Accelerator pump leaking?

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Crowther
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Accelerator pump leaking?

Post by Crowther » Fri Apr 26, 2019 3:19 pm

Gurus,

I'm still chasing rough running issues on my 5a. Last step was to clean the idle jets and blow some air through the carb.
Went out for a spin today and only just made it home. Really rough idle, hunting, and eventually dying.

I let the engine cool and fired it up again and it idled roughly with very low rpm. I did an air leak check and noticed that pinching the little vacuum tube attached to the accelerator pump made the revs jump.
The tube seems OK, but was wet around the end that connects to the pump - I took it off and inspected it for cracks. The carb is <2yrs old.

My curiosity got the better of me so I decided to inspect under the cover of the accelerator pump. No sooner had I loosened one of the lower screws when petrol started to seep out - is that expected?
I swiftly tightened it up again as the inlet manifold was still warm!


New and proud owner of "Scimba" ('72 SE5a).
Learning slowly and driving quickly...

Crowther
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Accelerator pump leaking?

Post by Crowther » Fri Apr 26, 2019 4:18 pm

Correction: that's the anti-stall unit I'm talking about. So I guess it makes sense that squeezing the vacuum pipe operates the diaphragm. Perhaps a red herring then.


New and proud owner of "Scimba" ('72 SE5a).
Learning slowly and driving quickly...

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philhoward
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Accelerator pump leaking?

Post by philhoward » Fri Apr 26, 2019 5:47 pm

I think it still has a diaphragm that should have fuel one side and vacuum the other (or atmospheric pressure in the case of the accelerator pump) - if the diaphragm is perished it will cock things up.


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Crowther
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Accelerator pump leaking?

Post by Crowther » Fri Apr 26, 2019 9:22 pm

Well... I inspected it. The gasket that surrounds the diaphragm is delaminated but that might have happened on separation.

A replacement is on the way from Burtons.

Since this latest problem - rough idle and stalling - only happens when the engine is hot after a run, it's a bugger to troubleshoot. Once I refit the anti-stall I'll get it hot and bothered and do some tests.


New and proud owner of "Scimba" ('72 SE5a).
Learning slowly and driving quickly...

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