1974 194 D-jet Too Rich

[RDudya]

Hello all, I have recently put the D-jet injection system back on my 74 Porsche 2.0l. The parts sat in a box for twenty plus years while I ran carbs. I built a new harness after looking at the old cracked wires. My 74 2.0l does not have a hole cutout in the cooling tin for cylinder head temperature sensor 2, and was not installed at the factory. The Haynes manual does show temp sensor 2 for a 74 in the wiring schematic though. When I built the new harness I left that circuit out. The car starts and runs so rich I have had to drop the oil several times. I have eliminated all vacuum leaks, thanks to others suggestions on this and other forums, valves, fuel pressure and timing set to specification. Cold start valve is disconnected, I did pull it off to verify not leaking. I did the injector test with four glass jars, three showed the same flow, I replaced one injector. I have several good MPS units, still sealed, and one I tried to adjusting leaner and actually works, sort of but not great. Thanks to Jeff Bowlsby, I have verified component part numbers, the MPS that came with the car was wrong, I changed it out with the same result. I pulled the harness and installed the circuit for the temp sensor 2 and grounded the wire that would go to the sensor with the engine running and got an immediate lean condition, so lean the engine died. I really want to thank so many people, this forum and others, three standouts that have helped in my understanding the D-jet, Jeff Bowlsby, Ray Greenwood and Dave Darling. I don't like asking for help but I am stumped. Thank you for any input.

[Dave at Pelican Parts]

If the cylinder head temp sensor is not present, the mixture will be so rich that the engine might not even run. All D-jet cars have some kind of engine temp sensor, and on the aircooled ones like the 914 that sensor is a head temp sensor. You really, really need it.

All of the 2.0 liter engine tin should have the TS2 hole near the hole for the #3 spark plug wire--that's the right-rear cylinder. That's because all of the 2-liter 914s came with D-jet, and all used that sensor. If yours does not, it is likely that someone welded it up for some reason. (I don't know if the AN-code 1.8 engines had this hole in their engine tin, but the spark plug holes are in the wrong location for 2-liter heads.)

We have seen people swap heads left-to-right during a rebuild so the sensor hole winds up on the driver's side head. Less common, we have seen people with two left-side heads so there really isn't a sensor hole in either head, but that's pretty uncommon indeed.

Getting into very foggy territory for me: I think there may have been some species of VW (possibly a Bus) that had a fitting that replaced one of the engine tin screws that you could thread the temp sensor into. I do not have any details on it, but it might be worth some investigation.

I suggest pulling the engine tin (only the parts that go over the cylinders & heads) to locate the hole for the sensor. You can also look to see if there is any evidence of welding on the right-side tin.

You really need the sensor. I suspect your engine will run lean when you get it hooked up correctly, though, so you will have other issues to chase at that point.

--DD

[RDudya]

Thank you Dave, I was hoping to get your input. I can assure that the 2.0l did not come with temp sensor 2. I resealed oil cooler and changed all of the slot screws to hex head bolts at the time twenty years ago. I own several 914's, and still do, I have always seen this sensor in all of my 914's, 2.0l 73's, 70, 71 and 73 1.7. This is my only 1974 2.0l. The tin was absolutely not welded. There is no drilled and tapped hole for sensor in the head, knowing they could have been installed wrong, I believe the engine has never been apart. When I removed the left cooling tin (replacing those slot screws), I would have noticed the right head having been installed on the left. Because even though twenty plus years ago, I remember these things with mental notes, at least so far. The old harness does have #23 wire to temp 2 and has the external connection for temp sensor 2. I bought the car off of Ebay in Phoenix and drove it home to Prescott Az with no noticeable problems though I immediately change to carbs and stuffed all the D-jet stuff in a box.

I neglected to mention Paul Anders in my homage, He more than any have contributed to my understanding and knowledge of the D-Jet.

[Dave at Pelican Parts]

EVERY 2.0 came with a head temp sensor. My 74 did, all of the other 74s I have seen did. All of them. Without one hooked up, the engine will run very rich.

Something has been done to your car, and it wasn't by the factory. You need to figure out how to undo that.

--DD

[RDudya]

Ok, I slept bad last night but I came to realize that my ECU is faulty. Mine though, not the cars. Misfiring on several synapses. The model is over seventy years old and parts are not available, I am going to run it till it quits though. Thanks Dave, I needed your input. If I find that, what I truly believed was correct I will let you know, I suspect I will not.

[RDudya]

Just to let you know Dave, you were right again.