ohm related questions,

[trucker677]

I looked through my WSM today and found some tests I can run on the car to try and narrow it down to what is wrong. I did the tests but I am not an electrical guy so some of this is none sense to me. I am hoping someone can shed some light on the subject and one or two other questions I have.

1) I checked the temp sensor II and I got a reading of 3.32. for the temp at 20 C it says it is supposed to be 2-3 k-ohms. Today in ontario it was 10 C. Is my reading ok for me to use this sensor.

2) I checked the temp time switch, again the temp was 10 C. For terminal G and the ground I got a 36.3 but I am suposed to get 0. For terminal W and ground I got .3 but I am supposed to get 0. For terminal G and W I got 36.2 and I am supposed to get a 0. the one that I am questioning is the first reading. when it says the ground (housing) I am going to assume they are talking about the copper nut that threads into the block.

3) I pulled off the air flow sensor I connected the ohmmeter to it,
between 6 & 9 OL but readjusted and got 560
between 6 & 8 OL but readjusted and got 360
between 8 & 9 202
between 6 & 7 123
between 7 & 8 323
between 27 & 6 2.9
All of these are within spec except for the first 2. I looked in the book a bit more and it says that if I have 042 stamped in housing of air flow then numbers change, I looked and I do not see the 042 stamped in there. With the numbers I got does that mean my air flow sensor is pooched.

4) I reset the oxygen sensor button, still never made a difference.

5) I did the fuel pump test, disconnected the return line and ran a hose from the line and ran into a jar, I want to confirm that I have the right line first. the supply line runs to the pressure regulator in the front of the engine and then branches off to the fuel rails, the return lines go from the back of the fuel rail and into a T in the fuel rail line. If I am correct I got 1400 ml. I ran it for 30 seconds and bridged the relay like it says in the book. According to the book I am only supposed to recieve 1150 ml. I got 1400. I am going to assume my fuel pump is working correctly and my filter is on the right way. In the pic it looks like mine is different but I followed the direction arrow, fuel flow is from the drivers side to the passengers side. right. The question I got is that one line down it says engine stopped, fuel pump bridged, 2,5 +- 0.2 bar. I dončt know what that means.

If everything is good above is there any suggestions that you can suggest that I can do. My car starts right up and then dies 3-5 seconds later, no sputter or backfire. just shuts off.

[Danglerb]

Starts and dies in a second or two usually means its starting via the coldstart, and main injectors aren't working at all.

Can you put more detail in you post, 3.32 what ohms, Kohms?

Model information, US or Euro?

Pictures.

[trucker677]

I just did a recheck on the air flow sensor with the ohm meter,
between 6 + 9= OL ohm, should be 200-400 ohms, .562 kohms
between 6 + 8= OL ohm, should be 130-260 ohms, .362 kohms
between 8 + 9= 202 ohm, should be 70-140 ohms
between 6 + 7= 123 ohm, should be 40-300 ohms
between 7 + 8= 325 ohm, should be 100-500 ohms
between 27 + 6= 2.9kohms, should be 2-3 kohms

for the temp sensor II it was in kohms. The rest of them are ok.

I am running the L jetronic fuel system. 1982 928. I redid the vac lines. is there a relay for the injectors. is there an easy way to check the injectors to see if they are firing. When I look at the door post it says the car was made in germany, It has both KMh and Mph, WP0JAO929CS820074.

[Danglerb]

Thats a US vin, all Porsche's are made in Germany, two easy ways to check injectors are to listen to them with a rubber tube or use a noid light. Yes on the injector power being through a relay, and a fuse, check those and also look at the green wire between the distributor and ignition box.

[trucker677]

in relation to checking the green wire do I turn the key on but engine off, will there be 12 volts running to it still, or do I need to get someone to start the car for the 3-5 seconds and check it off of that, if I get no voltage can I cut out the bad wiring and just run a normal wire, I have read on here that the wire is expensive, why is that.

Do you happen to know what relay it is for the injectors, and what fuse it is for them also, I have looked in the WSM but can't locate it.

Thanks for the reply.

[trucker677]

Will the car still start even if the green wire is defective, I don't exactly know what the green wire does.

[JhwShark]

If the car starts odds are the green wire is not an issue yet.

The "infamous" green wire is really a cable (kind'a like Cable TV). It should never be jury rigged. This wire has a green insulation then a very thin seath shield wire (webwire shield) with a core lead inside another layer of insulation. The cable end that plugs into a lead to the transistor ignition unit on the right side rear-wards of the T14 connector. This plug is very fragile with age, just checking it can make it crumble.

The FP relay (R#17) fuse (F#22) should be OK since it starts. The Start relay sends voltage to the AFC pin 30 then after start is over, pin 15 should carry the voltage to the AFC relay. The AFC (I believe means Automatic Fuel Control) relay #16 does not have a fuse that I can see; under run pin 86 should have voltage from 15bus. Check CE plug W for good contacts. If you have a relay #9 check it I do not see a name for it. If its there it is in the circuit.

Jon

Adding there is a Bal resistor (actually 2 one for start and one for run) in the circuit near the coil that could also cause no coil output if it is bad. The run one is 0,6 ohms.

[trucker677]

thanks for the explanation, My car will start and run for 3-5 seconds and then shut off, I didnt know if the green wire comes into effect after the cold start or before the cold start. I think it is running off the cold start but the injectors are not firing as someone mentioned earlier. My fuel pump is pumping the fuel, this was checked at the return line. I know I have spark. After that is where I am lost.

[stepson]

I would check the fuel injection relay (4th relay from the right on the top row- part # 928.615.119.00). It sounds as if your injectors are not working and you are just running on your cold start injector. If this is not the relay part number that is there, your car will not run.

[trucker677]

I checked the relay and the part number was 928 615 116 00, does the number matter if it is one number off, like the year or what type of fuel system. I will order that relay for sure though. I hooked up a test light to the injector as well for something to do, it stayed on steady even with the ignition on. I am not an electrical person so I don't know if should flash or not while the engine being cranked over.

[JhwShark]

As I mentioned earlier, the green wire is not the problem if the car runs. It sends the signal from the TIU to the distributor. You would not have spark if it was not functional. Since you say you have spark but no run the Bal resistor is not the issue either odds are neither is the TIU.

Check the AFC relay #16 and related wires and plug at the CE panel. This is the wiring diagram for the '82 on Cannell's http://www.cannell.co.uk/928_Workshop_Manuals/1982%20Current%20Flow%20diagram.pdf. Section I and II are the main ones to learn and use for diagnosis in this regard. DO you have a relay #9?

You could test the AFC relay by pulling it out and put pin 85 to ground and touching 12v to pin 86 does it click?

The cold start injector just adds fuel into the phlenum at start in the start cycle.
Jon