engine won't rev

[hibbo]

Good afternoon.
This is my first post, I've had my 1934 box saloon since October last year it was purchased for my wife who has wanted one for years.
I have over the winter been doing various things to improve it's running but one thing which has stumped me is i can't get it to accelerate unless I fiddle with the choke as I try and drive, this virtually makes it impossible to drive on the road.
If I don't touch the choke it will go to 30mph in second and that's it, change into 3rd and 4th and it will still stay at 30 unless we come to a hill.
My wife bless her is very frustrated at missing the opportunity to drive it in all this lovely weather we have had.
I have stripped and cleaned the crab (zenith 26va) including all the jets and drillings 3 or more times and blown through with high pressure air, checked for manifold leaks, made and fitted a new gasket, (adjusted the float height so it should now be running rich) timing checked and adjusted several times, new condenser fitted, fuel drained and replaced, fuel line blown out, getting a good supply from the pump.
Tappets have been adjusted, compression is 100psi in each cylinder, give or take one or two pounds. (amazing) , new ht leads fitted, plugs sand blasted and gaped (champion d16.
The car starts easily and will tick over well although when cold pops back in the crab a bit.
I am a motorcycle man in essence so am well used to old bike engines and the issues thrown up and have been tinkering with and maintaining my vehicles for 55 years but this little Austin has got me beat.
PLEASE OH PLEASE Somebody tell me what I'm missing.
If anyone is interested enough to have a look at it I live in Handcross west Sussex.
Any help or idea's will be gratefully accepted.
Thanks in anticipation from a man at his wit's end.

[Andy Bennett]

Hi Hibbo

Others will chip in with better replies than mine but quick question re the carb.
Do we assume it was like this when you bought it or had it become like this as you have tinkered and adjusted?
Does it have 7 stamped on the carb flange where it attaches to the manifold (it can be a bit difficult to see), and what jets do you have fitted?

Finally, to me 30 in second seems pretty fast (too fast?), mine will do about 15-18 in second if I am pushing it (but mine is tired). Have you checked speed using a sat nav?

Andy

[Chris KC]

If using the choke improves things it sounds like you have a carburettor problem - but there are so many unknowns here. Have you made contact with your local A7 club? I feel sure if you did you'd soon find a willing volunteer or two to come and take a look.

[Austin in the Shed]

Does the throttle pedal open the butterfly fully.

[dickie65]

Hi Hibbo,
Have you checked the filter that lives in the carb banjo.
Also remove the banjo and the float valve and make sure passages are clear.
Check the float level as modern fuel is a different density to the older fuels.
I have had problems in this area in the past, it is often overlooked.
It is also worth checking the fuel pump is performing well.

Best of luck in your task.

[Reckless Rat]

Blocked exhaust perhaps?

[Pricey]

Hibbo

I have had recent issues with the 26VA on my 1937 Ruby.

All documented here...
http://www.austinsevenfriends.co.uk/foru...p?tid=1458

You mention using the choke to assist therefore making the mixture richer in fuel. This is not dissimilar to my issue.

Turned out to be the emulsion block. With a straight edge it was minutely bowed.Once I had lapped it against the carb and made a new gasket performance was transformed.
I had tried carb cleaner but because the emulsion block is within the carb it did not highlight that air was bleeding past.

Since that I have also ensured the carb bowl to body is square and further transformed performance.

Been out today on a round trip from Derbyshire into Notts and back, holding a steady 40mph on the flat but as soon as there is any incline 30mph and less. 

If you look at the original carb repair instructions it describes lapping the emulsion block. Try it. At least you can then tick it off the list of possibles.  

HTH

Dave

[John Mason]

Hi Hibbo, I have consulted my bible on these matters(Oldhams Practicle Automobile Engineering Ilistrated) and it quotes the following for an engine that starts but will not open up. Some of which you have already addressed Damp or faulty condenser, faulty coil, plug insulation defective soothed up or incorrect gap, Ignition to retarded, Jet blocked, Petrol shortage, Choked exhaust system. I hope this may be of some help.

