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LS3 Connect & Cruise Starting Problems

This is a discussion on LS3 Connect & Cruise Starting Problems within the LS2/LS3/LS4/LSx forums, part of the Vehicle Specific category; LS3/4L65E Chevrolet Performance Connect & Cruise with Speartech wiring harness to add cruise control We completed a pro touring build ...

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    LS3 Connect & Cruise Starting Problems

    LS3/4L65E Chevrolet Performance Connect & Cruise with Speartech wiring harness to add cruise control

    We completed a pro touring build on my 1961 Impala SS in April 2015. I've put 20,000 miles on it since traveling the country with it. On our most recent trip this summer we started experiencing starting problems. The engine will turn over as usual, but won't start. If you jump it with a battery pack it will start right up. And, it will continue to start up without any problems as we stop for gas, dinner, etc. Next morning, same issue. Cranks, but won't start. I've noticed that the voltage screen (have Dakota Digital VHX gauges) will show low voltage 8.9V-9.2V as soon as I turn the key on. I've changed the battery and have had good mechanics look at it. We've not been able to find any bad grounds or significant voltage loss. The last mechanic (auto restorer, racer, custom builder) I had look at it found that by turning the key on and waiting 30+ seconds before turning it over, the car will start. A couple of things to point out. Three months after the build I experienced a similar issue, in that the car would sometimes start right up and other times would crank and crank but wouldn't fire. It was hit and miss. My ignition switch was the original and was sloppy and wouldn't hold in the lock position. So, I replaced it and the problem was solved, for the time being. Another point is that I have a kill switch in between the ignition switch and the coils. A month after the build, on its first shake-down run, the toggle switch (10amp) failed (actually melted somewhat). We replaced the toggle switch with a heavy duty (50amp) and it's been operating fine. Does anyone have any ideas as to what may be causing this problem?

  2. #2
    Spaz is My Mentor SMWS6TA's Avatar
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    Is the VATs still enable on the ECM?

    Are you using the BCM? There are 3 (maybe 4) spots that over time crack the solder that can cause issues with starting, windows, alarm, and radio.

    Low voltage - check the wire on the alternator to the ECM - it's the thin single wire. Check to make sure it's not melted or has a bad connection. If it's intermittent it will not charge the battery.

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    Not using the VATs or the BCM. Battery is new as of July and the car cranks like there's no battery problem. All the diagnostics we ran on voltage drops and grounds turned up nothing.

    As we're driving and using the car, even stopping for a 2 hour dinner the car starts fine. Leave it sit overnight and try to start it in the morning and it will crank and crank but not fire. But, if you turn the key on and let it on for 30+ seconds it will fire right up. Or, if you put a battery pack to the battery terminals (battery is in trunk, but I have external posts underneath the rear quarter panel that I use) it starts right up without needing to wait.

    Prior to having this problem, we did install a II Much fuel venting system and use a non-vented gas cap because I was having issues with gas sloshing out and gas odor issues. But I don't see how this could have caused this problem and everything was fine for four months before this problem appeared. Also, there have been no error codes.

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    Spaz is My Mentor SMWS6TA's Avatar
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    Fuel regulator?

    I had this issue last summer. Drove me F'ing nuts. I replaced my fuel pump, filter, Racetronix wire harness...in the end the regulator was going bad. Hit a bump in the road, it would go out, hit another back on. Car sat nothing, try it 5 mins later worked fine.

    It was by far the most frustrating thing to find.
    Last edited by SMWS6TA; 12-07-2016 at 02:09 PM.

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    Thanks for the help. Next thing I'm going to check is the fuel pressure at the rails and see if it bleeds off over time when the engine is off. I'm thinking there is a check valve somewhere in the line. Beyond that, I'm still looking for more ideas. Add another ground to the ECU? The thing that keeps bothering me is that if I wait that 30+ seconds before turning the key to start it, it starts every time. If I can get answer to that question, I think I'm getting closer to a fix.

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    Spaz is My Mentor SMWS6TA's Avatar
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    if ir does bleed down with the key on (not start) then check out the plastic fuel line for a crack.

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    I'm happy to report that I've found the problem, but embarrassed for being so stupid for not looking to the ignition switch again since we did melt the 10amp toggle switch right at the end of the build (replacement 50amp one still looks fine). The first ignition switch I replaced had no noticeable issues. This time, it's very apparent that the IGN terminal got very hot, enough to discolor the connector and wire. Now I'm looking for any info on putting in a relay or solenoid on the ignition wire (what type should I use, wire diagram, etc.). I'd like to be done replacing ignition switches.
    Last edited by DebevecLJ; 01-02-2017 at 12:30 PM.

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