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Midget cutting out
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Finch661



Joined: 19 Feb 2009
Posts: 163
Location: Edinburgh, Scotland

PostPosted: Tue Mar 10, 2009 4:23 pm    Post subject: Midget cutting out Reply with quote

for those who dont know me, i am the question guy! Wink
just another quick post regarding my 76 mg midget (stock everything (well almost)). you'll be gald to here that my mg passed its mot, one only one or two warnings (minor things!!!). on the morning of the test though, my car wouldnt start. the petrol gauge read about 1/4ish. i checked the fuel pump, cranked the engine and nothing came out. my first thoughts were that the guage is knacked.

i put about 5L into the tank and the car came to life. i then filled the tank but it only took about 20L, and thats on a 32L tank. the guy i bought it off said that the car will not start with the tank below the half mark.

my car is roadworthy, but not reliable, i dont want to have to keep filling every time i hit the half mark (i am taking it to the western isles of Scotland, so i cant stop every 100 miles)

where should i start looking, i was thinking about getting a new tank/pipes, but that is a big expense, especially if it is a simple problem?

oh i have noticed that when i removed the petrol cap, there was a pressurisation noise (hiss)

many thanks, and sorry for the essay!

oh i thought you would like a pic

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Rick
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Joined: 27 Apr 2005
Posts: 21180
Location: North-west UK

PostPosted: Tue Mar 10, 2009 5:18 pm    Post subject: Reply with quote

is there a blocked breather on the tank, or perhaps a small drilling in the cap? if the pressure is building up over time, ie as the tank drops to half full, it might be overloading the pump until it refuses to pull any more through. You top the tank back up, and the act of removing the cap to do so is releasing the pressure, and so it starts again. Worth a look in the manual for a breather anyway.

Rick
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Various 1920s-1960s - Austin, Morris, Commer, Dodge etc.
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Finch661



Joined: 19 Feb 2009
Posts: 163
Location: Edinburgh, Scotland

PostPosted: Tue Mar 10, 2009 5:28 pm    Post subject: Reply with quote

it would be annoying if it was as simple as a blocked breather! i dont think the late midgets had a breather pipe. there is only the hole for the peed pipe and sender. i know the us versions had one built into the fuel/vapour recovery system. i will have a wee look at haynes/google.

i will empty the tank to half full (shouldnt take too long with a 1.5 twin carb Laughing )


update: just had a look on ebay, and found my locking fuel cap (so i dont think it is standard) and it says that there are two varients, a vented and a non vented... what are the chances the previous owner bought the wrong one?


Last edited by Finch661 on Tue Mar 10, 2009 5:52 pm; edited 1 time in total
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Rick
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Joined: 27 Apr 2005
Posts: 21180
Location: North-west UK

PostPosted: Tue Mar 10, 2009 5:51 pm    Post subject: Reply with quote

next time it conks out, just release the filler cap and see if it magically transforms the car back to a runner, or not...

R
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Various 1920s-1960s - Austin, Morris, Commer, Dodge etc.
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47p2



Joined: 24 Nov 2007
Posts: 2002
Location: Glasgow

PostPosted: Tue Mar 10, 2009 6:11 pm    Post subject: Reply with quote

You could try running the car without the cap and see how it goes.

The other thought is if the pipe going into the tank is going far enough down into the tank. You want it to be just off the bottom of the tank by a few mm
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ukdave2002



Joined: 23 Nov 2007
Posts: 3519
Location: South Cheshire

PostPosted: Wed Mar 11, 2009 12:59 pm    Post subject: Reply with quote

If it were a blocked breather the wouldn't the problem would be worse when the tank was full, because air will compress but liquid won't? but its still worth checking, I suspect 47p2 is right as I think the fuel line out is a third to halfway up the tank on a midget ( it was on an old sprite I used to have), sounds as if the internal pickup pipe has detached its self or corroded away.
Cheers


Dave
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baconsdozen



Joined: 03 Dec 2007
Posts: 1119
Location: Under the car.

PostPosted: Wed Mar 11, 2009 3:10 pm    Post subject: Reply with quote

can't really remember what the Midget tank pick up is like,but maybe its corroded through so there's an air leak uthats covered as you fill the tank up.
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Wed Mar 11, 2009 4:06 pm    Post subject: Reply with quote

Dave,

The problem with no vent is the tank pressure is lowered as the fuel is used. There comes a point when the suction of the pump can't pull against the vacuum that is in the tank. That 's why as Rick says "open the cap and let the pressure equalise" IE Let air back in. If it is the vent the car should now be able to be driven.

Art
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Finch661



Joined: 19 Feb 2009
Posts: 163
Location: Edinburgh, Scotland

PostPosted: Wed Mar 11, 2009 5:36 pm    Post subject: Reply with quote

a little bit more research, and it seems that all mgs use a vented filler cap. even the 1275 midget (that was a vented tank) has one. like i said before i found my filler cap on ebay and after contacting the seller, it turns out that its a 'safety cap', that is " neither vented nor nonvented"....hmmm

i'll take the car out today and use some fuel up and see if i get a swoosh sound at the filler cap.

so my car is reliable aslong as i dont use the electrics or fuel system
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clan chieftain



Joined: 05 Apr 2008
Posts: 2042
Location: Motherwell

PostPosted: Wed Mar 11, 2009 9:07 pm    Post subject: Reply with quote

I would agree with 47p2. Run it with the cap off or loose. I had this problem a few years back with a Marina TC and the tank actually imploded.
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Finch661



Joined: 19 Feb 2009
Posts: 163
Location: Edinburgh, Scotland

PostPosted: Thu Mar 12, 2009 3:14 pm    Post subject: Reply with quote

thanks for all the support. i will try your suggestions out when my car is back on the road (for all those who havent ready my other pst, my alternator has packed up!!!)

Mr. Green
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Finch661



Joined: 19 Feb 2009
Posts: 163
Location: Edinburgh, Scotland

PostPosted: Tue Mar 17, 2009 8:37 pm    Post subject: Reply with quote

hey everyone, just had the car out and about today, burned off a fair amount of petrol. opened the filler cap, and it hissed. so i'm guessing that means my cap isnt venting properly!
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Keith D



Joined: 16 Oct 2008
Posts: 970
Location: Upper Swan, Western Australia

PostPosted: Wed Mar 18, 2009 1:22 pm    Post subject: Reply with quote

Cars over here have fuel pumps that pump through the delivery pipe all the time, with a return pipe back to the tank. The carby or injectors just use whatever they need. Consequently, petrol caps always hiss when you remove them to fill up. Apparently it's all part of the emission controls.

Keith
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Finch661



Joined: 19 Feb 2009
Posts: 163
Location: Edinburgh, Scotland

PostPosted: Thu Mar 19, 2009 12:08 pm    Post subject: Reply with quote

i have seen the haynes diagrams for the fuel system for the midget in both US and California midgets. there is a lot of extra plubing for vapour recovery and emissions control. non of that nonsense in the UK during the 70's Smile how times have changed though
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