too much air?

[vegfuel]

Has anyone here ever experienced over revving caused by to much air in the fuel lines?

[tSoG-84bit]

now I am no professional, but air in the fuel lines causes negative problems in the other direction, sputtering, loss of power, stalling, are all things that happen when you have air in the fuel lines. excessive blow by, or maybe a bad injector pump seem more probable. If the fuel screw is turned up too high, I believe you can have problems with your car running away as well. I can't say for sure, because I couldn't even pinpoint my own problem with overrevving. A mechanic did a compression test and it was OK, but my injector pump was junk. Sorry you are going through it, but trust me, you aren't the only one.

tSoG

[AdAm84]

yeah air in the lines wouldn't cause reving and such. it would cause sputtering and rough idle problems.

[vegfuel]

Well she starts great every time, so I would think that the compression is fine. In which case I might not have excess blowby. I even talked to a diesel mechanic and he said that air in the fuel can cause high rev.

[saurkraut]

Try disconnecting your breather hoze from you air cleaner and go for a drive.  If you don't have runaway then, you have bad rings and its rebuid time.

If its fully warmed up and you're still getting white smoke, your engine is drinking from its oil pan.  Does its smell like burned engine oil?  If it walks like a duck, quacks like a duck, and smells like a duck, its a duck.

i have a hard time believing air bubles in your fuel line would cause a runaway.  Going to have to raise the BS flag on that one.  Causing uneven running maybe.  But bubles in the fuel line, going to an extreme, means less fuel going into the engine.  Less fuel=less power.  Heck, most volks on here (mysef included) are trying to put more fuel in to get "high revving".

[jtanguay]

yea... rediculous myth busted.

your injectors require around 130 bar (non turbo) and 150 bar (turbo) pressure to open.  when there's too much air inside the pump, the plunger will try to compress the fuel, but there is no fuel, so it tries to compress air, which the pump was never designed to do.  therefore the extreme pressures are not built up, and the injector does not open which means that the engine *should* idle rough or stall out.

i think the only way would be a leaky injector causing runaway... it would have to be severely bad though!

[745 turbogreasel]

I even talked to a diesel mechanic and he said that air in the fuel can cause high rev.

NO.
 Not even a little bit.

[fatmobile]

Not in a VW but the local bosch pump rebuilder said folks with diesel trucks were getting high revs when air was in the fuel.
 We were talking about problems with air in the fuel system on my VW and he mentioned the result air in the fuel has on certain other vehicles.

[saurkraut]

Jeez, thats just goes against everything i've seen with regards vw diesel engines, and I've seen alot, including the good, the bad and the ugly.

If you can, find out what type of engine and injection pump this high revving with fuel bubbles phenom happens.  Also, the theory on why this happens.

[jtanguay]

Not in a VW but the local bosch pump rebuilder said folks with diesel trucks were getting high revs when air was in the fuel.
 We were talking about problems with air in the fuel system on my VW and he mentioned the result air in the fuel has on certain other vehicles.

that almost sounds to me like a computer related problem... such as the computer trying to compensate for a rough idle due to air...  were they mechanical pumps???  sounds very odd to me!  bubbles of hydrogen maybe??  :twisted:   :lol:

[clbanman]

We have had occasional problems with air in the fuel lines in our trucks, and NEVER had runaways or high idle speeds as a result.  I know diesels can run very lean, but less fuel (than optimal for given load/throttle position) can't possibly increase power.