Bad running after new head gasket - cause?

[rogerthechorister]

Is that still true as late as '96?

[TonyS9]

Yes!, no 940s use serial communication buses, its all relays and power. The 96 RFID key thing is an independant module with a relay in it connected to the EZK or ignition amp power I think.

[rogerthechorister]

Gadget built, got working after being advised the right way round to wire an LED and making sure the LED was a 12 volt one.

4-way rotary switch - position 2 being the EZK (fuel computer). Mostly zero output in that position - sometimes a faint glimmer. The other positions OK reading as expected.

Possibility 1 - duffas here has built it wrong. I doubt that as why would I have a faint glimmer if it was not connecting?

Possibility 2 - duff connections to the EZK. Well there was a lot of banging about when I first had problems in that field - but she seemed OK until I left her ticking over to charge a battery.

Possibility 3 - duff EZK.

Any more suggestions? Would she run at all if the EZK was on the fritz or not fully connected??



I am away for the weekend and have left garage to investigate possibility 2 (and to write down the EZK Bosch number in case I need a fresh one).

[Laird Scooby]

Possibility 1 - does it work on any of the ranges?

Possibility 2&3 - unless i've got the wrong end of the stick, the EZK is the ignition management system. If it was up the spout then i doubt the car would run at all - just my opinion of course. There is the possibility that for some reason it is either not advancing or not retarding as it should.

When i first got my 740 it was absolutely gutless and one day while sorting something else i found a small bore plastic tube with a rubber joiner on the end hanging in mid-air in the section of the dash where the EZK unit is. Looking around i found there was a stub on it that the tubing just happened to fit to. Could this be a possibility on yours? Don't discount it simply because "we didn't touch anything under the dash" - if it was caught/tugged/moved while the head was being removed/replaced it could easily have been kinked, pulled off the stub etc without anybody realising/knowing. Bear in mind that :

A) the cold start system will overcome the air leak
B) when it's warm, the closed-loop misture control will again overcome it
C) you won't be getting the correct advance/retard curve which could give a mahoosive flat spot.
D) If you've already checked it, could be worth double checking in case you've caught it since, perhaps during fitting the AMM which may well have cured the fault if there was one and it wasn't the pipe off.
E) Have you checked the knock sensor? Again the connections might have been caught during the HG repair or it might have been knocked. They're surprisingly fragile and even a slight knock/bang might damage them. As far as i understand it, if they are damaged (or open circuit due to disconnected/damaged wiring) the system uses a default value and doesn't advance the ignition as a safety thing. This could potentially cause a flat spot too.

[rogerthechorister]

Gadget works perfectly on the other three positions.

I might have another look later.

Just back from a festival...

[rogerthechorister]

Surely EZK is inside trim by driver's right foot, not in dash???

[rogerthechorister]

EZK appears to be ignition http://forums.turbobricks.com/showthread.php?t=71747

[Laird Scooby]

Originally Posted by rogerthechorister

EZK appears to be ignition http://forums.turbobricks.com/showthread.php?t=71747

That's wha i said earlier - "Possibility 2&3 - unless i've got the wrong end of the stick, the EZK is the ignition management system. If it was up the spout then i doubt the car would run at all"

not sure where your EZK is but it's hidden behind the trim under the dash on mine - don't forget mine is a 740, not a 940.

I still reckon it's something silly like a hose off somewhere.

[rogerthechorister]

Right. It seems that the EZK is ignition not fuel. So the position in which I am getting NO reading is the fuel computer, not the EZK.

Am I now right that the fuel computer is the one behind the trim panel by the driver's right foot, or is it somewhere else and if so where?

[Laird Scooby]

Right, i don't know this for sure and without seeing it i couldn't even hazard a guess but a lot of Bosch Motronics fuel injection had the fuel computer built into the AMM. Alternatively if there is a "black box" in the footwell as you describe, if you get the 10-digit Bosch part number off it and type it into the search bar on your browser, you'll almost certainly find out if that's it.

Just had a look at my general source of reference for vehicles i don't have a WSM for and the 940 turbo of 1995 vintage (think that covers yours?) has the ECM (Engine Control Module aka fuel computer) in the RH Kick Panel, i.e. where you described.

Not sure if any of that is of any help but hopefully something is!