LS2 engine swap wont start - help

So i have finished the LS2 engine swap after 8 months of work I can't gt any spark and the engine wnt start. I have an LS2 motor out of a ’06 Corvette with a 58 tooth reluctor wheel . I have a Holley 750 carb set up so I had to add the 58 tooth MSD carb ignition system to make the switch over from FI. Anyway, the car won’t start. I checked and am getting 12 volts to the MSD box, an getting 12 volts to the coil packs (which I got used on the forum, could be an issue), but I get no spark at the plugs. So any ideas? What resistance should I read on the crank sensor, the cam sensor and the coil packs? I’m thinking that is the only thing that could go wrong. The crank sensor is new from GM, the cam sensor came with the engine. I am told the jumper cable to the cam sensor needs to be deleted for the MSD box to work right, because it seems to reverse the wires to and from the connector and have tried to start the car with and without the jumper wire, but didn’t make any difference.
Any ideas?

Che k the crank sensor, cools also be a bas crank sensor.... I've seen that happen on used motors... If it were the. Cam sensor it would at least sputter and try to start, but if the crank sensor is bad the car won't even get any spark.... Do you have a timing pill in the msd? It won't start unless it has one in for the first start.....

Also try hooking up the serial cable to the msd box and check to see what it sees it should at least show a signal from the various sensors... And it will confirm the msd is powered on and working

Paul - what MSD are you using? Mine was plug in play, meaning, I did not have to delete anything... I find that odd. 6012 unit.

Paul - what MSD are you using? Mine was plug in play, meaning, I did not have to delete anything... I find that odd. 6012 unit.
Yeah what jumper?

Should be 5 wires...

Power, ground, pink power, cam, and crank sensors......
And make sure you have chip in.

The jumper I'm talking about the the jumper cable that goes from down under the crank chaft pulley in a black curved bracket up the the cam sensor. If you look at the wires, they reverse as they make the run. A friend that put an LS2 in his Backdraft said he had to by pass that jumper to get his engine to run. But I tried it both ways and no spark. :(

Paul, double check with what Eric mentioned on the "chip" or "pill" -- ensure you have one in the MSD unit. It's been known to fool a few folks.

On the "jumper" -- in my LS3 with the MSD 6012, I did not have to do anything like that.

Thanks guys.
1) yes I have a pill installed
2) the crank sensor is new from GM so I'm thinking it should be ok does anybody know a restance check?
3) the cam sensor came with the motor, so it could be bad, does anybody know a restance check?
4) I need to bring my lap top home tomorrow and do the check out you suggest, good idea.
5) I'm getting 12 volts to the coils but it looks like no triger input, could be sensors.
Thanks guys

Any luck?

One thing that stuck in my mind.... What crank sensor do you have? I remember reading about 2 different types of sensors... Grey and black, and you needed the correct one for the msd to work properly, I can't remember details but it's worth a little research possibly.

Thanks guys.
1) yes I have a pill installed
2) the crank sensor is new from GM so I'm thinking it should be ok does anybody know a restance check?
3) the cam sensor came with the motor, so it could be bad, does anybody know a restance check?
4) I need to bring my lap top home tomorrow and do the check out you suggest, good idea.
5) I'm getting 12 volts to the coils but it looks like no triger input, could be sensors.
Thanks guys


Hit CTRL-ALT-DELETE and install a stroked SBF motor.

:sarcasmsign:

Will it turn over? Did you open up the front of the motor to ensure it doesn't have a broken timing chain?

Thanks for the ideas guys, except for the stroker FMC thought, I've had this thought a couple of times, but I'm where I am.
Yes I checked both sensors and have the correct sensor for the LS2.
Yes, I had the engine apart when installing the new cam shaft. It turns over and cranks fine on the starter, just no spark.
Tonight I will connect the lap top and see if it gives me any codes, like a dead sensor or a fried MSD.
Keep the fath.

The problem is that I am not getting any spark at any of the cylinders.
To trouble shoot, I have replaced both the cam and crank sensors (gray).
I am getting 12 volts to the MSD box.
I am getting 12 volts to the coils.
I am getting 5 volts to both sensors.
I have the step retard unhooked.
I have the MAP unhooked.
When I crank the engine, with or without the spark plugs, I do not get a tachometer reading on the lap top. Engine is turning over at a good speed.
I also get a “no crank signal” on the lap top. This is why I replaced both sensors.
I am getting ~ 4.5 volts return from the cam sensor. (using a multi meter, so don’t know how good that volt value really is) back to the box.
I am getting ~1.3 volts return from the crank sensor. (using a multi meter, so don’t know how good that volt value really is) back to the box.
I am only getting ~0.05 volts to the coil packs to fire the coil from the box (using a multi meter, so don’t know how good that volt value really is)
So, I’m stumped. The box is new, but can it be bad?
What else would you suggest?

Paul, I have not seen this addressed, so, I'll ask:

Have you checked to make sure the coilpacks are on the right way? This may sound silly, but if #1 is on #7, it could cause the car to not start.

Devin

Honestly, best bet would be to call msd support!

I wish it was that easy, I dont get any spark, so I'm not even close to running. I'll also try MSD again, but the last time I got put on hold and never got a person.

I got hold of the expert at MSD and walked him through the trouble shooting I did with all the voltages I had recorded at all the places in the system and he said "its the box, send it back and we will fix it or send you a new one". Life is good. (at least for now, we will see when the new box comes back).

