Odd SU fuel pump behaviour (car cuts out). Fixed

[svenedin]

Over the last few weeks my car has cut out on quite a number of occasions but then re-started after a minute or so.

I fitted an Accuspark electronic distributor recently and was concerned that this was the problem but it all checked out electrically OK and it seemed to be a fuel issue.

On turning the ignition on the SU (points type) fuel pump would tick away happily so I did not immediately think there was a problem there. The car would die seemingly randomly.

Today the car started fine but then spluttered and died after about 5 minutes. I decided to have a look whether there was fuel in the float bowl. On opening the float bowl there was just a dribble of fuel at the bottom and rusty particles too. I mopped out the dirty petrol and rinsed the float chamber with carburettor cleaner. This is old grot because the car had a new fuel tank and hard fuel line from the tank a few months ago. I also rinsed out the float valve.

I put it back together and the fuel pump ticked happily and the car started fine but 5 minutes later it coughed and died again. Once again I opened the float chamber to find it dry.

A week or two ago I converted an SU pump to electronic so I put that in and all seems fine now. It seems a bit strange because the fuel pump that is playing up is really rather new (a few months old) and was replaced at the same time as the fuel tank and fuel line. I checked the earth and power feed to the pump, and the battery connections and found no fault. The float is also fine.

It's not fun breaking down in modern traffic with no hazard lights and sometimes nowhere to pull over. I do hope I have really fixed this!

Stephen

[KeithL]

Have you checked the filter in the fuel pump?

[svenedin]

I haven’t yet checked the filter because it has never run on a dirty system but I will do so now the pump is off the car. The replacement pump (the one I converted to electronic) is thoroughly cleaned up and has a clean filter. In fact I ran it into a jug to check the petrol was absolutely clean. I’ll give the car a run tomorrow but the weather is absolutely foul today.

[oliver90owner]

Your pump should not ‘tick away happily’. It should fill the carburettor and then stop ticking happily, only ticking occasionally to maintain fuel line pressure.

[svenedin]

Your pump should not ‘tick away happily’. It should fill the carburettor and then stop ticking happily, only ticking occasionally to maintain fuel line pressure.

Apologies for the lack of precision of my language. What I meant was, the pump made a few rapid ticks as it filled the float chamber at startup which is what I am accustomed to these pumps doing in normal operation. It did not just carry on pumping.

[Bill_qaz]

Needle valve sticking? Possibly new pump is creating more pressure and overcoming the issue.

[svenedin]

Needle valve sticking? Possibly new pump is creating more pressure and overcoming the issue.

Agreed. Could be. I rinsed the valve out (without removing the needle from its seat) with carb cleaner but the problem recurred. I did use a few tanks of E10 and I don’t have the stay up float or Viton tipped needle valve. Needle fell away with gravity with float lid in my hand and seemed fine but maybe not in actual use.