more on a no start

thekidd · 01:33 PM

I have a no start problem, as do some of us. I have check the starter, alternater, and battery all at a parts store, all tested good. Checked the ignion switch, good- got.2 ohms I think. Tried to jiggle the refernce sensers, and that didnt help, cant even get them to disconnect to check resitance. But today I was checking for spark. Took the ignition coil wire out of the D-cap, put a screwdriver in, placed it near the engine manifold, brother tried to start to engine and I got no spark. Replaced the wire to D-cap, Took out a spark plag (closest to the windsheild) connected plug to wire to the spark plug, put a metal peice of the plug onto the manifold, brother tried to start the car, and no spark. OK, the test I have done wasd checking the ignition coil. I got 12 DCVs with ignition on and off, with the positive wire (black) and the ground wire (green) connected to the leads. I did the primary test (Haynes Manuel) with an ohm meter from the (+) lead and ground lead and I got .6 ohms. I tested evry terminal, to every other terminal and got 0 ohms on all of them. The other test they say to put my meter to a high resistance and check from terminal 1 lead? to 4 (under the rubber cap) and got 0L on my meter, 0 ohms, but dont have a high resitance switch on mine, just Amps, ohms, ACVs and DCVs. Any help? My inital though was that my coil was bad because I wasnt getting spark, but when I checked for voltage (12DCVs) I though that I was good because I got voltage.

alantica · 02-10-2009, 09:28 PM

Played this same game this past month. Brother I have walked in your shoes. If you can swap an ECU with somebody, try that first. If not, pull out your ECU. Take a small standard screwdriver and pop up the chip. You don't have to take it all the way out, just pop it up a little bit then softly push it back down in place. You are simply re-seating the chip. Next take a soldering iron and a small amount of solder. Tin the iron and start on one side of the board and work your way across touching the solder joints. Just heat them up enough to quickly melt the solder then pull the iron off. The object is to eliminate cold solder joints. Be careful not to overheat and join solder points and not to burn any of the board wired in paths. On my boards I could not see any broken wiring, burnt paths or bad spots. But just reheating the board solder joints and re-seating the chip fixed my 944. Check this out on Clark's and PM me if you want more detail. Good Luck!

phoenix_iii · 02-11-2009, 11:52 AM

I live close enough. He borrowed my DME relay already, heh...

But OMG... He does not get TACH BOUNCE when he tries to start it...

I'll let everyone else chime in [do a search!]. =)

alantica · 02-11-2009, 12:13 PM

Hhhhhmmmmm....... No tach bounce means the odometer sensor is not picking up anything. I would disconnect the mark sensor & odometer sensor & pull them out. The switches are a little difficult where they connect at and easy to break. The big problem here is usually corrosion. When I first looked at mine there was a lot of white powder around the mark sensor connector, but that wasn't the problem. Another problem area is down at the bottom before it goes into the round cylinder. If it has been jiggled enough, the wire could be broken. It's not uncommon to see missing filler within the wire cylinder. A little bit of Bondo placed inside fills it up with no worries of heat or cracking. It's easy to pull the sensors out and wipe them off with a cloth. They can be interchanged because it is the same part number.

rmcdonnell · 02-11-2009, 12:51 PM

You only get tach-bounce if your tach works.
Then, you can deduce that maybe the sensors are duff.
cheers
Rissole.

phoenix_iii · 02-11-2009, 01:05 PM

His Tach worked previously (right?).

thekidd · 01:19 PM

Well, I tested the reference/speed sensers and got nothing. Tested them with a ohm/volt meter by means of Clarks geerajh and I got no Ohm and no voltage. Clarks didnt say anything about voltage, just wanted to check it out. They were a bugger to get off, but I got them ogg, but broke the hell out of them. Peices of the sensers (part that goes to the enging) are stuck in the female peice. They fit back in place, but not snuggly. If you get no Ohms, does that mean that they are bad? Or do you need a osciliscope to test to see if they are bad?
Dint see the other posts. My tach did work prior to the no start. I fixed my odometer gera (lots of super glue) and afetr thatthe odometer worked fine. Dont know if the trip worked before the super glue fix or not. I dont know where to look for the odometer senser, or what it even looks like, first time I even knew there was an odometer senser.

Outback Porsche · 02-11-2009, 01:32 PM

Quote:

Originally Posted by phoenix_iii

But OMG... He does not get TACH BOUNCE when he tries to start it...

