Engine losing Power at 4000 rpm

[vrs9]

Hello Guys,

This is my first post so sorry if it doesn't make sense!! I purchased Lucy's Red Zed ('77 260z with 2" SU Carbs) over a month ago... Some of you might know the car. In the last week the engine has been playing up. When i'm accelerating up the revs and change gear the engine loses power and struggles to pick up speed. Once i down shift again and change gear gear before 4,000 rpm (Not reving as high) it pulls fine. I decided to change the plugs, oil and oil filter which seems to have improved its response but still having the same problem. Personally I'm thinking the carbs are causing the problem but would like to hear what ye might think??

Thanks again

Paul

 

[Rob Gaskin]

Two simple things to check re fuel:

Dashpots for oil.

Is the Fuel Filter blocked?

 

[Dale]

Quite probably debris in the fuel system. Little flakes of paint and rust from the tank or some of the lines over the years that flow forward under acceleration and clog up and restrict the flow of fuel, the debris will then move back again when you come off the pedal.

A fairly common problem.

 

[vrs9]

Thanks Rob,

Will take a look and see.. By Dashpots do you mean inside the carb pot? Not very familar yet with carbs yet sorry.. Goin by pictures i've found on the internet SU carburetors On this link its referring to item 12.

 

[Rob Gaskin]

Thanks Rob,

Will take a look and see.. By Dashpots do you mean inside the carb pot? Not very familar yet with carbs yet sorry.. Goin by pictures i've found on the internet SU carburetors On this link its referring to item 12.

Unscrew item 15 and check that the tube is about half full of oil. Light engine oil will do, don't overfill.

If your problem is debris in the fuel then the symptom will gradually get worse as you use the car. I think it is likely to be this.

 

[status]

You might have something in one of your feul lines,ie every time you accelarate that bit of debris moves and causes a blokage and when you decelerate it clears and you have the power back,happened to someone i know,it was a tiny pebble in one of his feul lines

 

[jonbills]

Also could be distributor troubles - a timing light will show if timing gets unstable at 4k.
colortune might be useful in confirming probs with fueling.

 

[vrs9]

Changed the Fuel Filter last night. It was black with dirt. Brought the car out for a good run. Pulled hard through every gear.. up past 4krpm without any hesitation!! Hopefully that problem won't occur again.

Thanks for the advice guys

Cheers

Paul

 

[Rob Gaskin]

Glad it's sorted.

It should be the first thing anybody does with an old Datsun - change the fuel filter. I found out the hard way too.