Wont tick over

[captaincalamity]

Just passed the MOT, yeeha, driving home all is running well and get to a roundabout the van cuts out, it starts again, then cuts out immediately, starts again, give it some revs and if I keep the revs high enough I can pretty dangerously limp it along into a car park, call the recovery...home.

Van - T25, 1.9 standard water-cooled, just had new exhaust, new petrol pump, new water pump, new thermostat, new oil filter and oil, new oil pressure sensor switches and wiring.

So I remove the Dizzy, clean and WD, nothing odd looking in there, unplug practically everything I can see, clean and WD (plugs, to dizzy, plugs, ignition etc). Still the same problem starts but wont tick over on low revs.

NEXT MORNING, start the van, it ticks over...eeeerrrrr

Then after its been ticking over I gather on higher revs due to the auto choke, as soon as it drops to lower revs, it just wont tick over.

Get my wife to keep the vans revs up, while i unplug the vacuum pipe from the condenser, there is a reaction, so i gather this is working ok.

Im at a loss, hope my ramblings make some sort of sense

[ermie571]

Fuel??

You say it starts immediately...so less likely to be ignition.

Will idle at high revs...so I don't think its the idle cut out solenoid on the carb - but you could check that.

You list new fuel pump - has there been issues? Did the fuel filter get changed? There should be one in line around the driver's wheel arch...and then there is a cone filter in the carb itself....make sure both are clean. Could also be grot in the carb.... Was all that work done to get it through the MOT - or was it a list of recently done work...?

Em
x

Oh - hang on a minute...MOT....did the tester fiddle with anything to get it through the emissions....??

[captaincalamity]

Good point did the MOT tester fiddle for the emissions, couldn't check as Saturday after I left the garage closed, so will check today. although the van was running for 10 miles perfectly well.

This problem has happened before, but after we were recovered home and the next day the van fired up and ran fine, I put it down to the Oil pressure buzzers going off, thought it was linked, an old problem had earlier this year.
This was fixed, by two new oil pressure sensors, new oil pump, new oil filter and oil and complete new wiring to and from the oil pressure sensors, the buzzer has been quiet ever since.

Yes there is an inline fuel filter which looks fine, has no particles in it, took the top of the carb of yesterday and flushed it out with carb spray cleaner, all looks fine and clean in there.

[ermie571]

In those first ten miles did it idle successfully at 900 rpm (ie without choke?)

Em
x

[ghost123uk]

Symptoms could point to a failing coil, ignition amp or idle control unit (that last unit only on some vans), all of which, when "dying", can produce a weaker spark as they warm up. Hence why it is ok when cold but misbehaves when warmed up. If you can obtain (borrow from another T25 owner) known good replacements and swap one at a time you might well find the culprit. If your van is one of the ones with the idle stabilisation unit, you can, when the fault occurs, temporarily unplug the two plugs and plug them together and see if the fault goes away.

btw, Fuel blockages/shortages (pumps/filters etc) usually show the opposite symptoms, ticks over ok but misbehaves when any load is applied.

As Em says, it is well worth checking the electrical state of the idle shut of valve on the carb (see Haynes) as an intermittent fault there could cause this. Wait for the fault to appear, then, with ignition on, remove the spade connector and then "tap" it slowly on and off it's connector, you should hear the valve "click". If not, report back

[captaincalamity]

Anyone in the Sussex area, able to pop over and have a look, happy to pay, in cash, beer, food, crisps...

[captaincalamity]

Right there is fuel coming through the carb as you look down the choke flap, little squirt from there as you pump the throttle whilst engine off..

There is a spark coming from the ignition coil

Then removed the spade connector to test the idle shut off valve and it clicks fine

WHAT NEXT?

[kevtherev]

So to recap
It will start when cold and idle.
For about 4-5 mins it runs and drives OK.

Then after this it won't idle.

I would be looking at the mixture first, in particular the CO figure.
If it's too low (%) it will falter, miss and stall at idle when warm.
It won't stall when the throttle is pressed as the main jet is non adjustable.
This should tell you if it's fuel related
We are presuming the choke is set right and works OK

[itchyfeet]

Check the bypass air cut off valve connection should be 12v with ignition on
If I remember correctly van will run on choke and rev with this disconnected but not idle hot

[captaincalamity]

Where is the air bypass?

[kevtherev]

Where is the air bypass?

There are a lot of names for it, air bypass, anti dieseling, idle cut off.

You say you checked it and it clicked.. did you remove it to see if it's blocked?

[itchyfeet]

Then removed the spade connector to test the idle shut off valve and it clicks fine

WHAT NEXT?

Oh yeh missed that

[captaincalamity]

I'm going to try borrowing or seeing if I can get hold of a spare Ignition coil, see if its the coil breaking down, would this make a difference, does the coil take more load under tickover than normal running speed?

[ghost123uk]

It's the other way round, works (a bit) harder under higher loads.

[itchyfeet]

So to recap
It will start when cold and idle.
For about 4-5 mins it runs and drives OK.

Then after this it won't idle.

I would be looking at the mixture first, in particular the CO figure.
If it's too low (%) it will falter, miss and stall at idle when warm.
It won't stall when the throttle is pressed as the main jet is non adjustable.
This should tell you if it's fuel related
We are presuming the choke is set right and works OK

Assuming it never happened before the mot ^^^^ the co could as said have been adjusted to get it to pass

Try adjusting up the idle rev stop just possible mot man played with this also

No way you could have mis connected the by pass cut off to the thermostatic heater circuit is there? That would then switch off hot