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Fuel problem (probably)

PostPosted: Sat Jan 14, 2006 5:34 pm
by sparkey
Hello, It's my first time on here and you all seem very knowledgble so maybe you can help me with a problem on my +2s which I have been unable to solve for months !

The car starts and runs very well, pulling cleanly and with full power, but only for between 7 and 10 miles and then it starts to die, as if it's running out of petrol. It then usually stops altogether. If I then leave it for 20 or 30 minutes or so it may (or may not) start again and take me a few more miles.

It feels like a fuel starvation problem.

So far I have replaced the fuel pump with a new one (the old one still seemed to work, but had some crud in it so I changed it anyway). This caused the carbs (Webers) to flood, so I re-conned the webers. I have now re-tuned the car and again it is now running beautifully, but only for about 7 miles. The distance that it runs is independant of the heat in the engine. If i get it fully warmed upbefore I go it still works for about 7 miles.

I've checked inside the fuel tank for rust/dirt and it's spotless. Ive checked the tank breathers which are both clear.

The ignition system seems fine, as I'm getting good sparks, and it's fitted with a luminition system which has always been really reliable.

The car wasn't used much last year, but I want to use it more this year so I need to get it reliable.

Any advice greatfully recieved.

Re: Fuel problem (probably)

PostPosted: Sat Jan 14, 2006 5:42 pm
by type26owner
When it happens again just coast over to a stop and take an inspection cover off of one Weber. Remove an emulsion tube and look to see there's fuel in the well. Do this also when it's running okay observe where the height of the fuel level is suppose to be before it fuel starves so you'll know if it's lower or not. :wink:

Re: Fuel problem (probably)

PostPosted: Sat Jan 14, 2006 6:41 pm
by john.p.clegg
I seem to remember something about heat affecting the coil or was it the condenser(but if you have lumenition it won't have one)
John :wink:

Re: Fuel problem (probably)

PostPosted: Sat Jan 14, 2006 7:04 pm
by ianf

Check the earth on the Luminition. a friend had a similar problem with an Isle of Wight Frogeye years ago. It worked ok until it overheated then stopped the car. (It feels hot as well so easy to check). Also rotor arms are crap these days always change annually and carry a spare.


fuel problems

PostPosted: Sat Jan 14, 2006 7:53 pm
by worzel

For what it's worth- you say you cover 7 miles- check whether it's the distance or the time spent running. The reason- I had a very similar problem on an Excel- after about 25 minutes it would start to die and refuse to rev. Felt very much like fuel- but in fact it was the amplifier on the ignition.

In my case the unit was breaking down after a certain period of time. Left for half an hour or so it recovered and ran fine but would then display the same fault after about 15 minutes or so (probably because the breakdown cycle was shortening).

An unrelated fault also occurred when the immobiliser was wired into the feed to the amplifier- the symptoms mirrored those above- the reason- immobilisers apparently don't like a continuous feed thru them so I switched to the starter circuit and it was fine.

Might be worth considering if you have an alarm/immobiliser fitted.


Re: Fuel problem (probably)

PostPosted: Sat Jan 14, 2006 8:16 pm
by alaric

I had virtually identical symptoms on my old 1400 mini. Having stripped the carb, drained the fuel tank, cursed left right and centre, I phoned MiniSport and the engineer told me straight away that it was the ignition coil shorting, and that the short was only happening once it was warmed up. I replaced the coil and it was fine - back to winding up bmw drivers.

I'm not sure what a lumenition is, but it'll still have a coil in the system somewhere; isn't it just an amplifier that provides a higher switch rate to the primary of the coil (you drive dI/dt harder)? If that's the case, then if the coil is a standard one, then maybe you've overheated it.

Hope this helps.


Re: Fuel problem (probably)

PostPosted: Sat Jan 14, 2006 10:57 pm
by sparkey
Thanks guys, looks like I'll be busy.

I had thought that it was definately fuel, but I'll try the swapping out all the ignition tomorrow. I've got a pretty much identical system on a formula ford I can use to check against.

I'll let you know how I get on.


