Vapor lock questions for the hotter climate guys

[5thhorsemann]

The eastern seaboard is getting roasted lately, yesterday we hit 103 and I had parked the car in the sun after a spirited highway run. Like 15 min. later I got in started fine and off I went, I didn't make it a half a block when she started to go heavy lean so I ducked into a parking lot where it sputtered and died and I drifted into a shady spot and popped the hood.

I got a gallon of water and cooled the carbs (twin su r/t's) fuel pump and hard lines. After a little coaxing I got her to start again and got myself to an air conditioned bar.

Today its over 100 again, I did a short run to the gas station and the hardware store and back home. I parked in the sun for only 4 or 5 minutes, started it up and a half a block down the road it sputtered and stalled. I did the water trick and off I went. It seems to be that only when she's parked in the sun will she get hot enough to stall. It seems like opening the hood and splashing water on the fuel delivery components is enough to fix the vaporlock, so I'm not that concerned about it.

My question to the desert dwellers is, how did you modify your cars to combat the vapor lock issues on your early carburated 240 Z? I did a search and read a bunch of stuff, but vapor lock is a hard search.

[psdenno]

Typically, the daily temps reach over 100º every day from June to early October here in the SoCal desert. They're usually 110-115º this time of year. Even with the A/C on, I haven't experienced vapor lock with my '71 Z. The only mods on the car are a bigger radiator and aux electric fans that come on with the A/C.

Prior to getting my current Porsche 914-6 which has carbs, I had a 914-4 with fuel injection that was easily vapor locked. A wet towel on the fuel lines helped with that car. Slow stop & go traffic on hot pavement was deadly - had to keep the air moving through the engine compartment.

Dennis

[beermanpete]

These cars are know to have vapor lock problems. They came with asbestos insulation on the fuel rails. If yours is deterorated or missing the problem will be agrevated. One of the Datsun solutions starting in '72 or '73 was adding an electric fuel pump near the fuel tank to push the fuel against the vapor pressure. Perhaps you could add an electric fuel pump.

[FastWoman]

I've heard of carb guys recirculating their fuel. Maybe you could put a fuel pressure regulator right at your carbs, with a return flow line that feeds to your fuel/air separator (draining back into the tank). I don't know whether any of the lower pressure regulators are built that way (i.e. like the higher pressure EFI regulators).

FAIW, my 280 will get a momentary vapor lock now after only a few min of sitting. This heat is brutal! I feel for you!

Edited July 24, 2011 by FastWoman

[doradox]

There should already be a fuel return circut. Do you have it functioning?

Steve

[SteveJ]

Here are a couple of links for possible insulation sources:

http://www.amazon.com/Corvette-Natural-Protector-Insulating-Sleeve/dp/B003FCSKBQ/ref=sr_1_10?s=automotive&ie=UTF8&qid=1311518219&sr=1-10

http://www.amazon.com/Natural-Protector-Insulating-Sleeve-Spark/dp/B003FBNL8O/ref=sr_1_11?s=automotive&ie=UTF8&qid=1311518219&sr=1-11

I haven't measured the lengths of fuel line, but they might work, especially if they are wrapped in reflective tape.

[Walter Moore]

The 240Z has a fuel return line. Make sure that it isn't plugged.

With an electric fan, and an electric fuel pump I haven't had any problem with vapor lock, even at ZCON last July (When the temp was around 100). But my Z doesn't have air conditioning, so I don't drive it much when the temperature gets above 90F.

[Z train]

We are running temps of 105 to 114 these days.My 810 runs fine EXCEPT when i park it for 15 to 20 minutes.Then i have a start issue as the fuel has become so hot it has pushed past the reg.FI cars don't vapor lock.

Sarah,since you like tinkering,if you ran a momentary "on" switch to the fuel pump(or FP relay),you could over come this by turning the FP on with the switch.Datsun designed their FI cars to allow power to the fuel pump ONLY when the motor cranking or turning.

Carb guys like the OP-insulate every line you can get your hands on under the hood.A functioning return system is mandatory.

Another possiblility is the injector blower from the later 280 cars.

[FastWoman]

I already do that, ZTrain. I've got a switch wired in the console. I prime before every start. I have no trouble starting, but the engine runs a bit rough until I'm first able to take off down the street. Then everything is fine. Perhaps if I primed for longer... But as long as it starts, I'm fine.

[Z train]

Try priming for 30 seconds.If you can hear the FP,you SHOULD notice a change in pitch.

On a related note,tomorrow i have some running around to do.I'm going to bring my IR thermometer with me just for shits & giggles.

Edited July 25, 2011 by Z train

[5thhorsemann]

I recently went through the entire fuel circut and cleaned and blew everything out, including the returne lines. I Insulated the the lines using fiberglass matt insulation and reflective foil tape. It seemed to help a little bit, but Sunday the vapor lock happened again after sitting in the sun for 15 min. or so. I guess I will have to put the electric pusher pump back on the car.

When I went with the round top carbs, I was told by many that it wasnt necessary to prevent the VL problem, so it was omitted, one less thing to fail. I guess that was wrong.

I know there is a company called Pegasus racing that has the replacement fuel pump that was installed on the 73 recall, anyone use this pump? http://www.pegasusautoracing.com/productdetails.asp?RecID=85 This is the exact pump that was removed from my car, it has been internally modified since the original install to use less power and pump more efficently, but it is the faucet replacement.

[steve91tt]

If you are in the market for an electric pump you might look at the low pressure rx7 pump. I've got them on both of my 240's here in Texas and never had VL. They are very quiet and about $30 on eBay.