Stumped starting problems
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Stumped starting problems
2008 5.4
Drove the truck to taco bell, parked it for the night. The next morning, nothing when I turn the key.
This is what I have ruled out thus far:
Ignition switch, fuses, starter relay, pcm relay, neutral safety,starter, all wiring connected to starter.
This trucks driving me crazy.. I can supply 12v directly to the starter relay pin that goes to solenoid and get crank but no start.. I have fuel pressure on the rail, also checked spark on 2 cylinders. Nothing doing when it turns over.(with 12v jumper to relay). Will not turnover with key.Tried starter fluid, no luck,not even a backfire. Security system is functioning as it should.
How would I rule out the pcm at this point(no scanner) or even the ground pcm supplies to starter relay? Can I bypass that ground and ground it elsewhere. Any help would be much appreciated, I'm almost at a loss. Thanks!
Drove the truck to taco bell, parked it for the night. The next morning, nothing when I turn the key.
This is what I have ruled out thus far:
Ignition switch, fuses, starter relay, pcm relay, neutral safety,starter, all wiring connected to starter.
This trucks driving me crazy.. I can supply 12v directly to the starter relay pin that goes to solenoid and get crank but no start.. I have fuel pressure on the rail, also checked spark on 2 cylinders. Nothing doing when it turns over.(with 12v jumper to relay). Will not turnover with key.Tried starter fluid, no luck,not even a backfire. Security system is functioning as it should.
How would I rule out the pcm at this point(no scanner) or even the ground pcm supplies to starter relay? Can I bypass that ground and ground it elsewhere. Any help would be much appreciated, I'm almost at a loss. Thanks!
Last edited by Ckennedy1724; Dec 15, 2021 at 03:53 PM. Reason: Title
Hotshot
Joined: Jul 2005
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I can supply 12v directly to the starter relay pin that goes to solenoid and get crank but no start...
So how did you verify that the ignition switch is GOOD... Does it send 12v to the solenoid ? Besides sending 12v to the solenoid, the switch also turns on several other things ( fuel , ignition).
So how did you verify that the ignition switch is GOOD... Does it send 12v to the solenoid ? Besides sending 12v to the solenoid, the switch also turns on several other things ( fuel , ignition).
Logistics Pro
Joined: Jan 2001
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From: Central NYS
So if you turn the key to the “ON” position can you hear the fuel pump prime?
As Steve pointed out, the key turns on more than just the starter motor.
Or how did you rule out the ignition switch?
As Steve pointed out, the key turns on more than just the starter motor.
Or how did you rule out the ignition switch?
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Yes, I can hear the fuel pump prime, I even took the line loose at the rail and captured fuel in a bottle to have a look at it.Plenty of pressure. I ruled out the ignition switch with a test light. 12v coming in as it should and also verified 12v going out when key is turned to start.
12v is definitely making it to the end of the line before going to solenoid.....which far as I know is the starter relay. I'm getting 12v on the correct leg when key is turned to start.There is something keeping the relay from sending 12v to the solenoid.(I think) Thanks
12v is definitely making it to the end of the line before going to solenoid.....which far as I know is the starter relay. I'm getting 12v on the correct leg when key is turned to start.There is something keeping the relay from sending 12v to the solenoid.(I think) Thanks
Last edited by Ckennedy1724; Dec 16, 2021 at 04:39 AM.
Logistics Pro
Joined: Jan 2001
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From: Central NYS
Does the relay have battery voltage available?
Are the relay contacts passing current when closed?
Fleet Mechanic
Joined: Apr 2016
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Is the start relay picking up? The pcm supplies a ground to start relay if its happy with pats security system . It also pulses ground to injectors and plugs , they have 12vdc standing on them in run and start check that ..
Sounds like you are bypassing start relay to starter solenoid . You must have a working pcm with signals from crank sensor to hit plugs and injectors at the proper time .
You need to check all fuses ,the pcm has more than one feed , injectors have one ,plugs has one .It seems to me your pats is not satisfied , what is security light doing when you try to crank . The pats system is not bypassable .You must have a good pats key .
Sounds like you are bypassing start relay to starter solenoid . You must have a working pcm with signals from crank sensor to hit plugs and injectors at the proper time .
You need to check all fuses ,the pcm has more than one feed , injectors have one ,plugs has one .It seems to me your pats is not satisfied , what is security light doing when you try to crank . The pats system is not bypassable .You must have a good pats key .
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Update
Today I had a little time to mess with it again. I provided ground to pin 85 on the starter relay and it will crank with the key but not start. I don't think my truck has pats, the key I've used for several years is a regular key I had as a backup. Lost the original long ago. At this point without a scanner handy, I'm leaning towards the pcm. At least it's turning over with the key now.Can the dealership look up by Vin to verify there is no pats?gonna call in the am.Want to make sure previous owner didn't try and bypass. any thoughts would be more than welcome! Thanks in advance
Last edited by Ckennedy1724; Dec 17, 2021 at 05:58 PM. Reason: ...
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What do you think that flashing light is on your dash ? Its the pats security light ! Of course it has pats . Some one may have taped a pats key near the key transducer inside the column as a pats delete.
You can send your pcm off to a repair online and ask them to delete the pats program . But otherwise you can't delete or bypass pats yourself . It will not send a pulse to injectors or plugs unless pats is satisfied . Cranking is just one block feature . The pcm decides the timing and signal to the plugs /injectors .No way to fake that .
A pcm repair/delete is your cheapest way out of this . If you don't have legal owner ship it could get you in a lot of trouble .. After this fix a regular key will work . . It will be easy to steal . Paper trail will lead to you if not legal . . Involving dealer ship will be more costly .
You can send your pcm off to a repair online and ask them to delete the pats program . But otherwise you can't delete or bypass pats yourself . It will not send a pulse to injectors or plugs unless pats is satisfied . Cranking is just one block feature . The pcm decides the timing and signal to the plugs /injectors .No way to fake that .
A pcm repair/delete is your cheapest way out of this . If you don't have legal owner ship it could get you in a lot of trouble .. After this fix a regular key will work . . It will be easy to steal . Paper trail will lead to you if not legal . . Involving dealer ship will be more costly .
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Running
So, PATS it was. I found the transponder on a wire harness under the column. The previous owner had it somewhere I guess it came loose and fell.Started right up. Shoutout to redfishtd. Your information was awesome.
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Im having the same issue except mine is dumping fuel out of the injectors.
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