crank but wont start
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Joined: May 2021
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From: North Gower. Ontario
crank but wont start
So I own an 03 z06 and came this afternoon to go to a meet and got this problem:
car will crank but wont start, HUD shows "check gauges" and the gauge cluster dies after doing it`s restart dance, if i switch back one click with the ignition key, i get "low voltage/ charge system fault". obdII scanner showed also "p1637-39 generator I- terminal circuit" and "p1638-39 generator f-terminal circuit" occasionally not all the time.
Bought the car a year ago and put 10k km on it, replaced a bad alternator with a new one when purchased the car(drove 10k km on it), new agm battery a month ago.
cleaned alternator connector, checked fuses, cycled all the relays in the fuse box where the battery is. even tried a secondary key.
I'm lost here.
I will appreciate any help.
thank you.
car will crank but wont start, HUD shows "check gauges" and the gauge cluster dies after doing it`s restart dance, if i switch back one click with the ignition key, i get "low voltage/ charge system fault". obdII scanner showed also "p1637-39 generator I- terminal circuit" and "p1638-39 generator f-terminal circuit" occasionally not all the time.
Bought the car a year ago and put 10k km on it, replaced a bad alternator with a new one when purchased the car(drove 10k km on it), new agm battery a month ago.
cleaned alternator connector, checked fuses, cycled all the relays in the fuse box where the battery is. even tried a secondary key.
I'm lost here.
I will appreciate any help.
thank you.
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From: Cape Coral, Florida
You need fuel, air, spark and compression (at the right time) for the car to start…when you turn the key on do you hear the fuel pump prime for 2 seconds ??…also while cranking does the Tach move at all ??…if no Tach movement this leads me to a crank sensor…you have no spark or injector pulse with a bad crank sensor…you can check for spark visually and for injector pulse with a 12 volt test light.
Thread Starter
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Joined: May 2021
Posts: 64
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From: North Gower. Ontario
You need fuel, air, spark and compression (at the right time) for the car to start…when you turn the key on do you hear the fuel pump prime for 2 seconds ??…also while cranking does the Tach move at all ??…if no Tach movement this leads me to a crank sensor…you have no spark or injector pulse with a bad crank sensor…you can check for spark visually and for injector pulse with a 12 volt test light.
the car starts with starter fluid and dies in a few seconds.. the gauges cluster doesn't work in these seconds but the HUD goes crazy showing random speeds and rmp.. it means i get spark and no fuel
I do have com with an obdII computer and mange to actuate the fuel pump and such (xtool d7)
Last edited by biker_il; Jul 20, 2022 at 07:41 AM.
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From: Cape Coral, Florida
the car starts with starter fluid and dies in a few seconds.. the gauges cluster doesn't work in these seconds but the HUD goes crazy showing random speeds and rmp.. it means i get spark and no fuel
I do have com with an obdII computer and mange to actuate the fuel pump and such (xtool d7)
I do have com with an obdII computer and mange to actuate the fuel pump and such (xtool d7)
Last edited by C5 Diag; Jul 20, 2022 at 09:01 AM.
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From: North Gower. Ontario
OK, if you have spark and you hear the fuel pump bi directionally with your scan tool you should check for injector pulse with a 12 volt test light…remove an injector connector and hook the test light to battery POSITIVE or to the B+ of the alternator….touch the tip of the test light to the injector striped wire terminal….as you crank the engine the test light will blink if you’re getting injector pulse…it’s ground side switched so that’s why the test light is connector to battery positive. See if you hear the pump using the ignition key !!
I checked and blinks, but I think the fact that my cluster dies after it cycles when the switch turns on, should say something. after it dies I can`t access the dic or see anything.
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From: Cape Coral, Florida
…And do you hear the pump turn on for 2 seconds with the key on ??...the IPC receives power from 2 sources through the ignition switch...a pink wire which feeds the fuel pump too and an orange wire which feeds it too....the orange feed wire feeds the HVAC module...with the key on does the HVAC work ??...you can take a multimeter with one lead connected to battery positive and the other lead to any test point on top of Fue 25 (BCM1 and IPC) which is in the footwell fusebox...with key on or starting the car what is the number you see on the multimeter ??...we are doing a voltage drop across the ignition switch and don't worry whether you see a + or - on the multimeter....just look at the value....8 volts or so is no good...0.1 or 0.2 volts is good !!
