engine won't rev

[hibbo]

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.

Jeff I will and probably take the carb down there.

Thanks.
graham

[Ruairidh Dunford]

Hi Hibbo,

I too can recommend Steve.

A few quick things to try:

- firing order, it is 1342?
- Is the carb to inlet manifold sealing? Wrap a damp cloth around it and see if this improves pick up and/or spray WD40 or similar on the joint to see if it gets sucked in, this will indicate a leak.
- Have you tried a fresh set of plugs?

Good luck.

[hibbo]

Hi thanks for the reply.
Tried all apart from fresh plugs but they are on the list.

Regards
Graham

[Reckless Rat]

You say that you're getting a good supply from the fuel pump but a failing diaphragm or a partially blocked supply could be delivering enough fuel at low revs but not enough when demand is higher. It will cost nothing to strip the pump and check it over.

[John Cornforth]

Hi Hibbo

If you take 1934 box saloon with standard gearing and can get the engine to do 4000 RPM (about the realistic maximum), the speed in gears will be 13 in 1st, 22 in 2nd, 35 in 3rd and 59 in top.

It sounds as though your car is power limited rather than RPM limited, which suggests insufficient fuel or air flow rather than an ignition problem. There's little to go wrong with the air inlet side (assuming the choke flap is working properly), and a blocked exhaust seems to have been ruled out, so that leaves a restricted fuel supply to investigate. This is consistent with the choke use having a beneficial effect, as it will counter the mixture weakening by restricting the air supply to match so at least you have a decent air/fuel ratio even if there isn't much of it !

Look for blocked jets, blocked carb passages, blocked pipes and blocked filters. There is a gauze filter in the bottom of the petrol tank over the inlet pipe, but many have been poked through in the past. There are also gauze filters in the petrol pump and the inlet banjo on the carb.

[Ken Morton]

Another question-- How old is the fuel? . I had this problem years ago and after I tried fresh fuel all was well.
Ken Morton Vancouver Canada

[Hedd Jones]

I had similar issues with my departed special. If I richened the mixture it would rev. The bob weights in the distributor were stuck. There was no advance. I put the bosch dizzy off my other car on it, and it was a revelation.

[Bob Culver]

Ken beat me to it.
Years ago after a long spell my car would only run with the choke out until the fuel ran out.
 30 mph in 2nd would be way above bounce speed of a stock engine and such revs definerlt not advisable with original crank
.If removing the emulsion block have to be careful not to damage the gasket. Dunno if these are available but may be unique to the model.
In their day most owners would not have exceeded 30 mph in 3rd, and few would have ever braved flat out at 50 mph in top except for the very occasional thrill.
A very retarded engine will not rev under load, I dunno about very light load.
If htere was some gross cam timing error the compression would unlikley be so good. but valves and piston can be seen thru the plug hole. Valves should "rock" just after tdc.

[Reckless Rat]

I will echo what's already been said - those speeds in gears at 4000rpm are theoretical and in real world situations unobtainable given the aerodynamically challenged profile of the RP saloon. Mine has a few "go faster" goodies on it and I don't like to push it beyond 25-30mph in third when climbing. It will get to 50 and a bit on the flat (a long one) on a good day, but with a gradient or a head wind, forget it.

I'm sure you'll get a little more out of the old girl once you sort this problem, but don't expect it to suddenly change into the four wheeled version of a Manx Norton. An Austin Seven will get you there, but in its own time. Good luck.

[Eddamoo]

Sounds like a definite restriction in fuel supply. As you've already cleaned the carb many times, i would do As John Cornforth said and make sure there is no restriction in the fuel pipe gauze.

Modern fuel gels terribly and we found that after just a few months, the top of the fuel pump (with the 1-way valves) was completely blocked with crud. Give that a go