Complicated spark problem on 94/99 Northstar engine

[olaf_sc]

Hello Folks,

I hope it's okay with some deep technical question of a rather simple problem - I have no spark when cranking (trying to start).

The background is that I have a 94 Concours (i.e. NorthStar Engine) which had a shot engine (rod bearing). Then to get a low milage engine I bought a 99 Deville long block.

Now as a long block they are rather different but according to my checks the short block should be the same. Hence I thought it was an okay thing to do. However the blocks are only nearly the same. Everything fits just fine old heads and valetrain along with all the old stuff around it. The only diff is the crank sensors they are of HAL type on the 99 while the old 94 has inductor type crank sensors (or what ever you should call them).

I used my old sensors and put them in the same place as the new once where (it's the same place as on the old block). The diameter is slightly smaller on the old one but that can just be solved with a o-ring holding it in place.

I now put the engine back in the car along with everything else and it was time for startup. Nothing - no spark at all.

Checked error (diagnostic codes) nothing (except for memory rest due to removing the battery). Checked that the ignition module had power - it had. Check resistance over crank and cam sensors - 1.5k on the cam and nearly 0 on the crank once. Checked if they produced any signal by using a volt meter and cranking the engine. Sure there is some sort of signal when you crank the engine.

Still no spark . Now what to do?

Question is the crank positioning teethes totally different in a 99 versus a 94? If not it should work to use the old sensors since they have the same length as the old once hence sit on the same distance from the sensor wheel on the crank. The hole in the block is also in the same position except that it's a tad bigger in the 99 since the sensors has a bigger diameter.

If it's nothing strange with the cranks sensor wheel what can it then be that makes it fault so I don't get a spark?

Even if there as differences and the sensors wasn't really in the right position whoudn't I get a spark but a crapty one at the wrong time so to say?

Very thankful for any suggestion, answer or tip to my problem.

Cheers Olaf

[zonie77]

There is a recent thread about the differences is engines and sensors. It covered this thoroughly.

[olaf_sc]

Just to clarify,

I'm using all old sensors since crank and cam sensor from a 99 NorthStar is incompatible with a 94 NorthStar igntion module.

However since I use a 99 NorthStar block (short block) I use a 99 NorthStar crankshaft.

Hence the big question is the sensor wheel is totally different preventing the old sensors from working at all? Is this really why I don't get a spark at all. Using a normal volt meter (sensitive type) I can visually see that I get pulses from both cam and crankshatf sensors.

Is there any way to force a spark on a 94 ignition module so you can check that the module is okay? Note: That before the engine swap the ignition module worked just fine.

And yes I have read the thread in regards to crank sensors but it really doesn't give me the answer if the sensor wheel is different. In my view even if the sensor wheel was different I would get a spark even if it was at the wrong time.

Cheers and thanks in adv Olaf

[olaf_sc]

More info

This is actually not a 99 engine - was a bit confused a 99 should have the same cranks sensors as a 94. It was sold to me as a 99 engine and it very much is but it's built Oct 99 hence it's a 2000 engine . This is why the sensors are different. Still the question is is the sensor wheel on the crank different? And is there a way to verify that the ignition module works, hence force it to send a spark.

Cheers Olaf

[zonie77]

This is the thread I was refering to. http://cadillacforums.com/forums/showthread.php?t=5919

bbob is usually on during the week and can give you more info. It seems that you may have incompatible parts.

[olaf_sc]

Hello

Thanks fot the tip, that was the thread I was reading earlier today before posting and also before realizing that it's actually a 2000 engine and not a 1999 engine. Bugger that the dude selling it didn't check what year model it was out of and just checked the date stamp. Anyway, everything actually fits externaly bolting 1994 parts onto a 2000 short block.

What to think of (besides the ignition) is:

Front cover slightly different
Main seal front different
Blancer is different
Oil filter holder sligtly different but still same (just different casting)
Threads for heads different the lower row starts further down in the block. You will need to use bolts from a new engine on the lower row and from a old engine on the upper row.

I don't agree that the position of the crank sensors are different in the block. The sensors it self are different and the hole is bigger and has a sligtly different O-ring configuration to seal them.

Now since the old bottom is junk can I mount a 1993-1999 crank in a 2000 block - i.e. is the bearings the same? If so I can buy new main and rod bearings and swap crank but keep rods and everything else in the block.

Naturally I will need my special o-ring to center the old sensors in the new block but that is relativly minor. The whole thing will not cost to much compared to go and get yet another engine.

Cheers Olaf

[olaf_sc]

Hmm, maybe not to much options what to do:

1: Buy a new (rebuilt) short/long block - but is it really the old sensor new crank that is the problem - if not they it will not help. Cost $2000 to $4000 depending on where and how - tips on where to buy it would be very helpful
2: Buy a second hand 1994 engine at the junk yard including everything - definitly work - but you really don't know what you get - may fail after a month - cost $2500/$3000
3: Maybe maybe I can put my old crank in the new block - cost $500 new oil, water, bearings, gaskets etc...

- In all not to fun since the car is to old to spend $$$ on - even if it's otherwise is a perfect (mint) condition 94 Concours.

Cheers Olaf

[zonie77]

That's a decision only you can make. I didn't see bbob on the board today. Wait a couple of days and see if he can give you more info on your options.