Crankshaft position sensor?
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Crankshaft position sensor?
Does anybody have an idea of where exactly this is? Is it by the crankshaft bolt in the engine bay or is it underneath the car? Or somewhere else entirely? I’m having a crank no start issue so just want to check this sensor out.
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this is for an 87 corvette by the way
Melting Slicks
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The L98 doesn't have a crankshaft position sensor. It doesn't need to know where the crankshaft is in the firing order. The distributor sends a reference pulse at each cyl's TDC. The pulse is used to fire the injectors and to fire the ignition coil. The cyl that the spark goes to is the one that the distributor's rotor is pointing at.
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The L98 doesn't have a crankshaft position sensor. It doesn't need to know where the crankshaft is in the firing order. The distributor sends a reference pulse at each cyl's TDC. The pulse is used to fire the injectors and to fire the ignition coil. The cyl that the spark goes to is the one that the distributor's rotor is pointing at.
Melting Slicks
Joined: Nov 2016
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From: So Cal
2023 C4 of the Year Finalist - Unmodified
Turn key to RUN, do not crank, Fuel Pump will run for a few seconds and stop. Leave key in RUN.
Breifly crank engine. Just enough to turn the engine a single revolution or so. Listen for the fuel pump to be running, then stop.
If the above test = YES, the ECM received reference pulses. It uses these pulses for fuel injection.
A couple of other basic checks:
> With key in RUN, there must be a CHECK ENGINE light. If = NO, the ECM is not powered on.
> Is there spark? While the presence of reference pulses generally indicates that there will be spark, there are other components involved with spark. Particularly the coil and dist cap center button.
> Is there fuel pressure?
And: The 1987 requires an operating Cold Start Injector system to facilitate easy starting after an overnight sit. (<< This is the definition of "Cold Start"). The CSI is completely independent of ECM control, and is only activated with the key in CRANK. If your 87 cranks but does not fire at all, the places to look are Fuel Pressure, Spark, CSI system. If it has these 3 things, it should fire, but may not continue to run. At this point, it can be things involving the ECM, reference pulses, injection, etc.
Breifly crank engine. Just enough to turn the engine a single revolution or so. Listen for the fuel pump to be running, then stop.
If the above test = YES, the ECM received reference pulses. It uses these pulses for fuel injection.
A couple of other basic checks:
> With key in RUN, there must be a CHECK ENGINE light. If = NO, the ECM is not powered on.
> Is there spark? While the presence of reference pulses generally indicates that there will be spark, there are other components involved with spark. Particularly the coil and dist cap center button.
> Is there fuel pressure?
And: The 1987 requires an operating Cold Start Injector system to facilitate easy starting after an overnight sit. (<< This is the definition of "Cold Start"). The CSI is completely independent of ECM control, and is only activated with the key in CRANK. If your 87 cranks but does not fire at all, the places to look are Fuel Pressure, Spark, CSI system. If it has these 3 things, it should fire, but may not continue to run. At this point, it can be things involving the ECM, reference pulses, injection, etc.
Thread Starter
Intermediate
Joined: Jan 2024
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Turn key to RUN, do not crank, Fuel Pump will run for a few seconds and stop. Leave key in RUN.
Breifly crank engine. Just enough to turn the engine a single revolution or so. Listen for the fuel pump to be running, then stop.
If the above test = YES, the ECM received reference pulses. It uses these pulses for fuel injection.
A couple of other basic checks:
> With key in RUN, there must be a CHECK ENGINE light. If = NO, the ECM is not powered on.
> Is there spark? While the presence of reference pulses generally indicates that there will be spark, there are other components involved with spark. Particularly the coil and dist cap center button.
> Is there fuel pressure?
And: The 1987 requires an operating Cold Start Injector system to facilitate easy starting after an overnight sit. (<< This is the definition of "Cold Start"). The CSI is completely independent of ECM control, and is only activated with the key in CRANK. If your 87 cranks but does not fire at all, the places to look are Fuel Pressure, Spark, CSI system. If it has these 3 things, it should fire, but may not continue to run. At this point, it can be things involving the ECM, reference pulses, injection, etc.
Breifly crank engine. Just enough to turn the engine a single revolution or so. Listen for the fuel pump to be running, then stop.
If the above test = YES, the ECM received reference pulses. It uses these pulses for fuel injection.
A couple of other basic checks:
> With key in RUN, there must be a CHECK ENGINE light. If = NO, the ECM is not powered on.
> Is there spark? While the presence of reference pulses generally indicates that there will be spark, there are other components involved with spark. Particularly the coil and dist cap center button.
> Is there fuel pressure?
And: The 1987 requires an operating Cold Start Injector system to facilitate easy starting after an overnight sit. (<< This is the definition of "Cold Start"). The CSI is completely independent of ECM control, and is only activated with the key in CRANK. If your 87 cranks but does not fire at all, the places to look are Fuel Pressure, Spark, CSI system. If it has these 3 things, it should fire, but may not continue to run. At this point, it can be things involving the ECM, reference pulses, injection, etc.
Melting Slicks
Joined: Nov 2016
Posts: 2,244
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From: So Cal
2023 C4 of the Year Finalist - Unmodified
The CSI is activated at coolant temperature up to 105 deg F. 105F is definitely not "cold". In this context, "Cold" means the First start of the day.
I wasn't talking about fuel pressure. I was suggesting using the fuel pump by listening for it to verify that the ECM is receiving reference pulses. (I've been using this diagnostic for decades. It works.)You asked about "Crankshaft Sensor", which sends reference pulses to the ECM, in systems equipped with CKS's. In the L98, the distributor sends the pulses, I suggested a way to check for pulses because that's what you were asking about.
There's another currently active thread in Tech that has info pertinent to your inquiry: 88 L98 Hard Start Issue Getting Old. There's some good info in the beginning, but when it strays to data logging, timing and other stuff irrelevant to the hard start, jump to Post #87. There's an image of the CSI troubleshooting page from the FSM. It is for an 87, but your 85 is identical.
I wasn't talking about fuel pressure. I was suggesting using the fuel pump by listening for it to verify that the ECM is receiving reference pulses. (I've been using this diagnostic for decades. It works.)You asked about "Crankshaft Sensor", which sends reference pulses to the ECM, in systems equipped with CKS's. In the L98, the distributor sends the pulses, I suggested a way to check for pulses because that's what you were asking about.
There's another currently active thread in Tech that has info pertinent to your inquiry: 88 L98 Hard Start Issue Getting Old. There's some good info in the beginning, but when it strays to data logging, timing and other stuff irrelevant to the hard start, jump to Post #87. There's an image of the CSI troubleshooting page from the FSM. It is for an 87, but your 85 is identical.
