cant believe that i cant find this electrical gremlin...

ColoradoCryptoTrader

Well-Known Member
no crank no start, when i jump the load side of the crank relay (pins 30 and 87) I blow the crank fuse. When I jump pins 30 and 85 it cranks. 85 is a good ground. I think, but that isnt making sense to me. am I looking at the relay spot correctly?

could I have internal damage in my starter?

could the purple +12v signal wire connected to the starter be shorting directly to the battery and blowing the crank fuse?


obviously have a damaged wire somewhere I think...any ideas folks?? The car was running fine but something happened might have had a power surge in the electrical system and back to no crank.

i will double check continuity on the purple starter signal wire tomorrow. sick of this for now.

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Ross

Goblin Guru
I think you need to look carefully at the numbers on the bottom of your relay, not the misleading wiring diagram on the side of the relay.
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Your labels in the fusebox have 85 and 87 backwards?

When I jump my fusebox relay, I run the wire diagonally. (red line in this pic)
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So your no crank no start issue isn't the starter... it is working fine. Maybe the clutch safety switch?
I use to get this issue when the high speed GMLAN wasn't communicating correctly. Water in my power steering box caused issues.
When that occured, putting the key in the "run" position, and jumping the starter would allow the engine to start, and the car to run and drive, but no data going to my instrument cluster, and no power steering.
 
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Gtstorey

Goblin Guru
4 pin relays work off diagonal pins (normally). That way it doesn’t matter if you rotate the relay 180 degrees, it will still work.
 

ColoradoCryptoTrader

Well-Known Member
okay thanks!

I relearned my clutch switch using tech2 and the car was starting just fine before. double checked the switch and it was still learned.
 

Lndshrk Steve

Well-Known Member
I had the same problem. If you removed the fuel pump relay to "jump" it, to empty the donors fuel tank, you may have fried the circuit board in the fuse box. It is below the fuses/relays and above the connectors on the bottom. It easy to split the fuse box and look. But look closely. I've attached a picture of mine. I soldered on a jumper to restore power and it fired right up.
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ColoradoCryptoTrader

Well-Known Member
IF I JUMP THE CRANK FUSE DIAGONALLY WITH THE KEY ON THE CAR STARTS AND RUNS FINE BUT WHEN I TURN THE KEY NOTHING.

so I believe that I can conclude that the clutch switch, BCM, and ECU are all working correctly??

So I think I have narrowed it down to the ignition???
 
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ColoradoCryptoTrader

Well-Known Member
I had the same problem. If you removed the fuel pump relay to "jump" it, to empty the donors fuel tank, you may have fried the circuit board in the fuse box. It is below the fuses/relays and above the connectors on the bottom. It easy to split the fuse box and look. But look closely. I've attached a picture of mine. I soldered on a jumper to restore power and it fired right up.
View attachment 32824View attachment 32826
I dont this this is my problem, I pumped the fuel out of the tank with a hand pump. when i jump the crank relay the car starts and runs great.
 

Gtstorey

Goblin Guru
If you have access to a tech2 you should be able to see pretty much everything the car is trying to do. I’m pretty sure it will register the key switch as it tries to crank and pretty much everything else.
My guess is going to be a loose connection at the fuse box or bcm, our maybe a ground.
 

Ross

Goblin Guru
IF I JUMP THE CRANK FUSE DIAGONALLY WITH THE KEY ON THE CAR STARTS AND RUNS FINE BUT WHEN I TURN THE KEY NOTHING.

so I believe that I can conclude that the clutch switch, BCM, and ECU are all working correctly??

So I think I have narrowed it down to the ignition???
I wouldn't conclude that the BCM and ECU are all working correctly... My guess there is a data issue somewhere, and the ECU is deliberately not letting it start until the issue is fixed. Back to the basics? Reseat the bottom blocks in the fusebox, retighten the 7mm bolts. Clean the ground wires, etc.
 

