Topic: Horrific Hesitation... sometimes?!?!?

Hi Guys,

Now as I'm sure most of you may be aware I am running a 1600cc TP standard aircooled engine.

The engine has been running just fine for a long time. But recently it has started hesitating badly after it’s been driving for a while. This hesitation will start after the engine is up to a certain temperature, over 180 degrees C (i.e. after about 20-30 mins of driving). It starts as a gentle occasional miss and becomes gradually worse (over the next 10 mins) until the engine is barely running at all – i.e. it is farting/coughing holding back and not firing. If I pull over the engine idles perfectly fine! Added to that, if I leave the engine to cool down (by running or turning off) for 15 mins it will run 100% fine after that too!?!?! (until it gets too hot again)

Before now I have assumed that I had a timing issue. The timing and value clearances have just been reset. The points, coil, condenser and leads have all been changed.
I’m running out of ideas as to what to attack next! The general temp doesn't seem to rise much above 180 degrees C...?!?! I'm at a loss.

Manners maketh the van!

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Re: Horrific Hesitation... sometimes?!?!?

A couple of things to try.

Check the routing of the metal fuel line in the engine bay as it may be close to something warm and causing a vapour lock - fuel starvation.

As soon as it does it again, pull over and remove the fuel filler cap. If it make a sort of whooshing sound, your fuel tank breather pipes may be blocked causing a vacuum in the tank - fuel starvation.

When it is really bad, check the inlet manifold for condensation/ice. I seem to recall that you are running a stock engine setup, but it may be the the manifold hotspot tubes are block so the manifold/carb isn't quite warm enough - again fuel starvation.

Lastly, try changing the condenser.

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Re: Horrific Hesitation... sometimes?!?!?

I'm more concerned over your temperature. When you say 180C, where are you getting this reading from? If it's an oil temp gauge, like the one I seem to remember seeing fitted to your sump plug, then you're way over temperature. Your oil should be running at around 90C. At 180 you're burning your barrels and crank out.  If it's a cylinder head temp gauge I'd have to look it up.

Aim to please, but shoot to kill.
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Re: Horrific Hesitation... sometimes?!?!?

Eyup Fran, Yes typo there I meant 180 degrees F! I think there would be melted heads at 180 degrees C!!! If anything it seems to now run slightly cool... nearer 82 degrees C (unless my gauge is out).

Thanks also Ian - I'd not considered vapour lock! My metal fuel line does go right up against the manifold, so it could be that. Problem is also worse on warmer days.

I think I'll have a look at that fuel line and then at the carb for dirt in the float chamber and around the jets.

Mrs is camping in the van shortly so I need to get this one properly squared away or I'll be living in the van on the drive!

Manners maketh the van!

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Re: Horrific Hesitation... sometimes?!?!?

Have you got any fuel filters on the van?  Where are they positioned?

My bug had this issue a few years back with the filter inline in the engine bay.  It got warm so was vapour lock.

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Re: Horrific Hesitation... sometimes?!?!?

No never had a fuel filter fitted. May fit a quality one now though. I'll pop it downwind of the shutoff tap under my tank.

Thanks for your thoughts gents  default/smile

Manners maketh the van!

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Re: Horrific Hesitation... sometimes?!?!?

Update:

So last night I got home from work and attacked the van (again). I fitted the new fuel filter (next to the shut off tap - under the tank). I insulated the metal length of fuel pipe in the engine bay. I reset my points, changed the distributor cap and rotor. I then removed the carb and took it apart and cleaned it (found quite a few issues - lots of crud and damaged gaskets). I changed some fuel lines too (to get rid of the metal braided stuff - i.e. it could short the coil if in wrong position). Lastly I left the fuel cap on loose.

Then I went for a long drive...

...and even though I sat on the A14 at the heady height of 60mph the van didn't miss a beat. Relatively speaking I ragged it for an hour, trying to force the hesitation issue, but no issue came!

Sooo I think I'm the other side of this problem. My thought is that the carb was to blame. The van is much zestier and may actually be running a bit rich now. At the MOT the tester enriched the mix because it was running lean but I think that the carb was leaking all along.

So a question for the clever sticks - can I just wind out my air mix screw on the 30 pict 3 to thin out the mix?

Manners maketh the van!

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Re: Horrific Hesitation... sometimes?!?!?

If you have one of my disk, then you probably have the instructions for setting your carbs. Alternatively, this is a good resource.
http://www.ratwell.com/

Aim to please, but shoot to kill.
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Re: Horrific Hesitation... sometimes?!?!?

You sure its hesitation and not antici.....

