suddenly cutting out after starting up

[keith rogerson]

I recently bought a moggy pickup, and drove back home, about 70 miles.
Got fuel on route, no probelm.
No problems on hills, A roads or motorway, stay at 50 mph, all good.
I get home, leave it for an hour then start up, pull out of drive and its starts to chug, then pushing clutch in, it idles, then same thing as try to accelerate. I get it back to drive after much coaxing, first thing I check it damper pot in SU carb, dry.
So I pop some engine oil in and restart, same thing.
Float bowl clean.
Carb, all clean.
Leads clean, distributor clean.
I leave for an hour, turn key no clicking from petrol pump, could this be it?
It looks fairly new, but no SU stickers on it.
Any ideas.
cheers
Keith

[svenedin]

Yes it could be the fuel pump but you'll have to diagnose with a process of elimination. Spark. fuel etc.

You turn on after an hour and no clicking from fuel pump. The pump will not pump if the float bowl is already full so take lid off and check if it is full or empty. If empty next step is to check the pump and there are lots of thread on that. If the pump works fine when disconnected from the float bowl it's possible the float needle valve is sticking. Pump not working can be quite a few things. Loose electrical connections, dirty points, blocked pump filter etc.

Stephen

[simmitc]

Observe safety when dealing with petrol, good ventilation, no sources of ignition, recycle. etc.

It sounds like iot could be fuel related, but some simple tests are needed. Disconnect the LT supply wire (white) to the coil and insulate it. Disconnect the fuel hose from the carb and place in a suitable container. Switch on ignition. Pump should run continuously. Allow it to run for one minute and switch off. Measure the fuel pumped, it should be at least one pint. Whilst you have the fuel in the container, examine it - is there any trace of water or other contamination? Return fuel to tank and reconnect everything.

If the above is OK, then move to look at the carb: is the float and needle valve OK, is the piston rising and falling correctly?

[MM1949]

A long shot...but it could be a blocked fuel cap breather...

[myoldjalopy]

Observe safety when dealing with petrol, good ventilation, no sources of ignition, recycle. etc.

It sounds like iot could be fuel related, but some simple tests are needed. Disconnect the LT supply wire (white) to the coil and insulate it. Disconnect the fuel hose from the carb and place in a suitable container. Switch on ignition. Pump should run continuously. Allow it to run for one minute and switch off. Measure the fuel pumped, it should be at least one pint. Whilst you have the fuel in the container, examine it - is there any trace of water or other contamination? Return fuel to tank and reconnect everything.

If the above is OK, then move to look at the carb: is the float and needle valve OK, is the piston rising and falling correctly?

Good advice without doubt - except - if the fuel does show signs of contamination, do not return it to the tank. Drain tank and replace with fresh fuel

[mowogg]

Sounds like the r fuel pump. I find they tend to fail with intermittent use. Iin all liklihood it will need a clean up on the points.

Mine did this earlier this year after not being used over the winter. I took the cap off the pump cleaned the surfaces on the points and it's been fine since. I did this all by the roadside

[keith rogerson]

Hi all and thanks for notes, all very helpful.
I've removed and cleaned the pump, works fine on fuel output into clean utensil.
Carb, removed, cleaned and replaced 3 in one oil in the carb needle chamber.
Movement of parts all good nice and easy. Parts all cleaned in clean fuel.
Starts with choke, idles happily when warm without choke. Restarts without choke straight to idle.
But when accelerator depressed, it cuts out straight away.
I've left fuel cap loose.
So I'm now looking at float bowl next.
Should I clean jet, is there a filter or something that may be causing a vaccuum?
Cheers
Keith

[mowogg]

Not sure what year your pick up is. If its a later one it would have a olil catchpot on the tappet cover likely plumbed into the carb. I would check this line as a leak in this could created your observed issues

[keith rogerson]

thankyou, ill check this out. Its '67. not sure what the catch pot looks like? Ill check the manual, maybe theres a pic.
cheers K

[philthehill]

Whilst the 'catch pot' (breather and oil separator) is from a classic Mini - for identification purposes the cover is near identical to that fitted to a late Minor.
https://www.ebay.co.uk/itm/126018154914 ... R4jN5LSwYg

[StillGotMy1stCar]

I would change the carburetor dash pot oil from 3in1 to 20W50 engine oil, may not be your issue but can cause hesitation from idle on some A-Series engines.

