To rule out hall sender, wait till it cuts out then check for spark. When these break down they cut spark all together

So you've a freshly rebuilt engine.

Carbs which may not be ok.

Ignition off an old VW which may not be ok.

A fuel pump which you've had issues with.

You're gonna need:

Compression on 4 cylinders

No air leaks

Equally set carbs

Good plugs

Good leads/dizzy cap etc

Good supply of fuel to carbs

Air

Just think of everything you need, and everything you've read about poor running on any engine, then systematically carry out checks to eliminate these causes.

It could be something so obvious, cylinder 2 sounds a problem, but who knows why, carbs or engine itself?

Never assume if you're stuck like this.

All very good advice,

Guy I've had a hall effect sensor fail on me and it gradually went, and intermittently wouldn't generate the pick-up for a spark.

It could still be a good idea to try and known working one though, but my money is still on the fueling side of things!

If a hall sender fails you get no spark, if its not starting due to a dodgy hall then it won't be sparking, if you check it while it won't start and its is sparking then the hall is not the issue. The hall doesn't effect the strength of the spark so its not like you will be getting a spark but the wrong sort or anything like that, it just won't spark.

I've had one go which the first symptoms where it would miss under load as it started breaking down, then eventually it started doing the telltale cutting out and not starting for like ten mins, then starting and tuning fine for a mile or so and then cutting out again

It may be the hall, but all I'm saying is rather than changing things that might not be the cause, check it first as it will be obvious if its that by just checking for a spark when its refusing to start

As I mentioned in the thread on this issue I've seen exactly the same happen with a ltd midget running lean and over heating, but the colour tune says its fine so fuck knows

Edited 27 August, 201214 yr by Mclovin

Guy, the symptoms you have described above sound similar to what I have. So I may try a new one. Is there anyway to swap the senders over from distributors? (I'm thinking no here as I can't find a way to seperate them). However, I do always have a spark at the king lead (when disconnected from dizzy) when it cranks.

Nick: The problem with the fuel pump originally was having a 24v one, and then this one wouldn't pump for ages. This is now sorted and I can see plenty of fuel in the filter

I have 'balanced' the carbs by setting the butterflies open a similar amount visually, so I can see where they are set. They also sound similar enough (cylinder 2 sounds the most dodgey)

Leads seem ok and plugs are new. Dizzy cap has been swapped too to no effects.

I have tried to fix all of the things I can think of. I'm going to check again for air leaks though as I think this is going to be the problem (especially considering Guys friends experience)

Why would revs pick up with a hand over the carbs? This only happens with carb 2. Hand over the rest kills the engine

Because you quite possibly have an air leak or a blocked jet

Edited 27 August, 201214 yr by erixtar1992

If you are getting a spark when the car is refusing to start then the hall isn't your problem si. You can swap just the hall, the wheel on the back of it which connects to the cam has a pin going through it. Remove that and the shaft going through the dizzy can slide out giving access to the two hall sender screws

As for the rev's picking up, if that runner is allowing air to be sucked in it could be that that cylinder is running very lean and when you block it off the mixture is made closer to what it should be, and that cylinder starts burning better, picking up the rev's as it does

Edited 27 August, 201214 yr by Mclovin

^^makes sense out loud too mate :)

That does sound feasible Guy. I'm leaning towards air leak at the carb rubbers, I'll get on it tomorrow and see if it helps. Can anyone suggest a decent liquid gasket? I have blue hylomar; any good?

Edited 27 August, 201214 yr by prankstar2003

Spray wd40 on all the joins when running. If revs pick up its leaking.

Dont waste your money on more gasket stuff just yet si!

Why not? She's an even deeper hole than Toby's (and I mean his car ) I was going to get some in case it is leaking. You know where the car is and how remote it is (you even thought the nearest town was dead!) so if it is leaking, I'll want to get some in there and not dick about driving back to town (where I now live). Need some anyway to seal the rocker gasket yo

Fair enough yo!!

Any luck then simon?

Could well be a hall sender starting to fail, but its the hall effect sensors job to activate the primary windings on the coil, so if its always getting a spark at the king lead, you can rule that out!

My £10 is on air leak, mixture being out if that's happening on carb #2

I'll report back tomorrow. Not with the car atm

Updates in problems can be found here

http://www.clubpolo.co.uk/forum/index.php?showtopic=294025

(as much for future reference as anything)

All new jets fitted today to the tune of 34 Bob Anyway she idles well now whereas she wouldn't after the jet fiasco. Still a little erratic when warmed up, and wants to die when hot but she does fire straight up where she would have struggled earlier. The carbs aren't balanced yet and I think I have my timing a little retarded so these are avenues to explore next. I've borrowed a carb balancer from my brother so I'll have a play around with that.

Other than that, I've been fiddling around trying to get all 5 gears. Still the same problem; can get 1,2,3 and 4 or 3, 4 and 5 with reverse in both cases. Currently I'm using a 6n rubber ball and late mk2 cage, but I don't think these will work with the early set up. Stupidly the original rubber ball went with the egine/gearbox years ago and its slightly smaller than the later balls. I think I need to use a full early set up of ball and cage, which means trimming a spare rubber ball down. I know 5 gears can be had in an early car without swapping the rod over as Erico has managed to do it in his. I'll get on this aswell tomorrow and report back. I also had to modify the locating pin on the cage as it kept jumping out of the ball/bracket. Just drilled and tapped the pin and have put an M6 cap screw in it to lengthen it. This shouldn't really be happening (obviously) which is part of the reason I think I need to use a full early set up. Will take pics tomorrow to better illustrate what I mean

Edited 31 August, 201214 yr by prankstar2003

Take gear gaitor off, under it where the stick would sit in 5th theres a rubber strip think a sorta see through colour. Fuck that off

Nope, done that. Still not enough side to side movement

I had to keep playing with mine. Took a while. Just keep fucking about with it and making very small adjustments.

I have been. Must have spent 3-4 hours in total trying to sort this. I'll get there eventually, but I'm going to swap over to the early cage. The later type doesn't look to fit properly at all, hence it keeps falling out.

Simon, just been stripping down a set of ZXR carbs, as it made me think of your problem,

Have you whipped the tops of the carbs off where the needle assembly and rubber diaphram are situated?

As if there's a tear in one of these, you'll be in all sorts of problems, i don't know exactly yet but if you were to cover one of the breathers up (like you were doing) this could possibly be sealing a diaphram leak and showing up as a change in running condition, like you were experiecing with carb No2. Just a shot in the dark.

Cheers for that. I'm going to strip the carbs again this weekend and clean them thoroughly with plenty of carb cleaner and compressed air, considering the jets were so clogged. Another thing to try. I'll check the diaphragms again, though they looked fine the last time I looked.

If you want, you could send them to me and i'll give them a good few days in the ultrasonic cleaner? Strip them down aswell?

I've considered ultrasonic cleaning, but its the cost that puts me off. I'll see what they're looking like this weekend and let you know. Cheers though boss

Have to be careful on reassembly to ensure the diaphragms sit properly