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Odd electrical loss on LS1 swap after 100miles

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Old 05-17-2018, 02:43 AM
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Unhappy Odd electrical loss on LS1 swap after 100miles

THANKS in advance for this semi newb question.
My car has been running great and I finally have it plated for short test drives. I've put about
60 miles on it in about 4 trips. never an issue.
(1976 Trans Am, LS1/4L60E, Painless Harness.) (Started as a 79 shell roller)
Yesterday I cranked the key - and after engaging, but before firing up, my thumb slipped and the key
released a little off of "start" and I cranked it over right away to start again and everything died.
Not even courtesy lights or brake lights. Like the car didn't even have a battery.
I've checked and replaced every relay, fuse and ECM fuse and checked
every ground except what's on the starter.
I also disconnected the battery overnight hoping for a "reset" on the ECM. (?)
My battery has 12v (didn't kill a cell), there's 12v power going to the relay, switch and
interior connections...until I turn the key, then everything dies.

Today, I pulled the column, starter switch and again checked every fuse. I have all power, even radio, dome, etc
until I engage the key, then it all turns off until I release the key. That's better than yesterday but still no joy.
I don't hear the fuel pump priming.

I thought about a new ignition switch, or new battery, or even key switch
(I just rebuilt my column and am still not pleased so I ordered a new column that will come with a new ignition switch).

Does anyone have any suggestions?
Thanks,
Duff

After numerous internet searched for possible causes I'm stumped.
Could it be a fried ECM? a shorted wire somewhere, a ground I missed?
Starter solenoid?
Has anyone with an LS swap ran into this issue?

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Old 05-17-2018, 06:48 PM
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Bad ground, check your negative & positive battery cable connections at the battery. Clean your battery posts, I am confident it is a bad battery cable connection
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Old 05-17-2018, 07:14 PM
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Have to agree, first step on anything like this is wire brush the battery posts than fully charge the battery with an external charger.
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Old 05-17-2018, 09:34 PM
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Thanks, lizeek and Pop. Tried that this afternoon. Cleaned both ends of the battery ground cable and also checked for voltage drop
during cranking (minimal @ 1.2v). Battery stayed on a charger overnight and is holding at 100%.

The next two things I'm trying are replacing the ignition switch on the column and the starter solenoid.
After that I'm out of ideas.

I does seem the longer I wait the better the system recovers. At first EVERYTHING died out, but today the dome even stayed on during cranking,
and the fuel pump activates with the key "on". It's very confusing.
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Old 05-17-2018, 11:33 PM
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If you have a standard GM column with the key in column you may have a loose switch located about half way down the column. Note there is a rod running from the key switch to the actual electrical switch. That switch is bolted onto the column but may have come loose and slipped out of adjustment. If you can grab the switch and move it up and down the column it will need to be readjusted so that in the start position all circuits are cut out except the start/ignition.
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Old 05-18-2018, 09:12 AM
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Your symptoms sound exactly like what my beater Subaru did last year when the ignition switch died. Obviously it's a completely different platform, but I just thought I'd throw that possibly useless information out there.
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Old 05-18-2018, 09:46 AM
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You can turn the key on to where it kills everything. Then disconnect the negative battery terminal and get a multi-meter. Use the multimeter to jump between the negative battery post and the negative terminal on the cable.
If its pulling amps, you have a short and something is grounding somewhere. If its not pulling anything noticeable, then your switch is likely bad.
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Old 05-18-2018, 11:35 PM
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Thanks Joe, I'll try it.

So far:
Checked starter: OK
New ign switch: OK
all new relays/fuses
battery good: will check level again tomorrow
ground good: batt to block, block to frame, frame to body. (so far)

I'm worried my ECM has an issue, or crank position sensor?, or there's a mouse eaten wire
up under the dash, or something more serious. My nice organized wiring under the dash is now all pulled
out of of the loom. I can't remember if or where there's a fusible link other than the firewall maxi-fuse
I think I'll be pulling more wire loom tomorrow and checking every circuit for continuity.

