HELP NEEDED ON DEAD 412LS ON THE D-JET

[nick sparrow]

Hello there I am currently having some problems with my D-jet injection. I have just replaced my gearbox last week, now I have been driving the car all week, and a problem has started; where once up to running temp it would cut out when stopping at lights. Now this happened a few times during the week at random, not all the time but upon stopping at lights the revs would on occasion drop down below idle then pick back up; but this Saturday it did again but this time it would not run after, well you could keep the engine running just by keeping the accelerator pedal moving constantly but as soon as you kept your foot still, or took it off the pedal the engine would die.

It was while running like this it was backfiring through the exhaust. Now while standing in the rain and cold (it our winter here) at the side of the motorway, on the way to work, and now running late for work, I checked all the connections in the engine bay. They all seemed good and there was a good fuel supply and electrical power.

Also I have notice in the last few weeks my rev counter was jumping all over the place even if the engine was at a steady rev it would bounce all over the place, it gets it negative feed off the coil.

Anyway to cut to the chase, I have assumed one of two things, the coil is not working (it was very hot when I stopped on the motorway), and or the head temp sensor is not working? And thus the engine would be flooding? Now the coil is easy to replace but I do not know where I could get a new head sensor, are they available in the USA? If so where could I order one from? I am wanting to get it back on the road ASAP as its my current daily driver and taking the train is such a drag, and it takes for ever.


Any help on this would be really really appreciated

nick sparrow

[ray greenwood]

Nick, a couple of things to look at. This is a very generic type of problem. Its hard to track. A couple of things to start with. It does not like to idle right? So what happens at low rpm? Well...vacume is low and the rate at which theinjectors inject is low.
Things affected by low vacume: (1) pressure sensor. You may have a cracked diaphram in the back. Disconnect the hose, apply vacume with your mouth or a pump and make sure it does not leak down. (2) the PCV valve...which you may not have. If it leaking...they all do....it will disturb the MPS at idle causing a stall.
Low RPM: If your trigger points are dirty or have high resistance, the low rpm will make the occasionally missing injections...cause a stall.
This symptom you describe is also caused by a drop in fuel pressure from a bad fuel pressure regulator when it heats up.
Test the CHT with a thermometer and warm water. They are still available through most Bosch dealers. Ray

[nick sparrow]

Thanks Ray I think it might be the pressure sensor as I have just replaced it with another one. It seems to run, there is still a bit of uneven running but this may now be the timing?

I also have a few spare pressure sensors one of which has not been played with still with the seal in the end of it. The one I took out seems to hold a vacuum but I have to test it with a gauge to check how well it does. I tested the connections between 7 and 15 with a reading of 94 and between 8/10 with a reading of 345. The end stop has been moved out but I have no idea by who or what has been done inside, it has been apart at some point as the epoxy has gone and the rivets have been replaced with small screw head bolts.

The other one I have and tried still has the epoxy and rivets, but this too gave the same results as the one I have taken out. It has a white and a brown dot on the side; its readings were 7/15 88 and 8/10 333. I don’t know what would be wrong but I will do a bit more reading on this. I hope to try and solve it tomorrow, if its still not raining… The car is as I said running but it feels and sounds somewhat uneven; hope to get to this tomorrow.

Terminal 7/15 8/10
Faulty one from car VW part # 022 906 051A 94 ohms 345ohms
Bosch part # 0280100 019

Spare with epoxy still there
Bosch part # 0 280 100 068 88ohms 333ohms


I will have a look at the one in the car tomorrow to see its numbers, but for now I will see if I can get it to run any better. I have been to Paul Anders site and have found it and your help most useful, again thank you.


nick sparrow

[ray greenwood]

Hello, 88 is a bit off for the reading on that one. But at least it low and not high...so it can be adjusted for. You will need to set your timing up properly before playing with the sensors, as the vacume signature from poor timing may affect your settings. The outer stop screw...and I know mine may be much different...try this for a base line setting. With the car idleing....and the screw threads so clean that you can turn the screw with your fingernail, turn the outer stop plug in until it just contacts the rim on the copper plate. If you go too far it will try and stall. Turn it out 1/2 turn. ONLY DO THIS WHILE IDLEING! You cannot adjust this with the engine off...because the plate will not be vacumed in...and you will get a faulty setting. This should work fine...but if you get a serious power loss...with some miss firing at the 2000-3000+ rpm range, the plate it bottoming out against the outer stop screw....so give it another 1/4 turn...try it again. Move 1/4 turn at a time until it no longer binbs up. Give 1/4 turn extra. If you get a bog down...and black smoke...you have gone too far...and it is over-enriching. Ray

[nick sparrow]

thanks, Ray I will try that when I get the chance.......work just seems to be getting in the way these days......oh well it pays for the cars.....

again thanks


nick sparrow