choob

Hesitation after WOT

15 posts in this topic

Had a problem crop up today on the RRC. It's got a 3.5 carb engine. After driving WOT, e.g. to overtake, the engine started hesitating when driving more slowly, reluctant to rev and needed the revs kept up or it would threaten to stall.

The problem goes away after a few minutes but comes back if I drive at WOT. I dunno how carbs work, any help would be great.

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Sounds like fuel starvation to me... Dead fuel pump or kinked/blocked fuel supply lines, filter, carb float needle etc...

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A partial blockage of the fuel tank breather may cause these problems - while the fuel flow is greater at full throttle, so is the suction, but with the tank vacuum building up and the carb choke chamber vacuum reduced at partial throttle, the fuel flow may be stagnating.  Worth checking the fuel pump too.

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Surely #1 suspect for fuel starvation on an old RR would be the fuel filter?

Also the SU's need oil topping up every so often.

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Well yes, I thought for some reason I had included that in my list above, must be going senile :)

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Thanks for the replies.

The breather is ok, and I changed the fuel filter today. Let's hope that helps. Thanks again, I will report back.

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It should have Strombergs, not SUs, but they could have been changed. In any case, unless you actually know the carburettors have been rebuilt, then you should do that, because once they age the engine will never run right. Other than that, you have to go through the usual service items as mentioned above, and definitely include the ignition system as well. Once everything is up to standard, then either you won't have any more problems or, if you do, then you can start troubleshooting in a methodical way instead of just poking away at the thing and hoping for the best. 

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It does have Strombergs, not SU. Ignition seemed ok, was hoping it wasn't the pump as previous car (3.9) had in tank pump but this has an external pump so if that dies shouldn't be too much of a pain to fix.

I don't know how to rebuild carbs, and I sure don't trust anyone here (east africa) to do it except maybe a couple of old rally drivers who used to race them.

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On ‎3‎/‎25‎/‎2017 at 7:19 PM, choob said:

Had a problem crop up today on the RRC. It's got a 3.5 carb engine. After driving WOT, e.g. to overtake, the engine started hesitating when driving more slowly, reluctant to rev and needed the revs kept up or it would threaten to stall.

The problem goes away after a few minutes but comes back if I drive at WOT. I dunno how carbs work, any help would be great.

What does WOT stand for ??? :unsure:

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Wide Open Throttle

The way I rebuild carbs is to un-bolt the inlet manifold complete, sell it to some luddite who still likes carbs, and then bolt on the EFI inlet manifold and a Megasquirt kit. :P

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16 hours ago, FridgeFreezer said:

Wide Open Throttle

The way I rebuild carbs is to un-bolt the inlet manifold complete, sell it to some luddite who still likes carbs, and then bolt on the EFI inlet manifold and a Megasquirt kit. :P

:lol::lol::lol:

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17 hours ago, FridgeFreezer said:

Wide Open Throttle

The way I rebuild carbs is to un-bolt the inlet manifold complete, sell it to some luddite who still likes carbs, and then bolt on the EFI inlet manifold and a Megasquirt kit. :P

Oh dear God . . . :rolleyes:

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On 4/1/2017 at 7:12 PM, choob said:

It does have Strombergs, not SU. Ignition seemed ok, was hoping it wasn't the pump as previous car (3.9) had in tank pump but this has an external pump so if that dies shouldn't be too much of a pain to fix.

I don't know how to rebuild carbs, and I sure don't trust anyone here (east africa) to do it except maybe a couple of old rally drivers who used to race them.

Ooooh, East Africa, I follow you now. These carburettors are easy to rebuild, especially if you've got the internet. There's not much to them at all, kits are easy to get, and you just have to be methodical. If the throttle spindles are really loose in the bodies then you would need someone to help with that. 

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23 hours ago, FridgeFreezer said:

Wide Open Throttle

The way I rebuild carbs is to un-bolt the inlet manifold complete, sell it to some luddite who still likes carbs, and then bolt on the EFI inlet manifold and a Megasquirt kit. :P

 

5 hours ago, Davo said:

Oh dear God . . . :rolleyes:

Bloody kids eh :rolleyes::lol:

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It seems ok since I changed the fuel filter...although the oil pressure sensor started leaking today. 

My mechanic says 'see you next week' everytime I go there >.>

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