Last edited by C5 Diag; Jul 20, 2022 at 11:54 AM.
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From: North Gower. Ontario
there a relay noise that comes from the fuse box. i cant hear the fuel pump.. maybe i should test for fuel pressure in the fuel rail?
Last edited by C5 Diag; Jul 20, 2022 at 12:05 PM.
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MMMM ????...no fuel pump so probably concentrate on the pink wire....the coils are fed by that circuit so if the car tried to start we can "assume" you have the coil packs working...with key on check the voltage on the pink injector wire and also check the pink wire at the MAF sensor...what does the voltage read...should be battery voltage...the pink wire on the coil packs should also read battery voltage....this may be an ignition switch !!
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Moderator, Tech Contributor
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From: Cape Coral, Florida
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
If the pump isn't coming on with the switch I wouldn't worry about that right now...HIGH RESISTANCE on a relay feed wire will cause it to chatter or click !!
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Joined: May 2021
Posts: 64
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From: North Gower. Ontario
…And do you hear the pump turn on for 2 seconds with the key on ??...the IPC receives power from 2 sources through the ignition switch...a pink wire which feeds the fuel pump too and an orange wire which feeds it too....the orange feed wire feeds the HVAC module...with the key on does the HVAC work ??...you can take a multimeter with one lead connected to battery positive and the other lead to any test point on top of Fue 25 (BCM1 and IPC) which is in the footwell fusebox...with key on or starting the car what is the number you see on the multimeter ??...we are doing a voltage drop across the ignition switch and don't worry whether you see a + or - on the multimeter....just look at the value....8 volts or so is no good...0.1 or 0.2 volts is good !!
BTW thank you so much for all that help!
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From: Cape Coral, Florida
HVAC module gets fed by 2 power sources so it’s not the orange feed wire from the ignition switch…got to be the pink ignition feed possibly since the fuel pump is inop !!…you can hook the multimeter to battery positive and one of the test points on the fuse pump fuse…with key on see what voltage you have.
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From: North Gower. Ontario
HVAC module gets fed by 2 power sources so it’s not the orange feed wire from the ignition switch…got to be the pink ignition feed possibly since the fuel pump is inop !!…you can hook the multimeter to battery positive and one of the test points on the fuse pump fuse…with key on see what voltage you have.
Tested on the ignition switch: pink wire to ground shows 7 volts when key on.
Same 7v on the fuel pump fuse
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If battery voltage is 12.6 and you are seeing 7 volts you have a 5.6 volt “voltage drop”…there’s your problem !!…where was the multimeter hooked to ??…when I had a bad ignition switch a few years ago I knew in 10 seconds what it was…I cycled the key rapidly a bunch of times to clean up the internal switch contacts of some possible pitting and corrosion…the car then started fine but I changed the switch any way.
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So on the fuel pump fuse positive lead of multimeter to fuse test point and negative lead of multimeter to battery positive ??…or you checked each power circuit to ground ??…when you connect both leads to power you don’t have to subtract the voltage from your battery voltage…what you see is the voltage drop without doing the math !!…curious to see the voltages on injector, coil pack and MAF sensor…that pink wire feed a lot of engine circuits.
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Joined: May 2021
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From: North Gower. Ontario
So on the fuel pump fuse positive lead of multimeter to fuse test point and negative lead of multimeter to battery positive ??…or you checked each power circuit to ground ??…when you connect both leads to power you don’t have to subtract the voltage from your battery voltage…what you see is the voltage drop without doing the math !!…curious to see the voltages on injector, coil pack and MAF sensor…that pink wire feed a lot of engine circuits.
tested one injector port show 7v (6.94)
the coil pack receives full voltage (12.4v)
could it be that the fuel pump is toast and it`s dropping the voltage?
Last edited by biker_il; Jul 20, 2022 at 02:21 PM.
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From: Cape Coral, Florida
Moderator, Tech Contributor
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From: Cape Coral, Florida
Yes, you can test between IGN1 fuse 47 and fuse 13 (fuel pump) or PCM fuse 16 with key on or in start…I prefer the start position !!…if your multimeter leads are long enough or just test each point to battery ground and subtract that from your battery voltage.