ColoradoCryptoTrader

Well-Known Member
I wouldn't conclude that the BCM and ECU are all working correctly... My guess there is a data issue somewhere, and the ECU is deliberately not letting it start until the issue is fixed. Back to the basics? Reseat the bottom blocks in the fusebox, retighten the 7mm bolts. Clean the ground wires, etc.
when i disconnect the negative side of the battery and measure voltage across the connector to the negative post its 69 microamps and 9 volts
 
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Gtstorey

Goblin Guru
65 milliamps is about normal. You may have just drained the battery messing with it trying to start it. Just charge it up and see what happens. Your whole problem may be a weak/dying battery.
 

ColoradoCryptoTrader

Well-Known Member
65 milliamps is about normal. You may have just drained the battery messing with it trying to start it. Just charge it up and see what happens. Your whole problem may be a weak/dying battery.
the voltage across the negative battery terminal and the negative battery connector (with the connector disconnected) is 9 volts until I disconnect the alternator wire from the starter, then it goes to zero. I'm going to replace the alternator and see what happens. The alternator was taking power from the positive side of the battery and shorting it to ground I think.
 

ColoradoCryptoTrader

Well-Known Member
I have determined that my problem is that the ECU seems to be sending the starter crank relay 9.56 volts ALL OF THE TIME to pin #86. all of the other crank relay pins are working correctly.

I think I might have to take it all out, unwrap the wiring harness and inspect the purple/white wire for damage?? maybe run a new wire to the fuse box. im stumped. the car runs and drives fine if I jump the crank relay. I could just remove the relay and put in a push button start to send 12 volts to the starter purple wire but I want this car to be 100%.
 
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Gtstorey

Goblin Guru
I’ll say it again if you are getting different voltage to ground at the opposite end of the same wire/circuit then either you are not grounding your meter very well or it isn’t the same wire circuit. Run a wire directly from your negative terminal of your battery to use for ground to measure voltage. If you still get different voltage you have a damaged or different wire.

edit to add the above is assuming nothing else changed. If you moved the ECM connector around between measurements then you might not be getting a good connection for the pin when you got the 0.80 bolts.
 
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ColoradoCryptoTrader

Well-Known Member
you are right i had a bad connection to multimeter at the ecu plug . the ECU is for sure 100% sending 9.56 volts to the fuse box. i give up. time to install a push button start and be done with it. :) because race car
 

Gtstorey

Goblin Guru
You have confirmed that you have about 12.6v at the battery? 12.6v at the jumper/B+ post to the same ground point used for the 9v measurement? The 9v is only there when you try and start the car?

I would have thought 9v would have closed the relay but it’s probably getting marginal at that voltage.
 

ColoradoCryptoTrader

Well-Known Member
You have confirmed that you have about 12.6v at the battery? 12.6v at the jumper/B+ post to the same ground point used for the 9v measurement? The 9v is only there when you try and start the car?

I would have thought 9v would have closed the relay but it’s probably getting marginal at that voltage.
right now my battery only has 12.3 volts but its consistent everywhere i measure.

measuring ECU pin 57 to frame ground (crank relay pin 86 to ground matches this) same results if grounded to the frame or directly to the battery...
key off: 0 volts
key 1 click to switch on power: 0.03 volts
key 1 more click to on: 9.56 volts
key cranking with clutch depressed: 9.56 volts

going back to off from crank...
key 1 click from on to switched power: drops to 0.13 volts
key 1 more click to off: 0 volts

thanks for listening ha! i think its time to run a start switch between the crank fuse and the starter purple wire and forget about it.
 
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Gtstorey

Goblin Guru
I was able to activate a spare starter relay with a 9v battery. Voltage on the battery actually was 9.6 volts. Either your 9.6 v is stray voltage with no available amperage or something isn’t right with your relay or it’s grounding. Not sure what you can do with that info but I feel like you may still not be getting a start signal to the ECM.
 

ColoradoCryptoTrader

Well-Known Member
fixed it for now. ill be waiting months for registration so I may revisit this later. fused 12v directly from the battery to the starter. still requires the key switched on to actually start and run.

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