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MG Midget and Sprite Technical - Pump test 1978 1500

Hi Everyone,

Hope you are all still well.

Car laid up for 2 years for light overhaul but I ended up having to fix my own old worn out body first. At last on the mend. House still not finished - doh.
In the mean time biker daughter needs a car so she started working on my midge at weekends a few weeks ago with yours truly as the 'expert'. ;-)ha ha! It drove in the garage OK with a fix iffy bits list to do two years ago. A few weeks ago charged the battery, pumped the tyres, put fuel in dash pots, engine starts, car moves and stops, electrics work. etc :-) Found more stuff to fix; start with fuel system.
The original tank was leaking and the fuel pipe in many sections from my encounters with car parks mainly from Church Stretton and Hayfield holidays. Daughter has replaced the tank and pipework to the pump. The car starts off the dashpots still OK but we have no fuel from the pump. I intend taking the inlet and outlet off the pump tomorrow, holding a wet thumb / finger over the pump pipe ends, and seeing if there is a vacume / push. Just wondered if there is a better way of testing than this? Any thoughts welcome.

Thanks in advance, Dave
Dave Squire

Is it a mechanical pump and if so does it need priming?
Go electric instead if it's not an obvious fix?
Jeremy MkIII

Hi Dave welcome back,
you're in great position now your daughter has messed your car up, you can charge her parts and labour for all the repairs needed from it, to recalibrate the speedo, replace the oil that is now petrol starved, the list goes on.

I had to delete my first reply as I was on about the electric pump (I was as usual distracted by others from what I was doing and thinking).

Do you know the petrol is getting to the pump?

(Stating the bleedin' obvious - there is sufficient/any petrol in the new tank.)

Fill the pump with petrol from the outlet(?) to prime it (nicked from Jeremy).

You could check petrol is making it to the pump inlet, or syphon some through, remove the petrol filler cap if required. Perhaps check all hose clips are tight.

Give the pump a tap or two or three as you turn over the ignition or have the engine turning by other methods.

An idea pinched from Chris when he couldn't start his 1500 from some months of storage. -
"I was wondering how I could pressurise the tank via the filler tube to help get the fuel to the pump. A mountain bike inner tube cut in half, with one end sealed and the other end stretched over the filler cap. Attach a pump and inflate. I used that method successfully to check the tank for leaks when I had it off the car........"

Failing all above, wet your thumbs and . . .
Nigel Atkins

Mechanical. Works simples.

They are self primeing. Hmm - Greybeard will know; he does this pump stuff with boats methinks.

If you are reading this Greybeard a response would be greatly appreciated to save time rebuilding the pump for no reason tomorrow. Or anyone else that may know.

Cheers, Dave
Dave Squire

Hi Nigel I was slow responding. I can rebuild the pump but just wondered if there was a better test than finger over the pipes.
Dave Squire

Dave,
I don't know for sure but that sounds reasonable to me - but I'm a fan of if the car has been static for a while then many things on it will want more coaxing to get them working, and consistently and reliably (usually by regular reasonable length journeys).

Hence my previous suggestions.

Things usually look and work out better tomorrow, it's Sod's Law.

My simple thinking is apart from the lay up what has changed - new tank and pipework, so my first check on this issue would be is the petrol making it to the pump, or to get it there. Then have the pump, er, well, pumping, by whatever means to check the petrol makes it through and out of the pump.

IIRC from the thread Chris took his new pump apart but was never sure if that was what got it working or not.

You could rebuild the pump (not that I know, are the rebuild kits any good) but only if you know for sure that is the problem.

Obviously getting the engine running is one of the least important checks of the car after it's been laid up, only done after checking the brakes, steering, suspension, (all these include tyres that harden and crack from lack of use and aging) and lights/horns/glass.
Nigel Atkins

My Dolomite has the same mechanical pump as the 1500 midget. While it works fine for normal use, if the car has not been used for a few weeks it takes an awful lot of cranking to get enough fuel into the carbs to let it start.

Originally these pumps had a priming handle, but of course that got deleted in the 1970s cost cutting measures. Have you tried taking the top cover off the pump and filling it with petrol? That might just give it the impetus it needs to get going.

Or remove the plugs and wind the starter with the pipe to the carbs emptying into a jar. It will soon be obvious if the pump is doing its job.
Mike Howlett

I've put a mechanical pump on the 1275 Frogeye rebuild (12V engine with pump aperture), similar to 1500 pump presumably. It didn't take long, with plugs out, to draw fuel from the tank. However, I've found you have to have half a gallon or so minimum in the tank or it stops pumping. I've thought there was a carb/ ignition problem a time or two and it's just been lack of fuel in the tank (it's not air locking btw).
Bill Bretherton

Thanks for the comments.

The daughter is inheriting a triumph 1500 later in the year so all good experience for her. Like you say maybe we just havn't cranked enough.

We are going out to the garage now.

Cheers,
Dave Squire

Hi Dave, sorry I've just seen this. Couple of busy days.
My two cents: since you've had the engine running off the dashpots that ought to have been enough to get the pump working.
Always assuming there is enough in the tank of course - I might try chucking in an extra gallon if you have it handy.
For what it's worth though I've never conclusively determined if an AC Delco pump is good or bad with a finger over the inlet and outlet as you suggest. I've tried it a couple of times but always ended up having a looksee inside the pump anyway.
The usual culprit with a pump that has stood a long time is the diaphragm. I think they go brittle, then tear when the engine turns over. Or something like that.
Personally I'd pop the top off and have a peep inside. It's only five screws, but take care not to let the springs escape.
DAHIK.
Personally, if I had the kit of parts already to hand I'd just go ahead and rebuild it anyway. It's so simple to do.
If you remove the pump from the engine for any reason be careful when refitting it because it's just possible to install it with the lever the wrong side of the cam. That's a sump off job to recover the broken lever.
Again, DAHIK.
Good luck and fair play to your daughter for getting stuck in.
Greybeard

Hi Greybeard,

I came to the same conclusion as you and after putting more petrol in the tank and doing a bit of syphoning to check the new pipework and tank was OK we removed the pump. It wasn't very tightly put together (An AA man replaced some bits in it one night in the dark at the side of the road maybe 18 months before I put it in the garage. He really enjoyed himself - said it reminded him of his apprenticeship - nice bloke probably retired now) but nothing looked broke so we cleaned it all out and washed all bits in petrol. Then reassembled and lo and behold we get a blow and suck pressures when we crank it manually :-) I have a new gasket and clips so started to get it on the car but its telling on both of us - a right pain - especially as I am not used to it anymore. So we left reinstall for another day.
Thanks for the heads up re the arm. Its probably that causing us reinstall agro. Touch wood we will get it right and back together this week.
Engine sounds fine. Needs a service and the brakes checking but hopefully a couple more weekends and top down driving once more - for her anyways.

Thanks for your help, Dave and Jess
Dave Squire

I recently had problems with my 1500 mechanical (new) pump. Now its sorted it happily self primes when turning the engine over even after being sat for a few weeks.

The problem was a dried out seal, and the screw at the top needed tightening up as it was sucking air rather than fuel.

With the pump off the car, you can hand pump the lever and it should draw fuel.
Chris Madge

Jess,
sit your Dad down with a mug of tea and biccies and before he finishes them you can get the pump sorted, without 'help'. 😁
Nigel Atkins

This thread was discussed between 17/04/2021 and 18/04/2021

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