What all of you are describing is real common on any brand of engine. The symptom will be no spark and no injector pulses. It is usually caused by a failing crankshaft position sensor or camshaft position sensor. They fail by becoming heat-sensitive, then they work again after cooling down for about an hour. While driving, natural air flow keeps them cool. When a hot engine is stopped, the heat migrates up to the sensors and causes them to fail.
To add to the misery, diagnostic fault codes often won't be set just from cranking the engine. They may only set while a stalled engine is coasting to a stop. For that, the best approach is to connect a scanner so you can view live data. Those sensors should be listed with some type of indication to show whether their signals are showing up during cranking. For example, on my Chrysler scanners, they're listed with a "No" or "Present". I know GM scanners show the same thing, but I don't know what their terminology is.
The two-wire coolant temperature sensors are low-level and only contribute slightly to fuel metering calculations. One notable exception is when starting a GM engine. Corrosion between the adjacent terminals in the connector will cause lower overall resistance, and therefore lower signal voltage, which equates to hotter coolant. In response, the Engine Computer will command a smaller priming squirt of fuel than is needed. You'll have hard starting or a long crank time, but you will still have spark. A common observation is the engine will start, then run fine after getting a squirt of starting fluid.
Coolant and air temperature sensors have an extremely low failure rate because they have just one component inside them. Ford had a rash of failures in the early '90s where it looks like an internal connection broke loose and caused resistance, signal voltage, and ultimately, idle speed to bounce around wildly. Other than that, temperature sensors are pretty trouble-free. Most problems are caused by wiring and connector terminal problems. Also, for any visitors who aren't aware, temperature sensors for Engine Computers will always have two wires in their plugs. If you find a coolant temperature sensor with just one wire, that's for the dash gauge.
For the comment about the fuel level gauge dropping to "empty", a common cause of that is a weak spring-loaded movable contact on the float arm in the tank. On most vehicles you can buy a new sending unit, but on the early to mid '90s Chrysler minivans, once the pump is lifted part-way out of the tank, it takes just a minute to lift a plastic hook, then slide the float arm off, then you can bend the contact a little to put more pressure on the sensing element. That fix is more reliable than installing a new sending unit which is likely to develop the same problem in a few years. I know that can be done on some other brands too. The common symptom on the Chryslers was the gauge will read correctly any time the level is between "full" and "1/2", and between "1/4" and "empty". It would drop to "empty" when the level was between "1/4" and "1/2".
Dec 21, 2017 at 7:24 PM
