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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?

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    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 01:09 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 11:30 AM.

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    Quote Originally Posted by DebevecLJ View Post
    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.
    Ok, so after months of searching the web, I finally find someone with the same problem as me. I too have a 525LS3 connect and cruise with the 4L70 setup in a 65 impala ss that will not start unless it's hot or has another car jumping it.

    From reading your description, I need a bit more detail. Are you saying that you had a bad ignition switch that was possibly not sending enough voltage to the IGN/on wire to the ecu while cranking so the ECU was essentially shutting off as the engine tried to light off? I'm using the original ignition switch which is now 52 years old and may need to try your relay idea for that IGN lead on the ECU.

    Report back if I'm reading your reply correctly....but I think I may start in that direction anyway!

    Many thanks!

    Matt

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    Right now, I'm thinking that the old ignition switches from the '60's are just not built to handle the amperage of these new LS electronic packages. I've gone through two ignition switches and one ten amp toggle switch (hidden kill switch). The toggle switch went out quick (first day) and it actually melted. The ignition switches took longer to start giving me problems. The first one started giving me starting issues after about 3 months and was intermittent. After putting in the 2nd switch, it took 9 months before causing problems. It started OK if cranked within a few hours of using the car (battery fully charged??). Leave it overnight and in the morning it wouldn't unless you jumped it. At this point, I'm thinking that there is just too much resistance in these old switches and the current draw too high which causes the switch to overheat. I don't know what internal damage is being done to the switch since I haven't taken it apart. I put a single throw 70amp relay in the starter circuit. The car started right up with a battery that had been off the battery tender for a week and a half. The 70amp relay has 3/8 terminals on the 30 (BAT) and 87 (SOL - purple wire that was on SOL terminal on ignition switch). Put a new wire from your SOL terminal on the ignition switch to 85 and run a new ground wire to 86. 85 and 86 are 1/4" terminals. Make sure your wire sizes are big enough. I would use 10 or 12 gauge wire. I found the 3/8 female terminals I needed at O'Reillys. I also used a split 1/4" connector for the BAT terminal on the ignition switch so I could use that to run a new wire to the 30 terminal. Hope this solves your problem. Nowhere have I found anyone mention that you have to use a new late model ignition switch when doing an LS swap or add a relay to isolate the switch from the high current draw and maybe because most builders will put in an IDIDIT column with the ignition switch incorporated. I wanted to use the ignition switch in its original location.

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    Sorry, a bit late to the party. Adding a relay was absolutely the correct fix to route the load around, rather than through, the switch. Good spot on the discolored connector - it can be very tough to diagnose oddball electrical issues like this.

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    the only two wires I have going through the 52 year old ignition switch are a hot feed for the solenoid on the starter which works fine, and the pink IGN wire which should only be 2A or less which is a relay control circuit on the GM fuse block for the IGN/ECU relay. Now, if i'm wrong, and it truly is a 5A or 10A circuit that feeds the IGN, then yeah, this rusty worn out 52 year old ignition switch is likely not up to the task especially since it sat in the barn for 15 years!!!!

    I'm going to bypass the ignition switch and run a test to see if this is the issue. I'm crossing my fingers that it is and if so, a $10 40amp radiator fan relay will fit the bill no problem and take about 30-45 minutes to test, fix and tuck away all the wires.

    Many thanks to you guys for posting this up. If it works and we are ever in the same town, I'll buy the beers!

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    Be sure to add a spare relay to the tool kit in the trunk as they can also go bad.

    Either of you gents up to posting some pics of your rides? I am currently working on reupholstering the seats in a '68 Impala for a friend.

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    Jeff,
    Here's a link to a story with pics done on my car by Chevrolet Performance while I was at the 2015 Woodward Dream Cruise as part of Street Rodder's Autopalooza Tour.

    https://theblock.com/news/angie-larr...ec-s-61-impala

    As an update on the starting issue, I mentioned to a couple of my friends at a local hot rod custom shop how I fixed this long standing issue that nobody, including them had been able to nail down. The owner mentioned that American Autowire sells updated ignition switches make/model specific just for these kinds of applications. I called the American Autowire tech support line and was told that he was not surprised that I've been having problems since those switches were not made to handle the loads of today's heavy use of electronics and other electrical loads. I was able to buy an upgraded switch made specifically for my 1961 Impala that enables me to use my current lock set. I looks exactly like the original but has upgraded internals. I haven't put it in yet, but plan to do so soon. I'll remove the relay and use it as a back up in case I run into future issues.

    Matt,
    I'm curious to hear how your changeover on your '65 Impala went.
    pajeff02 likes this.

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    Damn... that is one pretty (and badass) Imp!

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