Rover V8 Twin SU's overflowing petrol
Posted: Sat Jun 25, 2011 12:32 am
Re-built both my SU's (SD1 Hif6) on my rover v8. New seals, jets, needle valves & seats & o-rings. Car fired up fine after re-installing. I balanced the two carbs with airflow meter so I think thats fine. I also adjusted the screw for setting richness on each of the carbs. I'm told that if its setup right, when you lift the dashpot with the liftpin, the revs should increase slightly and then start dying off. Both carbs seem to be doing this now, so I think are adjusted ok. It starts no problem & idles smoothly.
It drove fine for a few miles, than it started stuttering. Eventually I found out that the overflow pipes on both carbs were pouring out petrol. If I turn off the electric fuel pump, the car runs ok for a few mins until, naturally, it runs out of petrol). If I turn back on the pump and re-start, it can be ok for a while, then it starts pouring out of both over-flows again and starts stuttering. The flow is strong, not just a drip. A strange thing I noticed with the over-flow pipes - while the engine is running normally (nothing coming out of overflow pipes), if I block the overflow pipe, the engine starts to die until I unblock it again. I tried the opposite carb and it does the same. It looks like its breathing through/venting through the overflow pipes??? I doubt this is normal..
The fuel bowl's are obviously overflowing because the petrol is overfilling the bowl. When I installed the new needle valve and seats, I did setup my floats again as spec'd in Haynes manual (approx 1 mm lower than base of carb, when carb held upsidedown). I did have to adjust the float a good bit (bend the little tab on the float), the new needles must have been a little shorter the the old ones.
I have a facet fuel pump, without any fuel pressure regulator. There is no fuel return line from the carb (Dont know where you could fit one to the carb??). I've always been running this way and I never had this problem before...
Do you think adjusting the idle mixture screw could cause this (I cant really see how)?
I doubt both my floats are leaking...both overflow pipes start flowing at the same time, so hardly that?
Fuel pump too much pressure? Same pump I've always had, never had this issue before. Pressure reg needed?
New needle valve combo bad...might not be closing correctly and allowing fuel to keep filling the bowl... most likely?? Are you supposed to do anything with needle valve combo when you install them? Tap the back of the needle to it 'forms' a good seal with seat?
Anything else I could have installed wrong when I was re-building that might cause this. I was very careful to put everything back as it was, so I'm hoping not...
Thanks...
It drove fine for a few miles, than it started stuttering. Eventually I found out that the overflow pipes on both carbs were pouring out petrol. If I turn off the electric fuel pump, the car runs ok for a few mins until, naturally, it runs out of petrol). If I turn back on the pump and re-start, it can be ok for a while, then it starts pouring out of both over-flows again and starts stuttering. The flow is strong, not just a drip. A strange thing I noticed with the over-flow pipes - while the engine is running normally (nothing coming out of overflow pipes), if I block the overflow pipe, the engine starts to die until I unblock it again. I tried the opposite carb and it does the same. It looks like its breathing through/venting through the overflow pipes??? I doubt this is normal..
The fuel bowl's are obviously overflowing because the petrol is overfilling the bowl. When I installed the new needle valve and seats, I did setup my floats again as spec'd in Haynes manual (approx 1 mm lower than base of carb, when carb held upsidedown). I did have to adjust the float a good bit (bend the little tab on the float), the new needles must have been a little shorter the the old ones.
I have a facet fuel pump, without any fuel pressure regulator. There is no fuel return line from the carb (Dont know where you could fit one to the carb??). I've always been running this way and I never had this problem before...
Do you think adjusting the idle mixture screw could cause this (I cant really see how)?
I doubt both my floats are leaking...both overflow pipes start flowing at the same time, so hardly that?
Fuel pump too much pressure? Same pump I've always had, never had this issue before. Pressure reg needed?
New needle valve combo bad...might not be closing correctly and allowing fuel to keep filling the bowl... most likely?? Are you supposed to do anything with needle valve combo when you install them? Tap the back of the needle to it 'forms' a good seal with seat?
Anything else I could have installed wrong when I was re-building that might cause this. I was very careful to put everything back as it was, so I'm hoping not...
Thanks...