1.3 Driver hesitates

This is doing my nut in   and its spoiling Matthew's driving lessons.

If I come back onto the throttle after being on a closed throttle for a few seconds (for example coming up to a roundabout) and then I come back onto the throttle below about 2,000rpm, there is a BIG hesitation, and then it will finally pick up and off we go. If I come back onto the throttle with the revs higher than about 2,500rpm, its hardly noticeable.

What I have done

>recent plugs, dizzy cap, rotor arm
>Weber (34ICH), with all the right jets for a 1.3
>replacement advance/retard unit on the side of the dizzy
>carb set up using a gas analyser and timing strobe light

Other relevant factors

>I've checked that the advance retard is working by sucking on the hose - it rotates a few degrees - about 5-7mm of movement of the plate.
>It has electronic ignition
>It runs very nicely when fully warm and when on throttle
>I've checked (and re-checked) the accelerator pump - it squirts nicely into the venturi when the throttle pedal is pressed.
>The car also hunts a little on very light throttle openings, and just recently has been reluctant to tick over until fully warm (about 7+ miles)

Its always been a little bit arsey to start (no choke until it starts to fire, then a few stabs of the throttle, THEN when it catches, pull the choke out fully). Even once its started, as soon as the engine is given any load, it will cut out unless it has LOTS of revs.

The only thing that I know is not right is that I couldn't get hold of a Weber base for the carb. the Weber base has a vacuum outlet which is supposed to be connected to the airbox (for the warm/cold air valve, I believe) and the vacuum outlet on the carb is to feed the advance retard. At the moment, I don't have the warm/cold air valve attached to a vacuum source.

I still reckon its ignition-related - I'm wondering if the dizzy simply isn't getting enough vacuum to advance the spark at very low revs.

However, if the car is allowed to reach tickover, there is no hesitation at all coming back onto the throttle.

Sorry for the essay chaps - I'm far more used to plugging a laptop in and twiddling with maps. I just need some theories to check out.

Thanks in advance

How is it for oil and water? Does it use any, is the oil cloudy?

Reason I ask is they are known to blow head gaskets, the replacement head gasket has a rubber ring in it which the standard one doesn't have.

Madferret said

How is it for oil and water? Does it use any, is the oil cloudy?

Reason I ask is they are known to blow head gaskets, the replacement head gasket has a rubber ring in it which the standard one doesn't have.

both fine.

oil is just licking the max mark on the dipstick.. and water is.. umm enough

and the head gasket has been replaced (on the long list of things done before i got the car)

now what

if your warm air feed isn't connected this could cause the carb to ice up now we are having cold weather again.

I thought carb icing only affected the Solex, not the Weber

Something else I thought of….

Just to see what would happen, I disconnected the advance/retard vacuum hose. The car ran fine and the hesitation picking up from the over-run got slightly better. However, it didn't pick up the revs as well coming off tickover, which made pulling away a bit more difficult, so I've re-connected the hose.

The instructions for the Weber appear to suggest I've used the correct vacuum point (near the bottom of the carb)  for the advance / retard, so I'd be surprised if I'm not getting enough vacuum (and thus not enough advance)

Looks like I'll have to re-fit the vacuum hose to the airbox that actuates the cold / warm air feed thingy - there are two unions on the plastic valve in the bottom of the airbox - does it matter which hose is attached to which?

^^^^ also, My dad has said something about the electrical solonoid not getting the required current to do.. um.. something :dontknow:

but we'll check that aswell at some point

could be all manner of things i suppose

Ahhh the joys of classic car ownesrship

Plug leads and coil?

Clean tank and fuel lines/filter?

i'm pretty sure carb icing can affect any carb i may be wrong tho  :dontknow:

Madferret said

Plug leads and coil?

the car pulls quite strongly and cleanly once on the throttle - I'd expect a coil / plugs problem to manifest itself at high rpm / higher load (again though, happy to be contradicted here, its a long time since I worked with carbs, coils, dizzies etc)

just thought of something else…..

When coming back onto the throttle from a dead throttle AND the revs are below 2,000rpm, if I am VERY gentle with the throttle, it won't hesitate - its only if I come back onto the throttle normally that it hesitates

It also pulls well, all the way to the redline (or as close as my ears will let me take it ) so I'm guessing the fuel supply is more than adequate.

I wouldn't discount anything until you can really say its working fine.

Maybe its something to do with the shifting of weight. Could be you have a faulty electrical connection somewhere. You say you have electronic ignition did this come with the car or was it a 'mod'? Are the connections secure?

Hows the choke flap operation is it getting stuck maybe, or maybe too loose?

Just a few 'out of the box' thoughts.

I appreciate all and any suggestions - they will all be checked out.

The electronic ignition is an aftermarket mod that was already on the car when Matthew bought it. It seems to work just fine at all other revs (and didn't give any trouble of this kind when the Solex was fitted)

The big hesitation has only happened since I fitted the Weber, which makes me think it has to be fuel, or vacuum.

If course it could be that the Solex was so crap, it was masking the problem

Solex arn't really that bad, they just get a bad press

Could still be fueling like you say, could be the weber itself, are you sure it was fitted correctly and all the vacuum pipes, gaskets etc. are all intact?

I'm pretty confident the Weber is fitted correctly. I bought new gaskets and I cleaned it thoroughly before fitting. all mating surfaces were cleaned properly and the carb was fully serviced before fitting (new jets, O rings, accelerator pump diaphragm, that sort of thing).

I guess its probably time to strip and refit again, just in case somethings blocked

If i didn't know better I'd say it was sticking points, but you say it hasnt got them any more  8O

Is the Cambelt timed correctly?

I'd guessed at points or a duff condenser too - I even went out and bought them both, only to find the leccy ignition when I took the dizzy cap off  :roll:

I'd also wondered about cam timing - this might also explain the horrible starting and the very occasional backfire through the carb when its trying to start from stone cold

It could do with a cambelt anyway, so I might as well do it - I guess its a stupidly simply job on one of these lumps?

maybe try swapping the electric ignition for points and condensor and if problem persists at least you can count out the elctronic ignition?  :dontknow:

I have a Weber on mine (34ich) and mine did the exact same yesterday morning, a little awkward to start, and a pop through the carb and then needed the throttle feeding in really slowly or high revs and slip the clutch in. It hasn't done it before, normally starts perfect. I'm not sure what its like when driving properly though as it's not on the road, i've only moved it about on the drive while getting it ready fr its mot.

I still have the points ignition fitted but its all brand new and if your having the same problem i doubt it's anything to do with that. My carb came with a K&N filter so i have that fitted but it gets rid of the warm air feed, i'd put it down to that and the cold weather as the car was fine when it was a little warmer.

if it carrys on playing up i might try adjusting the fueling slightly. I set it up in the summer and if its anything like my motorbike it needs a adjusting a little for summer/winter to be just right.

sounds dumb, but have you got any holes in your fuel filler neck?

Right - cam timing is perfect and I've reconnected the vacuum to the cold / warm air feed thermostat on the airbox.

Also checked the tickover solenoid on the back of the carb - working fine.

Off for a quick drive to see if its made a difference.