Su Carb Problem?

[jwc11170]

72 240 - Original engine

I need some advice about a problem that has recently started with my Z. It starts fine with minimal choke and runs well (throttle response is very good) until after driving for about 30 minutes to an hour. Engine temp is still normal, but after turning off the engine it's hard to restart. Also it starts to stall and not pick up RPM's when applying throttle. When this happens if I pull the choke the engine runs well again and it makes the problem go away. But after using the choke to avoid the stall, it gets even worse. I don't have a lot of experience with the SU's. What do you guys think? Any help would be very appreciated.

[d240zx2]

Take a look at Z Therapy carbs. Bruce Palmer will likely address your problems. He's the resident SU expert....

[Gary in NJ]

Sounds like a vapor-lock issue. I agree, Bruce can give you the quick, and right answer.

[beandip]

jwc, to me it sound like you are running lean. Now this could be from throttle shafts being worn. A leaking vacuum hose or just mixture set too lean. If when idling you step on the brake peddle , does the engine speed increase or decrease? If there is any change check the hose for leaks. Is this Z a automatic. If so there is a vacuum line going to the tranny. Check them especially where it connects to the module on the trans. Also check for any ATF in the hose, this would be from a leaking module.

If you buy some Carburetor cleaner, with the engine at idle and warmed up. spray some of the cleaner around the throttle shafts and around the carb insulators and intake manifold . Any change in RPM indicates a leak.

DO NOT USE STARTER FLUID OR ANY OTHER FLAMMABLE , FOR THIS . Carb cleaner is nonflammable.

Gary

[Zs-ondabrain]

What Gary said........

Sounds like th heat may be expanding the gap in your throttle shafts and the carbs are running lean. Maybe an electric fuel pump might help keep some fuel in the bowl.

Dave

[jwc11170]

Thanks guys for all your responses. Sorry to get back so late, on east coast time and working too much.

Beandip- the Z is a five speed out of a 280. At times I have noticed RPM drop when sitting on the brakes at a stoplight.