Idles but wont rev.

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Idles but wont rev.

Postby Tinman » Mon May 28, 2018 9:58 pm

Hey, wondering if anyone can point me in the right direction. My traveller will start and idle no problem. But as soon as i add throttle the car splutters and cuts out. Ive cleaned the Carb checked the float for leaks etc, checked the needle, set the points and plug gaps, dizzy cap ok.
any help or advice would be great. Thanks
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Re: Idles but wont rev.

Postby TeHoro » Tue May 29, 2018 8:24 am

Fuel pump working OK?

Ignition timing advance working?

Anything else changed before it started happening?
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Re: Idles but wont rev.

Postby Panky » Tue May 29, 2018 9:48 am

Check the dash pot oil level. Also check if the carb piston is sliding up and down smoothly.
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Re: Idles but wont rev.

Postby Custard » Tue May 29, 2018 4:34 pm

Did you remove the needle from the piston when you checked it.

They can be refitted too far in when the shoulder should be flush with the piston.

Too far in would mean too rich, which when starting from cold is not much of a problem, but would then cause a problem just the same as it being too rich because the choke is on.

Sean.
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Re: Idles but wont rev.

Postby Tinman » Tue May 29, 2018 5:11 pm

Just fitted brand new su fuel pump to it. Advance is working as vacuum tested it through the pipe at the cab and it move. The car has been sat for years. I have just bought it. Wondering if it's a ignition problem. The rotor arm is a bit slack on the arm, but not sure if that's normal for these.
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Re: Idles but wont rev.

Postby Tinman » Tue May 29, 2018 6:28 pm

Yeah I replaced the oil in the dashpot. The piston is sliding well up and down. I never touched the needle as I know they need to be set at a certain position. However someone before hand may have moved it. It starts no problem first time without the choke. So it must be to rich. What is the needle setting?
Thanks guys for the replies.
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Re: Idles but wont rev.

Postby don58van » Tue May 29, 2018 9:30 pm

The car has been sat for years.


Is the fuel old? It should be completely replaced with fresh.

Wishing you success
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Re: Idles but wont rev.

Postby Tinman » Wed May 30, 2018 6:05 pm

Update. The needle was set to far down. But that didn't cure the fault. However found it is leaking in air at the inlet/exhaust manifold. New gasket on its way. So hopefully up and running soon. Anyone know if it makes a difference which order the manifold bolts are tightened up?
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Re: Idles but wont rev.

Postby Custard » Wed May 30, 2018 7:30 pm

Don't think I have seen a specific order, but usual rules apply for anything with a few bolts on a flat surface nip up gently then alternate so you tighten it evenly. A while since I have done a standard manifold as I have a larger single carb. But getting the nuts started on the two end ones stops it falling off while you get the others started.

Don't nip any up too far, if I remember correctly if you do you may have to back them off again to get the middle nut started. As with a few jobs it helps if you are double jointed.

Also if it doesn't seat properly I have had to disconnect the exhaust to allow the manifold to sit up square to the head and then go through the pain of cleaning out any paste in the exhaust to manifold clamp and refitting that.

Which is in itself fiddly to make sure it is positioned so it does not knock where it goes through the chassis.

Enjoy.

Sean.
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Re: Idles but wont rev.

Postby Tinman » Fri Jun 01, 2018 3:11 pm

Right. Fitted new manifold gasket. And that helped slightly. I can now blip the throttle but it still won't hold in a rev. I need the idel screw right near the bottom for it to blip/rev. So I think it's still running lean. Replaced the gaskwt at the carb and inlet also
Also i am running the fuel from a fuel can at the engine. I can see air in the fuel line between the (brand new) fuel pump and carb but all connectors are tight.
Strange one!
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Re: Idles but wont rev.

Postby pgp001 » Sat Jun 02, 2018 5:00 pm

Hi

If its been stood a long time you might find there is a blockage in the fuel feed to the main jet.

Have you had a look in the float chamber and checked it for dirt or being gummed up with old fuel residue, I once had a similar problem and the old fuel had thickened and set like a sort of brown resin substance.
It may well be something as simple as that if it was running fine prior to being stood idle.

The SU is such a simple device there is not much to go wrong that causes an engine to not run at all, there is always a strong temptation to start changing parts when an engine will not start after being stood a while, this is the worst thing you could do.
If the car was running perfectly well when it was parked up, there are only a few things that could have happened to it, but parts going faulty when not being used is probably not going to be the first problem. Bad fuel or corrosion of electrical parts caused by damp might be more likely. In your case you seem to have sparks, so a fuel problem is the most likely culprit, I assume nobody has snook in and sabotaged your carburettor while it was stood and your piston is moving freely so that leaves us with a bad fuel or dirt problem.

I thing the base setting for the main jet adjusting screw is two full turns out (12 flats) and then fine tune it once running.
The main jet adjustment is really only going to have a big effect on tickover running, once the piston has started to lift the needle taper is the main thing controlling the fuel rate.

Have a look in the float chamber, and more importantly see if you can easily blow through the main jet to check it is fully clear.

You mention "blipping" the throttle, will it rev beyond tickover if you open the throttle at a very gentle rate rather than blipping it ?

Phil
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Re: Idles but wont rev.

Postby Tinman » Fri Jun 08, 2018 9:28 pm

FIXED after stripping and cleaning the carb again with no difference. I got a 2nd hand carb. Fitted it to the vehicle and it purrs like a cat :D Will refurb the original at another date. thanks for the comments and advice.Appreciated.
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