[Mgs] 74 B acting fuel starved

PaulHunt73 paulhunt73 at virginmedia.com
Sun May 20 04:26:26 MDT 2018


You do need to drive until you get the problem then remove the cap and see if you get a 'whoosh' or not - you should not even with the non-vented cap as the venting comes from the charcoal canister.

Pump chattering when you seem to be suffering from fuel starvation is a sign that either the pump is sucking in air, or cannot pull fuel through.  You need to remove a delivery pipe from a carb (be prepared for a spurt of fuel if the ignition has been on recently), direct it into to a container and turn on the ignition.  It should deliver a minimum of one Imperial pint per minute - and in practice at least double that -  in a continuous series of pulses with minimal bubbling.  

If you get a low delivery rate with lots of bubbles it is sucking in air, which could be a bad joint, or the fuel level below a perforation in the pickup pipe.

If you just get low and erratic delivery with negligible bubbles then it indicates a blockage in the pickup pipe, or possibly the non-return valve in the pump inlet leaking back.

If the pump is chattering away when it shouldn't be then that's the main problem.  IF there is a spark issue, you need to fix the delivery first, then see how it runs.

PaulH.
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  Something I couldn't help but notice is that the fuel pump was clicking like it was pumping out of an empty tank even though that wasn't the case at all. It wasn't clicking as quickly as I've heard it do before, but still not shutting off even though there was no reason for it to be pumping. There are no signs of leaks, no fuel smells. I also wonder if it could be as much a spark issue as a fuel one.
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