Low Volts to Coils=No start
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Teching In
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Low Volts to Coils=No start Trying to finish up my LS1 swap into an Austin Healey replica and ran into a little snag.
Here's what I have:
I had the PCM programmed out the VATS. Which should at least let me start the engine from what I've read from you guys/gals here.
It's a 04 GTO engine and harness. There's one nice big plug with most of the wires I needed plus a few from another plug. I subscribed to AllData so I'm almost certain the wiring is ok.
I checked the 5 volt ref and that read fine, the fuel pump runs, the Cam and Crank sensor plugs have 12 volts, and I can hear the TPS calibrating which helps me believe the wiring is good, as well.
With the low voltage does it seem like something is not grounded?
It's a spanking new battery. I even charged it to 13.26 volts tonight just to make sure it was full.
Any tips, ideas, comments?
Please?
Update!!
Just like the older harnesses theres a C101 plug that feeds the banks for both sides. A little misleading I was thinking it was a plug for the air cleaner or some other junk I wasn't using.
Man! I connected those wires and it popped off on the first try. Open headers sound fookin great! Too bad it woke up my kids.
Here's what I have:
After wiring everything up I read @12 volts to the Crankshaft Position Sensor as well as the Camshaft Position Sensor.
Fuel pump turns on to build pressure just before cranking, then off, then turns back on during cranking.
Shrader valve shoots fuel across the garage when depressed=Good pressure.
Heres what I think is a problem:Fuel pump turns on to build pressure just before cranking, then off, then turns back on during cranking.
Shrader valve shoots fuel across the garage when depressed=Good pressure.
Less than 1 volt going into the coil packs during cranking.
I am getting no spark and the spark plugs are dry.I had the PCM programmed out the VATS. Which should at least let me start the engine from what I've read from you guys/gals here.
It's a 04 GTO engine and harness. There's one nice big plug with most of the wires I needed plus a few from another plug. I subscribed to AllData so I'm almost certain the wiring is ok.
I checked the 5 volt ref and that read fine, the fuel pump runs, the Cam and Crank sensor plugs have 12 volts, and I can hear the TPS calibrating which helps me believe the wiring is good, as well.
With the low voltage does it seem like something is not grounded?
It's a spanking new battery. I even charged it to 13.26 volts tonight just to make sure it was full.
Any tips, ideas, comments?
Please?
Update!!
Just like the older harnesses theres a C101 plug that feeds the banks for both sides. A little misleading I was thinking it was a plug for the air cleaner or some other junk I wasn't using.
Man! I connected those wires and it popped off on the first try. Open headers sound fookin great! Too bad it woke up my kids.
Last edited by jtune; Apr 12, 2007 at 12:09 AM.
You need to source a feed for the voltage to the coils that has power under crank. Some ign. switched voltage willl drop off when cranking to give more power to the starter. Probe around the fuse block and the back of the ignition switch for this power. This voltage will need to be present at the pink wire on each seven pin coil pack harness for the car to start.
Thread Starter
Teching In
Joined: Feb 2007
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ah...so probably the wires I have going to my fuse block IGN X is getting drained from the cranking so it's not getting enough juice for the coils?
I'll give it a shot!
Thanks for your help, Chris.
(Someone told me how fast the forum members here are to respond and you were like greased lightning!)
Jerry
I'll give it a shot!
Thanks for your help, Chris.
(Someone told me how fast the forum members here are to respond and you were like greased lightning!)
Jerry
Thread Starter
Teching In
Joined: Feb 2007
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Even at the ignition switch the voltage drops just under 11 volts when cranking. Then again I did crank it quite a bit after charging so I may need to charge it back up a bit.
Not sure how much voltage needs to go to those coil plugs but I'll give it another go tomorrow.
Not sure how much voltage needs to go to those coil plugs but I'll give it another go tomorrow.
Thread Starter
Teching In
Joined: Feb 2007
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I feel like I'm so close to getting this started but I am also thinking I have no clue! If the Crankshaft or Camshaft sensor were hosed, would that cause the low voltage to the coil plugs on either side?
Teching In
Joined: Oct 2006
Posts: 30
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From: Auburn, WA
Are we talking about the main power feed to the plugs? If I'm not mistaken, there should always be a good 12-15 volts there, and the ECU fires the coils via a different signal. Long story short, I wouldn't think it would be caused by a bad crank/cam sensor.
I would think at least 9 volts would be needed, but there is no reason why it would be that low. Something in the harness and where it get's its +12v is wrong...or a ground.
I would think at least 9 volts would be needed, but there is no reason why it would be that low. Something in the harness and where it get's its +12v is wrong...or a ground.
KOEO you should have battery voltage to the coils...if you dont start tracing back between connectors with a DVOM until you figure out where your short/excess resistance is. IF you have voltage to the coils, until you crank, your coils may be collapsing, but not rebuilding (bad ground(s)), because switching grounds are what turn the coils on and off. IDK just a few things you could check, or start looking into.
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Thread Starter
Teching In
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Thanks for your help. I figured the voltages should be up higher.
I was talking about the two plugs on either side on top of the heads that plug into the coil packs. (one plug branches to 4 coils)
I'll start tracing and let you guys know if I have any luck.
Thanks again for the ideas!!!
I was talking about the two plugs on either side on top of the heads that plug into the coil packs. (one plug branches to 4 coils)
I'll start tracing and let you guys know if I have any luck.
Thanks again for the ideas!!!
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