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Vapor Lock - Help Please

urbancowboy420

New member
Location
Basalt, CO
Car(s)
Charcoal Gray GTI MK
Hi. Newbee here. Having vapor lock issues with my 07 GTI. Problem only occurs when ambient temperature is above 90 degrees at altitude (typically 7000 plus feet) after car has been running for two plus hours. Has happened in Denver on 100 degree plus days with long run times as well (5280 ft).

Issue has perhaps been slightly improved by mods, but still shows its face on the hottest of days. This has been an ongoing issue for the past few summers, but I haven't delt with it as I live in the mountains of Colorado and it's typically only an issue when I go to Denver (where it can get crazy hot - like it was this past weekend).

Mods Summary: APR Stage II, Neuspeed intake, Audi piston diverter valve, 3" downpipe with hi-flo cat, Neuspeed torque mount, Neuspeed sport springs wiht Koni FSD's, Rial Wheels, Falken FK452's.

I've changed out fuel filter - minimal improvement.

Anyone have similar issues in hot climates? Anyone try BSH PVC fix for vapor lock issues? Success? Alternative ideas?

Thanks.
UC
 

kosmo6

Ready to race!
I had the same issue happen to me last summer. I was driving my 06 GTI MkV (completely stock, sadly) to Utah from LA in mid July and was in Cedar City (5600 feet in altitude and 107+ F) when my car started losing power suddenly. No matter how much I pressed the gas, it was just slowing down. Releasing the pedal and pressing might give it power for a second, but I ultimately had to pull over. The check engine light never came on, either. Thought it was an electrical issue but a mechanic found no issue.

It seemed fixed when I left in the morning but it kept happening my whole drive home - I pulled over to let the car cool probably five times on the drive and was often "drafting" behind semis that were going 45 mph since I couldn't accelerate without it sputtering. When the temperature got below 102 F the problem stopped occurring (was probably at or below 2000 ft when this happened).

I spoke to my VW mechanic just this morning about the issue (I'm making that same trip this weekend) and he said that vapor lock is impossible since it's a closed, pressurized system. Especially since it is direct injection, it definitely makes sense that heat / altitude extremes shouldn't be affecting fuel pressure within the system. It had all the symptoms of vapor lock, though, and the check engine light never came on.

Any other people with this issue? Find any causes or fixes?
 

kosmo6

Ready to race!
Should've searched for "fuel cut" instead of "vapor lock". My fuel cut happened again outside of Vegas and in Saint George, Utah when it was above 115 F. Got a CEL (the infamous code P2293 - fuel pressure regulator valve malfunction), but I was able to drive home with no problems at all (a full 7+ hours of driving) by leaving early in the morning when the ambient temp was below 95 F. Clearly the fuel cut is worsened by extreme temperatures. I'm taking it to the dealership on Wed as I still have my powertrain warranty. I almost hope they have to replace the cam so I can avoid or at least postpone this in the future...
 

kosmo6

Ready to race!
Update - Took my car to the dealership and the cam follower is "beautiful, looks like new." Unfortunately they want $743 for parts and labor to replace the high pressure fuel pump, saying the HPFP is not under the powertrain warranty. They weren't clear on the exact issue, but said something to the effect that the spring in the pump can start to go.

Blows, but I expected so much. Wrote down the part numbers, paid the diag fee, and drove it home. Time to buy some parts online...
 

ThumbThumbs

Banned
Location
Newark Nj
Update - Took my car to the dealership and the cam follower is "beautiful, looks like new." Unfortunately they want $743 for parts and labor to replace the high pressure fuel pump, saying the HPFP is not under the powertrain warranty. They weren't clear on the exact issue, but said something to the effect that the spring in the pump can start to go.

Blows, but I expected so much. Wrote down the part numbers, paid the diag fee, and drove it home. Time to buy some parts online...

The 743$ was just to replace the fuel pump? If so that's a rip off, you can an Apr pump for that kind of cash.
 

RRacerguy717

Go Kart Champion
Location
ny tristate
Update - Took my car to the dealership and the cam follower is "beautiful, looks like new." Unfortunately they want $743 for parts and labor to replace the high pressure fuel pump, saying the HPFP is not under the powertrain warranty. They weren't clear on the exact issue, but said something to the effect that the spring in the pump can start to go.

Blows, but I expected so much. Wrote down the part numbers, paid the diag fee, and drove it home. Time to buy some parts online...

Not soo fast !!!!!

The low pressure pump plays a even bigger roll in vapor lock, its pressure is increased almost DOUBLE @ cold start and very high ambient temps. Now lets back up if your low side pump is not feeding enough fuel to your HPFP it will LOOK like your HPFP is weak and failing .

ALOT of marginal mechanic's fix the effect NOT the cause , I call them parts changers LOL :lol: Bob.G

p.s. log your low side pump @ cold start and when up to full operation temps check it at idle Block 103 or 106 with Ross vag tool . When warm should be around 40% .

Scroll down to the fuel system it will show you the fuel contol logic

http://www.golfmkv.com/forums/golfgoodies/mk5golfengine.pdf
 
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