I am you club camping responsible adult for booking for Battlesbridge VW Show

SEND ME ALL YOUR MONIES default/big_smile

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Re: Horrific Hesitation... sometimes?!?!?

Following on from RD's post, I found this:

http://www.vw-resource.com/34pict3.html

To be invaluable when I had my carb issues

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Restoring Ruy - my restoration blog

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Re: Horrific Hesitation... sometimes?!?!?

Hi chaps...

Well I left for a camping trip on Friday and then after 30 mins had to turn around due to excessive hesitation (Grrrr). The engine was as smooth as silk until the issue started. As I approached Thrapston (A14) I noticed that the temperature was sneaking up past 80 degrees C and headed for 100. As it met and started to pass the 100 mark, the hesitation came on in full force. Alas we turned and headed home, where I switched to the daily driver.

Last night, after we got back from camping, I switched the carb for a solex 34 pict 3 I had knocking about and again the van drove beautifully... until, after about 30/40 mins of driving, the temp suddenly started to climb to 100 degrees C and then the hesitation set in.

I've now changed the coil and I'll check my valves again. If this doesn't cut it then I suspect I've got something seriously amis in one of my cylinders... like a stuffed piston ring or sticky valve.

It never normally takes me this long to solve an issue but then I never normally have to do such a long drive to force the problem to appear!  default/sad

Manners maketh the van!

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Re: Horrific Hesitation... sometimes?!?!?

How is your air intake?

Ruy is currently engineless and HG has identified the firewall covering the air intake on the fan housing as the culprit.  Hopefully this will solve the one issue for Ruy but he nearly shook apart on the drive over to Brampton and developed a death rattle so there may be other things for us to sort.

I would certainly say check the fan housing for debris, oil cooler all that stuff too. Also the thermostat (I don't have one).

Also, again, thanks to Ian for the link (same place as I use for the carb set-up):

http://www.vw-resource.com/overheating.html#009

This may help

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Restoring Ruy - my restoration blog

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Re: Horrific Hesitation... sometimes?!?!?

Thanks for this link. I think a lot of this relates to running with a 009 distributor and I'm rattling around with a vacuum advance unit.

I'm going to have another 'tinker' tonight. As I've changed soooo many components in the engine bay I'm starting to run out of action points. That said tonight I'm going to remove the fuel tap (from by the fuel tank), change the condenser and check the valve clearances (again).

As the problem only happens after such a long drive and whilst the engine is under load (i.e. high revs or a hill) I'm also thinking that maybe the timing is too far advanced and therein running too lean at high revs. This would cause the temp to go up and the engine to miss/hesitate.

I think I'm going to ask Fran/Ian to take a strobe gun along on Thursday as this problem is really becoming a bit of an obsession.

Manners maketh the van!

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Re: Horrific Hesitation... sometimes?!?!?

The overheating section includes 009 but covers a wide range of issues, so worth scrolling through the whole page just in case.

Keep going with it though, you will find the issue sooner or later!

http://restoringruy.wordpress.com
Restoring Ruy - my restoration blog

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15

Re: Horrific Hesitation... sometimes?!?!?

I'll take strobe and dwell meter with me on Thursday. Also check the alternator belt for tension/wear and that the vac advance is working correctly.

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Re: Horrific Hesitation... sometimes?!?!?

H-G wrote:

I'll take strobe and dwell meter with me on Thursday. Also check the alternator belt for tension/wear and that the vac advance is working correctly.

Saves me asking Ian for the strobe back

Aim to please, but shoot to kill.
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Re: Horrific Hesitation... sometimes?!?!?

.. pation  default/big_smile

I am you club camping responsible adult for booking for Battlesbridge VW Show

SEND ME ALL YOUR MONIES default/big_smile

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Re: Horrific Hesitation... sometimes?!?!?

Technohippy wrote:

.. pation  default/big_smile

It does a step to the left.

Aim to please, but shoot to kill.
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19

Re: Horrific Hesitation... sometimes?!?!?

And makes Lee put his hand on his hips...

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Re: Horrific Hesitation... sometimes?!?!?

That ten days wasn't wasted then default/smile

I am you club camping responsible adult for booking for Battlesbridge VW Show

SEND ME ALL YOUR MONIES default/big_smile

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Re: Horrific Hesitation... sometimes?!?!?

Technohippy wrote:

That ten days wasn't wasted then default/smile

Neither was the anticipation  default/big_smile   default/roflol

Aim to please, but shoot to kill.
http://i88.photobucket.com/albums/k194/franmac1/scan0025-cropsmall_zps9b343323.jpg

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