GTI 1996 Air in fuel line

[fishingfund]

Hi,

Struggling with a 1996 GTI. New fuel lines, new plugs cut back and reconnected, professionally rebuilt carbs, new rectifier, new selector valve and new water seperator gasket. Also repalced the check valves on vent. Still getting bogging and max speed of 25-30 mph. Compression around 150 in both.

So I went ahead and changed all lines to clear just for testing purposes. No bubbles coming from tank but getting alot of air after the selector into water/fuel filter on both "On" and "Res". Is it possible that the separator gasket would cause air bubbles coming into the separator?

Once resolved, if it gets resolved, I'll go back to my black lines.

 

[Legacy37]

The separator has an O ring that if not sealed will cause all sorts of issues

 

[fishingfund]

Just went out and put on an inline filter to bypass it and still getting bubbles. Ugh

 

[mikidymac]

Yes, could be the separator o-ring and could be the new fuel selector, some are junk.
Do not use and inline filter, all you need is the stock strainer.
For testing you can bypass everything, straight from the fuel tank to the carbs.

 

[fishingfund]

Thanks all. Bypassed selector. Cranked it up and no bubbles. Idled pretty smooth. Also smooth up and down when increasing rpms. Dropping it in the water later today for the real test.

 

[fishingfund]

No luck. Had to test in very choppy conditions. Ran fine for 5 minutes until I hit a wave and it revved high. Starting bogging again and every once in a while would catch. Seemed like it wanted to go. Choking it stopped it. Carbs have been rebuilt 3 times, the last time by a pro. Tank has been cleaned. Should I try another set of carbs?

Going to test rectifier next.

 

[Grim]

Do you know if they used OEM kit for carb rebuild. Don't matter how good you are if you use "not good" parts. Nothing but OEM works well with these carbs.

 

[fishingfund]

Not sure but I gave them the carbs with OEM parts that I had put in on with my rebuild attempt. I just pulled them to go them again. There's a film of goo and blackish carbon looking residue on both butterflys and they're dirtier than when I first pulled them off the machine. Odd. Not sure if that's normal.

 

[Grim]

Not sure but I gave them the carbs with OEM parts that I had put in on with my rebuild attempt. I just pulled them to go them again. There's a film of goo and blackish carbon looking residue on both butterflys and they're dirtier than when I first pulled them off the machine. Odd. Not sure if that's normal.

I would recommend another rebuild and I would change out fuel filter and clean the gas tank. There is a good sticky on this forum on how to rebuild them, its not hard, just take your time. Also, may want to look for an exhaust leak that may be putting exhaust fumes back through the carbs. That may be where your blackish stuff is coming from. Just an idea.

 

[mikidymac]

The butterflies should be clean, no black residue.
Are you sure your rotary valve is turning and timed correctly?

The carb rebuild link is in my signature line below.

 

[fishingfund]

Pulled carbs, got them cleaned up. Pop-off on both around 50. Pressure test OK. High/low screws checked for factory setting. Checked RV timing with degree gauge. All lined up and no damage to RV or body. Put back together and still same symptoms. No symptoms of exhaust leak. Ran the same with seat off. No water leaks.

Could I have leaky crank seals? Saw something about testing that by spraying WD40 near seal while running to see if engine changes rpms.

 

[Grim]

May want to pull the gas line going to the carb and put it in a container of gas/oil mix and see if maybe something upline from the carbs is introducing air. This will tell you if it is at the carbs or in the line. Did you also install the gasket that goes between the carbs and engine.

 

[mikidymac]

Typically if you have a leaking crankcase seal your engine will run away, basically go full rpm without touching the throttle when out of the water.

 

[fishingfund]

Have bypassed selector valve and put clear fuel lines on to confirm no air bubbles coming in upstream of carbs. Gaskets installed. On first start the engine does run away for about 15 seconds but drops down to normal idle after wards.

 

[Grim]

Have bypassed selector valve and put clear fuel lines on to confirm no air bubbles coming in upstream of carbs. Gaskets installed. On first start the engine does run away for about 15 seconds but drops down to normal idle after wards.

What do you mean by run away? What kind of RPMs are you seeing? Does it do it every time you start it? Did you torque the carb bolts? Does it rev up well? Can you take it out on the water and check full throttle spectrum?

 

[fishingfund]

What do you mean by run away? At first start it will rev high for about 15 second and then drop to idle.
What kind of RPMs are you seeing? Not sure (no gauge) but sounds similar to 2/3 full throttle out of water.
Does it do it every time you start it? No, but about 3 of the last 5 times it has.
Did you torque the carb bolts? No
Does it rev up well? Yes, out of water
Can you take it out on the water and check full throttle spectrum? No it bogs in the water. Only been able to test it choppy water so it seems like it starts out well but if I hit a wave when trying to plane it revs high it then bogs completely.