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MG Midget and Sprite Technical - Engine cutting out after a short run..

Evening all,

I kinda posted this tagged to another thread which got messy with replies!

Run the car 1275 midget but after only a short distance it loses power (will carry on running if you stop ie does not cut out fully) but does not have sufficient power to 'drive' turn it off and leave it 2 mins then it will run fine for about another mile then same again.

Car had been stood for 3 years so I fitted a new QH pump as the old one had siezed, after giving it 2 mins turn the key and you get the clicks from the pump but for ages.... anyhow I had this bright idea to bypass the fuel tank incase its internal filter was blocked up ( It was Bobs Idea really)! basically to prove the tank out so i ran a new temp fuel feed to the pump from a fuel can in the boot fuel hoes weighted down so that it was actually getting fuel & hey presto I got about 6 miles.. then it happened again!
Ive had the pipes off both carbs and both are emitting fuel but how the pump 'ticks' it sounds like the engine is using it faster than it can supply.. so im a bit beat so to speak..
Rob Flint

So you got 6 miles Rob!!!!!!!!!!!!

Blimey I bet you thought you had cracked it!! :)

Rob at 6 miles then using the spare fuel supply did it do exactly the same as Sunday?
Robert (Bob) Midget Turbo

could it be air getting sucked in (?) from the metal pipe off the tank, rubber pips to/from pump, metal pipe from tank, connections at rubber pipes

have you tried pulling or push the the choke cable at point of power loss?

what do your spark plugs look like?

how your coil?

this isn't the way to sort it, hopefully someone'll be along to carry out proper step by step logical systamatic diagnostics with you
Nigel Atkins

Hey up... lol yep I thought I had it sorted! so in a way Im glad I havnt as it hopefully rules out my fuel tank! (saved £100) I did say hopefully!!

Yep Bob just the same as Sunday! about a mile between 'stops' fuel pump clicking like mad, it seems as if its OK to start then after it 1st cuts out it uses all the fuel in the pipes from back of the car to the carbs then dies... refills and then just cycles like that..

Nigel, yep tried choke out/in makes no difference, 4 spark plugs whiteish coloured tops! sorry excuse my wit.. or lack of all looked the same when I took them out :-)
Rob Flint

Rob,
"Fuel pump clicking like mad" usually signifies either an empty tank (ruled out) or a leak on the supply pipe between tank and pump. This may well not leak petrol out, but allows air to be drawn in by the pump. This then runs too freely and will click like mad as described.

But another simple check is make sure that your fuel filler cap vent isn't blocked. Try either loosening the filler cap, or remove it completely and take a drive to see if the problem still persists.

Guy
Guy

Rob what we need to do now is fill the tank with fuel and connect the tank back up to the fuel pump. Then take the pipe off the carb. Place a pipe from there to another container (I have some 5 gallon drums if you need one) Now start the pump and see if it will pump all the fuel out of the tank at a good rate.

LOL
Robert (Bob) Midget Turbo

Sorry Rob,
I didn't read you first message properly. But if this is currently running from a fuel can in the boot, what arrangement have you made to allow air into the tank so that you don't get a vacuum?
Guy

my plugs are metal colour on top :)

I always forget the petrol cap

if not fuel itself then electric lives and earths maybe(?)

but run minus cap first
Nigel Atkins

Bob, I love the word 'we' I dont mind 'doing with guidance'

Guy i used a gallon petrol can, outlet pipe fed in through its filer neck weighted down so it wouldnt come above fuel level, pipe held in at top with gaffer tape 'loosley' so plenty of air so no vacuum
Rob Flint

tempory direct live and earth from battery to pump(?)
Nigel Atkins

Nigel, why? its running (or am I having a blonde moment)?
Rob Flint

Rob,

These things are sent to try us, what ever you do don't give in! I'm the "vaporisation" post after you in the topic list at present.

The first thing I try to figure out is whether it's fuel or spark, and I assume you've checked spark? I'd suggest you get a can of easy start and try spraying that into the carb mouths once the issue has started(spray directly in i.e. remove filters) if the engine isn't being fuelled for whatever reason this will get it going again, even just for a few combustion events. This will tell you whether you're on the right track or not.

I ran a car once with a plastic 1 gallon tank on the bonnet bungy cord'd to the wiper blade, and feed ing a carb via gravity to short cut the whole tank and pump. This might be an option for you fault finding? I'd also consider taking the tops of the float bowls off the carb once you're experiencing the issue and check the levels.

The diffeculty with these issues is that I've found once the issue is experince you onlty having a short period of time to fault find it before it cools and fixes itself, so it's good to have an idea of what you're going to do prior to the issue starting. Good luck.
James Eastwood

It doesn't sound like an electrical problem as the car continues to run on tickover, just without power. But you can double check this by watching the behaviour of the tachometer. It will flick about violently if its an ignition problem.

