Gordonm

Looks cool as all he)) but it is not a runner, YET


As some of you know this LS swap has been taking forever due to life circumstances and so on. The car has sat way to long and this winter I vowed to finish it up. I did make a lot of progress but now it is stopped. I got a chance to day again to get moving but was about ready to pour gas on it and light it. I thought better and did not want the clean up mess.

Long story short the car has been running(poorly) for the last few years but not driveable due to a bad tune. It has been in/out of the garage many times. Short runs but it always fired right up even if it had sat for months. I had another car in for some work and was moving it in and out. It started giving me som etrouble starting. It would crank over fine just not fire. Couple of cycles on/off of the key and it would eventually fire and run no problem. So I sent the computer out for a much better tune. Install it fired right up and ran way better. Idled good and had some good throttle response. Now a few more starts and back to the same issue now it won't fire at all. Just cranks. Check all circuits and fuses and have power where needed. Good fuel pressure and fuel pump clicks on fine. I have a cheap ecm reader and I am getting an RPM signal. Tried some things the LS forums recomended but nothing yet. Going back and forth today with forum member F22 and he gave me some ideas with some different tools. So I have some more tools, electronic diagnostic stuff on the way. I did check and I have 12 volts at the injectors, but I have to see if I am getting injector pulse and or getting fire from the coils also. Just had to pull the cover back over it today and walk away again. I'm close to the end but tie and patience are wearing thin on this.

Not looking for anything just venting I guess. I know most of us have all been here and I have been here on many cars just have to work through it all. Fortunately the Cobra fired right up and the smell of gas, oil and burning rubber soothes the itch.

kanvasman

The vette is probably upset it has to share a garage with a FORD...Hoping the venting helped. It always does for me. And walking away always works. When I come back I usually start all over, even looking at the simple things. I had trouble with my L98 transplant and found out I had almost run out of gas sitting in the garage, starting and stopping it a lot with just a gallon or two in the new tank. Simple things. Don't give up. Think of the story you can tell when you finally figure it out.

Rescue Rogers

I know very little but for the experiences my neighbor had. He did a swap with similar symptoms. He reused the stock computer but not the tranny. Turns out the computer was looking for input from the tranny and would shut the motors power down to about 40% and half the cylinders. What are you using for a computer (controller)?

Gordonm

It is the stock Ecm that has been reprogrammed. I know the computer works because I have had the car running for up to fifteen minutes with no trouble. I personally know the guys who did the tune on it and they have done hundreds of these so I', not to worried about that. It is like a relay or circuit has gone dead somewhere. The wiring harness is from PSI and has worked fine before. Somewhere power is being dropped for some reason.

PainfullySlow

I have not the experience to offer advice on what to do about the car so all I will say is that your perseverance has gotten you to this point. You are almost at the finish line and just have a few things to button up to have your perfect ride. Perspective often helps me when I run into things like this.

Good luck Gordon!

Kacyc3

Is it wired up to show engine light if there is a problem?

Gordonm

Yes the Check engine light works but I have no codes in the ecm.

Some electrical diagnostic tools just arrived on my door step. I'll get back at it in the next few days.

F22

Now that you've got the tools, the first thing I'd do is check every single ground that comes off've that engine and wire harness. Then the voltages on all the inputs. That'd be a good starting point. Try to find a bad ground, just so you can see the Power Probe green led, flickering instead of being a solid bright green.

platinummaker

Hang tough. We’ve all been there. Kinda like raising kids, equally frustrating and rewarding, but always worth it.

platinummaker

Hang tough. We’ve all been there. Kinda like raising kids, equally frustrating and rewarding, but always worth it.

Gordonm

Will do. I have to pull it out of the package and get familiar with it then start checking grounds and such. Always like new tools.

Yea I can relate on this. I had just gotten my 2 kids off to college when divorce loomed in. I have now remarried a newer model but she came with 3 younger daughters. So I'm back in the kid raising role. Now you know where all my time has gone. Finding a few moments to work on the car can be difficult.

3X2

Do you hear the fuel pump run for 2 seconds with the key in the run position? Have fuel pressure? Spark?

Gordonm

Yes the pump primes and I have a gauge plumbed in the fuel rail right now. Have plenty of fuel pressure. Spark and injector pulse will be checked tomorrow.

3X2

Plenty fuel pressure as in 50-60 psi? Would a Tech2 work? I've seen reversed cam sensor wires cause a long crank/hard start/no start concern. I'd look at check, clean, and tighten all grounds. What series LS? Whose computer are you using? A C5 or C6? I can ask my tuner tomorrow for any thoughts on this. Some big cammed LS engine we've had to covert to speed density.

Gordonm

58 psi give or take a pound or 2The strange thing is the car has run fine before. Nothing has changed. No sensors or wiring has been removed. it used to start on 1 or 2 revolutions. Very quickly. Always did. About 6 months ago I had it backed out and went to pull it in and it just cranked. Tried to 4 or 5 times. Tried it one more time and it fired immediately. Pulled into the garage and shut it down fired right back up. Since then I have started it multiple times. Sometimes it fired right away. Others it would just crank. Let it set and it fired right away. This kept getting worse and now I get just cranking. Its like someone has a switch and if it wants it fires right away, or it just cranks. I'll check all grounds again for corrosion.

Stock 09 LS3 motor and ECM with just a tune on the stock ECM. It has a slight upgrade in cam and headers. Those are the only mods.

Richard454

Hey Gordon-

When it doesn't crank- give it a shot of ethanol. No fire- I'd look at the crank/cam sensor.

If you do have a start with the fluid--

Could be a bad regulator...-I had the issue with a bad o ring on my regulator.

The software I'm running can check for correct cam and crank signal-

Gordonm

I just changed out the fuel filter/regulator to no avail. It is showing plenty of fuel pressure while cranking. I’m also curious on the voltage while cranking. I have had some over on the LS forum say you need a good 12V while cranking and others say it will fire on as little as 8 volts wile cranking. Mine drops to 10.3 while cranking. Is this enoug to fire the coils and injectors? I don’t know yet.

I’ll pick up some starting fluid tomorrow and see if I get fire.

Gordonm

No injector pulse. The noid light does not light or blink while cranking. I am getting 10.3 volts while cranking. Spins the motor over easily. Don't know how much voltage is needed to properly run the ECU.

3X2

If battery voltage drops below 9.6 volts, even for a split second, it won't start.

Using a 2010 Corvette LS3 as my bogie, do you have battery voltage at each injector? Is there a odd and even injector fuses? These are powered through the powertrain/ign1 relay.

Whose harness are you musing? I deal with production based Corvette race cars, so some of the items I mention may not apply to any aftermarket stuff.

Gordonm

Yes I do have 12v at each injector. I am using an aftermarket PSI wiring harness. It has been working fine up until now. The only fuses are at the terminal block on the PSI harness. And I have checked multiple times voltage across fuses and while cranking. Getting power across all of them.

Let me check again voltage drop.

Ok with the POwer Probe it measures min voltage and holds it in memory. It went down to 4.8. while cranking for about 5 seconds I see on the screen it drops to about 8 then gradually comes up to 10.3 while cranking. I'm going to be real embarrased if it is a bad battery with a dead cell or something. It shows key off 12.4 volts and key on it goes to 11.9. Its not tha told but it has been drained a few times down to nothing. Its an Optima which I'm not real fond of