LS Engine won't start

I haven't seen the wiring harness for an LS engine, but is there anyway that the firing order could be wrong? For example, the wiring to the banks switched? Otherwise, you could try looking for a short in the harness, which could cause more than one plug to fire.
 
Thanks for the suggestions.

I have tried pushing the accelerator pedal while starting, but it didn't make a difference.

Good suggestion on the harness potentially being swapped to the wrong banks. The GM harness does requires some modification. I confirmed that the color coded wires for both the injectors and the coils match with the appropriate cylinder number (Driver's side, front to back: 1-3-5-7, passenger side, front to back 2-4-6-8, where "front" is the drive belt side of the engine). I have not tried checking for a short in the coil harness. Would this be a short to ground? That being said, would a short in one of the coils prevent the others from firing? (i.e. even if only half the cylinders were firing, shouldn't it sound like it's at least trying to start?)

I have not removed the intake to see if the valve is open at startup. Should it be? I have not installed this kind of engine before, but on other carb engines, the valve has been mostly closed at startup.
 
Dave, you may try opening the throttle by hand and squirting some fuel into the intake manifold, and seeing if it starts, even if it stall right away. This would indicate a lack of fuel for whatever the reason may be. If it does run, would verify the mechanical integrity of engine and ignition system are working.
 
I think the PCM uses spark advance/retard and/or IAC/throttle blade movement to control idle/startup. If IAC or DBW have issues, stepping on throttle which may be all thats needed to get the car started may be doing nothing. However, you are not getting ignition at all so I don't think this is your problem after all. Plus given your code, I agree this could be bank/harness issue.
 
The GM harness does requires some modification.
What was changed? You probably have already, but I'd check every wire, for continuity and shorts to others, on any branch of the harness that was changed.
I have not tried checking for a short in the coil harness. Would this be a short to ground? That being said, would a short in one of the coils prevent the others from firing? (i.e. even if only half the cylinders were firing, shouldn't it sound like it's at least trying to start?)
A short seems unlikely, but if it connected the signal wires for 2+ coils together, you could be firing early. However, as you said, other cylinders should fire. I was trying to think about what could cause a firing to stop the engine from turning. Another culprit could be the position sensors - that's my best current guess.
 

marc

Lifetime Supporter
I am setting up a new LS 7, I haven't decided if this crate motor will use the standard computer or aftermarket. I do know that I will use an ITB intake and that will make for a more difficult setup. The LS 7 has a fly by wire TB, and will not work with a cable operated one. also you must use the correct accelerator pedal to operate the fly by wire. To get around this with the LS 7, Lingenfelter makes a 58 to 24(?) tooth electronic conversion for the motor to work with a 2002 camaro or other ls1 controller that is cable operated. Then you can use the racing pedals of the slc. the programming of the ls1 controller will need the program changed to accommodate the larger cubic in of the motor and the larger size injectors. there is other programming capable but that is for the good tuners to due. Do not use a corvette version controller as all are drive by wire (ctsv also). If you have setup with the correct DBW then the issue is somewhere else.

I have a HP tuner that I use on the CTSV so I know it will be "fun"
You need to read what is going on so if you don't have a tuning program you should get a cheap diagnostic reader. You should have already gotten codes thrown from not starting. Given how much you spent for the car I would get HP tuner. You should be able to con a programmer/tuner given that you are having him do a super car. and let him use a picture of it for his benefit. If you know what I mean.
 
Dave,

You should call Chris Delgado at 832-230-1094. He is the owner of D3 Performance Engineering located in Houston. D3 Performance Engineering (They also have a dyno in the shop) I know you have had trouble getting guys to your place. I think he will make the trip to you. This is a guy that will stand behind his work. He will be able to trouble shoot your engine and get it started. He tuned my old car and more friends cars than I can count. He also tunes cars for John Hynessey when they can't figure it out. He can also sell you HP Tuners or whatever tunning software you require.
 
Thanks for the responses guys and sorry for the long delay in this response.

The car is still not starting.

I acquired a copy of HP Tuners and have spoken to GM Performance Tech Support several times, but so far, everything we have tried has not worked.

