2+2 losing power at high revs-fuel starvation maybe?

[phatmendus]

Hi All,

I am having problems with my 2+2 s130 where when I want to go fast, i.e high throttle settings, It performs fine for about 20 seconds or so, then I loose power as if its suffering fuel starvation. If I am then put in to idle it will just stall as if it is unable to maintain idle due to lack of fuel pressure and flow. After re starting and holding the idle on the throttle for a bit it returns to nomal and will drive ok again. This all points towards fuel starvation I was thinking. Basically not enough fuel being pumped to the carbs to maintain the float chamber level under high fuel demands. Once back at slow speeds/idle the car slowly recovers suggesting the pump refills the float chambers etc.

Anyway, with that being my idea I thought I either had a faulty fuel pump or a filter blockage. I have subsequently replaced both in-line filter (which I put in just to help clean the fuel) and the fuel pump. I then thought this had fixed the problem, but no it hasnt. The same thing happens under high acceleration. The carb inlet gauze filters are also clean.

Does anyone have any ideas that may help? Not sure if its important but it is fitted with lumenition. As is said before it operates fine for a period of time at high revs then the problem begins which really makes me think its fuel as the problem. Is there maybe a filter inside the tank that may be restricting the flow?

All suggestions welcomed

many thanks Simon

[leifanten]

webers? Strombergs?

electric fuel pump or original?

fuel tank and fuel lines clean and clear?

did it suddenly get this way or did you buy the car in this condition?

check float height in fuel bowls

[phatmendus]

Hi there,

I have owned and run the car farly trouble free for 6 years now, and know it pretty well, (obviosuly not well enough!)

It has a mechanical fuel pump, standard fit to replace the glass bowl type, running off the cam inside the block. Its on dellortos, when have run fine for a very long time and it was only a year or so ago that I checked the float settings and they were fine.

I have not checked the fuel tank for deposition, which may be the next option, and the fuel lines from the pump to the fuel tank havent been touched since I have had the car. As I was saying in my prior post the onyl time this problem occurs is at high levels of acceleration, thus high fuel demand.

cheers

Simon

[bob_rich]

Hi

I had a similar problem may years ago on a Crossflow engine in my 7 at high fuel demands it just would not go any faster as though it was load/rev limited. Turned out to be holes in the diaphragm of the mechanical pump. Fuel flow OK at moderate performance but inadequate at close to maximum.
I had a glass top pump so just changed the diaphragm. suspect a modern mechanical pump is sealed so only option would be to try another one

hope this helps

best of luck

Bob

[phatmendus]

Thanks for your thoughts Bob, but as I hopefully mentioned, I too thought the mech. pump was the issue so have changed it for a new unit, as I have also done with the in-line filter I have. I cant really see what else it could be apart from a blockage of some sort, but I think that would give an indication straight away on full load rather than after a period of time.

Simon

[alaric]

Hi. I had similar symptoms from a short in the ignition coil some years back. I thought it was fuel, changed the fuel, rebuilt the carbs, the pump etc etc but it was the ignition coil shorting inside when it got hot. I had dropped it shortly before... The problem corrected itself after idling or stopping the engine for a short time.

Ok I know I gave the same suggestion on another thread yesterday and it turned out to be a two year old thread - I'll keep trying - maybe one day I'll be right.

Sean.

[leifanten]

Sean has a good point. A worn coil can crap out at high load, whilst working at low to moderate load. Next time you try out the car, check the temperature of the coil after the car stops working. (or put in a replacement coil if you have one lying around). It can also be the distributor cap having small hairline cracks that creates a high load loss of power. Someone once said that most carburetor problems are electrical......

[phatmendus]

Thanks guys, good tips. I have a spare coil as the one on there is reasonably new and I kept the old one, so i can swap them round to try it. Again the distributor cap is less than a year old as well, but you never know.

The only other thing I would say is that the issue remains at idle straight after the problem has manifested at high speeds, and if i switch the engine off straight away with the problem still there, then an hour or so later start the car, it still has the idle issue for the first ten seconds or so and then the idle picks back up to normal which i thought is because the fuel is slowly topping up the float chambers back to normal levels.

Anway, I will try these suggestions as they are easy to do, and see what happens, but to be honest, and im bound to be wrong, but I am still leaning towards the thought that it is a fuel delivery problem as opposed to electrcal.

cheers

Simon

[robertverhey]

Worth checking the points, condenser and advance too!

[DavidLB]

Make sure that the tank is vented to the atmosphere

[phatmendus]

electronic ignition, and venting tank to atoms is fine.

cheers

Simon

[Higs]

If it is fuel starvation then you can test this by getting the car into its failure mode i.e. driving fast and then killing the engine (turn off ignition) and coast to halt with clutch in (remember that power assisted braking will begin to reduce so be careful). If you then take the top of the carbs off and see what the float level is this will prove (or dispel) the fuel starvation theory.

[phatmendus]

Hi Higs,

That was exactly my plan for tomorrow, its just timing it well so i can tare into my drive just as its doing it then then take the top of the carbs off! but yes, seems like the easiest first step.

Simon

[nigel+2]

hi i had the same problem with my +2,to cut a long story short , i removed the fuel pipe from the bottom of the fuel tank and found like a miniature birds nest in the end, it looked like an accumilation of dirt and fluff,after removing it and reconnecting the fuel line , never had the problem since .hope this helps.c

Hi All,
I am having problems with my 2+2 s130 where when I want to go fast, i.e high throttle settings, It performs fine for about 20 seconds or so, then I loose power as if its suffering fuel starvation. If I am then put in to idle it will just stall as if it is unable to maintain idle due to lack of fuel pressure and flow. After re starting and holding the idle on the throttle for a bit it returns to nomal and will drive ok again. This all points towards fuel starvation I was thinking. Basically not enough fuel being pumped to the carbs to maintain the float chamber level under high fuel demands. Once back at slow speeds/idle the car slowly recovers suggesting the pump refills the float chambers etc.

Anyway, with that being my idea I thought I either had a faulty fuel pump or a filter blockage. I have subsequently replaced both in-line filter (which I put in just to help clean the fuel) and the fuel pump. I then thought this had fixed the problem, but no it hasnt. The same thing happens under high acceleration. The carb inlet gauze filters are also clean.

Does anyone have any ideas that may help? Not sure if its important but it is fitted with lumenition. As is said before it operates fine for a period of time at high revs then the problem begins which really makes me think its fuel as the problem. Is there maybe a filter inside the tank that may be restricting the flow?

All suggestions welcomed

many thanks Simon

[512BB]

Simon,

Be very careful if carrying out the test that Higs suggests, as when switching off your ignition and then altering the cars direction, the steering lock will kick in, if you have one fitted.

Good luck with the fault finding,

Leslie