TheSamba.com :: View topic - Fuel line fitting to avoid fuel air lock ideas?

Sun Apr 29, 2012 3:05 am

My rigid fuel line that cmes into my 1500 engine bay keeps resting back onto the manifold and in the past the car has been hard to start. Is there anyway of positioning this rigid line in a better way to avoid a potential air lock in the system being created by the heat?

The pipe at present can be pushed into the 3 way clip that holds the HT Leads and the fuel line but it consistenly pops out again rendering it back ontop of the manifold.

Also, should the line have a sheath or insulator of some form around it to keep the heat out as mine is just the bare bone rigid pipe as you can see on the left of the pic coming up behind the manifold?

Sun Apr 29, 2012 6:01 am

I used a split piece of hose as insulation on mine. I'm sure there is a more correct way to route that pipe to prevent the heat transfer, but insulating the pipe with the hose has worked fine for me.

Sun Apr 29, 2012 6:14 am

Slipping a piece of split hose over the line will also keep it from getting a hole rubbed in it where it contacts the manifold-or just bend it so it doesn't lay on the maniifold if /when it pops out of the holder,or zip lok it into the holder so it doesn't pop out-
That's three easy solutions-probably quite a few more out there

Sun Apr 29, 2012 7:24 am

Mine which is still stock has a small bracket, factory on the line keeping it away from the intake manifold.

Sun Apr 29, 2012 3:33 pm

So a bit of fuel hose wrapped around it should stop the heat penetrating so much...I'll cable tie it up to the clip in the shroud too, thats not a bad idea. (i may pull the rigid pipe though and rebend it though also.

Does anyone have any other ideas how to prevent a potential airlock? (Is a hot rigid fuel line the only reason air locking can be caused?)

Wed May 02, 2012 3:25 pm

Does anyone have any other ideas how to prevent a potential airlock? Is a hot rigid fuel line the only reason air locking can be caused?

Wed May 02, 2012 3:32 pm

It can also happen in the fuel pump. And I think most people call it "vapor-lock".

Insulating the hard-line will slow down the rate at which it heats up, but it will still heat up. It will just take longer.

Max

Wed May 02, 2012 3:45 pm

Tox56 wrote: My rigid fuel line that cmes into my 1500 engine bay keeps resting back onto the manifold and in the past the car has been hard to start. Is there anyway of positioning this rigid line in a better way to avoid a potential air lock in the system being created by the heat?

The pipe at present can be pushed into the 3 way clip that holds the HT Leads and the fuel line but it consistenly pops out again rendering it back ontop of the manifold.

Also, should the line have a sheath or insulator of some form around it to keep the heat out as mine is just the bare bone rigid pipe as you can see on the left of the pic coming up behind the manifold?

Is it hard to start when first firing it up in the morning or does it die in traffic and is then hard to start.? Vapor lock happens when the engine bay overheats and boils air out of the fuel within the line. The only thing that worked for me to cool the engine bay was to put in engine lid standoffs.

crvc

Wed May 02, 2012 5:07 pm

When it gets my bug is after travelling for an hr or so at 50+ mph consistently...I then turn the engine off and she's then hard to restart.

Wed May 02, 2012 5:12 pm

Are you sure it's vapor-lock? Do you know what the test is for that?

Max

Wed May 02, 2012 10:24 pm

I thought it was vapour lock...can you clarify the test though? If ts not Vapour lock any idea what else it could be?

Thu May 03, 2012 10:39 am

Vapor lock is caused by the fuel reaching the temperature at which it turns into a gas. The stock fuel pump can only pump a liquid. The condition goes away when things cool down and the fuel is again a liquid.

So the test is this. As soon as the engine stops, get out and spray some cool water on the pump and the hard-line feeding it. If the engine can then be restarted, vapor-lock is indicated. If not, the problem is elseware. Be advised that since the carb has been run dry, a little cranking may be required to start it.

The main problem is heat of course. And it generally is not the fuel-line routing. There isn't much inside the engine room that gets hot enough to boil your fuel. So when vapor-lock is happening, the whole engine is probably running too hot, not just the fuel line.

If it isn't vapor-lock, there are plenty of other reasons an engine might die right after getting off the freeway. Most of them are also heat-related.

