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Manta B Carb adjustment and hot start issues


Simon Dobbo
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2 hours ago, cam.in.head said:

it doesnt sound like a distributor issue itself(main unit)but i mentioned the arm ,cap etc  because you say you have a good spark to the main ht lead .  its a strange issue indeed .  when the car stopps running after a while you definately still have good main lead spark but very poor spark coming out of ever cap plug lead ? is this correct .

cannot see how it would run for miles up to this and then only do 1/4 mile and fail ? 

very strange . 

so logically if theres a good spark going into cap but not coming out changing the rotor and cap is a good place to start !

and not ignition related . we dont have any tank vacuum now ?

 

No tank vacuum that I can tell

and fuel in fuel filter

by the time I got spark plug etc to test spark it had started to cool down so not 100% sure

connector from module to side of distributor wasn’t in the best condition with bent pins but guess if there was no connection then no spark at all

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black power wire to spade terminal (any !  its the same piece of metal)

green round connector to pin . 

if you are trying a new coil make sure its designed for 12v electronic ignition as the earlier points coils look very similar in terminals and construction  but have a different primary resistance . ( maybee compare to yours)

 

Edited by cam.in.head
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35 minutes ago, cam.in.head said:

black power wire to spade terminal (any !  its the same piece of metal)

green round connector to pin . 

if you are trying a new coil make sure its designed for 12v electronic ignition as the earlier points coils look very similar in terminals and construction  but have a different primary resistance . ( maybee compare to yours)

 

Great - thanks

 

Will do

 

 

Wonder though if the one I have is incorrect if been swapped - maybe thats is an issue 

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if anyone had put a non electronic coil on then it would get very hot and be cooked by now !  havnt got an haynes in front of me at the moment but if you have im pretty sure it tells you the coil resistance . 

if you change the coil , the amp( module) and the arm and cap then you might sort it but i must admit this is s bit of a head scratcher ??

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18 minutes ago, cam.in.head said:

if anyone had put a non electronic coil on then it would get very hot and be cooked by now !  havnt got an haynes in front of me at the moment but if you have im pretty sure it tells you the coil resistance . 

if you change the coil , the amp( module) and the arm and cap then you might sort it but i must admit this is s bit of a head scratcher ??

Tell me about it - ha

 

The problem seemed to start when i went to rolling road tuner and he changed the Weber jets so my head initially went to fuel issue - but when did it again this weekend my mate met me with a spare plug and tried it off plug leads and had very weak spark. then we remove air filter and checked we have fuel squirt in on throttle - which we did

I wonder if when the tuner was messing with ignition wires to connect his old Sun machine he may have caused an issue/short.

 

My mate has an old autodata book with ignition system in and all tests there for voltages etc come out ok - but then that was when car had cooled down whilst pushing home etc. and after the tests the bloomin thing fired straight up

 

All i can do for now is change the rotor arm and coil and amp as they are on the way from MrCarlos - will try and get a dis cap also

then fit them and go for a drive.

Just dont really want to be half way to NEC Thursday and break down.

🤞

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if you change all that lot then the only other thing electronic ignition wise is the hall effect sensor inside the distributor but they are usually pretty trouble free !

the only thing baffling me is that when you say you got a very good spark from the main coil output ( the centre feed into the distributor cap)  this would suggest that the distributor hall sensor,module and coil and all voltage supplies and earth points are ok . IF  it happens again try to double confirm this ( and that you have weak spark out of cap like you said before .)

see what happens when you get the other bits on from carl  ??

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1 hour ago, cam.in.head said:

if you change all that lot then the only other thing electronic ignition wise is the hall effect sensor inside the distributor but they are usually pretty trouble free !

the only thing baffling me is that when you say you got a very good spark from the main coil output ( the centre feed into the distributor cap)  this would suggest that the distributor hall sensor,module and coil and all voltage supplies and earth points are ok . IF  it happens again try to double confirm this ( and that you have weak spark out of cap like you said before .)

see what happens when you get the other bits on from carl  ??

Will do

I didnt see the spark myself as was 'on the key' and it was bright outside.

Maybe by time we tested the coil again it had started working again but didnt go for another start while doing multi meter tests.

As you say - fit the bits and go for a drive then see if issue has gone.

I was convinced was like a vapour lock but my mate the mechanic says its spark - he should know better than me.

If your boilers broken then im your man! - HA

 

Carl said the same - he doesnt have a distributor but he has never known one to have an issue.

