86 Vette cranks but won't start

[SuperRob]

Hi guys - I'm a rookie mechanic

i was checking for error codes shorting pin A and B on the ALDL but the check engine light keeps flashing showing no error codes. The coolant fan starts would that mean the temperature coolant sensor needs to be replaced?

l started by replacing the fuel sensor relay, filter and you can hear the pump start up, there's fuel to the rail by pushing the shrader valve. I also had a new key make to ensure it had the proper resistance. What else should I do if not the coolant temperature sensor?

 

[dougelam]

Check for spark

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[SuperRob]

Just pulled a plug crank her over and I didn't see any sparking

 

[dougelam]

Do you have a 12 volt test light?

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[SuperRob]

No I just pulled the plug pushed it back into the wire and cranked the car over, didn't see any spark. I'll pickup a test light tomorrow and research how to check the distributor and coil. I'll let u know how I made out or is there's something else I should do?

 

[dougelam]

Nope, not without a test light

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[Hib Halverson]

Hi guys - I'm a rookie mechanic

i was checking for error codes shorting pin A and B on the ALDL but the check engine light keeps flashing showing no error codes. The coolant fan starts would that mean the temperature coolant sensor needs to be replaced?

l started by replacing the fuel sensor relay, filter and you can hear the pump start up, there's fuel to the rail by pushing the shrader valve. I also had a new key make to ensure it had the proper resistance. What else should I do if not the coolant temperature sensor?

The fan runs because there are codes set.

The temperature sensor does not control the fan. The ECM does. If you have the aux. fan, it is controlled by a temp sensor screwed into one of the heads. There are two temp sensors in that engien. One under the TB provides ECT for the ECM. The one screwed into the left head provides the data for the IP display of ECT.

When the check engine light flashes, is that with the engine running or with key on/engine off?

Just pushing the scrader vale in the fuel pressure test port is useless because you can have fuel squirt out there but still not have enough fuel pressure to run the engine. You need the appropriate fuel pressure gauge then test fuel pressure according to the Factory Service Manual.

If you have no spark, consult the FSM's diagnostic info for "cranks but won't run".

 

[SuperRob]

Do you have a 12 volt test light?

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Ive check the power side of the coil using the 12 volt tester power is there but nothing on the tach side. Can the VATS shut down the coil from sending spark to the plugs? I pulled the cap and coil cranked it over and the little spring was bouncing does that mean the distributor was turning?

 

[dougelam]

Ive check the power side of the coil using the 12 volt tester power is there but nothing on the tach side. Can the VATS shut down the coil from sending spark to the plugs? I pulled the cap and coil cranked it over and the little spring was bouncing does that mean the distributor was turning?

Were the wires still connected when testing?
With the coil cover removed and everything plugged in, KOEO (key on engine off) you should have power on both sides.
12 volts on the power side and nothing on the tach side is a bad ignition coil. (Open in the windings)

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