I'm still seeking advice...until it cranks over I'm also still stumped. Things were fine until the double tap on starter.
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Old 05-19-2018, 02:14 PM
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Thanks for the tips, I'm getting juice from the negative side.
I just have to find the cause. I swapped out or checked all the usual culprits:
ign switch, starter, grounds (engine bay), and relays/fuses.
I'm going to work my way backward from the battery and try to trace it down.
I'll be unplugging all the unnecessary points one at a time (radio, lights, door locks,
seats, windows, etc.)
One thing I neglected to check is when I replaced the ignition relay
I may have installed a normally open relay in place of a normally closed relay.

What's puzzling is this is something sudden that happened, not an intermittent
issue. I feel like I broke something during the starter double tap.

I'm weak with electronics, I can barely read either one of my multi-meters.
I really appreciate all the help.
Thanks
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Old 05-19-2018, 02:31 PM
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I had something similar with my 98 S-10. It ran fine since new and one morning I started it to go to work and it sounded like it was going to turn over and WAM I lost all power. I took everything apart, I didn't find ****. I pulled the battery out and put it on a charger and it took a charge. I brought home the shop jump box......clamped it to the + and - cable a verooom it started right. Took the battery to Oriley next to the shop and they told me it was shot. I bought a new battery and it been running ever since. It's worth a try.
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Old 05-19-2018, 03:10 PM
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2Toeracing might be right, It doesn't happen often but a internal hard short can happen on a new or newer battery. Just testing voltage doesn't tell you much, The battery needs to be load tested.
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Old 05-19-2018, 09:17 PM
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Thanks, gents,
I bought a new battery and I still have the same problem.
I'm going to walk away from it for a few days (family and work responsibilities).
I'm on a mini vacation next week (I WAS going to final wet sand and buff the car but now??) so I'll come
back at it with a fresh pair of eyes. I've swapped out everything for new parts and added grounds but still no joy.
Some of the more unusual things I've tried:
-cleaning the mounts to the starter/block (Wasn't sure if starter housing is grounded..it didn't hurt)
-Tried hot wiring the ignition switch - did the same as before
-swapped for a new battery - didn't do anything
-unplugged everything not connected to the LS harness except the gauges so far, even the trunk release
-added extra grounds from the block to frame, (I still need to add an extra permanent frame to body ground)
-pulled the seats to be able to better look up under the dash (I'm 6' 2", I needed the room, )
-Pulled the console to check the neutral safety, back up light switch and a few grounds.t

Next time I work on it I'll pull out the LS swap harness instructions to make sure it's connected correctly.
I'll jog the starter to make sure the car will turn over manually
I'll look at Holley HP EFI if I get angry enough. I'm close now.

A few questions for anyone willing to answer:
Could I have fried my ECM? (I don't get any error codes on my reader, but the car's not running.
Could I have fried my alternator? would a bad alternator cause this kind of prob?
(I have a spare going on with an alternator relocation kit)
Could something mechanical cause this kind of issue, or a sensor? Like I wrote before,
it feels like something broke/happened/occurred that had never happened before. Things were fine for the last
year or more.

Last edited by Duffinatur; 05-19-2018 at 09:47 PM.
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Old 05-20-2018, 12:22 AM
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The ecm shouldn't control the starter, That should be wired to the original Trans Am wiring so if the starter isn't even turning the car over than that isn't ecm related.
Another thing you said that got me thinking, When you said "I have all power, even radio, dome, etc until I engage the key, then it all turns off until I release the key." Many cars are setup so that when you turn the ignition switch to the point that it powers the starter it also cuts powers from all other accessories so that the starter gets the proper amperage. So in the run position everything works and then you turn the ignition to the start position only the starter see's power.

Two things I would test. (1) That the wire going to the starter solenoid is getting 12 volts when the key is turned to the start position. If it is and you don't hear the solenoid clicking then the solenoid is likely bad or the connection is. (2) If the solenoid is getting 12 volts and is clicking but the starter is not turning the car over then you either have a bad starter or not getting enough power to it.

You can also pick up a 12v remote starter switch like this from Harbor Freight You hook one lead to the solenoid "S" terminal and the other to the positive on the battery. When you push the button it should turn over if the starter is good and has power.
It's harder to explain than to actually do it lol.
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Old 05-21-2018, 04:32 PM
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maybe i'm misunderstanding, so for clarification, is anything happening when you turn the key from run to start? does the starter solnoid click or the starter turn over?

seems common that we jump to what we don't understand or can's see in the box (ecm and wiring) but i would start with the basics first like the previous post mentioned

Originally Posted by LLLosingit View Post
Two things I would test. (1) That the wire going to the starter solenoid is getting 12 volts when the key is turned to the start position. If it is and you don't hear the solenoid clicking then the solenoid is likely bad or the connection is. (2) If the solenoid is getting 12 volts and is clicking but the starter is not turning the car over then you either have a bad starter or not getting enough power to it.

You can also pick up a 12v remote starter switch like this from Harbor Freight You hook one lead to the solenoid "S" terminal and the other to the positive on the battery. When you push the button it should turn over if the starter is good and has power.
It's harder to explain than to actually do it lol.
the other thing i've had happened is having a flywheel tooth break or the starter gear get stuck engaged. it sounds more like a starter solenoid issue...maybe the s solenoid wire was touching something hot and finally grounded out on that start attempt.
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Old 05-21-2018, 04:50 PM
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Nothing happens at all when I engage the starter except everything dies. When I release the starter, everything comes back on.
It acts exactly like a bad starter switch, except it's a new switch. I also had the starter checked at Napa and it checked out OK.
I haven't done anything yet today...bought a few new diagnostic tools safe for computer boards and a remote starter switch so I
don't have to have another set of hands. I'll be looking for wiring continuity and bad grounds, etc.
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Old 05-21-2018, 07:48 PM
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Originally Posted by Duffinatur View Post
Nothing happens at all when I engage the starter except everything dies. When I release the starter, everything comes back on.
It acts exactly like a bad starter switch, except it's a new switch. I also had the starter checked at Napa and it checked out OK.
I haven't done anything yet today...bought a few new diagnostic tools safe for computer boards and a remote starter switch so I
don't have to have another set of hands. I'll be looking for wiring continuity and bad grounds, etc.
I think your missed what I said earlier, When the key is on "run" power is going to everything and by design when you turn the ignition to the start position it's supposed to kill power to everything else but the starter. So you loose power to the radio and several other function while cranking. It's the way it done from the factory. What you need to do is see if you are getting 12volts to the starter relay when you turn the ignition all the way to the start position, If you have power that far then it's either a bad relay or the wire going to the starter solenoid is bad.
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Old 05-21-2018, 09:01 PM
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Originally Posted by LLLosingit View Post
I think your missed what I said earlier, When the key is on "run" power is going to everything and by design when you turn the ignition to the start position it's supposed to kill power to everything else but the starter. So you loose power to the radio and several other function while cranking. It's the way it done from the factory. What you need to do is see if you are getting 12volts to the starter relay when you turn the ignition all the way to the start position, If you have power that far then it's either a bad relay or the wire going to the starter solenoid is bad.
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Old Yesterday, 02:29 PM
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Originally Posted by LLLosingit View Post
I think your missed what I said earlier, When the key is on "run" power is going to everything and by design when you turn the ignition to the start position it's supposed to kill power to everything else but the starter. So you loose power to the radio and several other function while cranking. It's the way it done from the factory. What you need to do is see if you are getting 12volts to the starter relay when you turn the ignition all the way to the start position, If you have power that far then it's either a bad relay or the wire going to the starter solenoid is bad.
Just a quick update:
I only had a few minutes before work this morning so I quickly ran a remote
switch between the bat and start wire post on the starter and she fired right up.
(Thanks for the tip on the switch, LLLosingit)
no hesitation. It turned off with the key. I agree now the problem is probably the
starter wire or relays

SO: no mechanical damage or any of the other things I was worried about.

Now I just have to find the cause...At least I know what circuit to check when I get back at it tonight.
I may just remove and replace the starter wires and relays(again).
Thanks for the advice, gents.
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Old Yesterday, 03:30 PM
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You're welcome, At least you have it narrowed down and it's not something more serious.
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Old Today, 12:54 AM
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Sounds like the Park-Neutral switch is faulty or not adjusted properly
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