John Mason

[hibbo]

Hi Hibbo

Others will chip in with better replies than mine but quick question re the carb.
Do we assume it was like this when you bought it or had it become like this as you have tinkered and adjusted?
Does it have 7 stamped on the carb flange where it attaches to the manifold (it can be a bit difficult to see), and what jets do you have fitted?

Finally, to me 30 in second seems pretty fast (too fast?), mine will do about 15-18 in second if I am pushing it (but mine is tired). Have you checked speed using a sat nav?

Andy

Andy thanks for your reply, I can't answer your question my wife went for a test ride with the P.O driving and she said it was fine but it was the first time she had been in a 7 however it has never run correctly since we first tried to use it.
Yes there is a 7 on the carb flange.
No I haven't checked the speed but I have been flashed by a 30mph matrix sign which is outside my house.

Regards
Graham

---

If using the choke improves things it sounds like you have a carburettor problem - but there are so many unknowns here. Have you made contact with your local A7 club? I feel sure if you did you'd soon find a willing volunteer or two to come and take a look.

Thanks for the reply Chris.
No I haven't but its probably the next step.

Regards
Graham

---

Does the throttle pedal open the butterfly fully.

Thanks for the reply.
Yes the butterfly opens fully, I have an old land rover and I've been caught on that one before.

Regards
Graham

---

Hi Hibbo,
Have you checked the filter that lives in the carb banjo.
Also remove the banjo and the float valve and make sure passages are clear.
Check the float level as modern fuel is a different density to the older fuels.
I have had problems in this area in the past, it is often overlooked.
It is also worth checking the fuel pump is performing well.

Best of luck in your task.

Rickie thanks for the reply.
Yes I have checked all the things you list, more than once.

Regards
Graham

---

Blocked exhaust perhaps?

Thanks for the reply
The exhaust is relatively recent and in good condition, but I will check it.

Regards
Graham

---

Hibbo

I have had recent issues with the 26VA on my 1937 Ruby.

All documented here...
http://www.austinsevenfriends.co.uk/foru...p?tid=1458

You mention using the choke to assist therefore making the mixture richer in fuel. This is not dissimilar to my issue.

Turned out to be the emulsion block. With a straight edge it was minutely bowed.Once I had lapped it against the carb and made a new gasket performance was transformed.
I had tried carb cleaner but because the emulsion block is within the carb it did not highlight that air was bleeding past.

Since that I have also ensured the carb bowl to body is square and further transformed performance.

Been out today on a round trip from Derbyshire into Notts and back, holding a steady 40mph on the flat but as soon as there is any incline 30mph and less. 

If you look at the original carb repair instructions it describes lapping the emulsion block. Try it. At least you can then tick it off the list of possibles.  

HTH

Dave

Thanks for the link Dave.
I will whip the carb off again and check. Thanks.

Regards
Graham

---

Hi Hibbo, I have consulted my bible on these matters(Oldhams Practicle Automobile Engineering Ilistrated) and it quotes the following for an engine that starts but will not open up. Some of which you have already addressed  Damp or faulty condenser, faulty coil, plug insulation defective soothed up or incorrect gap, Ignition to retarded, Jet blocked, Petrol shortage, Choked exhaust system. I hope this may be of some help.

John Mason

Thanks John.
I have not tried changing the coil and I will in desperation get another set of plugs but the plugs have been degreaser and blast cleaned and checked out in a single cylinder motorcycle ok, the rest has been checked.

Regards
Graham

[Jeff Taylor]

Graham,

You have a very highly regarded Austin 7 engineer almost on your doorstep - Steve Hodgson trading as SMH Services Ltd, The Barn at the rear of 56 Sea Road, East Preston, West Sussex BN16 1LP - stevehodgo@hotmail.co.uk - 07870 731074. I understand Steve is very knowledgable about Zenith carbs - give him a call.