Vapor lock

[MelZ]

Hi guys,I have a standard 71 240z with twin hitachis on it.after driving it hard after about 20 mins it runs rough and then loses power, after sitting at the side of the road for about 10 mins I can restart and am away again----- is this classic vapor lock?-- it has the standard return pipes that circulate the fuel from the pump to them carbs then back to the tank which I thought was to alleviate this.When I stop and hold the pipes they are pretty hot which you would expect as bracket is bolted to inlet manifold but how hot does the fuel need to get to vaporize ?. Appreciate any thoughts ,thanks. Mel

[Scoota G]

Repeat the process and when you do open the fuel door and release the cap. I'm betting the tank is sealed tight and you're creating suction back into the tank causing the fuel pressure to drop. Does it happen more when it's hotter?

[zeds4ever]

 

 

            Scoota, when you say repeat the process does that mean wait till it heats up & then release fuel cap asap.

 

                                                  Regards: Alan.

[Zedman240®]

Vapor lock usually happens when you're in bumper to bumper traffic and everything gets real hot. After checking Skoota's recommendation, I'd be checking float levels and fuel filter/s. Sound like a fuel delivery issue.

[Scoota G]

Scoota, when you say repeat the process does that mean wait till it heats up & then release fuel cap asap.

 

Regards: Alan.

 

I meant drive the car and wait till the problem occours again, it may not be vapour lock at all.

[Enzo]

If you are running the standard mechanical fuel pump a small pinhole in the diaphram will allow the vehicle to operate normally at lower revs but at higher continuous revs will starve for fuel if it can't keep the volume up to the carb. Also check for a blocked fuel filter .

David

[MelZ]

Thanks guys, yes I was talking to some other guys and they also suggested the non vented fuel tank but am not totally convinced as this is anew problem that has developed.The problem is that I only drive the car about 10 times a year , never in the rain etc.i have had fuel issues in the past and had changed fuel filters etc, blown out lines and float bowls so might be bit of trial and error.Also no fun being stranded on the side of the road miles from anywhere with just a screwdriver and crescent for company but that's part of the fun of a 40 year old car right.

Mel

[MelZ]

After investigation I have found the fuel pump is not delivering enough fuel so starving the carbs. I am finding it difficult to obtain a kit for the  original pump, do you guys have any reliable/ good sources in Australia?

Thanks mel

[NZeder]

Put an electric pump in it was an option for some markets and as such Nissan made the loom with the wiring already there. Most car parts manuals aka Haynes should show you what colour wire to look for but it will be under the car in the rear and finishes near the centre console if I recall correctly.

[MelZ]

Thanks, but would rather keep it all standard in the engine compartment, so am after a fuel pump kit if possible. So who is the best source in Australia ?.

Thanks mel

[Linton]

i got a new pump from repco

[fluegel]

I fitted a carter 4070 to my 1976 260Z 2+2 last year. In the past I did sometimes have vapour lock problems I took the car on the Bay to Birdwood the day was warm and the traffic slow sometimes bumper to bumper but it didn't stall at all. When I bought the car it had a mechanical fuel pump but I am told it should have originally had an electrical pump.

 

Richard

[Lynton]

Vapour lock back in the 70's for the 240/260z was heat in the engine compartment after turning the engine off for a short period then trying to start the car again with the starter cranking many, many times before engine would start. Hence the heat shield over the manifold/extractors introduction of electric fuel pump and the vents in the late zeds bonnets, and foil insulation wrapped over the fuel lines. Hope this helps Lynton