Sir Nick

Hello,
I'm sort of new on this site, but I'm a long time Porsche owner. In fact, I've had the same 914-6 for over 30 years. However, I'm seeking help with another of my projects. I have a wrecked 1986 Carrera parts car and a 1982 SC roller that I'm installing the drivetrain from the '86 into. My problem is integrating the DME wiring harness into the '82 body. I've searched through these posts without coming up with anything definitive. Everything is installed, yet I can't get it started. I do not get spark or the fuel pump to work. I've 'dewired' the '82 fuel pump relay and K-jet harness. I have '82 and '86 wiring diagrams and thought I've made proper connections. I've separately tried both the DME fuel pump relay and DME control unit in a friend's Carrera and his car will start and run, so I know it's not those components. The '86 car had a factory anti-theft unit in it, the '82 does not. Looking at the wiring diagrams, it appears that the DME fuel relay is actually two relays with the first one being energized by the anti-theft unit which in turn energizes the fuel pump relay. I have jumpered the anti-theft input to +12v and the fuel pump will still not come on during cranking. I have also jumpered the fuel pump itself to +12v and it works (I'm still using the SC pump, which I have read here produces too much pressure, so I'll have to install the 3.2 pump). The car still will not start. I pull the # 1 spark plug wire and stick a spare plug into it, ground it to the intake manifold where all the other ground wires are attached and no spark during cranking. It's getting +12v to the hot side of the coil so I assume the DME is not providing the ground necessary on the negative side. Therefore, I think I have a miswire somewhere on an input to the DME. After I had removed the drivetrain from the '86, I installed new clutch components and rear engine main and trans. input seals. I did not intentionally move either of the flywheel sensors (speed or TDC). Is it possible I bumped one and knocked it out of alignment? If I did, would that cause a no start or just rough running? Also, I'm not sure I got the wires on the correct connectors for those (near the fuel filter). Silly me, I did not mark them before disassembly. I've tried connecting them both ways to no avail. I don't have an O'scope to test them with but I assume I could use an analog meter and look for a spike every time TDC comes around. How about the speed sensor? Repetitive spikes? Does the rev-limiter run off of the speed sensor? I've hooked up the '86 tach and speedo. I guess I need the oil combo gauge as well since I'm using the '86 oil tank, lines and cooler (I don't know what happened to the '82 engine. Grenaded? Shrapnel in the old oil lines?). With full disclosure, yes it was me who wrecked the '86. But it ran so well (1 qt. oil every 3k miles!) with a factory ltd. slip, short shifter, etc.; I had to buy it back from the ins. co. I would appreciate any suggestions! Thanks.

P.S. The wife has a '92 C2 (purple with a tip.) and one of the sons has a 944.

theiceman

This could be an interesting one . i dont have a carrera so cant really add much but at first glance i would makes sure the DME is actually getting power and then check the sensor inputs as you have suggested. I think Loren has posted on here before on how to check the DME . you can also grab the coil off the SC if it has one too right ?

Mark I

Nick: I did such a swap 2+ decades ago & have only vague, fragmented recollections. But, some things I seem to recall. A fuel pump that has remained out of service (paticularly dry) will varnish and seize quickly. Your '86 literature will explain how to run the fuel pump by jumping within the fuse panel, although, as you point out, it's the absolute wrong pressure. Spring for a new or known good pump. I recall fashioning the fuel line connector by using the banjo fitting from a discarded oil line. Check my accuracy on this, but I seem to recall that the distrbutor also rotates in the opposite direction. I'll try to think of other info that might be more useful & advise.

Sir Nick

Thanks for your replies. I'll get back to the car, hopefully, Monday. Whatever I find, I'll post here the results.

Sir Nick

Sorry it's taken so long to return to this. I found my problem to be the black wire from the tach to the DME. It was in the harness in the trunk with the blk/vio tach. wire. Once I swapped in the '86 tach and connected that wire the car fired up and runs great. By the way, that wire from the '86 anti-theft system does, in fact, energize the fuel pump relay. It needs to be tied to +12vdc or the fuel pump will not run. Thanks.