The car sometimes throws a P0341 (Camshaft sensor) error and sometimes throws a P0016 (Camshaft to Crankshaft correlation) error, but all of the diagnostic checks pass, except for removing the engine and inspecting the timing chain. If the engine ran before leaving GM, then the timing chain shouldn't be the cause of the problem. However, one GM tech support person said that they run each engine before leaving the factory and another GM tech support person said they don't.

The easiest thing at this point is to replace the computer and hope that the fault lies there. Jeg's is sending me a replacement to try. If that doesn't work, then the next step will probably be to remove the engine and inspect the timing chain and the physical gear-end correlation of the crankshaft to camshaft.

In response to some of the other comments:
- The wiring for both coils and injectors has been double-checked by color code and cylinder position against the GM wiring table as well as a running Corvette.
- I have tried starting with the MAF unplugged (limp-home mode), with no effect.
- Spark plugs/coils/leads on both banks have been tested by pulling the spark plug and grounding it against the block while cranking to confirm a healthy spark.
- The butterfly valve on the intake is cracked open for starting and moves when the gas pedal is pressed. I have tried starting while pumping the pedal.
- HP Tuners shows an increment in the Camshaft Active Position Counter when I pass a screwdriver over the end of the Camshaft sensor, which seems to confirm that the sensor and wiring is correct through to the computer.
- HP Tuners shows the gas pedal position changing when the pedal is depressed, so the pedal sensor to the computer appears to be working correctly
- You can smell fuel when cranking. Fuel vapor was ejected from the cylinder when the spark plug was removed for the above plug/coil tes, so it's getting fuel and a previous noid test showed the injector firing at regular, expected intervals.
- I'm pretty sure there isn't a short in the ignition circuit, given that the plugs spark when held against the block. Even if there was a short between a couple of the cylinders, at least one should be firing at the right time, which would give better results than I am seeing. I'm also pretty sure there isn't a short in the injection circuit, as the noid tester flashed regularly when cranking and the short would have to affect all the cylinders to produce the current results.

Bottom line: I'm getting fuel, spark, compression and air. The DTC's are indicating a timing of spark issue and that matches what I am seeing in terms of extensive cranking with the occasional "phhhttt" as something tries to fire out of order and momentarily stops the cranking (loading up the starter motor with physical resistance).

The only thing left I can think of is a computer problem or an internal (e.g. timing chain) engine problem. Hopefully I'll be able to do the easy one (computer) in the next few days. If that doesn't work, it's time to pull the engine. If that doesn't work, I'll take you up on your suggestion to call D3 Performance (thanks, Dave).
 
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WOW...What a pain in the ass. I would be one pissed off customer. The few crate engines I've seen shipped completely dry and did not appear tested. My guess is that at best they test only periodically for QC. Hope the new ecu solves the problem, but given the codes, the apparent lack of issues with HPT, and ruling out limp mode in the old ecu, my bet, sorry to say, is with the engine setup/timing. I don't have any experience with this sort of thing, what's the likelihood they will take care of the parts you've replaced (sensors, battery, etc) trying to resolve what may be their mistake?
 
This is painful. Did the ECU, wiring harness and crate engine come from the same supplier? If so, they be getting it back as a job lot from me. You've been more than patient, for something that should be almost turn-key, IMO.

I hope that it gets fixed soon.
 
Latest update:

The replacement ECM didn't make any difference. After two or three 10 second cranking sessions, it threw the P0016 (Crankshaft to Camshaft correlation) error.

The compression is 210 psi on all cylinders.

I'm going to try once more with GM Performance tech support and some local experts before pulling the engine and opening it up; everything seems to be pointing to some kind of internal error; maybe with the timing chain or the pickup wheel for either the camshaft or crankshaft sensors.
 

Ken Roberts

Supporter
Just a long shot but perhaps a 24x reluctor wheel was pressed on the crank by mistake instead of 58x. Perhaps worth it to remove the sensor and look at the reluctor wheel.
 
How would I identify the type of reluctor wheel or cam gear? Is this possible while it is installed in the car?

In the case of the reluctor wheel, would I just count the teeth for one revolution of the crankshaft (is this possible to do accurately while looking through the crankshaft sensor hole)?
 
Question did you fit a new cam, if so check it was an LS1 stick identified by the reluctor on the rear end of the cam, if it isnt there you have a gen 4 cam and will need the gen 4 timing set so the ECU can figure out TTDC on NO. 1

kaspa
 

Ken Roberts

Supporter
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