[ROVERNET - UK] Loss of power problem again

[Magnet]

Hi Gavin,

I would certainly suspect the fuel pump, but there is another faint 
possibility...  I had the same problem ages ago on a Fiat Multipla, and 
it was caused by a blocked air inlet to the fuel tank.  As fuel was used 
up, a partial vacuum was created in the tank, preventing the pump from 
sucking out the fuel.  Taking off the cap resulted in a "whooosh" as air 
entered the tank.   But this problem tended to be more acute with a full 
tank, and yours is evidently more likely when the tank gets down a bit, 
and there's less hydrostatic (petrostatic?) head helping the pump.

On the Fiat, the problem only occurred on cold, icy days, and was caused 
by ice in the vent hole.  I don't imagine that's **your** problem!  

Cheers,

 -- Bill

Gavin.Walker at csiro.au wrote:
> Hi Everyone,
>   The loss of power problem in my SD1 has resurfaced.  So far I've done
> about 280km on this tank of fuel and I didn't have any hint of the
> problem until about 250km.
>
> First showed up again last night.  Running along at 100km/h then power
> loss with faint surges that eventually recovered as I slowed down.  At
> that point I got stuck behind a car doing 90km and didn't have a problem
> for the rest of the night.  Despite another 10-15km.
>
> This morning I get 4 km at 60-80km/h, no problem.  After 30sec at
> 100km/h I lost power for long enough to have to pull off the road.
> After some idling I have a go getting back on the freeway. Get up to
> 3000rpm in second and lose power again.  The tacho registers about
> 1000rpm but that's just the torque converter spinning down.  If I hold
> the throttle open during power losses it will eventually stall, but if I
> stop it will idle contently.
>
> After limping to an exit I was able to drive around at 70km/h for a bit
> and then at 60km/h up a hill I loose power again and had to pull over
> and idle.  No more problems after than but the rest of the trip is
> around campus at 40km/h.
>
> I suspect a failing fuel pump.  I have twin strombergs on my SD1 but the
> system has a return line (legacy of a previous EFI setup).  I fitted a
> restrictor to the return but it doesn't seem to have solved the
> problems.  Next step is clamp off the return line.  The car if fitted
> with a repco electric fuel pump (loud) outside the tank and I suspect
> that when the tank gets down the pressure differential between the tank
> level and the engine is too great and the float bowls slowly wind down.
> Idling helpd refill the float bowls and gives a burst of power.
>
> Gavin Walker
> 1982 SD1
> Canberra, Australia
>
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