Replace the sensors. This was my problem (only intermittent) a while back. I used the BMW 6 series sensors - half the price. Only difference is the last number in the bosch part number, and the tail is longer.

Another 'Intermittent Start' Problem

alantica · 02-11-2009, 05:50 PM

Quote:

Originally Posted by alantica

No tach bounce means the odometer sensor is not picking up anything.

Duh.... Sorry it's been a long day. Speed/mark/reference/odometer sensor. Whatever you want to call it, there are two of them and they are the same sensor. Regardless, everything is controlled by the Motronic ECU. I haven't mapped out the ECU yet as far as what should happen when ignition is applied so I can't point to the schematic and say this is what will happen when the key is put in the start position. http://www.frwilk.com/ http://www.the944.com/ I agree with Outback to a point. I don't know where the sensors come into play as far as the ignition schedule. Example: No power or reference from the sensors seen in the ECU at a certain point may be an ignition killer. But in the scheme of things I wouldn't think the sensors would have that much control over ignition. Continueous running, yes, but not the simple start up until everything kicks in and feedback comes into play and the engine becomes governed. Simply put - I don't know. I do know that I replaced everything in the ignition sequence between my two 944's. On one, I had a bright light with a tester at the coil & plugs and correct voltage. Pulled everything out one at a time and put in the other 944, testing with the light with each part. The light was dull. When I swapped the only thing left, the ECU, it started with no problem. I know exactly how frustrating it is and wish I could be of more help. Good Luck!

Outback Porsche · 02-11-2009, 07:10 PM

Quote:

Originally Posted by thekidd

Well, I tested the reference/speed sensers and got nothing. Tested them with a ohm/volt meter by means of Clarks geerajh and I got no Ohm and no voltage............but broke the hell out of them. Peices of the sensers (part that goes to the enging) are stuck in the female peice. They fit back in place, but not snuggly. If you get no Ohms, does that mean that they are bad? Or do you need a osciliscope to test to see if they are bad?

You should have a resistance reading. The sensors are buggered!

Alantica - Yes, the DME could cause this also. As thekidd has 'broke the hell' out of the sensors removing them from their mounts, and they measure incorrectly, they need to be replace first. The speed sensor is essential to the starting sequence. The DME needs to see the engine crank before it will latch the fuel pump relay.

Once you have replaced the sensors and it still doesn't want to start, then look at your DME.

Mask of Destiny · 02-11-2009, 07:13 PM

Quote:

Originally Posted by alantica

I don't know where the sensors come into play as far as the ignition schedule. Example: No power or reference from the sensors seen in the ECU at a certain point may be an ignition killer. But in the scheme of things I wouldn't think the sensors would have that much control over ignition. Continueous running, yes, but not the simple start up until everything kicks in and feedback comes into play and the engine becomes governed.

I'm pretty sure the speed and reference sensors are used for ignition timing. The DME needs to know when to energize the coil. So no sensors no spark. Maybe no fuel too (I imagine injector duty cycle might be fixed for cranking, but you would still want the period to match the RPM for consistent fuel delivery).

joshl1978 · 04-24-2009, 04:34 AM

my 944 will start run for about 30sec. then die as if some shut the car off. my ? is would the speed/ref sensors cause this condition? I have narrowed things down to dme, speed/ref sensor,ignition coil or altitude sensor. havent had time to switch coils out mine has an aftermarket ignition will do this then try again. looked at speed ref sensors I see some corroding but not much I will also check for tach bounce I have already replaced dme relay and fpr same condition as before.

thekidd · 04-24-2009, 01:14 PM

I have the same problem. I replaced my speed/ reference sensors, and finally she ran. She will not run for a long time, but will cut out after a few minuets and then she would have cut out. Clarks garage has a check fot the speed and reference sensors, and the ignition coil. Go to Clarks down below in my signature.

thekidd · 04-26-2009, 11:34 AM

I had her running for a few days. Replaced refernce sensors and she started for a while, but would shut off after 10-15 minuets. The car will turn over, but not run. My battery was dead fromsitting for so long, so I got new one and put it in. Stiil no go, just cranking. When she was running the fump was running. I did have some water coming from the tailpipe, so I put some STP fuel cleaner in (to get water out) and some fuel system cleaner in (to try to clean fuel sytem up) Any opinions? Thanks guys.