed to 40 it is fine. However, when going up an incline, it got worse and I couldn't get the car into 5th at all.

Do you think the fuel pump is going? What else could it be?

Thanks

[essextom]

Could be the flange between the carb and manifold, they are prone to splitting. Or rust in fuel tank

[mark1gls]

Carb or fuel injection car?

[scrumpyone]

Filler neck.

[moser]

Filler neck.

Thats what i was thinking. Bits from the filler neck in the tank blocking the pick up.

[essextom]

I can supply filler necks, out of stock currently but should have some more within next couple of weeks. https://dreadnoughtcustoms.co.uk/collec ... ical-parts

[Lukeh17]

Carb or fuel injection car?

It's a carb.

I can supply filler necks, out of stock currently but should have some more within next couple of weeks. https://dreadnoughtcustoms.co.uk/collec ... ical-parts

Can you let me know when they're available?

Thanks for all the advice so far, I didn't want to buy/replace things that I don't need to.

[unknownmale]

Inspect the filler neck, pull the sender out and have a look with a torch (Not an incandescent one though! :) ) put a magnet in there with a bit of string, see if you get any rust, or look at the fuel filter, pull it apart.

For the carb flange, with the car just idling, grab the airbox and pull it to 12, 6, 9 and 3 0clock and listen for any dips in revs, or spray some starter fluid at the base and listen for a rise in revs (Be a bit more careful with this one though, had some close calls with starter fluid and poorly timed cars)

From what you've said though it sounds like a lean condition. If you have a weber with a manual choke, next time this happens, give the car some choke and see if it evens out. If it does its a vacuum leak, most likely the carb flange. Typically shows itself once warmed up as the rubber is more pliable, but check all vacuum lines and the brake booster!

Hope that helps

[mark1gls]

You can also check the fuel filler neck by removing the filler cap and shine a torch down there and look for any rusty holes etc as the mud sits on top of the filler neck at the cap end and that’s what rusts them out.

[chopperoli]

carb icing

[Lukeh17]

Just an update on the situation. I haven't driven the car since the last episode and after the snow has finally gone, I went out this afternoon to do some checks rule some stuff out.

Firstly I started the car and let it warm up, I then sprayed carb cleaner all around the base of the carb and nothing happened, same when I tried pulling/pushing the airbox to 12, 3, 6 and 9 o'clock.

Secondly I then shone a torch all over the outside of the filler neck and all seems ok, and when I shined it down from the fuel cap end, it seemed black inside and couldn't see any obvious sign of rust.

I've attached images of the filler neck and cap area:

















I'm not ruling out rust in the fuel tank but was wondering whether it could be the fuel pump?

Cheers

[Lukeh17]

Today, I sprayed carb cleaner around the brake booster where it goes onto the manifold and also disconnected it from the vacuum advance system and nothing happened with regards to revs. The carb flange also appears to be fine.

I've replaced the fuel filter and had a look in the old one and watched fuel go into the new one and there was no sign of rust passing through the system and back out through the return line to the tank.

Therefore, my conclusion is, there is something blocking it at the supply feed from the tank towards the fuel filter and pump or could there be a problem with the carburettor e.g. jets blocked or something? Could the fuel pump also be on the way out?

Thanks

[Eagle1]

I've recently renewed my fuel pipes, carb car. It wouldn't start. I found my problem to be the concerned with the two pipes out of the sender. After replacing them the car started. Now I've only got to deal with the wonderful Pierburg end of life

[mark1gls]

What carb have you got, original Pierburg or Webber?
If you have changed to the Webber how old is it.

[Lukeh17]

I've recently renewed my fuel pipes, carb car. It wouldn't start. I found my problem to be the concerned with the two pipes out of the sender. After replacing them the car started. Now I've only got to deal with the wonderful Pierburg end of life

I'm gonna jack it up over the Easter holiday and have a good look at the fuel lines. I will check those pipes out. Thanks

What carb have you got, original Pierburg or Webber?
If you have changed to the Webber how old is it.

It's a twin weber carb and it's been on since I've owned it which is 3 years now. Not sure when it was put on!