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+--- Thread: engine won't rev (/showthread.php?tid=1607)
RE: engine won't rev - Jeff Taylor - 20-08-2018
And if you're taking the fuel pump apart, it may be an idea whilst you're on to fit one of the new red diaphragms that are specifically designed to handle the mix of modern fuels better than the old black diaphragms which can deteriorate with modern fuels. They're available from most of the Cherished Suppliers - for example The Seven Workshop, link below.
https://www.theaustinsevenworkshop.com/products/f0213-petrol-pump-diaphragm-t-type
RE: engine won't rev - hibbo - 21-08-2018
(20-08-2018, 08:24 PM)John Cornforth Wrote: 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.
Thanks for your suggestions I will work though them.
Regards
Graham
(20-08-2018, 08:32 PM)Ken Morton Wrote: 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
Thanks Ken but the fuel is fresh.
Regards
Graham
(20-08-2018, 09:08 PM)Eddamoo Wrote: 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
Thanks, will do.
Regards
Graham
RE: engine won't rev - Andy Bennett - 21-08-2018
As others have confirmed, 30mph in second in an RP is not likely unless being revved at engine screaming levels (and then I still wonder). So I am still wondering if there is actually a problem back down the line here in what speed is actually being achieved and in which gear?
Andy
RE: engine won't rev - Chris KC - 21-08-2018
(21-08-2018, 11:31 AM)Andy Bennett Wrote: As others have confirmed, 30mph in second in an RP is not likely unless being revved at engine screaming levels (and then I still wonder). So I am still wondering if there is actually a problem back down the line here in what speed is actually being achieved and in which gear?
Andy
Yup. It's necessary to understand the problem properly before reaching detailed conclusions. Basics first.
RE: engine won't rev - Reckless Rat - 21-08-2018
Usually erratic running is either due to ignition, timing or carburation problems but dont forget to think outside the box.
Go back to the beginning and think about what you've done since you got the car because the solution may well be there.
Have you perhaps been messing with the brakes and they are binding a bit therefore sapping some of the car's strength? Just a thought.
RE: engine won't rev - hibbo - 21-08-2018
(21-08-2018, 11:55 AM)Reckless Rat Wrote: Usually erratic running is either due to ignition, timing or carburation problems but dont forget to think outside the box.
Go back to the beginning and think about what you've done since you got the car because the solution may well be there.
Have you perhaps been messing with the brakes and they are binding a bit therefore sapping some of the car's strength? Just a thought.
Yes I have relined the front and degreast the rear and adjusted and yes they are bedding in but I can turn all the wheels easily by hand not enough friction to be slowing the car to any extent but the issue remains that it won't rev without jigeling with the choke.
Regards
Graham
RE: engine won't rev - Andy Bennett - 21-08-2018
Hi Graham
Sorry to labour the point, but if you are getting 30mph in second gear then whether or not you are jiggling with the choke, and so perhaps have a mixture issue, revving is certainly not a fundamental problem, as you must be revving its nuts off to get to 30mph in second, unless you aren't.
I wonder what speed you would get to in second if you didn't jiggle the choke. It might be that jiggling the choke is a false indicator, as you might be using to exceed reasonable performance expectations.
Can you do a baseline test, no choke jiggling, what speed to you get to in each gear, at reasonable revs, both on gauge and on sat nav. Then you have a baseline which others may be able to help you from, as right now I am not sure that it is really clear what the car is actually achieving.
I also wonder about your brake comment, there should be no friction at all when not operating the brakes. Wheels should spin freely, not just rotate by hand. I set mine so that when you manually tug on the cable you get about 5mm of movement before the shoe bites, effectively slack in the cable. This gives some free movement in the system before anything binds up.
Andy
RE: engine won't rev - Reckless Rat - 21-08-2018
Graham could you indicate to us which distributor is fitted to your car, and whether or not the manual advance/retard connection is operating, or is locked off. Whilst you say you've checked the timing can you tell us what you've set it to, and how.
RE: engine won't rev - Colin Wilks - 21-08-2018
(21-08-2018, 04:36 PM)Reckless Rat Wrote: Graham could you indicate to us which distributor is fitted to your car, and whether or not the manual advance/retard connection is operating, or is locked off. Whilst you say you've checked the timing can you tell us what you've set it to, and how.
When I acquired my first Seven last year the manual Advance/Retard mechanism was set up back to front, ie. moving the lever to advance the ignition rotated the distributor clockwise, so retarding rather than advancing it. The link between the lever on the base of the steering column and the distributor should run across a line drawn between the centres of the column and the distributor, not in parallel to it. As a newbie it was easy to assume "it must be right".
RE: engine won't rev - Scarlet O'Hara - 21-08-2018
Hi all, here's another crazy idea! I once came across a seven fitted with an auto advance DK4 distributor but fitted with internals, bob weights etc., intended for an anti clockwise rotation. Net result - statically it timed right, started OK, seemed to rev OK but on the road under load because it never auto advanced it wouldn't pull the skin off the proverbial rice pudding.