Couple Of Issues After Diesel Conversion Options

[trevorbrady]

I've put a 1.6TD into a B4 Passat, originally fitted with a 1.8 SPI petrol. Obviously engine management has gone out the window.

My issues include:

Oil light flashes constantly, there is plenty of oil on the dipstick

Coolant light flashes constantly, there is plenty of coolant in the system

Airbag light stays on. I read the fault codes and it gives an "airbag ignitor resistance too large" fault. I put another airbag into the steering wheel (the only airbag in the car) but the light stays on. I don't have the fault code reader to cancel the light. I'm hoping the fault code just needs to be cancelled.

The clocks in the dash are still those from the petrol engine/ECU. The rev counter is now defunct since there's no coil to get a signal from. Can I make the rev counter work with the diesel engines? How do diesel rev counters work anyway?

any ideas? I presume the airbag light is an NCT fail, the flashing oil/coolant lights probably are too.

[Geo]

The airbag fault code is probably a broken wire in the clock spring type loom that is behind the steering wheel.

For the coolant light try a different header tank.

How many oil pressure switches were on each engine?

Diesel engine rev counter signal comes from the alternator. I reckon if you fitted diesel clocks the rev counter would work.

[timmy]

the oil light & coolant warning will stay flashing if you dont have rev counter working discovered this when doing my mk3 the diesel revcounter reads from load signal wire from alternator(red/black wire iirc)
you will prob need to fit dsl clocks as usually petrol rev counter is 7000rpm & dsl is 5500rpm
petrol clocks wont read from alternator

[trevorbrady]

thanks guys, I'll check the wire behind the steering wheel for the airbag fault and look for some diesel clocks to try and cure the other problems

[trevorbrady]

The airbag fault code is probably a broken wire in the clock spring type loom that is behind the steering wheel.

right on the money George! The "clock spring" ribbon cable is broken. I'll pay the Chicken a visit and see what he has, from a small bit of research online the same part was used in a pile of mid-90s VWs.

Fair play

[Jimmy Diesel Jun...]

Have a 94 tdi passat for parts here if you're after bits 087 2314317 Cheers

[trevorbrady]

got the "clock spring" wiring loom thingy (out of a 6K Polo saloon BTW) from the local scrappy today. I tested it for continuity before I paid for it so I know it's good. I fitted it in the Passat with the right amount of turns left and right so it doesn't get pulled apart when turning the wheel or restrict the turning of the wheel.

The airbag light still comes on but presumably the trouble code would need to be erased to turn off the light? Am I right?

Anyway, another issue: what oil to use in a 1.6TD (SB code) engine? And how much oil for a complete drain and refill?

[Retroloose]

I've put a 1.6TD into a B4 Passat, originally fitted with a 1.8 SPI petrol. Obviously engine management has gone out the window.

My issues include:

Oil light flashes constantly, there is plenty of oil on the dipstick

Coolant light flashes constantly, there is plenty of coolant in the system

Airbag light stays on. I read the fault codes and it gives an "airbag ignitor resistance too large" fault. I put another airbag into the steering wheel (the only airbag in the car) but the light stays on. I don't have the fault code reader to cancel the light. I'm hoping the fault code just needs to be cancelled.

The clocks in the dash are still those from the petrol engine/ECU. The rev counter is now defunct since there's no coil to get a signal from. Can I make the rev counter work with the diesel engines? How do diesel rev counters work anyway?

any ideas? I presume the airbag light is an NCT fail, the flashing oil/coolant lights probably are too.

Hi, i did exact same conversion , my car had clocks with a digital mileage display, i fitted clocks from a 95 petrol car which had the standard mechanical mileage display and a speedo cable , this sorted the oil light and the coolant light . I just took the bulb out of the airbag light , the rev counter runs off the altenator which i just left out but it is possible to get working , you will need to find which wire in the loom going to your clock controls your rev counter , if you could borrow an origional diesel car and use a multimeter between the wire on altenator and each pin on the block connector to your clock unit so you can find which pin it is and then just run a wire down to your altenator, you may also need diesel clocks so that it will run at the right revs. Did a coversion on a mk2 recently and used this method and it worked out fine.

Good luck with the rest of the job

[trevorbrady]

yeah I've got a cable operated speedo drive already and the lights are flashing in them. I'm keeping an eye out for a set of diesel clocks. Waiting on a response from a couple of sellers.

I'm hoping the airbag issue is sorted, just need to erase the trouble code to turn off the light (hopefully).

[Retroloose]

yeah I've got a cable operated speedo drive already and the lights are flashing in them. I'm keeping an eye out for a set of diesel clocks. Waiting on a response from a couple of sellers.

I'm hoping the airbag issue is sorted, just need to erase the trouble code to turn off the light (hopefully).

My brother has a set of diesel clocks rekon he would take 30 euro, did you go to chicken b yet

[trevorbrady]

I'd take those clocks at €30, will you find out?

yeah I was up at Byrnes alright, got the airboag spool from a Polo Saloon. No B4 Passats in though, just one B5 in the corner...

[Retroloose]

I'd take those clocks at €30, will you find out?

yeah I was up at Byrnes alright, got the airboag spool from a Polo Saloon. No B4 Passats in though, just one B5 in the corner...

Ill ask him and let you know later trevor

[trevorbrady]

The saga goes on. I got the diesel clocks from Retroloose's brother (still need to pay him for them, by arrangement ) and plugged the whole assembly straight in to see if they solved my problems.

Unfortunately not

The rev counter still doesn't work but I think it's because I have to run the load sensing wire from the alternator, it was omitted in the conversion. So let's presume the rev counter works, I'll just have to find the wire in the loom to plumb it into.

The fuel gauge in the petrol clocks was working fine but when the diesel clocks are plugged in, nada. I put the known working fuel gauge into the diesel cluster and it failed to work. I put the fuel gauge from the diesel cluster into the petrol cluster and it works. So I presume the problem is in the wiring on the circuit board of the diesel clocks.

While the oil light flashes at me constantly in the petrol clocks (coolant light has stopped flashing, curiously) it doesn't work, even with the engine off and ignition on in the diesel clocks. The main beam warning light does the opposite of what it's supposed to do (illuminated with main beams off, goes out with main beams on) and the indicator LEDs don't work with the emergency lights.

So in summary, I have no reason to think the diesel clocks aren't working fine but I don't think the diesel clocks are the solution I was hoping they would be. There appears to be too much of a difference between the wiring loom of the petrol passat and diesel passat to allow the diesel clocks to just "plug'n'play" in the formerly petrol car.

Anyone got any more hints?

[trevorbrady]

right, in case anyone's interested, or for future reference for anyone else considering this conversion, I have most of my problems sorted.

The coolant light was just the coolant system needing to be topped up. Duh. Once properly filled it went out.

The oil light I eventually figured out, I just swapped the wires to the two oil pressure switches. Light went out and behaves like you'd expect it to, comes on with the ignition but goes out once the engine has started.

The temp gauge I sorted by using a black two-pin temperature sensor instead of the black 4-pin one. Since the petrol fuel injection system has been binned the 4-pin sensor isn't needed. I just figured out which two wires controlled the gauge in the dash and wired them into the 2-pin sensor.

The last one I haven't sorted is the rev counter. I have the diesel rev counter plugged into the petrol clocks but I have yet to figure out where to plumb in the wire from the alternator to feed the gauge.



Simply plugging the diesel clocks complete didn't solve any problems, in fact it made more problems. I am still running the petrol clocks but with the diesel rev counter plugged in (but not yet working).

Hopefully this will help someone in future.