1986 (944) turns over but doesn't start
 

1986 Porsche 944, i love the little bugger but its being a pain in my ass. it turns over but wont start... a diagnostic was run on the computer, finding that the speed sensor/s is bad. And sure enough one appeared to have wire damage, and I've replaced it. But still nothing, i no the fuel pump is working, but its not sparking. And I don't think fuel injectors are firing. Any ideas, pointers, or suggestions would be a great help. Thanks for reading.

-andrew

the speed/ref sensors may have been switched... try switching the wires?

Do a search from a guy called SoCal Driver and search for "five minute test". That will give you detailed instruction on how to find the problem. You are not the first to see this. Also check out clarks-garage.com a lot of good information there.

I thought the wires may have been switched as well, but changing them made little difference. While i was in the shop i had a owner of a 911 explain to me that the reference sensors sit on a bracket which can be adjusted. Additionally he explained that when the reference sensors are working that the tachometer will jump, when the engine is turned over. Which when the bracket (holding the reference sensors) is in certain positions it does. Is there anyway to tell (without actually starting the car) if the sensors are switched?


-andrew

I read the article in clarksgarage.com on "Speed and Reference Sensors", i have a few questions... what happens if you don't disconnect the negative battery terminal? and The speed sensor and the reference sensor both do different things right? But are they the same piece of hardware? Would they be interchangeable?
Thanks

-andrew

they are interchangeable, however their position when plugged into the harness is not - i.e. the leads get different signals from different portions of the flywheel, and go to different parts of the computer. the ref. references TDC i believe, and speed counts teeth on the flywheel relative to time if i am not mistaken.

cool thanks to all i am gonna work on it tonight and tomorrow after i get of work, we'll see how it turns out. i also heard a tip from a friend, not sure if works but i'm gonna try it: disconnect both battery terminals and connect them (the wires), leave it sit for twenty minute. it resets everything on the car, which makes sense if you consider it.

-andrew

Did you check/replace DME sensor?

Disconnecting the battery will have no effect on this car. That is to reset the computer on an ODB II computer placed in cars from 96 forward. Go through the diagnostic procedure...it takes five minutes and will reveal what the problem is. Probably will be the DME relay but you need to test to be sure.

This is in no way a rational replacement for sound trouble shooting techniques, but it worked for me:<p>Go down to where the the sensors bolt into the housing (probably 10mm hex but could be allen head 5-6mm) and swap em. Then, of course, swap the plugs. I doesn't hurt to chant "A pox on Bosch sensors! Cursed is your wispy copper coils!". Well, it doesn't hurt if no one overhears you.

clarksgarage.com is badass, it helped alot, but im still not set. i have changed both of the sensors (speed and reference) im afairly certain there a no issues with the fuel pump. i released pressure from the fuel line tightened the bolt, turned the engine, and there was pressure in the line again. I finally got it running but it has to turn over quite a few times. i thank everyone for the advice but i'm still having trouble. not sure why. the engine also sounds like it running harder also running harder than it was... any ideas?

-andrew

any ideas for selling a 1986 (944) porsche in san antonio? it needs alot work (obviously). i have to leave for mississippi next week and i cant drive something this unreliable down there. thanks

-andrew

Sure...drop it off in Houston along the way and I'll be glad to drive it around for you until you return! :)