dfroelicher

Just in case here is the problem,

It started with taking longer to start, then it turned into not starting when it was cold out, now it won't start at all.

So far I have changed the fuel pump, the temp II sensor and jumpered the fuel pump relay, checked fuses. Nothing worked. The Temp II sensor was bad, tested out at infinite ohmage (open circuit). The fuel pump was good, now I have two . Then I started changing out the fuses, some with the glass type replacement, no luck.

Now I noticed that the vehicle has no spark and is not sending voltage to the fuel pump relay when you crank the engine. When I jump the relay it pumps and there is a hissing nose in the rear passenger side of the engine compartment near the firewall. I have not tested, nor know how to, test the distributor, rotor, or coil, other than by pulling a plug and grounding it to the engine.

So my question is, how do you test these things and am I just wasting time in trying to test these components. Can I pull a plug and wire and connect to the coil to test the coil? If so do I need to ground the plug on the engine like regular?

Also I do have access to the WSMs, unfortunatly I do not fully understand some of the sections layout and how to find some of these parts.

Any help is greatly appreciated as I am know to the 928 and in some cases the maintenance of cars. However I am quite knoweledgable in electronics and circuits basic setup and function.

AO

what year car?

Rich9928p

The TZS spark box sends the engine speed signal to the L-Jet controller and fuel pump relay. You will get no fuel pump turn on nor any fuel injection if there are no engine speed signals to the L-Jet. Look to the schematics [note, the schemtics posted are scans of the same circuit page. The page was too large to fit into my scanner, so what may look like one big schematic is really two copies of slightly different positions of the same page. This enables you to see the top and bottom of the page] and you'll see the ouput of TZS 16 to connector O7 - the signal goes into 31b of the fuel pump relay.

Your best bet is to start at the distributor and check the "green wire" which probably is no longer green in your '83. This wire has a Hall effect sensor that sits inside the distributor and provides engine rotation pulses to the spark box. This wire is a shielded cable, with an external ground (TZS 31d) and signal conductor (TZS 7) inside the shielding.

From the spark box TZS 15, you have output to the coil (via two ballast resistors) and the signal that connects to the L-Jet controller via connector pin 1.

You should check all these connections and check the resistance of the ballast resistors.

dfroelicher

woah!! You guys are great that is awesome info Rich.

Sorry forgot to mention, It is a 1983 928 S US spec, AT , A/C, 4.7L L-Jet.

Imo000

Check the fuel injection relay, take the aluminium cover off and "jump" it with your fingers !!!!!! If the eniginer roars back to life make sure you replac eit with an exact part. Other reays might look the same but they don't operate the same.

dfroelicher

FINGERS!!!!!!!!?? Why not use a little jumper wire like the fuel pump relay? FINGERS!!!!!!!!???

Imo000

I knew you'll be asking that! The aswwer is pretty simple. By pushing the contact together with your fingers, you are assuring that the relay will work the way it was supposed to. There will be less of a chance jumping the wrong pins and it's a fale save method of testing the relay. Trust me on this one, it works. Sniper21 tried this method and managed to diagnose the relay faliure. He tried all kids of other ways like swapping the relay without a sucess.

BUT before you do this, make sure there is spark. You jumped the fuel pump already so that is not an issue anymore. To check for spark, just pull off one of the spark plug boots and stick a spare spark plug it it, then crank the engine over and look for a spark. Also by this time if there is fuel, you should be able to smell the unburnt fuel vapours coming out of the tail pipe.

There is also a good chance that the engine is flooeded and you might have to pull all the spark plugs out and let the cylinders dry out.

dfroelicher

So today I go out to the porsche armed with lots of knowledge from all of you great guys. Started following the little green(now brown) wire from the distributor to the spark computer and found that the connector was totally green inside, like moss growing on a tree, cleaned it off with my knife and viola!! She Lives!!!


I would like to thank all of you that posted to both of my threads and especially to Justin and Rich for sticking through all my stupid non-stop questions. Thanks for all of your help.

Now that being said, I must "pilot vehicles at unsafe velocities" (lets see if anyone knows where that is from), also the car is in much need of a bath.

Imo000

Way to go ! Electrical problems are always a bi$ch to fix.

littleball_s4

So perhaps your hard-starts problem and no-start-at-all problem were completely unrelated to each other. Perhaps you fixed first one with the temp II sensor and second with the contact cleaning.

Good job!