Max

Thu May 03, 2012 2:21 pm

Thats great, I'll do the test and draw a conclusion...may I ask though:

What are the other reasons then it has to be cranked hard to get it restarted? (then I can investigate further pending results)

Thu May 03, 2012 3:03 pm

Have you read your Owner's Manual?

If not, you may be using the wrong technique to crank the car when it is warm.

Do not pump the pedal. Instead, start cranking while slowly depressing the pedal. According to Volkswagen themselves, the pedal may need to be pressed to the floor if the engine is "very warm:"

Try this, and you may find your car starts right up when warm.

(And read that Owner's Manual. It is full of information of this sort that you need to know!)

Thu May 03, 2012 3:09 pm

Well ...

Mis-adjusted valves (too tight) can cause the valves to be held slightly open at higher engine temps. Engine can be restarted after it cools down. Valves that are held slightly open allow valve and valve-seat erosion due to the passage of very hot gasses through the space.

If the carb itself is sufficiently heat-soaked, the fuel can evaporate out of the bowl. I've had this problem with a type-3 with dual carbs when missing the phenolic (insulating) spacers. It would run fine unless I shut it down, then attempted to restart 10 minutes later. Lotsa fun at the gas pump.

I believe there are failure modes with the coil that manifest with higher temps. I have no first-hand experience on this one. The only failed coil I've had ... stayed dead.

Then there would be a range of mechanical issues (oil-starved bearings, too little crankshaft end-play, ect), but if any of these get to the point of stopping the engine from turning at the bottom of an off-ramp, the end has already arrived.

Not an exhaustive list by any means.

Max

Thu May 03, 2012 4:26 pm

Why dont you put on a 2 dollar plug wire clip that also has the fuel line holder in it? :)

You really don't want it touching the manifold. :wink:

Thu May 03, 2012 6:03 pm

Tox56 wrote:
The pipe at present can be pushed into the 3 way clip that holds the HT Leads and the fuel line but it consistenly pops out again rendering it back ontop of the manifold.

Also, should the line have a sheath or insulator of some form around it to keep the heat out as mine is just the bare bone rigid pipe as you can see on the left of the pic coming up behind the manifold?

If you need to, bend the pipe as necessary so it is relaxed when you snap it in the three way clip, it shouldn't pop out unless the clip is old and weak.
There is also a bracket that was fitted to some years that attached it with one of the fan shroud screws that will hold it more securely. Can't find as picture, but the clip should suffice anyway.

They never used any sheathing or insulation on the fuel pipe, so you shouldn't need to do any supplemental insulating.

And as Hammarlund has said, sometimes hot re-starts require you open the throttle for best results=see owners manual.
My '66 does the same thing, but only once in a while.

Fri May 04, 2012 5:30 pm

Might be you need to add a second gasket to the fuel shut off valve in the carb float chamber. That way the valve is just a tad lower and the float pushes up against it that much more to shut it off. Did that and fixed the problem in our 1960 bus in 90+ F heat.

All 40 HP and later engine (non-FI) fuel line bracket as shown:

Personally would not want to put metal fuel line next to high voltage cables. If one cable went bad and shorted out on the metal fuel line it could burn through and start a VW BBQ.

Sun May 27, 2012 2:06 pm

I've treated myself to the posh fuel line clip that I should have had in the first place so now the fuel line sits right...however.

I've just done the vapour lock test, drove about 60 miles at a steady 60-70mph, stopped at the Service Station for a cuppa. Went to get back in the car and fire her up:

Cranked and fired but sounded like it was missing and then died.
Cranked again and she fired and then cut out sooner.
Cranked again, she barely started and the immediately died so I stopped....

I then got out and poured a few glugs of water on the fuel pump, one glug, two glugs, three glugs.

Cranked her again and she fired, sounded again like it was missing but not as bad and I held the throttle in a little so she was idling at about 1200rpm, it cleared and began to idle out level at a stationery 750rpm.

I then drove on...that surely is vapor lock but how do I cool the engine down to avoid that happening then? (The flaps are working perfectly by the way, valves are also spot on.

(I did then do the journey home in reverse...stopped the car upon arrival back and the 5 mins later fired her up, she started fine and idled fine although there was a tiny little pop backfire upon firing just once)

I dunno, anyone got any thoughts to iron this out?

Sun May 27, 2012 2:17 pm

Check underneath and see if the fuel line is close to the heat exchanger, a source of a lot of heat.