I just need to source a dis cap now for piece of mind

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New coil and ignition module and distributor cap and rotor arm fitted.

also got a spark tester between lead and plug

driven 15 miles beautifully 

parked for 30 mins

started - 300 yards driven and died again

fairly convinced spark is good now as can see a consistent spark

has to be some kind of fuel issue I think?

running out of ideas

might have to try the rolling road guy again and go down in jet size to see if makes a difference?

can’t figure it out as drives great when it’s going

🥵

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Well, so we are back to fueling. And we are at a point that is saying fuel starvation at the carb tbh.
So we are confident that there is no tank vacuum. 
Happens only after a short run, so heat soaked

There used to be issues with the alloy covers warping on some carbs, but never heard of it with a Webber. But it could be possible I guess. Seems to be related to the cover been off just swap jets, so definitely speak with the tuner for sure. But have you checked carb screws are all tight ? 

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1 minute ago, Jessopia74 said:

Well, so we are back to fueling. And we are at a point that is saying fuel starvation at the carb tbh.
So we are confident that there is no tank vacuum. 
Happens only after a short run, so heat soaked

There used to be issues with the alloy covers warping on some carbs, but never heard of it with a Webber. But it could be possible I guess. Seems to be related to the cover been off just swap jets, so definitely speak with the tuner for sure. But have you checked carb screws are all tight ? 

I going to spend some time in morning checking fuel pump fixings and carb bolts etc

have emailed Eurocarb to ask what jets they have in the kit as standard

dont really understand why bigger jets would cause an issue and it runs so well when it’s running

 

supposed to be doing 97 mile run to NEC tomorrow afternoon

dont know if I do without stopping if it will make it or not

i just wish before I had it tuned I could be certain the problem wasn’t there 

don’t think I ever drove the car then parked and went back to it same day - only ever went out on round trip then put away and left for a week

I think the spark was probably fine and I was thinking weak spark when holding a plug against the block and trying to turn it over etc

the little red acuspark indicator gives me a better view and seems like good spark now anyway

Has a pressure regulator between pump and carb

what should that be set at?

currently at 3. (Bar I guess?)

wonder if turning up will help or if there is an issue with that

car has new fuel pipe from tank to fuel pump

removed the breather valve thing and put pipe straight to tank - I can blow up it and hear it in filler neck so think breathing is ok

guess I can drive it without filler cap to fully rule out an issue

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Do you mean 3psi, not 3bar? 
It’s ok, but could be an issue tbh. In the past with std lift pump, never needed a regulator at all. Maybe loop it out and see. It could also be a point of failure.
When the car dies and refuses to start, pop off the air filter so you can see the Venturi and pump the accelerator at the carb a little. There should be a jet of petrol from the enrichment pump easily seen. That will determine if any petrol in the carbs bowl. 
I do recall a sticky float valve, but that was on a different carb that had the brass into an aluminium housing, not the same on the Weber. You can see what it looks like though here https://www.ebay.co.uk/itm/296574402658

Edited by Jessopia74
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11 minutes ago, Jessopia74 said:

Do you mean 3psi, not 3bar? 
It’s ok, but could be an issue tbh. In the past with std lift pump, never needed a regulator at all. Maybe loop it out and see. It could also be a point of failure.
When the car dies and refuses to start, pop off the air filter so you can see the Venturi and pump the accelerator at the carb a little. There should be a jet of petrol from the enrichment pump easily seen. That will determine if any petrol in the carbs bowl. 
I do recall a sticky float valve, but that was on a different carb that had the brass into an aluminium housing, not the same on the Weber. You can see what it looks like though here https://www.ebay.co.uk/itm/296574402658

Thanks

i will either adjust the regulator or remove it for now

i guess if pump is too powerful it causes over filling or flooding?

must be 3 psi - adjusts from 1 to 6 I think

total carb novice to be honest which is why I went to the tuner that did wonders with my Spitfire twin carbs

wish I had made him write down exact changes he made but am still not sure changing 2 of 4 jets could cause the issue I have

i have removed air filter before and seen fuel on operation of throttle which was why I ended up thinking spark. But this may have been when cooled right down

plugs were dry tonight when I pulled them so not flooding I don’t think

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Has the rubber carb mounting been checked out ? Just reading through everything don't think it's been mentioned. 

Prone to cracking and porosity,  can weaken the mixture enough when warm to cause these problems.

Spray some brake cleaner around the base of the carb when idling and see if you get an increase in revs?

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