ls1 rx7: cranks but doesn't start
07-24-2008, 09:41 AM
#1
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ls1 rx7: cranks but doesn't start The car is a 93 rx7 with a 99 trans am ls1
THe car cranks and the fuel pump is coming on. I have fuel pressure to the rails but there is no spark, injectors arent firing, and no tach signal.
-The crank sensor (brand new) and cam sensor are plugged in.
-all grounds are good: block, chassis, harness, and ecu.
-all fuses are good
-power is getting to the injectors and coils, but the ecu isn't telling them to fire.
any help is appreciated...
THe car cranks and the fuel pump is coming on. I have fuel pressure to the rails but there is no spark, injectors arent firing, and no tach signal.
-The crank sensor (brand new) and cam sensor are plugged in.
-all grounds are good: block, chassis, harness, and ecu.
-all fuses are good
-power is getting to the injectors and coils, but the ecu isn't telling them to fire.
any help is appreciated...
07-24-2008, 01:39 PM
#2
Is your PCM running? Do you have someone with a scanner that can plug into your OBDII port and check if it can see the PCM?
Do you have power during crank? Their are some leads on the RX7 chassis that have power in accessory and run, but not during cranking. You wouldn't be the first to plug a PCM into one of those.
If the PCM can be reached, and the power stays on during cranking, you need to check continuity on you crank sensor wires. The car should fire without the cam sensor, so that shouldn't be your issue.
If all else fails recheck your grounds a few more times. They're sneaky little wires...
Hope that helps a bit.
Do you have power during crank? Their are some leads on the RX7 chassis that have power in accessory and run, but not during cranking. You wouldn't be the first to plug a PCM into one of those.
If the PCM can be reached, and the power stays on during cranking, you need to check continuity on you crank sensor wires. The car should fire without the cam sensor, so that shouldn't be your issue.
If all else fails recheck your grounds a few more times. They're sneaky little wires...
Hope that helps a bit.
07-24-2008, 01:47 PM
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pcm is running, the scanner can read codes, only code is a coolant voltage high/low, or something. i ran the switched power directly to the battery for temporary purposes to try to start it. still nothing.
i am getting 12v out of one of the crank sensor wires, 0.0v out of the middle and 0.3v out of the other end wire, while key is in on position
I'll go over the grounds again, all help is appreciated. thank you.
i am getting 12v out of one of the crank sensor wires, 0.0v out of the middle and 0.3v out of the other end wire, while key is in on position
I'll go over the grounds again, all help is appreciated. thank you.
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07-25-2008, 12:02 PM
#8
How is your tach wired? I can see RPM on my tach while cranking (1998 F-Body PCM). Do you see anything?
Somewhere on this forum is the instructions for testing a Crankshaft Position Sensor; I don't have the link handy right now though.
It almost has to be the crankshaft position sensor, as you verified you have both power at the coils, and no spark from the coils. If you have power at the coils, and the PCM tries to start the car, you should be seeing spark even if the injectors weren't wired correctly. No CPS and it can't tell when to fire spark.
Have you ohmed out the wires to the CPS from the PCM yet? That only takes a few minutes if you have a helper to hold a wire (and a voltmeter or test light). Make sure you unplug the PCM before you put 12 volts for a test light on those BTW (obviously).
Somewhere on this forum is the instructions for testing a Crankshaft Position Sensor; I don't have the link handy right now though.
It almost has to be the crankshaft position sensor, as you verified you have both power at the coils, and no spark from the coils. If you have power at the coils, and the PCM tries to start the car, you should be seeing spark even if the injectors weren't wired correctly. No CPS and it can't tell when to fire spark.
Have you ohmed out the wires to the CPS from the PCM yet? That only takes a few minutes if you have a helper to hold a wire (and a voltmeter or test light). Make sure you unplug the PCM before you put 12 volts for a test light on those BTW (obviously).
07-31-2008, 08:09 PM
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I have 12v going to the pink and orange wires to the coils and injectors, and power in crank position.
I'm not getting a tach signal at the tach, or in the data logging thru the 0bd2 port, nor a maf signal either
The crank sensor is brand new, and the ohms readings for the crank position sensor, are 12v, 8v, and 8v
another bit of info, is that when i crank the car, the voltage drops to .5v on the coils power
I'm not getting a tach signal at the tach, or in the data logging thru the 0bd2 port, nor a maf signal either
The crank sensor is brand new, and the ohms readings for the crank position sensor, are 12v, 8v, and 8v
another bit of info, is that when i crank the car, the voltage drops to .5v on the coils power
08-03-2008, 09:28 AM
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08-03-2008, 09:52 AM
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where is the pcm located at.reason im asking is i had the same problem initially before i mounted the pcm. it was sitting close to the motor and causing some kind of interference with the coils. as soon as i moved the pcm back it fired right up!
08-04-2008, 10:01 AM
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its inside, under the passenger footwell
08-07-2008, 03:27 PM
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08-07-2008, 04:25 PM
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also, i rechecked my switched power after checking the fuse block. it was cutting out during cranking. so now i have it back directly on the (+) terminal temporarily. I am now getting 10v to the coils during cranking... all other symptoms are still occuring
08-08-2008, 08:57 AM
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i'll check and get back
i've had a jumper pack connected to the battery, and ive also had the battery on a charger over night. Its getting plenty of juice
i've had a jumper pack connected to the battery, and ive also had the battery on a charger over night. Its getting plenty of juice