Regards John

[paul 300358]

It could be a lot of things and everyone will have a different idea as its difficult to diagnose without the car in front of you. I personally would now look at the condenser and coil.

[kevin s]

ours does the same when the dashpot runs dry, in our case topping up the dash pot fixes it though, I think out carb is just worn out and the dashpot jams without the oil damping (it also sucks the oil out every 300 or so miles). With the air cleaner off does the dashpot rise smoothly as you open the throttle, I wonder if it's sticking.

[keith rogerson]

Well, I've looked at the fuel pump and its not an SU, its some dodgy looking creation that hasnt been mounted onto the battery housing as usual.
I'm thinking its best to replace with proper SU carb first?
Any ideas where best to get a replacement?
Also looking at the distributor, I cant see the vacuum unit/ does this mean the distributor has been changed for a later one or maybe a different one?
Its a standard 1098 engine, everything else looks as should be?
Im a bit stumped as I just want to get it running propery and go for a spin!
cheers for any ideas...

[simmitc]

It's a bit concerning if you've only just noticed that it's a non standard fuel pump that isn't mounted correctly That aside, the real question is whether it is delivering the fuel correctly, and if you are cruising at 50 mph then the answer is probably yes. Easy enough to check: Put output hose into a suitable container and run the pump for one minute. There should be at least a pint of petrol in the container. Observe usual safety precautions for handling petrol.

The dizzy could be a later unit - is it points or electronic? If there is no vacuum advance then has the connection been blocked off at the carb, or is it sucking in air?

A few pictures of the engine bay, pump, carb and dizzy might be helpful.

[svenedin]

Hi all and thanks for notes, all very helpful.
I've removed and cleaned the pump, works fine on fuel output into clean utensil.
Carb, removed, cleaned and replaced 3 in one oil in the carb needle chamber.
Movement of parts all good nice and easy. Parts all cleaned in clean fuel.
Starts with choke, idles happily when warm without choke. Restarts without choke straight to idle.
But when accelerator depressed, it cuts out straight away.
I've left fuel cap loose.
So I'm now looking at float bowl next.
Should I clean jet, is there a filter or something that may be causing a vaccuum?
Cheers
Keith

From these symptoms it seems the engine dies when you open the throttle. This opens the throttle disc and the extra air flow should cause the carburettor piston to rise, raising the needle with it and giving the required fuel. If the carburettor piston does not rise properly, the extra air flow from opening the throttle will immediately give a very weak mixture that will stall the engine. I would do the "clunk" test on your carburettor. Remove air filter and lift carb piston with your finger and let go. It should fall back down with a metallic clunk. If it is stiff or fails to fall back nicely the jet is probably not centred correctly or needle bent or some problem with piston sticking in the dashpot.

[jaekl]

This statement is a bit misleading. "If the carburettor piston does not rise properly, the extra air flow from opening the throttle will immediately give a very weak mixture that will stall the engine. " The damper on the piston purposely slows the rise of the piston. More air flow from the open throttle but lower piston increases the vacuum over the jet which pulls more fuel that enriches the mixture for acceleration. Conversely if the piston rises too rapidly, the mixture will be leaner than required to accelerate and it will stumble. How fast is the fuel pump pumping? That is a good indication of whether it is fuel starved or not. Even when not pumping but the bowl is full, you can accelerate to fourth and travel about 1000 ft. What type of distributor rotor does it have?

[keith rogerson]

Clunk test all good,
Dashpot oil all good.
Fuel pump pushing out fuel good.
Carb cleaned, floatboel emptied, flushed, all filled up etc.

[simmitc]

And...? Did it solve anything, or does the problem still exist? If yes, then, depending on what you did when you cleaned the carb, it might be worth checking the jet and its sealing ring at the bottom of the float chamber. It is possible for a piece of loose rubber to act like a valve: open at low demand, but then closes and blocks the flow when there is a high demand. It's unlikely, but might be worth checking. I have asked before, but can you post some photos of the overall setup, unless you have cured the problem.