Hi guys. I just stopped by due to interest in the topic, but I did not read everything. Allow me to add a comment that may be of value. You are one of the few people who understand how the ASD relay works and gets turned on, but starting somewhere around the late 1990's. It was possible for some Chrysler engines to run with one failed sensor, but once shut off, the engine would crank but not restart. It has to do with the spacing of the notches in the ring on the torque converter that are read by the crankshaft position sensor. Some use a varying number of notches in each group, and the computer can tell by the number of notches which pistons are coming to top dead center. On others, all three sets of notches have the same number, so the computer needs another input from the cam sensor to know which pistons are coming to TDC. That one, at least on the newer years, can continue running when the cam sensor fails because the back-up strategy for the computer is to simply calculate which ignition coil comes next, and next, and next. I am told those can also do the same thing by running on just the camshaft position sensor, but not once the stopped engine has to be restarted.
To add to the misery, there are some where the ASD relay will turn on during cranking when one sensor has failed, but I cannot remember what year that started or if it involved all engine sizes that year. The clue you might be overlooking is you may be stuck on the ignition coils. The injector pulses are also timed off the cam and crank sensors, so check if you lost those too.
You were lucky enough to get a diagnostic fault code for the crank sensor. Those often do not set just from cranking the engine. They need time to set, as in when a stalled engine is coasting to a stop. There are two real common problems with these crank sensors. First is either sensor on any car brand commonly fails by becoming heat-sensitive. Typically they fail during hot soak when a hot engine is stopped briefly, as in when stopping for gas, then they work again after cooling down for about an hour. This is where you may never get a fault code. The second is the crank sensor needs its critical air gap set with a thick paper spacer on the end, or, a lot of aftermarket sensors have a thin plastic rib molded on the end. If you remove and reinstall that style, you are supposed to cut off the remaining part of the rib, then use a paper spacer.
To show the importance of that air gap, when we got behind on transmission replacements at the dealership, I was asked a few times to take one on. My specialties are suspension and alignment, brakes, and electrical, but I am able to replace an engine or transmission. For the first couple of transmissions, (which require removing the crank sensor), I used the paper spacer, and everything went fine. Later I cut those spacers in quarters to use fewer resources and save the dealership a few pennies. For the last few, I became too arrogant to need the spacers. I just stuffed the sensor in all the way, then pulled it back a fuzz. Well, I heard through the grapevine that my thirteenth one developed a stalled engine about twenty miles from the shop. Another mechanic diagnosed the code as a failed crank sensor, replaced it, and there were no more stalling problems. I am convinced I caused that by not setting the air gap correctly.
To condense all this wondrous information down to something useful, you have the fault code and the perfect symptom for a failing crankshaft position sensor. A real easy way to verify that is by driving the vehicle with a scanner connected so you can view live data when the problem occurs. You are familiar with the record capabilities of most scanners, but I have a Chrysler DRB3 for all of my vehicles, and those list both sensors with a "present" or "no" to show if their signals are showing up. Watch if one of those switches to "no" while you're driving, even if the engine does not stall right away. You could be getting a weak signal that the computer interprets as "something", so it keeps the ASD relay on, but it is too weak to accurately read the timing. Some engines, like on the Neon's, will be shut down by the computer when the timing of those sensors do not agree, as in a jumped timing belt, (cam and crank sync fault code), but I can tell you for sure, the ASD relay will still turn on or pulse on and off during cranking even though there is intermittent spark and no injector pulses.
Wednesday, September 20th, 2017 AT 1:18 AM
