Stuttering / Cutting out, petrol starvation

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Pommy
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Stuttering / Cutting out, haven't a clue

Post by Pommy » Sun Nov 26, 2017 11:46 pm

Peter, have tried from a can, same problem as soon as car warms up.
Jim, fitted the pressure valve because the mech pump overwhelmed the carb, totally drowned it, have tried elec pump without pressure valve, no diff.
Rebel, as above, pressure on this mech pump is higher than the old ( nackered) one.
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Stuttering / Cutting out, haven't a clue

Post by rebel alliance » Sun Nov 26, 2017 11:50 pm

What mech pump have you fitted ?



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Stuttering / Cutting out, haven't a clue

Post by Pommy » Mon Nov 27, 2017 10:33 am

Rebel, the pump was sold as OE equipment, same patten and fitment list as the old one, ie. 3ltr Essex, scimitar, Capri, Granada. Pommy


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Post by rebel alliance » Mon Nov 27, 2017 10:53 am

Should have no need for any pressure reducing valve in that case..just read previous posts ..is the float valve working ok ?



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Stuttering / Cutting out, haven't a clue

Post by peter freeman » Mon Nov 27, 2017 11:36 am

Sounds like you have done everything but I cannot see mention that you have tried fitting the old carb back on. Having read through the posts again like Rebel one would think it has to be the carb as you have changed everything else. Apart from needing four pumps on the throttle peddle to start the engine the old carb I have fitted is much better than the "new" one.



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Stuttering / Cutting out, haven't a clue

Post by Pommy » Mon Nov 27, 2017 4:19 pm

Rebel, as I have worked through the system and arrived at the carb, it has to come off and be checked, but still don't get why the filters are emptying, would a dicky float cause that ?.
Peter, your right the old carb has to go back on, at least the car did run, like you say, not all improvements improve.
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Stuttering / Cutting out, haven't a clue

Post by Pommy » Sun Jan 21, 2018 9:22 pm

After a prolonged case of 'man flu' managed to fit the old carb. Used a electric pump from a container via a filter, car started, the filter filled (mostly), could see petrol pulsing through, ran up to temp, then for a further 30mins, so changed over to the mech pump, filter filled but in a short time filter stopped filling, again, switched back to electric, filter filled but after a few mins started to empty, pump still ticking but not pumping, engine stopped. So back to square one. I really don't have any idea what's wrong, the cure or were to go next. Any suggestions would be welcome. Pommy


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Stuttering / Cutting out, petrol starvation

Post by 747PETE » Sun Jan 21, 2018 11:45 pm

A little late into this conversation,now you say the pump is ticking away all the time? I could not see in the thread what sort of pump..it’s my eyes😀 If it is an S.U. one,just put your finger over the end of the carburettor fuel delivery pipe,switch on and after a short time it should stop ticking,if it carries on it is either sucking air or....and I have had this problem...debris has found its way under the inlet valve and it will not close.Regards the filter notfilling,don’t worry,I have had that on two types of filter.Myrunning Classic is an MGB GT and I had similar problems,it took ages to narrow it down to the inlet valve.Its also worth checking.if it’s anS.U. the inlet banjo union seals,I had to dress the pump mating surfaces on mine to stop a tiny inlet air leak.If you do have an S.U. fitted,the constant ticking is the dead give away,it should stop if you block that outlet....enc some very helpful info from a friends site..MG I am afraid😳😀 http://www.mgb-stuff.org.uk/fueltext.htm#test



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Stuttering / Cutting out, petrol starvation

Post by Pommy » Mon Jan 22, 2018 5:00 pm

Thanks Pete, the electric pump is not a SU, its a 'sucker' made in New Zealand and when all is cold seems to deliver fuel OK but not at 1 1/2 to 2 pints a min , my tired eyes would say fuel going into the filter is a bit bubbly, after running for 20-30 mins the delivery of fuel dwindles to nothing. The mech pump seems to have similar problems, initially ok fills the filter well but as the engine gets to operating temp, fuel delivery is erratic then fails. Both these scenarios do the same wether from the fuel tank or a container. Could both pumps be faulty, they are relatively new with only 400 miles on them, and having changed carbs the problem is the same, could the fault lie elswear, in the manifold, the vacuum side, just grasping at straws there, stumped..... Pommy


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Stuttering / Cutting out, petrol starvation

Post by scimjim » Mon Jan 22, 2018 5:38 pm

Have you run it without the filter?


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Stuttering / Cutting out, petrol starvation

Post by Roger Pennington » Mon Jan 22, 2018 6:51 pm

As well as running it without the filter (which I would definitely try too), the logical next step would be to run it with a straightforward gravity feed from your jury-rigged petrol tank, straight to the carb. No filter, no pump, just a plain piece of pipe? The ultimate "Keep it Simple" philosophy :wink:


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Stuttering / Cutting out, petrol starvation

Post by Pommy » Mon Jan 22, 2018 10:38 pm

Jim, Roger, I will try with no filter, left it on to monitor the flow, will also try gravity, but I thought the carb needed a working pressure of 3psi ish to work, nothing ventured nothing gained.. Pommy


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Stuttering / Cutting out, petrol starvation

Post by scimjim » Mon Jan 22, 2018 11:06 pm

The carb just needs fuel in the float chamber. 3 ish psi is what it needs to keep the float chamber full at max chat (it’s easier to measure pressure than volume).


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1300 SS1 (Number One) & Sarah's coupe.
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Stuttering / Cutting out, petrol starvation

Post by Pommy » Sun Jan 28, 2018 5:44 pm

Peter/Jim, today tried a gravity feed direct to the carb, ran for 40 mins, tickover and light reving, then a little fuff, touch the throttle and the car stops, engine is now hot (90°) but not overheating, restart immediately ticks over, tickle the accelerator to build the revs allows tickover for another minute or so but eventually it stops again. I can't detect any airleaks at the W spacer, but its me so the check must be suspect, and fuel is def getting to the carb. Were next ?, replace W spacer, at 60 quidish not a small purchase, but I need to bottom this if I want to use my cherished Scummy. Any suggestions ???. Thanks Pommy


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Stuttering / Cutting out, petrol starvation

Post by Dennis Nicholas » Sun Jan 28, 2018 7:47 pm

Pommy
perhaps a quick summary of EXACTLY what you have done so far.

Your above sounds as if the carb is suffering petrol starve. (however seem to remember though you changed carb at some stage? but possibly more than one fault on car.)
Sounds like carb petrol inlet valve getting stuck closed or partially closed or float not adjusted to correct height as per manual.
Check ....a. inlet valve free to move ;b. float height setting; c. 100% no muck blocking ANY passages in carb.....may be encrusted muck inside that breaks off and blocks valve once engine running.

Suggest you say how you check what you check and use more technical terminology to give us a clue. ("tickle the accelerator" ???)
Just before cutting out do the revs fall then rise then fall on tick-over.....i.e. anti-stall device in carb working......what revs at tick-over?

Gravity feed.....how high container with petrol above carb and what size tube connected from container to carb?

We'll get there in the end :)

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