If the symptom of the madly racing pump is accurate and consistent whenever the car faulters, then this is surely the relevant clue. Is it possible that your jury-rigged fuel can is allowing the petrol to slosh around to the extent that the fuel pick-up tube gulps air? Or is there any part of the fuel supply tube before the pump that is common to both jury-rig and permanant system/ The connector to the pump itself perhaps? It certainly sounds like it is darwing in air somewhere!
Guy

as with my first post I'm with Guy and possible air sucking in rather than petrol leaking out of a metal or rubber pipe or their connections

a direct supply of petrol to the carbs will show this up as its taken out the faulty supply pipes but I'm not sure a gallon on your bonnet would be appreciated on the road so the spraying into the carbs, problem with this is it's on a static car but might work

sometimes it's the actual movement of the car that promotes the problem by putting the fault into a position or situation to to come into effect

in the same way as above direct electrical feed to the pump eleminates the the possible faults in wires and connections to the pump

it also highlights the jumping around scatter gun approach to problem solving as opposed to the logical step by step systematic diagnostic appraoch
Nigel Atkins

Nigel, It shouldn't be necessary to add a direct wire feed to the pump as Rob knows it is working because he can hear it clicking.

Pumps don't do the racing thing when they cannot supply fuel,(blockage ate tank or in downstream supply to carbs). Rather, they race when they can supply too easily, either because the carb float needles aren't closing (flooding) or as in this instance I think because the pump is drawing in air and pumping too freely.
Guy

Guy,
I doubt it's the wiring but we don't know that Rob hears, or listens for, the pump working all the time especially when the car is playing up

I was just thinking after checking everything else before and if no fault is found then a direct electric supply to the pump eleminates any intermitent wiring and connections problems that happen when the car is on the move

a lot of wiring faults can only be found with a two person wiggle test or when on the move

as I said I very much doubt a dodgy wiring or connecetion is the problem this time but ones that are just a bit iffy and normally with enough connection to work can be a pain to locate, you get ones that only play up under certain conditions or circumstanes
Nigel Atkins

Sounds like it's getting enough fuel to idle on, but that's it. I think I'd look at fuel supply first, and failing that, dig into the electrics.

Best of luck,

-:G:-
Gryf Ketcherside

Did you do the fuel delivery test yet mate?
Robert (Bob) Midget Turbo

Noo not yet Bob! need to come borrow a big drum or something & have an assistant... but dont like to pester you on a school night!

Tried again earlier with a bigger weight on the end on the 'New feed pipe to pump' to make doubly sure its not curling up n sucking air, fuel can brimmed & gaffer taped up but with another smaller pipe taped in so my can doesnt 'squish' Same result!

Was going to try with the can & pump tied on the roof wired direct but chickened out! I think if plod spotted me it would be 3-6 points for sure & I would prolly get arrested as Scu*thorpes only 'car bomber'!
Rob Flint

Rob,
Is any part of the pipework for your temporary fuel can system the same as you were using when connected to the proper tank? Rubber hose connection to the pump perhaps?
Guy

Call round tomorrow around 5 and I will give you a container. :)
Robert (Bob) Midget Turbo

Noo not yet Bob! need to come borrow a big drum or something & have an assistant... but dont like to pester you on a school night!

Tried again earlier with a bigger weight on the end on the 'New feed pipe to pump' to make doubly sure its not curling up n sucking air, fuel can brimmed & gaffer taped up but with another smaller pipe taped in so my can doesnt 'squish' Same result!

Was going to try with the can & pump tied on the roof wired direct but chickened out! I think if plod spotted me it would be 3-6 points for sure & I would prolly get arrested as Scu*thorpes only 'car bomber'!
Rob Flint

Gi Guy, nope, new pipework

Bob, see you @ 5!
Rob Flint

Lol I love the way it puts the * in Scu*thorpe! lmao!
Rob Flint

Presumably it reads letters 2,3,4 and 5, misspells letters 6,7 and 8 and ignores the rest!
Guy

Lol I love the way it puts the * in Scu*thorpe! lmao!
Rob Flint

& not sure why my posts are coming up Twice!
Rob Flint

Update!

Well today I camehome early and thought I would put things back together after the makeshift fuel tank rig up, did that and then thought I would take another look in the float bowls. Wierd how one job leads to another... i had the tops off earler in the week and wiped out a small ammount of debris best I could, well today I managed to sheer one of the 3 retaining screws god knows how as I had only days before so wasne tight!!!

So moving on i saw a small ammount of 'crudd' in the bottom so started wiping out with cotton buds and then had another crazy idea got my wet n dry vac and sucked it all out petrol n all!

Well ive now been out in the car and covered 100 miles with no faltering or cutting out! Wish I really knew what had caused the problem as I dont really know what ive done to solve the problem....

