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Is the resistor plugged in behind the LF head light...?
Cam position sensor looks like it had new harness repair, it passes right in front of cylinder head on top of water pump, it's not smashed there is it...?
I have a running condition (battery dead) '87 944S in my shop.
I can compare if you need anything.
Going back there in a few, have two automatics to finish this weekend and I'm way behind.
Is the resistor plugged in behind the LF head light...?
Cam position sensor looks like it had new harness repair, it passes right in front of cylinder head on top of water pump, it's not smashed there is it...?
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Or melted? If you're talking about that harness beside the PS reservoir, wow, that's awefully close to the exhaust
Behind the left front headlight, I don't see a resistor or a place for one. The ignition module or "ignition final stage" as the manual calls it is the only thing back there. There is an injector resistor pack near the cruise control servo which tested OK.
I did the repair on the cam position sensor. The original housing was cracked so I soldered on a pigtail from an old reference sensor. The hall sensor output is one thing I cant match with my oscilloscope testing to workshop procedures. I've also tried starting with the hall sensor disconnected, which according to the manual should set the idle timing to 4 degrees before TDC. I'm going to replace it to eliminate variables, just haven't yet as it is a bit pricey, same goes for the O2 sensor.
It does have a genuine 944S DME. I've tried the one that came with the car as well as a known good one from a running car I picked up from John at just joshin. Incidentally, I think the DME connectors are keyed differently to prevent mis-connections. Combing through the TE Connectivity catalog, I found a 55 pin connector; all the pins match up but there is a key-way where the end of the connector latches on to the DME that does not match up.
It does have a factory alarm. The module was gone when I got it with a jumper installed. I've verified the jumpers against clarks-garage and the factory wiring diagram which both show the same thing.
It seems to be getting both fuel and spark, and presumably air. It just seems not in the proper order and/or ratio.
I know you say the plugs are wet and you have spark but try this: pull the fuel pump fuse and remove the air filter. Try starting the engine by spraying starting fluid in the AFM. If it fires you have fuel problems. If it doesn't then your spark is weak or your timing off. Reversed ignition coil leads (+&-) will produce a weak spark on a good coil. A loose distributor rotor will produce a random "pop" now and then, backfiring thru the air box. A bad O2 sensor will make it run very poorly but at least start.. YMMV
Removed the fuse and gave the starting fluid a go this morning, no joy. I was able to watch the air flow meter move as it sucked in air. It moved past the point where I measured change in voltage.
I measured AFM voltage at the meter with jumper leads between the harness and meter as per the workshop manuals. I don't think it is possible to test at the DME end without a break out box (which I've been considering building out of my old harness) as it seems there are solid state electronics involved, not just a simple resistance measurement.
I was able to dial in the advance with my timing light last night while my daughter cranked it, it is firing at 5 degrees before TDC while cranking.
I'll double check the coil wiring when I get home, we're at cars and coffee now. I put a new coil in it (Bosch), and the terminals are two different sizes, but it never hurts to double check.
Just checked your list again and looks like you haven't verified no vacuum leaks. Is that right? Could be a big one somewhere. Make the diy cap/plug with a male air-tool fitting and use your air compressor as per Test Plan to test for leaks. 5psi
I did a rudimentary smoke test using some big puffs from a cigar and didn't see any leaks. I did only test the throttle body to engine side though, which doesn't eliminate the possibility of pre-throttle body unmetered air leaks. That setup is a few bucks from the hardware store, so I'll round up the parts this afternoon and give it a go.
I did a rudimentary smoke test using some big puffs from a cigar and didn't see any leaks. I did only test the throttle body to engine side though, which doesn't eliminate the possibility of pre-throttle body unmetered air leaks. That setup is a few bucks from the hardware store, so I'll round up the parts this afternoon and give it a go.
It's a long shot: you'd need a pretty big leak to keep it from staring, something like forgetting to attach one of the large pipes amhik. But, if you have no other lead today, might as well make the tool: it's handy. I used a white cap with the square top with male threads that I threaded into a matching piece. Then I installed the air fitting (with shut off, though that's unecessary) by drilling a hole and threading with teflon tape
More pics
Last edited by Dan Martinic; 03-23-2019 at 12:23 PM.
Reason: Added pics
OK, interesting results here with the pressure test: it won't hold any. Best I can tell so far is it is pressurizing the crankcase. I can detect some air leaking by the oil fill cap so far. My compressor is refilling now; can't run it and test at the same time as it is deafeningly loud in my one car garage. Going to crank up the pressure and try to track it down.
03-22-2019, 07:00 PM