Re: Fuel problem (probably)

PostPosted: Sun Jan 15, 2006 12:01 am
by JJDraper
Sounds familiar to me... After replacing the head gasket on my +2, I hit a similar symptom. It started fine, ran sweetly on tick over and for a few miles. Tried checking cam timing, trashed a cam cover gasket; tried the coil... nothing cured the problem. Called Mattey's spoke to Paul (must have been late) he agreed with one of the other contributors - fuel starvation. He suggested an interesting course of action - find a suitable, quiet road; drive until the problem occurs, go to full throttle , kill the engine with the ignition switch, dip the clutch & pull over to the side of the road. Phew!! whip off the tops of the Webers & check the fuel height in the bowls. I did this & lo, the fuel was almost all gone!

While the head was off having some TLC prior to the new head gasket, I had 'serviced' the Webers with new needle valves & reset the float heights, using instructions in the manual. However, retracing my actions, the penny dropped & I realised my error. I had set the float height with the floats resting on top of the needle valves, not just touching. This depresses the spring in the needle valve, making you set the little brass tab too high - result - low fuel height & fuel starvation in normal road use. I reset the floats correctly & the problem disappeared. A little knowledge is a dangerous thing.

Back to your problem - sounds to me like fuel starvation. Could be crud in the filters feeding the carbs, or sticky needle valves or float height, or something else I can't imagine. PM's advice helped me identify the cause - fuel starvation. But if that hadn't worked, at least I could have eliminated fuel starvation tried something else....

Hope this helps


fuel starvation

PostPosted: Sun Jan 15, 2006 1:43 pm
by worzel
Re my earlier comments about ignition systems- I should have added that whilst normally electrical problems usually appear "suddenly" the one I described with an Excel came on slowly so I ended up going right thru the fuel system even to the extent of removing/emptying the tank.

I now do recall that years ago on my elan and with the first lumenition I ever used that something similar used to happen to me- it would play up, then refuse to rev and then finally die as soon as it fired up. Every time the RAC called out the fault then disappeared but when they did their following act after a breakdown the problem would re-appear after about 2-3 minutes.

Eventually (and fortunately) one day it totally refused to start which meant that I could finally work out what was wrong- it was the amplifier pack in the lumenition.

Hope this helps you


Re: Fuel problem (probably)

PostPosted: Sun Jan 15, 2006 1:50 pm
by sparkey
I think I've fixed it !

Tried the coasting to a stop thing and I'd lots of fuel in the carbs so I ruled out fuel.

I then moved the earth for the Lumenition electronic ignition to a better position and replaced the coil with one from my formula ford and it appears to be working.

I've had two test runs of 20 miles and 15 miles at varying degrees of pace and so far it's still working. It'll take me a few weeks to rebuild confidence in it's reliability I think, but so far so good.

Thanks to all for the advice.


I was about to say............

PostPosted: Sun Jan 15, 2006 7:18 pm
by elansprint71
......... years ago I had exactly the same conversation an Alaric with Mini Sport on a 1430S, it WAS the coil!



PostPosted: Mon Jan 16, 2006 4:59 am
by poiuyt
This can be a common problem on motorcycles caused by a clogged fuel tank vent. This results in a cutting off of fuel because there is a vacuum in the tank. Next time this happens, open the fuel filler cap and see if you hear a rush of air being sucked into the tank. If so, check the vent.

The car may be running fine until the vacuum in the tank exceeds the fuel pump's ability to suck out the fuel.

Steve B
1969 S4

Re: Fuel problem (probably)

PostPosted: Mon Jan 16, 2006 1:32 pm
by Hamish Coutts
You say the fuel tank is clean and there is not dirt in it.

Have you checked the rate of fuel flow through the fuel pipe because there could be something partialy blocking it. e.g. a small piece of duster or dirt in the tank or in the banjo bolt at the tank outlet.
This would let enough fuel through to keep the enging running happily at tickover but whenever the fuel demand rises, say by normal running on the road, the fuel supply can't cope and you effectively run out of fuel.

Another long shot - do you have a fuel filter/pressure regulator fitted. Is this adjusted correctly?



Re: Fuel problem (probably)

PostPosted: Mon Jan 16, 2006 4:29 pm
by gjz30075
Sparky, what Keith meant was that when the car quits running again and you HAVE to coast to a stop, then pull the emulsion tube to check for fuel. Sounds like you did the second half of the experiment and checked for fuel with the car in normal running mode and found fuel. At least now you know what to compare it to. That's if it quits again! Sounds like you might have it solved.

Greg Z
'72 Sprint

Re: Fuel problem (probably)

PostPosted: Mon Jan 16, 2006 4:54 pm
by type26owner
Gotta ask this. What type of formula ford you got there? There are bonus points awarded if it's a Lotus! :lol: