I'm baaa-aack. Referring to some previous comments, on all fuel-injected cars, other than for one second when you turn on the ignition switch, the fuel pump will never run unless the engine is rotating, (cranking or running). If a fuel line is ruptured in a crash, the pump would dump raw gas on the ground creating a major fire hazard. Instead, the engine can't run without fuel pressure to the injectors, so it stalls. With a stalled engine there will be no signal pulses from the crankshaft position sensor or the camshaft position sensor. Lacking those pulses tells the Engine Computer the engine isn't running so it turns off the fuel pump by way of the fuel pump relay, fuel injection relay, automatic shutdown (ASD) relay, or in your case, "circuit opening relay". The names are different but the function is the same. The fuel pump gets turned off and stops dumping fuel on the ground.
Where checking the oil level comes in is some manufacturers have some engines that turn the fuel pump relay on by grounding its coil through a tap on the oil pressure switch or sending unit. A stalled engine has no oil pressure so the fuel pump gets turned off. Low oil level will, in a round-about way result in lower-than-normal oil pressure and that can result in a relay that turns off well before the low-oil warning light turns on. This goes way back to the early Chevy Chevettes that had carburetors and an electric fuel pump in the tank. I worked with a fellow who had one and had this problem on his way to work. We had never seen that before, but after some head-scratching on the side of the road, he added a quart of oil and made it to work. His engine was stalling about every two or three miles.
As I mentioned earlier, the fuel supply system is responsible for a very small percentage of crank / no-start problems as is the ignition system. It's the cam and crank sensors that cause most of the problems. We never replace one to "try it" except as a last resort. Doing so could inject another problem and a new variable. These sensors are listed on the live data screen on a scanner with some type of indication as to whether the signals are showing up during cranking. Chrysler, for example, lists theirs as "No" or "Present". To further complicate things, a diagnostic fault code can be set related to the missing signal for either sensor, but due to the long list of conditions that must be met to set a fault code, one is often not set in the short amount of time a stalled engine is coasting to a stop. Also, the list of conditions usually includes, "the signal is not monitored during the first five seconds of cranking" or something similar to that. That means without the scanner to view live data, you may not find this with a simple code reader. Even when a fault code has been set, if the battery is disconnected before the codes are read, they will be erased and may not set again from just cranking the engine.
Those two sensors are the first thing we think of when anyone mentions "stalls after running for... ", Or "stalls when hot", or "won't restart when warm until it cools down for an hour". The mistake the largest percentage of competent do-it-yourselfers make is getting hung up on the first thing they find missing, and that is fuel. Our first question is always, have you also checked for spark", because spark AND fuel are lost when a signal is missing from one of those sensors. That tells us whether you have a fuel supply problem, an ignition system problem, or the more common sensor problem that's common to both systems.
Your comment about "Circuit Opening Relay" not being printed on your relays made me chuckle. One of my best Electrical students made the comment that he could follow my drawings on the chalk board, but there were no red and blue chalk lines under the hood of the car, and the parts weren't so nicely labeled. Up till then I had never given that any thought as to why some people have trouble with electrical parts they may have never seen before. I forget that this applies to you and most other people too.
Sunday, September 18th, 2016 AT 7:33 PM