Think I might buy another fuel pump too keep as a spare.. I have virtually everything else in the boot!
Rob Flint

Rob,

You should check your vacuum manual but as a general rule you shouldn't use it to vacuum up flammable liquids due to the possibility of igniting them. I'm glad you didn't find that out the hard way.
David Billington

:-) I know....................
Rob Flint

chances are is was crud so why carry a spare pump

get the car working and keep it serviced and maintained then you wont need all theses spares in the boot - your giving classics a bad reputation by having to carry spares :)
Nigel Atkins

Do you have a fuel filter?
Gary & Gaps

Nigel,

I think having to stop and fix your car at the side of the road is part of the fun of owning a classic car. Maintenance is great so that your engine doesn't blow up and run bearings etc... but routinely replacing parts which are perfectly okay is boringly pointless.

C L Carter

"I think having to stop and fix your car at the side of the road is part of the fun of owning a classic car."

I couldn't disagree more. I really don't see the fun in having to stop to fix the car under any circumstances, because it means that something has gone wrong. Tinkering with it at home however is fun. Especially if it means that you don't have to stop at the side of the road to fix your car.
Gary & Gaps

Now then.. Now then... I only carry points, plugs, coil, condenser& fuel filter, spare wheel & 2 inner tubes so im not going over the top... oh & water & oil.. so a pump wont break the bank...

You never know one day I might come across one of you lot broken down.. needing a spre 'something' :-)
Rob Flint

Words of wisdom say that a fuel filter can damage the fuel pump, if you stick it before the pump, and it clogs with debris.

So make sure it is installed between the pump and the carbs, not between the tank and pump.

I learned this courtesy of Dave DuBois.
Lawrence Slater

C L,

I'm with Guy I see no fun in road side repairs, I've had loads of them and have never enjoyed them

servicing is not 'routinely replacing parts which are perfectly okay' - items can contiune to work well past their optimum and best and continue to work when worn enough to be fault thus effect other items and perhaps causing a rodside 'repair' and perpetuating the myth that classics are unreliable

if you enjoy the breakdowns good for you (not so good for your car or next owner) I think you should have some kind of sign to say so that way people like me wont stop to help and spoil your fun

course you could be winding me up :)
Nigel Atkins

Eh? Nigel, I never said a word (unusually!)
Guy

sorry I meant Gary - I got some sort of raging Man-illness and my attention and typing are even worse than usual
Nigel Atkins

Lawrence Facet insist that a filter is placed BEFORE the pump to protect it from damage, I assume originally SU thought the same as the tank has an internal filter before the pump and at the end of the pickup line?

How did David suggest it would damage the pump?

I think that Robs problem may be on the mend and could have been a none return flap in the pump not working correctly?
Robert (Bob) Midget Turbo

Hi Robert, here's a summary of what Dave DuBois says. It makes good sense.

David, I hope you won't mind me paraphrasing.

If the filter is put in before the pump, on the inlet side, and then it clogs enough to stop the fuel flowing, the pump will stop with the current still on. If the power is left on, the internal resistor that protects the points in the pump will burn out. This will cause the points to burn out.

If the pump is a newer electronic type of SU pump, the internal electronic circuit board will burn out.

That's the gist of it, but the full explanation is on his website. under "SU Fuel Pumps Facts and Myths"


Lawrence Slater

Blimey... thought I only caused this much discussion/hassle at work! right Midge up for sale.... will but a New Mx5! ONLY JOKing... I love bouncing about in a cold 42 year old car.. have had a midget from beng 16yrs old n im 46 now!! just struggle with 'engines' errr hows it go... cant cook wont cook....!
Rob Flint

Thing is Rob F, if you ask a question around here, along with the answer, --- which you will eventually get, --- you will also get the collective wisdom (and I use the word wisdom advisedly lol), of about 30000 years worth of spridget ownership.

Now if you also want cooking lessons, well, you should have said earlier.

Do you know the BEST way to boil and and eat an egg?

ALWAYS have it at room temprature before you boil it, and NEVER let it boil hard. 3.5 mins is best.

ALWAYS bang the top with a t spoon and then peel and scoop.

NEVER cut the top off with a knife. :)
Lawrence Slater


Lawrence

That's exactly how I do an egg.

My wife cuts the top off. Does thi mean I should never allow her near a fuel filter?
Gavin Rowles

No let her clean the fuel filter, but keep her out of the kitchen. :)

Men are better at cooking anyway. :)
Lawrence Slater

Should this thread be moved to 'General' now ? lol
Rob Flint

Well thats another 100 miles on it this morning and 'All OK' a steady ride out to Donna Nook to see the baby seals then a fast blast back on the motorway home..

Cheers for all your help..
Rob Flint

Yeah, but, no but, how do you cook and eat YOUR egg?
Lawrence Slater

Allergic to eggs...
Rob Flint

This thread was discussed between 21/11/2011 and 27/11/2011

MG Midget and Sprite Technical index

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