Club 80-90 Forums

Hi,

I have 1989 T25 1.9 Waterboxer engine. The problem I am experiencing is, after say 3-4 mins of the engine running(from cold), it suddenly runs rough and has no power, without throttle it immediately dies. It is like someone flicks a switch it happens that quick.

I have attempted to clean the carb, but it was my first attempt at a carb, I didn't find anything and it hasn't changed anything.

Can't find any vacuum leaks and cannot see anything obvious.

Any thoughts?

Thanks

OK
If the van runs on choke ok then as the choke comes off it stalls and runs lumpy then it is a classic case of running too lean.
Some reasons for this are:-
Mixture screw not set correctly (gas analyser needed for this)
Blocked idle jet (use a bristle to clean it)
Faulty idle cut off (anti dieseling valve) electrically operated valve, should open fully with the ignition on.
Vacuum leak into the manifold (leaks from distributor diaphagm, choke pull down, second throttle diaphragm, Vac lines/connectors, brake servo hose/none return valve, carb gasket, isolator gasket, )
Fuel pump not pumping enough (Pushrod worn/ pump diaphragm holed)
Blocked fuel filter (plus the one in the carb)

quicksnac wrote:It is like someone flicks a switch it happens that quick.

Have you had the van long? Has it always done this, or has it recently started doing it? There are a couple of electrical connections which, if swapped over by mistake, might give this symptom. One is for the idle cut-off valve, which needs power all the time to stay open (when the ignition power is turned off the valve closes to cut off the fuel for idling), and one is for the throttle body heater, which is only powered during warm up (once the engine reaches a certain temperature the power to this heater is cut). If these are swapped over by mistake, then the idle cut-off valve would close when the engine warms up, so it won't idle. It's a bit of a long shot, since the terminals are the wrong gender to get them wrong accidentally, but if someone's been messing and has wired them the wrong way it could explain the 'switch-like' behaviour.

Hi,

The bus has been in the family for about 20 years now. There was no gradual decline to get to this fault, it suddenly did it one day and hasn't stopped since. We took the bus to a garage to get this fixed. They misdiagnosed the fault and gave up. I received it back with most of the engine in a box, cylinders included. Anyway, during the rebuild, I have had to change the fuel pump and filter(including push rod), spark plugs, cap, thermostat and both senders. When I fired it up again, it ran fine but unfortunately after 5 mins or so it stalled, exactly the same as before the rebuild.

During the rebuild I was not able to identify a home for a black cable with yellow ends, does anyone know what this is for?
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I messed around again with the bus today, changing the vacuum pipes for new ones. I recorded the bus idling, and have dropped it on to You tube. You can see it just dies with absolutely no signs of anything happening at the carb end. Probably best to skip to 40 seconds into the video, btw, it has been idling for about 4 minutes before I start filming.

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

Once it stalls, then it can be restarted but then has no power and will not idle. Only when I have allowed it to cool will it idle again.

Thanks

OK, I'm pretty sure the carburettor electrics are wrong. I think the red wire is controlled by the water temperature - once the engine gets up to temperature the power to that wire is cut. That cable should feed the throttle body heater and the choke. At the moment it looks like it is feeding the throttle body heater (black wire) and the idle cut-off valve (the white connector with two red wires in it).

I'd guess the purple wire is the ignition controlled live. On yours it looks like it's currently connected to the choke. The purple wire should be the feed to the idle cut-off valve I think.

It's worth swapping the wiring around to see if that makes a difference.
- Disconnect the white plug that has two red wires in it.
- Disconnect the purple wire from the black wire.
- Plug the purple wire into where you just removed the plug-with-two-reds.
- Connect the plug-with-two-reds to the black wire that was connected to the purple.

No wait, that's not right. I think the purple wire comes from the manifold heater (inside the lower face of the inlet manifold), so with it currently connected to the choke I think neither of those is getting power.

Just a minute.

OK, I think the black with two yellows is the ignition controlled feed. On your 1989 van I think that should feed the choke (the black wire which is currently connected to the purple) and the idle cut-off valve (the cylindrical item that currently has the white plug with two reds connected to it).

I think the red wire is probably the one that is turned off when the engine gets up to temperature, so that should feed the manifold heater (purple wire) and the throttle body heater (the black wire that currently already connected to the red).

It would be straightforward to check this with a voltmeter. If I'm right, then the black with two yellows should be live whenever the ignition is on, the red will be live until the engine reaches temperature.

I'm getting muddled now - anyone else care to correct me?!

Yeah, I think that's right. My confusion comes from the fact that my van is earlier than yours, and on mine the choke power is also controlled by the engine temperature (this changed for later vans), plus I've just noticed that my own wiring has a non standard wire 'splice' covered up with electrical tape. Tsk.

quicksnac wrote: [/URL]

Yes that wiring is completely wrong
Thick red wire connector to purple wire connector
yellow connector with two black wires to the idle speed cut off (which has to open when the ignition is turned on)
second yellow to the choke heater
connector with thin red wire to the carb heater

As it is the idle speed cut off is connected to a temperature controlled circuit that turns off at 67 deg C (4mins)

kevtherev wrote:As it is the idle speed cut off is connected to a temperature controlled circuit that turns off at 67 deg C (4mins)

That explains why it suddenly cuts out at 4mins, when the engine warms up....
I can't fathom why the van was OK one day though, then the fault suddenly appeared as per OP's second comment on the thread. I suppose you could only assume some work was carried out on the wiring and/or carb before the issue started (for another reason,) and not put back correctly?

OK, I have rewired as suggested and it now runs.

Many many thanks to CJH kevtherev and Smiffo. What a numpty to wire it so bad in the first place, I wired it based upon where the wires relaxed to. I suppose it would have helped if I had taken it apart in the first place...

Cannot for the life of me explain what was wrong before the rebuild, I did have trouble restarting after the build, that was why I needed the new fuel pump, maybe it was that....

Thanks Again