Could this be vapor lock?

[silkysix]

My 87 BII 2.9l has less than 5000 miles on its total makeover. The engine has had no problems until this week. There have been three episodes when I have driven the truck 10 plus miles, shut it down for a half hour, and it will not start. Cranking fine but no start. In each occasion, after I relieve the fuel pressure at the fuel rail Schrader valve, the engine fires up and runs fine. I never heard of vapor lock in a fuel injected engine, but this sure acts like it. Could this be caused by a malfunctioning fuel pressure regulator? I recently replaced a leaking fuel reservoir. Could there be a connection there?

 

[Bird76Mojo]

Leaking fuel reservoir? What? Any pictures of that part?

You surely mean a fuel vapor canister. (charcoal canister) If it was full of fuel then you have other problems. Either the recirculation valve wasn't opening, which isn't allowing a burning off of those vapors, or you have a vent plugged on the fuel cap/tank which is shoving raw fuel in to that canister when the fuel tank heats up and builds pressure.

 

[silkysix]

Bird, Thanks for your reply. I will definitely check vapor canister and fuel cap! Regarding the fuel reservoir: It is mounted on the frame under the driver's seat. Google it for pictures

 

[Paulos]

I would check the fuel pressure at the fuel rail with KOEO and KOER, and check the vacuum line to the regulator for any sign of fuel. The pressure should be around 40-45psi engine off, and 30-35psi engine running. I wouldn't think that high pressure caused the reservoir to leak. The pressure would make it's way to the tank, and eventually the vapor canister.

 

[rusty ol ranger]

Leaking fuel reservoir? What? Any pictures of that part?

You surely mean a fuel vapor canister. (charcoal canister) If it was full of fuel then you have other problems. Either the recirculation valve wasn't opening, which isn't allowing a burning off of those vapors, or you have a vent plugged on the fuel cap/tank which is shoving raw fuel in to that canister when the fuel tank heats up and builds pressure.

The fuel resivor hes reffering to if that little black canister that sometimes holds a filter. It resides on the frame rail after the tank and before the high pressure pump.

.....and no that isnt (or shouldnt be) the issue here

 

[Dirtman]

Most people just bypass them and throw those things away...

 

[RonD]

You issue reads more like TFI(spark) than fuel related

Have a read here: https://therangerstation.com/tech_library/TFI_Diagnostic.shtml


Vapor lock occurs when a fuel line gets hot enough for the gasoline in the hot fuel line to turn to a vapor instead of a liquid and fuel pumps can't pump vapor.
This occurred when there were mechanical fuel pumps on the engine, and metal fuel lines from the gas tank to the pump and this metal line ran near exhaust system and had 0psi pressure in it.
So on hot days with hot exhaust you could get vapor lock

When you raise the pressure of any fluid you raise the vapor temp point of that fluid, the boiling point

Your system runs at 30psi from under drivers seat to engine, where exhaust and heat are, so it can't get hot enough to vaporize gasoline at even 10psi.
From gas tank to front pump you run 7-10psi, and its not near any exhaust or extra heat point, so unlikely to occur there

To see if its spark or fuel issue you could spray gasoline into the intake when there is a No Start to see if engine starts, if it doesn't then its a Spark issue