belching black smoke. 2.1 mv petrol. why???

[vwjon]

a few weeks ago i fried my motor by blowing a rad hose, i cracked a cylinder head.
so i replaced the damaged unit with a good second hand one.
since then when i rev my motor belches out black smoke it also appears to be missing slightly.

i've cleaned the lambda probe- it was totally blocked and sooted up, its not made any differance.
apart from the cyl head i've changed nothing!
my local place says its "ok" but i'm not convinced!
many thanks jon

[Ye Olde Syncrospares]

lambda probe has died.

[vwjon]

hi cj.

i swapped the lambda probe and cleaned the plugs. it didnt make any differance.

i swapped the ecu, no change there either.

now i'm guessing a leaky injector pouring fuel into the inlet manifold.
all 4 plugs were equally sooted up, the old lambda probe was just a great big rod of soot as well.

any ideas guys? cheers jon

[T'Onion]

is the compression ok ?
sounds like the rings are worn

or the air fillter is blocked

[vwjon]

t'onoin, good answers. air filter is clear and good.
worn rings would give blue oil smoke? oil is ok. not losing oil.
i will comp test tomorrow.

i'll also check injectors for leaks.

any other ideas?

[HarryMann]

Checked AFM?

Disconnect lambda probe completely until you get it running decently.. will default to reasonable open-loop mixtures

Sounds like you should check fuel system pressure and blocked vac pipes to fuel press regulator too (Andy Mc had such a incidence)... but signal to injectors sounds bad.. earthing/wiring disturbed during head work likely?

[T'Onion]

also check the oil breather tower , could be nearly blocked with cack

[vwjon]

ok, i checked a whole bunch of stuff
the oil tower is clear, theres plenty of stuff (gasses) coming out.
the injectors are not leaking
the fuel system is OK, the vac is ok to the pressure regulator.

the compression test is as follows.

No1 140, 140
No2 140, 140
No3 110, 125
No4 105, 120

i adjusted the inlet valves on No 3&4, the comps are now 135 & 130.

i havn't driven it today - yet, and the tests were done with a cold engine.
the oil is very black like a diesel motor, but when i see the sooty smoke its really no suprise!

i'll do the loop thing later. cheers jon

still no nearer to solving this problem. yet.....

[vwjon]

ok, after a couple of hours its running better,
i swapped the air flow thing- no difference
i swapped the air pump by pass thingy, sort of. but not really
while i had pipes on & off, it made a difference to the running, usually better then stalled

i've ended up swapping the air by pass pipe and the oil /crank breather pipe, so the air by pass pipe now has some sort of sensor on it. dunno what it does but its stopped smoking now, it does stall when the motor is shut down to idle, i.e. changing down for a roundabout, or to stop at a junction.
the exhaust gasses smell petroly but not exessive!

so what does that small sensor thing do? is it supposed to measure gas goin into the inlet manifold? if so mines now working in reverse!

cheers jon

[syncroandy]

Sounds like the injectors are being held open, either the ECU is seeing an input that's causing this or maybe a short to ground on the 'cold' side of the injectors. I'd do the following:

re-make all grounds
check sensors and throttle switch are OK (the best way is to check these at the ECU connector, so you checking both the sensor/switch and the cable)

If you don't already have it, download the Digifant Vanagon Pro-Training doc, which has really useful info to help debug problems on the MV.

Andy

[vwjon]

after driving for a very short while the black smoke came back.

so i've checked and changed almost everything, inc a second earth strap, i spent 4 hours messing about yesterday and another couple today, but while i was at work i had a real lonnng good hard think.

the only thing i've changed is the cylinder head, before that the motor ran well.
so is the head faulty? if the valve seals were dodgy the petrol would find its way into the sump, it would thin the oil and then burn when the cylinders are lubed, also the fumes will go up the oil tower and into again back into the burning chambers creating the impression of over fueling and black smoke. does this theory make sense? cheers jon

[Fritz]

You say in your first post that the motor had been "cooked",,,,
But all you have replaced so far is one of the cylinder heads due to it being cracked.

Personally I would expect to have to change all the other ancillary temperature related items (Thermostat/Temperature transmitters etc) as these would also have been cooked in the process.

Regards

Fritz,,,,,,,,,

[vwjon]

cheers fritz, i'm begining to think the same, i'm currently running my van (after more tinkering) with out the blue temp sender thingy, it starts off quite fast (high revs) then settles down, the belching black smoke is now more of a burp of black smoke, and she seems to be running alot happier. i'll get another couple of temp senders and see what happens.
thanx jon

[gwolf65]

Hi,
You may be going along the right road with the temp sender.Are there two senders one for the temp gauge and one for the ecu?If the one for the ecu is knackered perhaps the ecu is thinking its cold and putting the equivalent of the choke on all the time,hence too much fuel=black smoke.
Probably worth a shot as you seem to have changed just about everything else.Was it the left hand/passenger head that was u/s ie the one with the thermostat and temp senders?

[MikeB]

If the one for the ecu is knackered perhaps the ecu is thinking its cold and putting the equivalent of the choke on all the time,hence too much fuel=black smoke.

Exactly what happened to mine (2.1 DJ), changed the temp sender and all OK.

Mike.