Air cooled 2ltr CU in Portugal - running like a pig.

[porthyt]

Thanks for that,

I have taken the fuel outlet off the tank and it pours out of there. Should I be able to blow through from the carb end back down the line or will the fuel pump stop me from doing this?

[porthyt]

I just tried big herbs hall sensor guide I.e. a piece of wire in the centre on the plug and the central HT lead removed. Ignition on, sparks coming from the HT lead. Does this def mean the hall sensor is faulty or would this always happen? Parts are difficulty to get in Portugal so I need to know what’s wrong really before ordering if possible. Thanks

[937carrera]

Have you done the checking of the voltage across the two outside pins as well (the second post) ?

If so, then it does indeed look like the hall sensor. Where's the crossed fingers smiley.

TBH, for what an ignition amplifier costs, you may as well buy one and have a spare to carry round with you.

[porthyt]

Hi,

Just tried that and I get 9.87 across the outside 2 pins and around 5v for the middle and the earth.

Is this too low?

Cheers for helping.

[porthyt]

Is the ignition amplifier the big square plug in the rear lhs of the bay? I just found an old one in my spares - plugged it in and the reading on the wires is 10.81v whereas the other was around 9.8v. Would this cause the problem?

[slowcoach]

I've not read the whole thread sorry, but have you tried clean new petrol? I got in a pickle in France last year after a full up of bad fuel from a motorway services. Chuggy, lumpy revving, no power, didn't show itself until a day later. Ran rings round all the electrics etc and spent loads of time and money diagnosing. Could u have bad fuel in the tank?

[937carrera]

Ignition module

https://www.brickwerks.co.uk/ignition-a ... -most.html



Sounds like your spare module is better than your fitted one, but, you should be seeing a full 12 volts across those two pins, assuming the battery has ~12.7 volts

Can you check the feed to a good engine earth as well as the hall sender earth. You need to know if the voltage is down because of a poor earth on the hall sender, or a poor supply. Make sure you actually do have a good engine earth for the test by also checking the coil voltage at terminal 15..

[porthyt]

Ol so tested the coil and got 11.97v then tried the plug going to the amplifier and it is 11.97 on 2 of the prongs. What does this mean?

In terms of fuel it happened after driving a 100or so miles on the last fill up. Have put fuel in twice more andproblem still there. Would have been great if it was that though.

Thnaks

[porthyt]

How do I check the engine earth?

[937carrera]

Engine off

Measure battery voltage - say 12.7v

Measure voltage from terminal 15 of coil to a clean earth point on the engine and / or chassis (tailgate latch is usually good for the body)

Typically, this should be around 12V (there will be some voltage drop compared to the battery)

If it's around 12V and the same reading using the earth on the engine and the body, then the earths are OK. If the voltage is lower on one of them, then that earth route is not as good as the other.

[937carrera]

Ol so tested the coil and got 11.97v then tried the plug going to the amplifier and it is 11.97 on 2 of the prongs. What does this mean?

In terms of fuel it happened after driving a 100or so miles on the last fill up. Have put fuel in twice more andproblem still there. Would have been great if it was that though.

Thnaks

Just seen your earlier post.

So the coil was 11.97V, that's bang on what I expected, so the feed and earth route you used there are fine.

Now do the test with the outside pins of the hall sensor again, what does that read ?

Finally, measure the feed from the hall sensor and earth the other side to the point you used when testing the coil

[porthyt]

Hi,

Just drove it with the different amplifier. Started up really well - almost instant. But still drives the same.

Checked the voltages of the hall sensor outside to outside it measures 10.84v and the same outside to an engine earth.

Losing a volt somewhere - is that normal?

Is there a screen/mesh inside our tanks?

Thanks

[937carrera]

No, it's not normal to lose a volt. On the basis that the value to both earths is 10.84v (but 11.97V on the coil) then it sounds like a bit of weak / dodgy wiring on the feed side to the hall sensor.

AFAIK there is no screen / mesh in the tank, but more importantly you have already checked and verified that fuel is getting to both carbs.

Here's a link to a wiring diagram. This is for a DG, but I doubt the CU is much different http://syncrosport.com/info/wiring/VW_T ... _SP_DG.pdf

Page 3 is where you need to be looking. I'll need to have a think about what other tests you can do to narrow the problem down. Maybe someone else already has that experience.

For now can you check the voltage at terminal 4 on the connector to the ignition module.

If that's 10.84v but terminal 15 on the coil is 11.97v then the problem would seem to be in that bit of the loom

[porthyt]

Video of my problem. Hopefully those of you who have been helping will see this and go “aha it’s this”!

https://youtu.be/GU1CSU-lWWw" onclick="window.open(this.href);return false;

I will check that terminal tomorrow as I need a rest from it before I snap a plug or something.

[937carrera]

One other thing I read: If you have idle stabilisation, remove the plugs and connect them together to eliminate that from the equation.