No spark after timing belt change

[dmw319]

So this weekend I did the timing belt, balance shaft belt, water pump, plugs and wires, battery, and a new distributor cap on my 944t. The car is not starting and I think I am not getting spark. (It was late last night when I was trying thats why I said I "think" haha). I'm pretty positive all the wires are in the right place and everything. I've heard it could be a fault alarm issue that i could bypass but dont know why this would randomly go bad over the course of a weekend? (maybe since the battery was unplugged.. i dont know how this system works really).

Any ideas??

[mytrplseven]

Usually it's something simple after a complicated bunch of work. I'd check these points initially: Check that the coil and coil to distributor connections are properly installed and tight. It's easy, especially with new wires for them not to plug fully into the coil, cap or plugs. Make sure that the Distributor cap is properly seated on the housing. Verify the timing order on the plug wires is correct and they are fully plugged in on both ends. Make sure the rotor is turning inside the distributor (Possible belt problem and I'm sure that if you tackled this job you've got it right). When you installed the new wires it's possible that the coil to distributor High Voltage wire was damaged internally if you tightly bent or stretched it. If you still have the old one, try putting it back in to verify this. I'm not well versed on computer faults causing things to stop but I can't believe that simply doing what you've done would cause this issue. You didn't mention how healthy the battery was, i.e., charge level. Sometimes there's enough to turn the starter but not fire the engine. Put a charger on it overnight and try again or jump from a good battery. Now here's a real stretch: Did you take out the flywheel lock? Anyway, drop a line so we'll know what the issue was. Good luck.

[dmw319]

Originally Posted by mytrplseven

Usually it's something simple after a complicated bunch of work.

my thoughts exactly. I double checked everything like you said.. still cant figure it out! I am going to run over everything again tonight though. I guess I need to start testing individual components?

also, battery is brand new and yes i took out the flywheel lock lol

[John_AZ]

When you tried to crank---does the tach bounce/jump 1/16" at all?

If yes,

Put the old wires back in.

Wire cap info:

This was posted by forum member
TexasBlake:
Since the rotor turns, and the firing order is 1-3-4-2, it has to
be in the 1-3-4-2 order starting at some point. I don't
remember exactly if this one has it, but nearly all
distributer caps have a 1 on the cap so you know where to start.

I took magic marker and labeled each cylinder for the cap.
The spark plug boots cover it up.

Looking at the cap while standing in front of the bumper it is:

4 2
3 1

EDIT and like mytrplseven mentioned above, recheck the rotor and make sure the bolt is tight.


GL
John

[txhokie4life]

Is there a kill switch?

A buddy of mine was prepping our race car for the start of the race while I attended the
drivers meeting.

He had pulled the car cover off, which had caught the kill switch.

When I got back to jump in and head to grid, she wouldn't fire.

Scramble, Scramble --- no tach bounch -- ahh must be the DME sensors,
took them out looked at them, put them back in. Still nothing.
Started to check wiring, etc. Since the hood was up we hadn't notice
the kill switch being cocked.
Sure enough, reset the kill switch and she fired right up :-)

Good to know the kill switch works.......

Had to settle myself down.
I think I was calmer during the race than just prior :-)

Add it to the check list!

M

[dmw319]

car doesnt have a kill switch, but i will check to make sure tach is bouncing tonight when i get home and also double check the distributor cap/wire order. i already tried putting the original wires back on also..

[mytrplseven]

Question: how did you determine you weren't getting spark? If you pull a spark plug, put the wire one it and ground the plug to the engine you'll see the spark if there is one. Let me know.

[dmw319]

Thats what i tried.. Not getting spark i double checked all wires and rotor and cap etc. Hellllllp

[dmw319]

Also... Tach does not move when i try to start the car

[John_AZ]

That is not good.

Quick tests:

Try to jiggle/gently tap the DME computer, the 35 pin connector & wiggle the connector wires while starting. (This test may lead to a connection problem or a bad solder joint)

Change your DME/Fuel pump relay with your spare or make a jumper:
DME Relay Information and Testing

Check the connection for the reference sensors--clean connection. Check for frayed wires.
Do the resistance check:
Speed and Reference Sensors - Checking, Replacement, and Adjustment

Now to to Clarks-Garage.

You need to go to Clarks Garage and begin the No Start Trouble shooting pages.
Troubleshooting - Engine

GL
John

[dmw319]

should the tach bounce when i turn the key on, or when i try to crank?

[John_AZ]

It will bounce when you crank. The flywheel pins cause the bounce passing by the sensor.
Look real close at the tach needle for the bounce. 1/16"th of an inch--just moving is good sign.

John

[dmw319]

yea, its not moving and my coil does not have 12v

[pjs77]

If you have no Tach bounce it really comes down to two things, Your DME ECU or your reference/speed sensors. Trust me on this, I did hours of trouble shooting this same exact "no tach bounce - no spark" thing and got it narrowed down to the reference sensors. I measured resistance on both and one was infinite so I just replaced them both. The reference sensors operate magnetically and sends the ECU a signal based on the pickup screw on the flywheel. This tells the computer where TDC is for firing and timing. So the tach isn't bouncing because either the ref sensor is bad or the pick up screw is gone and the signal isn't getting picked up. If you haven't done anything to the flywheel or the pick up screw then its probably the sensor, Be careful removing them and label the connectors because if you mix them up it still won't start. Just use plenty of PB Blaster and patience. Gentile upward twisting motion should do the trick. I had mine swapped out in 30 min and she fired right up.

I swapped a buddy's ECU in on my car before ordering parts just to make sure and it still didn't fire.

I got two brand new Bosch sensors for $66 a piece. There is a BMW cross reference for the sensors and they are half the price, same sensor. I was quoted $203 each at my local dealer hahahahaha!

[dmw319]

do they just randomly fail though? i mean the car was only down for 2 days for a timing belt swap then tried starting it right back up. car didnt move and i didnt even touch the sensors? i understand that they may fail just seems kinda a stretch that it could be that coincidental. oh well. i guess ill start troubleshooting the dme and sensors..

[pjs77]

Yes, I have put about 10k miles on my car in the last year with no issues. I was out running errands one day and it left me stranded at my office two weeks ago. Poof just like that, no sputter, no weird noises, nothing, just no start. Very frustrating isn't it? It took me 10 days to figure it out even with all the forum threads on this.

Something could have shorted them out. Inspect the connectors too, some people say they get very brittle and just fall apart. You just never know with these cars.

Try the sensors, really. Look up the resistance measuerments. If you don't have moisture in the passenger footwell, or your DME box is rust free it then your DME is probably ok. Good luck and keep us posted.

I also paid $15 for next day delivery because I was so anxious to get those sensors in.

[dmw319]

Ok. Well assuming the sensors areall good what else could it be?

[pjs77]

If your sensors are good than its either the pick up screw on the flywheel or the DME computer. My money is on the sensors.

[Arizona_928]

probably a loose ground, not completely plugged in spark plug wire, or unplugged AFM......

[dmw319]

I didnt disconnect any grounds. Triple checked wires and just checked afm..nothin...