LS2 engine swap wont start - help

[Paul Buxe]

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.

[Paul Buxe]

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).

[Paul Buxe]

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.

[Fast Viper Dan]

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.

[eric1h]

Originally Posted by Fast Viper Dan

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!

[Paul Buxe]

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.

[Panoz26]

Engine ground wires?

[eric1h]

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!

[Paul Buxe]

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

[Paul Buxe]

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

[eric1h]

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

Good Luck

[Paul Buxe]

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

[eric1h]

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

[Cobra4B]

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.

[NZGTRA17]

Originally Posted by Paul Buxe

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.