That awful colour MGB GT

[SiC]

You have now fannied about with so many things that even when it runs again you won't know the cause of the problem.

Ben

What a silly thing to say.

Yep, I'm silly.

But you seemed to be thinking that the oil pressure could be affecting it.

Had oil pressure. Oil pressure when cranking too.

How silly is that?

Ben

Thankfully it's not silly that the engine had normal oil pressure. It was good news as it meant oil is still flowing around the engine and limits many possibilities of different types of catastrophic internal engine failure.

Also stating all the facts allows better diagnosis of problems. If you don't have all the data, you can't come to an accurate conclusion. Often data that seems inconsequential, can be important.

[Hooli]

Poor old Ben, on an less encompassing forum he'd get banned as a boring troll. it must be difficult with his lack of thinking and social abilities.

[PhilA]

Well, that is no less reliable than an SU pump, TBH particularly when laid up for a while. I always had to give mine a wallop on Monday morning to get it going after the weekend.

Just goes to show you need to drive it more!

[SiC]

Well, that is no less reliable than an SU pump, TBH particularly when laid up for a while. I always had to give mine a wallop on Monday morning to get it going after the weekend.

Just goes to show you need to drive it more!

It's only been sat for three months and I'm trying! Guy at the garage did tell me off that I shouldn't be driving it in this salty weather. Especially as the underside isn't particularly undersealed well.

I'm really interested to see what it how it's failed. Even though it is supposed to be a solid state pump, I reckon it's a diaphragm and solenoid job like an SU. Just with a hall effect or similar at the end to detect when it is needing to actuate. My suspicion is still on something being bunged up in either the pump or further down the pipework.

[fried onions]

Actually, I agree with some of what Ben says.

[The Reverend Bluejeans]

It makes comedy reading though. 'The Plank', 2019/20.

[SiC]

Got the car back today with a new Hardi pump on. Didn't manage to speak to the guy that did it, so not sure exactly what was done. Hopefully it was properly diagnosed. If not, it'll be going back for them to sort again...

I pulled the pump apart. Couldn't see anything obviously wrong with it. The electronic driving circuit is pretty symbol. Looks to be a Darlington pair driver connected to a 4000 series IC - probably a Schmitt trigger set up as a debouncer. The solenoid position is done by a switch, which is a bit of a disappointment. I was expecting optical or magnetic to make it fully solid state. Contacts are ok but they do wear and get dirty.

Basically these pumps are essentially SU pumps with driver electronics on the end. The driver electronics is like a mini version of a ignition points assistor.

Here are some pics from pulling apart.




You can see the points here


Diaphragm like an SU


Bottom is a cavity with two small plastic discs on the input and output that acts as valves


Close up while actuating it
[youtube][/youtube]

[richardthestag]

slightly insane question SIC

Does your fuel setup have a return feed to the tank? i.e. tank-pump-carb#1-carb#2-tank?

Reason I ask is because Staaag doesnt and with these types of pump it can easily overwhelm the carb float valves and flood the engine. Stag V8 is an arse to unflood and get started. Rover v8 is slightly better but cranking it over for 3 minutes will eventually start to clear it with throttle wide open etc

I found that SU pump in Stag puts out 4.5psi. Carbs are stromberg CD175s and the float valve is rated 2-2.5psi. I fitted a simple pressure regulator between pump and carbs to control the flow to 2psi.

Range Rover with same carbs doesnt suffer because there is a return line to the tank, smaller bore but it does take excess pressure straight back to the tank.

[SiC]

Good question. There is no return on the MGB and I don't believe there ever has been one on them.

I have never had a problem of flooding on it. However the original SU pump had knackered points and conked out. After then I replaced it and then not after I rebuilt the carbs - including with new float valves.

The Sprint has a mechanical pump. Not really used it yet of course but that has a Petrol King Fuel Pressure regulator fitted. I know I've seen on the Dolomite forums that it's a common problem with flooding.

So I'm not quite sure what's different between them.

I believe the pump comes in different ratings. Perhaps the MGB one is a weaker pump and doesn't push the needle valves too hard?

[SiC]

From the pump instructions