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MG Midget and Sprite Technical - Fuel Pump Leaking?

I filled the car up today ('66 midget MKII) and then drove for about 6 miles before a planned stop.
I noticed a petrol dripping from around where the fuel pump is,the ignition was ignition off.

Cut the planned journey short and headed home to investigate...

I could not see any new signs of a leak after I stopped. I checked the fuel pipes and no signs of wear and the clips where tight.

When the ignition is on I can hear the pump and it sounds as if it continually pumping.

Before I order a new pump is there something I am missing?

Tony
Tony Brough

Tony,
If the pump is ticking away continually it is unlikely that you need a new one! And replacing with new wouldn't cure the problem. It is ticking because either it is drawing in air on the inlet side of the pump. or because there is a leak on the outlet (downstream) side. As you spotted fuel dripping before than the latter is likely.

Check again for leaks, but this time with the ignition on so that the pump is ticking. Often rubber pipe connections will appear sound until there is a pressure build up from the pump when they then start to weep.

Guy
Guy

Yes agree with Guy try checking for leaks with the ignition on. The SU pump does however tick all the time but should be very slowly maybe 1 tick every 5 seconds depending on condition.

On the Spridget SU fuel pump the connections fuel pipe connections are via plastic bago fittings held on to the bottom of the pump by a metal ring and a couple of screws. From time to time these plastic banjos occasionally crack and leak fuel as a result.
Robert (Bob) Midget Turbo

Guy / Bob

Thanks for the tips.

I will have a look tomorrow after work.
I will check all the connections up and down stream and hopefully find something that is causing the leak.

I take it if one of the banjos is cracked then I will need to replace the pump?

Tony


Tony Brough

Unless you can find some spare parts.

I've got a couple of dozen pumps in need of rebuilding, so if you need a part, I may be able to help.
Dave O'Neill 2

I had a similar experience a couple of years ago. Due to bulding work at home the midget was confined to my mother in law's garage for about three months. I had filled up with petrol before putting her away and when I restarted her after the confinement, petrol was spewing out of the fuel pump. Went and had a cup of tea for ten minutes to assuage my frustration and restarted her to put her back in the garage and to my surprise no fuel leak so I drove her back home Its been fine ever since. I assumed that perhaps there was some overflow/pressure aspect to it or perhaps it was just one of those quirky idiosynchrasies that make spridget ownership such fun!
Matt1275Bucks

If the pump is a SU AUF 214, it has those plastic banjos that are very prone to cracking (as Bob suggests, they are really rather miserable little devices), particularly if they are old. They can be ordered from Burlen Fuel Systems http://www.burlen.co.uk/ under P/N AUB 663, or in the couple dozen pumps that Dave has, you should be able to find one that doesn't leak (but from my experience, I wouldn't bet on it).

Guy's suggestion that a fuel line can be leaking bears checking too, before replacing the banjos. As Guy states, if the line on the outlet side of the pump is the culprit, you will see fuel leaking out. If it is on the inlet side, you may or may not see fuel leaking, but it will suck air into the pump which will keep the pump running continuously. To check for leaks on the inlet side of the pump, run the following tests: You can check this by removing the fuel line from the carbs and route it to the bottom of a glass jar, turn the ignition on and watch the stream of fuel going into the jar. If the stream is full of bubbles, then there is an air leak. Remove the line from the tank to the pump (loosen or remove the line from the fuel tank first to remove stop any fuel from siphoning out of the tank [not sure this holds true for Midgets]) and replace it with a flexible line that can be dipped into a can of fuel. Once again turn on the ignition and observe the flow of fuel into the jar, watching for bubbles. If no bubbles occur with this set up, then the air leak is in the line to the tank or the pickup tube in the tank. If there is still bubbles in the outlet stream, then the pump has an air leak in it, most likely the plastic banjo. Cheers - Dave
David DuBois

Just finished having a go at solving this and hopefully I am done.

I started by tightening all the hose clips on the pump and where they connect to the pipes and then the connection at the carbs and the union into the fuel tank. I managed to get them all a bit tighter..

Turned on the ignition and the pump started to work then stopped pumping after about 10 seconds. I left it running for about 2 minutes at a time. Each time the pump bid the initial charge then stopped (this is better than before as it seemed to always run. After about 10 - 15 seconds the pump kicks in again, this time only for about a second. Checked all the joints and could not see (or smell) any leaks.

As a final check I tried as David D suggested with the jam jar and could see no air.

I will give it a drive later in the week and see how it goes.

Dave thanks for the offer of help again, but hopefully I am sorted this time.

Cheers

Tony



Tony Brough

Sound good Tony, well done mate.
Robert (Bob) Midget Turbo

Wow,

That's a clean looking pump, and an even bigger WOW, how clean is the underneath of your car?

I eat off plates that aren't that clean lol.
Lawrence Slater

Thats the result of the winters work (with a lot of help from here) I stripped and rebuilt the suspension, replaced the petrol tank, had a bit more metal stuck on the shocker mounts as they were getting a bit thin... It seemed a shame not to paint it. Not done many miles this year yet but intend to keep it fairly clean as 46 years of rust, underseal etc was a pain to remove.

Its a shame the rest of the car is not as good yet but given a few more years I will get there.

Tony Brough

Well done Tony, don't worry about keeping it too clean go out a lot and get it a bit dirty, cleaning will be easier now

once fully road tested you might want to copperease over nuts,bolts, clips and connections with a small artist's brush or dare I suggest Waxoyl or similiar for the whole area
N Atkins

Yup you deserve a round of applause for all that effort.

I'm way too lazy to have done all that. That's real determination and motivation for you.
ClapClapClapClapClapClapClapClapClapClapClapClapClapClapClapClapClapClapClapClapClap :)
Lawrence Slater

Checked again on Friday night and petrol came pi55ing out. I left the pump running so I could see where it was coming from. It was the flexible hose on the upstream side. Replaced both of them, up and down stream for £2.50 including jubilee clips.

Tony Brough

This thread was discussed between 24/07/2011 and 31/07/2011

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