Vapor lock questions for the hotter climate guys

[cygnusx1]

Here we go again. FI cars can, and do vapor lock. It's the fuel that vaporizes. Fuel does not care if the car is carb or EFI, if fuel gets hot enough to exceed vapor pressure...it vaporizes. In a hose, a bucket, a tank, a fuel rail, or ANYWHERE.

[Bruce Palmer]

The electric fan on the radiator with an adjustable cool down setting makes about as much sense as anything. Cars sitting heat sinking from the engine compartment plus what the sun's adding would benefit greatly, I'd think from a cooling fan on the radiator trying to get the cooling system cooled down to say 180 for 15 minutes blowing air thru the engine compartment whole you are in the hardware store. Your cooling system will think you are pampering it while in reality you are cooling down everything else..... too.

[Z train]

Bruce,here it's actually the heating radiating upwards off the asphalt that magnifies the heat.If i pop the hood and leave it sit on the safety catch,i have no issues restarting.

THe wifes 620 is my only carbed vehicle.I have a functioning return system and NO insulation and i have zero vapor lock issues.

Edited July 26, 2011 by Z train

[doradox]

Here we go again. FI cars can, and do vapor lock. It's the fuel that vaporizes. Fuel does not care if the car is carb or EFI, if fuel gets hot enough to exceed vapor pressure...it vaporizes. In a hose, a bucket, a tank, a fuel rail, or ANYWHERE.

Fuel injection runs at higher fuel pressure. Fuel and physics DO care about that. That increases the boiling point of the fuel. Also most FI have the pump either in or by the fuel tank. The pump itself never has to try to pump hot vaporized fuel. Also with the higher volume pumps that are run with EFI, if the fuel under the hood is vaporized the pump quickly displaces it with cooler liquid fuel. A properly functioning FI system is highly unlikely to vapor lock. If, while the vehicle is turned off, the system is bleeding off fuel pressure due to a faulty pump check valve, regulator, or injector then the system will be much more susceptible to vapor lock.

Steve

[doradox]

The electric fan on the radiator with an adjustable cool down setting makes about as much sense as anything. Cars sitting heat sinking from the engine compartment plus what the sun's adding would benefit greatly, I'd think from a cooling fan on the radiator trying to get the cooling system cooled down to say 180 for 15 minutes blowing air thru the engine compartment whole you are in the hardware store. Your cooling system will think you are pampering it while in reality you are cooling down everything else..... too.

Bruce, you hit the nail on the head. Heat soak is the major component driving the problem. With the engine shut down the cooling system is no longer carrying away the heat from the engine. That's why cars have catch tanks on the cooling system. Coolant temps rise after shut down because that big hunk of cast iron and AL is HOT. A hot day, hot engine, no air flow, one can get vapor lock. Popping the hood induces air flow as the hottest air rises and escapes and cooler, relatively, air replaces it. Heat radiating from asphalt is not helping but is just one contributing factor.

Steve

[Z train]

Fuel injection runs at higher fuel pressure. Fuel and physics DO care about that. That increases the boiling point of the fuel. Also most FI have the pump either in or by the fuel tank. The pump itself never has to try to pump hot vaporized fuel. Also with the higher volume pumps that are run with EFI, if the fuel under the hood is vaporized the pump quickly displaces it with cooler liquid fuel. A properly functioning FI system is highly unlikely to vapor lock. If, while the vehicle is turned off, the system is bleeding off fuel pressure due to a faulty pump check valve, regulator, or injector then the system will be much more susceptible to vapor lock.

Steve

S.O.B,we actually agree on something.

[cygnusx1]

Yes less likely to. But they still can and do. Saying that they DO NOT vapor lock is FALSE, especially in our older systems. Why else would Nissan add the cooling snorkel in the latest evolutions? For the comfort and pleasure of the injection system?

As a matter of fact, the hot fuel that sits INSIDE the bodies of the hot injectors WILL flash vaporize when the injectors are first fired, as the pressure drops to near atmosphere for the split second, each time the pintle fires. Yes, it happens that quickly, and affects how the FI car runs, until it clears up with cooler fuel. Note: Nissan pointed the blower snorkel at the injector bodies, not the rail.

I have datalogged the effect and can offer hard evidence of this.

Vapor lock in the rail of a 240Z is the same as the vapor lock in an injector of a 280Z. Just on a different scale.

Edited July 26, 2011 by cygnusx1

[Z train]

Yes less likely to. But they still can and do. Saying that they DO NOT vapor lock is FALSE, especially in our older systems. Why else would Nissan add the cooling snorkel in the latest evolutions? For the comfort and pleasure of the injection system?

As a matter of fact, the hot fuel that sits INSIDE the bodies of the hot injectors WILL flash vaporize when the injectors are first fired, as the pressure drops to near atmosphere for the split second, each time the pintle fires. Yes, it happens that quickly, and affects how the FI car runs, until it clears up with cooler fuel. Note: Nissan pointed the blower snorkel at the injector bodies, not the rail.

I have datalogged the effect and can offer hard evidence of this.

Vapor lock in the rail of a 240Z is the same as the vapor lock in an injector of a 280Z. Just on a different scale.

Really?Then explain why my Z engine(below) has NEVER "vaporlocked(for lack of a accurate word)

But my daily driver 810 has warm start issues due to the fact that the check valve in the fuel pump is basically shot,thus letting pressure bleed off allowing the vapor to form.But the Z's system is perfect,thus no issues.

Edited July 26, 2011 by Z train

[cygnusx1]

They don't all do it. It depends on how much heat transfers into the fuel rail and injectors. How do you know it's not happening? If you have a wideband O2, it can correct for it and you would never feel it. Nice engine bay BTW. Can you watch the EGO correction factors in a cold vs hot start? Is the hood vented? Oh yeah and you are the "merchant of cool!"

Edited July 26, 2011 by cygnusx1

[Z train]

1)They don't all do it. 2)It depends on how much heat transfers into the fuel rail and injectors. How do you know it's not happening? 3)If you have a wideband O2, it can correct for it and you would never feel it. 4)Nice engine bay BTW. Can you watch the EGO correction factors in a cold vs hot start?5) Is the hood vented? 6)Oh yeah and you are the "merchant of cool!"

1)Right.The ones with MECHANICAL problems are the ones that do.

2)Are you saying that the engine bay of my turbo stroker is COOLER than the factory issued 810?

3)On cranking?

4)Thanks.

5)Neither hood is vented.

6)Yes,Yes- i am.

[doradox]

S.O.B,we actually agree on something.

It was bound to happen sooner or later.

Steve

[cygnusx1]

Right, because yours does not vapor lock, no cars with FI do? Read the FSM. What is the allowable decay time for the factory fuel pressure after shutdown?