V8 No Start - Failing Sensors
From Knowledgebase
Have you ever had a hot-start problem with your [[V8_(model)|V8]? You drive home in traffic, stop into the grocery store that is a block away from your house, grab a gallon of milk, come back out and the car won't start? Do you notice that the Tach doesn't bounce as you are cranking it (stays at zero)? You have a failing RPM Sensor!
Have you ever had a problem where your V8 is driving along just fine, but when it warms up the engine dies? If you let it cool down it fires right back up and then dies again after you drive a few miles? You have a failing Ignition Timing Sensor!
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The Parts
Your V8 comes with these two sensors mounted to a plate attached to the bell housing. From the factory, the only difference between these two sensors is that they are color coded; grey - RPM Sensor, black - Ignition Sensor. They are actually the exact same sensor and are interchangeable.
Some parts counter list one or the other as NLA (no longer available) and as always, the V8 parts fetch a pretty penny (~$200 IIRC). You can purchase the same sensor off a 5ktq (which is what I did) for under $100; the only difference is the 5k sensor is longer. They grey one I bought from SJM was cheaper than the black one ($92.75 vs. $157.39).
The Fix
It is a pretty easy job if you have patience and small hands. One dealer charged him $200 for the part and $200 for the install.
You start by jacking the car up to give you room to work. I took extra time in doing so as my life is worth a few extra min. I have a buddy who lost a friend when his car (on jacks) fell and crushed him. Don't buy cheap jacks / jack stands. Find 2 good spots to place the jack stands and bump the car with your weight once it is up to make sure it doesn't move or seem unstable. I also leave the jack extended as a fail safe if something was to happen.
Next remove 2 10mm bolts, unhook 2 connectors, and swap out the bad sensor (1 10mm bolt per). Re-installation is the reverse of removal. You are done!
Well, I did leave out the yoga-like positions, the swearing, the endurance required... It is really not bad, but I would give yourself a few hours.
Pictures
Here are the pics...
A view from the bottom:
Here are the 2 10mm bolts. I used a open-end wrench to break them loose, and then just used my fingers to get them out. Reinstall was helped with a swivel head socket and a fine toothed ratchet.
Here is a view from the bottom of the connectors. My camera was able to squeeze in there (unlike my big head), but I unfortunately don't remember any reference points to give you.
Tip: The connector spring-clips used on German cars don't have to be removed to unplug the connector - just squeeze the spring into the body of the connector and pull the plug loose. You probably already know that, but I figured this out on my own after several months of ownership
Here is a view between the last 2 headers on the driver's side. Note that the sensors are mounted to a plate that can now be removed (once you unplug the connectors).
Conclusion
Lastly, it has been suggested by some that you want to replace both connectors at the same time. This is not a bad idea considering it takes a few hours (not to mention the wear and tare on your knuckles), but again I am broke. I would rather have a temperamental RPM Sensor than a vehicle that dies once it warms up. One will get you to work in the morning, the other will not. I chose to put the new sensor as the Ignition Timing Sensor and moved the old one to the RPM Sensor spot. I haven't had any problems with the other sensor, but Murphy says I will now!
Content in part from a post by Jeremy Ward