Got the box back from MSD, installed it, cranked the engine.
F&*^, no spark and the same code "no crank signal"!!!
I guess its time to call MSD again.

Start at the beginning. Do you have a diagram for the MSD box?
12v, 12v switched, etc.
I had a crack in the switched wire and the motor would turn over but no spark.
Make sure your wiring is correct. Most likely something simple.

Start at the beginning. Do you have a diagram for the MSD box?
12v, 12v switched, etc.
I had a crack in the switched wire and the motor would turn over but no spark.
Make sure your wiring is correct. Most likely something simple.

Silly question but are you sure the engine has the reluctor ring installed? Only a couple things it could be.... Bad/wrong sensor, bad reluctor ring bad wiring harness or bad msd

You've already replaced the msd so youre that much closer!

You know there are no dumb questions when trying to trouble shoot. But yes, i can see the reluctor wheel when you remove the crank sensor, thats how i knew it was a 58 tooth wheel. Anyway, i went on JustAsk.com and spent a few hours emailing with Jeff the Chevy expert. He even had me measure the gap from the end of the crank sensor to the reluctor wheel teeth, should be between 0.030 -0.050". Mine was within spec. Anyway, i guess it back to the Chevy dealer to try crank sensor nunber 3, its got to be that. One interesting thing, he sent me a Chevy posting that talks about having to have the ECU mated to to the crank sensor some time when you change sensors. Chevy will do that on a stock ECU for $100. Doesn't help m much, but maybe MSD will have to do that to the box.

Engine ground wires?

i guarantee when you figure it out, it will be a big AHA/DUH! moment! the install is so bloody easy it can only be one of a few things!

I'm sure it will be one of those dumb things, i just wish I could find it. !!!!!!

I don’t want to celebrate victory before it happens, but…………………
After talking with the local nationally know LS2 engine builder (Mike), and talking to the GM Performance Hot Line and finally talking with the MSD expert while standing next to the Panoz we discovered that the return signal wire from the crank sensor had a break in the harness somewhere. The interesting thing is that the broken wire would carry 1.4 volts back from the sensor, but not the full 4.8 volts the sensor was trying to send, and as a result the box would not trigger the coils.
So, MSD is sending me a new wiring harness which should fix the problem. Because I was finishing the Chump Car and packing for the flight to Boston last night, I didn’t have the time to run a jumper wire from the sensor to the box to see it really will fix it, but I give it 99% that the new harness will cure the problem.
Like you said, once you find the problem it will be a simple item that was overlooked.
Good news is that I now have 2 new crank sensors. J

Told you it could only be one of a few things.... MSD, Harness or sensor

Good Luck

Well the new wiring harness fixed the problen and the LS2 is alive after 12 months!!! Now the next issue.
How much is too much oil pressure? I'm running 5W30 with a dry sump system and at 2000RPM it was pumping out 75psi. So is that too much and can you adjust the dry sump pump? I was unwilling to run it up for fear of over pressuring the bearings.
Paul

cold I see 75-85PSI... iot drops down to 65ish after its warmed up, and after a hot track session it might drop to 45-50psi

So i'd say its normal

On my old LS6 with the older version of the LS4 high volume pump running 10w40 I'd peg the oil pressure gauge when cold. Hot idle with that setup was in the 49-52 psi range.

On my current LS6 (new car) I run a newer version of the LS4 high volume pump with a 42lb relief spring (vs. 52 in the older one) and I still see a nearly pegged pressure gauge when cold, but now hot idle is in the low 40s.

This is with a wet sump through a Setrab 625 oil cooler. I'd say your oil pressures are perfectly fine, but I have no direct experience with dry-sump LSX setups.

Well the new wiring harness fixed the problen and the LS2 is alive after 12 months!!! Now the next issue.
How much is too much oil pressure? I'm running 5W30 with a dry sump system and at 2000RPM it was pumping out 75psi. So is that too much and can you adjust the dry sump pump? I was unwilling to run it up for fear of over pressuring the bearings.
Paul

Paul, I have run a couple of dry sump engines and 75psi at 2000rpm for a dry sump setup is very high. Dry sump setups are normally the opposite of a wet sump set up regards oil pressure. Whereas a wet sump has an initial high'ish pressure and rises to the relief setting early in the rpm, a dry sump is usually lower at idle and far more linear with pressure rise with rpm increase.

I would get the oil hot by running at fast idle and then do some oil pressure checks. My cars have usually only had 20 - 25 psi at say 1200 rpm and there after have had around 10 - 12'ish psi per 1000rpm, so around 50 - 60psi by 5000, 60 - 70psi by 6000 and 70 - 80psi by 7000 (with oil at race temp). My last car would be up over 100psi over 5000rpm if the oil wasnt up to temp but would drop back as the oil got hot to around 75psi at 7200 rpm. I had a big tank in the car and often got caught out with not quite having the oil hot enough by the time we got the green light........something to watch out for.

Adjustment is normally pretty straight forward, there is normally an adjustable pressure relief valve on the oil pump. Remember that each setup is a little unique so you may get different figures but the above should be ballpark.

Another thing to watch out for is if you adjust this, make sure it is properly secured. I have seen a number of racers lose engines due to the relief not being securely locked, backing off and actually coming right out of the pump. Problem got my attention as I have had a spin on someones oil at 125mph due to this exact issue!!

Good luck, Kel.

Thanks guys for the advice. Sounds like i need to get the package up to temp and se where I am, then adjust as required.:cool: