Spontaneous Power Loss

[Zombie666]

Good Day,

I have a cruise & connect kit for my 68 Chevelle. Its an LS3-525. As in the title I've been having complete power loss. Car starts great and runs great for about 15 ish minutes while driving then it absolutely loses power. Try to restart and there's nothing. I've never tried just letting it sit there for 15 minutes to see if it bails on me. I Wait for a bit of time and she starts but for only 15-20 seconds just long enough for me to put it in gear and punch it to get me to a safe place and wait for a tow truck

So here's my initial problem. I didn't realize that my starter had a builtin in solenoid, so during the build, I installed a remote one. I took the exciter wire from the ignition to the remote solenoid then to the starter. I've since removed the remote solenoid and have no issues with starting except right after it bails on me. Only time I have issues is if the car has been running for a short time.

Just before my car dies, I see some flickering lights in my tach gauge. Its those small yellow lights that start to light up as you approach redline. Then it dies. It won't turnover or nothing. My first thought was the alternator. I removed it and found it wouldn't start charging until 3000 rpm, so my battery was taking a **** kicking and ultimately replaced it. I have also replaced the alternator. Old one was only rated for 140A, new one is 240A. I checked voltage before and after replacing the alternator, before it was 9.8V and after trying to drive it, it was 12.8V which is great.

I got an OBD2 reader to check for codes. Never used one before. As soon as I plugged it into the DTC connector from the engine harness, the message that pops up says; "No powertrain DTC's or freeze frame data is presently stored in the vehicles computer". I'm assuming DTC means drivetrain codes?? So if that's what it means, I guess that's a good thing.

Its very very frustrating that after the car sitting for a bit of time, it starts. Its like it resets itself until it stall again.

Heeeeeeeeeeeeeeeeeeeeeeelp :) Anyone out there ever experience this same issue. Thanks in advance.

Perry

[dhutton]

Do you have a neutral safety switch?

Don

[Zombie666]

Don,

I do have a neutral safety switch and it works. Even when I put it back in park, engine will not turn over. I've checked all my grounds and they seem solid. I keep going back to heat being the issue. I built a rudimentary heat shield, started it up and the surface temp of the ecu got 124F. At 20 minutes the engine crapped out. I let it cool off and I used a large fan blowing on the ecu, started it up and at 15 minutes engine crapped out. The ecu is close to the headers, its 7". I am at a loss. My next step is to pull the ecu out far enough where heat will not be an issue. I have enough slack in the wiring harness. If that doesn't work, I don't know what to do other than get someone with a computer that can look into the ecu.

Perry

[dhutton]

Are those circuit breakers on the driver side inner fender? Are they self resetting after they trip? I would not expect a part like that to be happy with under hood temperatures. How closely are they running to their rated current?

Don

[dhutton]

Next time it happens measure the voltage on the output side of those circuit breakers. $10 on eBay, I don’t trust them… ;)

Don

[icemanrd19]

Location? Maybe someone local can help. Sounds like a electrical connection is getting hot and eventually resets after it cools down

[dhutton]

Also make sure the ignition switch on your steering column is aligned correctly and not on the edge of making contact.

Don

[Zombie666]

Don,
Yes those are circuit breakers and are a manual reset. One is for the starter and the other for the car fuse block. I will check the ignition switch for sure and voltage after the circuit breakers.

icemanrd19:
That's the same direction I've been heading in. If it was a loose connection (ignition switch) as Don mentioned, its very strange that at 15 minutes the engine shuts down and won't turnover or restart until it cools off some and then its good until it warms up and will shut down again. I'm not sure what could reset itself other than the ECU. I don't know if these LS ECU's have thermal overload protection. I did mention the ECU is quite close to the header. I have lost of slack in the wiring harness so tonight I plan on pulling the ECU out and have it dangle off the side of the car.

Thanks again for the help. Keep the ideas coming, I really appreciate it!!

Perry

[Hotwire]

I don't think your ECU heating would cause power loss @ the gauges and starter?

Do a nut and bolt check of all your main power connectors. If you're using the stock chevelle bulkhead connecter at the fire wall check the connections there as well.

[streetk14]

So when you say it won’t “turn over”, I’m assuming you mean it won’t crank. Or does it crank, but not fire?

If the engine dies and then won’t crank, it has to be some kind of main power supply or ground issue. Also, 12.x volts isn’t a good number; assuming you’re talking about battery voltage with the engine running. To me it sounds like a connection issue that’s influenced by heat. Could be a whole lot of things. If it’s reproducible (and it seems to be), get out a DVOM and start measuring.

My approach to this type of diagnosis is to step back and look at the big picture. If multiple systems are simultaneously having an issue, look for the common denominator. I’m not familiar enough with the GM crate motor harnesses to be much more help, but give us some more info and maybe we can pinpoint what’s going on.

[WTX806]

So when you say it won’t “turn over”, I’m assuming you mean it won’t crank. Or does it crank, but not fire?

If the engine dies and then won’t crank, it has to be some kind of main power supply or ground issue. Also, 12.x volts isn’t a good number; assuming you’re talking about battery voltage with the engine running. To me it sounds like a connection issue that’s influenced by heat. Could be a whole lot of things. If it’s reproducible (and it seems to be), get out a DVOM and start measuring.

My approach to this type of diagnosis is to step back and look at the big picture. If multiple systems are simultaneously having an issue, look for the common denominator. I’m not familiar enough with the GM crate motor harnesses to be much more help, but give us some more info and maybe we can pinpoint what’s going on.

Hello, my post count is low so I cant dm you. I'm interested in the holley screen.

Can you pm me a number or someway I can reach you at?

[streetk14]

Hello, my post count is low so I cant dm you. I'm interested in the holley screen.

Can you pm me a number or someway I can reach you at?

It doesn’t look like it’ll let me PM you either. Is that a new thing?

[dhutton]

It doesn’t look like it’ll let me PM you either. Is that a new thing? Either way, you can email me at BMWMD82 at gmail.
Did you get your problem solved?

Don

[streetk14]

Did you get your problem solved?

Don

It wasn’t me with the issue. I’m not sure where the thread starter went.

[dhutton]

It wasn’t me with the issue. I’m not sure where the thread starter went.
Oops… :)

[CarlC]

Might be a bit off base, but if the ECM is an Erod, everything must be connected and functional. That means all the EVAP stuff. If not connected the ECM will not allow the engine to make big power. The cure is to go into the ECM and turn off the EVAP's. We found this out the hard way on an Erod LT4.