MGB Not starting - fuel pump?

[hardcastlephil]

Hi again,

MGB was delivered today and looks in sound condition. As per the other thread - it was sold on the understanding that it was running rough and the seller felt the carbs needed a tune.

Anyway, I put some petrol in her today as it was out and took it for a blast round the lanes. Put £8 petrol from a jerry can in and did about 8 or 9 miles max. Seller is right that it seems to run badly as there is good oil pressure but little power - its ver choked up which makes me think it was running rich.

Anyway, turned it off and came back to it 10 mins later to move to the garage - throttle stuck on starting but I managed to catch the ignition quickly and hoping no damage done. Sorted out the sticking issue (cable connection) and then tried to start again but with nothing happening, just the engine spinning.
At this point the fuel pump was super loud too so i was guessing that it had ran out of fuel. Went to petrol station and filled with another £8 and she still wont start. Petrol pump also still really loud!

Checked the plugs and they didnt look too bad. Don't have anyone else here to check for a spark though.

Does anyone have any ideas here? I think the rough running is a choke sticking issue, but the non starting could be the petrol pump? Im a bit stuck as its stuck on my driveway now too!

Any thoughts appreciated

Cheers

Phil

[davepoth]

It will always sound louder if you are listening for it.


Turn the key to the "on" position rather than "start". You will hear the fuel pump click a bit as it pumps the fuel line and carbs full. It should do that a half dozen times and then stop once the fuel line and carbs are full. If it doesn't stop then the fuel system isn't filling, which means there's a leak somewhere, either on the pipes or at the carburettor.

However, I'm going to guess that the plugs are fouled if it's running as badly as you say.

[hardcastlephil]

Thats just it - the pump doesnt stop, just keeps going! No pools of petrol under the car though, so could there be a blockage between the tank and the pump?

[davepoth]

hardcastlephil said:

Thats just it - the pump doesnt stop, just keeps going! No pools of petrol under the car though, so could there be a blockage between the tank and the pump?

From memory (it's been a while since I've had a broken one!) the pump will keep pumping until it "feels" pressure in the fuel line. So if it doesn't "feel" any pressure it'll keep pumping.

Of course there is the other option - that it can't suck any fuel out of the tank. There's a possibility that running the tank so low has disturbed some silt from the bottom of the tank which has got into the fuel line.

Easiest way to check for fuel pumping is to disconnect the fuel line in the engine bay (the one at the fuel filter is probably easiest) and put the tank end into a jam jar so you don't spill fuel everywhere. Turn the key to "run" for a couple of seconds and then see if any fuel goes into the jamjar.

[nta16]

have a look at the fuel filter just before the carbs and see if petrol is making it that far - or with the help of an assistant disconnect the fuel pipe before the fuel filter and get the assistant to turn the ignition switch to on and measure how much petrol gets through

you could also try removing the petrol cap in case it's not venting

I always suggest with a car new to you looking at the Driver's Handbook (buy one if you haven't got one) and doing a full 36k-mile service of the car, in stages whilst regularly driving the car

don't guess at causes like running rich do a full step by step diagnosis of each problem, you're already falling into fiddling with the carbs even though you've already found things like accelerator and choke cables to be faulty

set the carbs comes after a service (of the whole car not just the engine) including setting tappets - CB points - plugs - timing - carbs in that order

important things on the car are brakes - tyres (& wheels) - steering - suspension - lights - windows

once those are sorted things like the engine and carbs can be set

you can check the spark plugs by removing them, one at a time, reconnecting the HT lead and holding the plug close to the block to look for spark - BUT - why bother checking the plugs yet when it sounds like the pump or fuel supply might be the problem

has the pump got filters that might be full of crud, have the rubber hoses collapsed or corroded on the inside, you got lots to check fuel side first

[shambollic]

If my memory serves me right there is also a gauze filter in the inlet side of the fuel pump, very similar in appearance to a thimble. It could be that this is blocked with crud from the tank.

[williredale]

hardcastlephil said:

Thats just it - the pump doesnt stop, just keeps going! No pools of petrol under the car though, so could there be a blockage between the tank and the pump?

I had this with mine. I replaced the fuel pump as I was leaving small puddles of petrol everywhere which was leaking from the pump body. I clamped the rubber fuel lines with mole grips to stop me having to drain the tank. Anyway, when I got the new pump on it kept ticking rather than the half dozen ticks and stop which I normally have. It ran roughly but well enough to drive to the local MG garage who had to replace the rubber pipes which I'd split when clamping them...

Anyway, that was my experience but it matches yours in that it was running roughly and the pump kept ticking because air was getting in to the system.

[williredale]

Good tip on checking at the fuel filter if there is one. Mine didn't have one before but has now. If you have a bigger jam jar you can check the rate at which fuel is delivered to the carbs. SU pumps should be 2.4 pints per minute so if vastly different there is a problem.

Then a good service and some driving!

[skeggysteve]

In your other thread you mention your in East Yorks, if your not to far away from Market Weighton send me a PM and I'll gladly come over and help you out. I'm an old git and know a bit about older cars!

[hardcastlephil]

Well Steve, I'm at South Dalton so in your back yard!

I'll have a quick check tomorrow afternoon then send you a PM

Cheers!