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Engine Swap Woes

Hi, I recently replaced the engine in my 1999 Nissan Altima 5 speed. We ‘finished’ recently and when we went to crank it, sadly it would not. It has no spark. I purchased a used yard engine. We re-installed my perfectly working distributor from my old engine. What gives??! My mechanic pulled out the plug wires and grounded them and nada. Did we simply cross a couple of wires somewhere on the harness? We haven’t really had time to troubleshoot yet but id love to start on the right track. Could the old distributor have gone bad in the two days it was out of my old engine?

On another note, we had to drain the manual tranny of fluid to remove the front CV axles. After re-installing the axles the transmission starting leaking fluid! Is there a known vent on this transmission and we simply overfilled it? I put approx 3 quarts of oil in it. I’m pretty sure it wasn’t drained fully to start so that is what i’m hoping.

Thanks again for your excellent advice.

Is the spark triggered by a pick-up inside the distributor or is the trigger sensor located someplace else on the engine, like a crankshaft position sensor?? With today’s electronic engine controls, engine swapping is always an adventure because of incompatibilities in the engine control systems…

As for the transmission leak, you need to determine where it’s coming from…

I have no idea where the problem lies but the next step for your mechanic is a wiring schematic and follow the colors.

Hopefully the engine that was installed will actually work in that year model car and that the engine is also a good one; not one that has shucked a timing chain in a past life.

Yeah, I hope the timing chain or belt is not broken.

Just a shot in the dark, but does this Nissan have any kind of anti-theft system on it that would disable the ignition because there’s a different engine (and whatever peripherals/computers/harnesses) in there now?

Well, it does have a Security light, etc and I thought about that, but the light is sup to blink or stay on I believe while you try to crank it if the anti-theft system has disabled the car from starting.

When I swap engines that are in the same family (i.e., not upgrading from the stock 4-banger to a V6 or something) I swap engine wiring harnesses too. The engine harness that the original engine had is known to work with that engine - yours might be wired slightly differently, and lead to your problem. Unfortunately, the time to do this is when the engine is on the engine stand, because it’s a lot easier to access and see what you’re doing. You’re going to need to check all of the wiring, and make sure that it’s the same. If it’s different, you’re going to have to rewire.

Is the mechanic swapping the engine for you, or is he trying to diagnose the swap that you did? If it’s the latter, it might be easiest to yank the engine again to trace the wires - tracing wires under the hood can be very frustrating.

Today, good salvage yards keep engines, their wiring harness and the ECM that was in the vehicle all together as a package…This eliminates a lot of problems…

Any Codes?

One time I did an engine swap, I found out the hard way that the SENSORS are the most important part to make sure they are from the original engine. Even in the same engine class, the manufacturers make sensor and engine control updates year to year in some cases. So, with the donor engine out, this is the best time to swap over all the sensors from the old engine to the newer one and use the original wire harness.

As for the transmission leak, I agree with the others. Find out where it is leaking from first. Then, go from there.

The engine has a crankshaft position sensor mounted on the side of the engine. It could be that the used engine has a defective crank position sensor and that’s why there’s no spark. Try swapping the crank sensor from your old engine to the new used engine and see if she fires up.


Well we figured out the problem. The cable that connected to the distributor had one wire loose and coming out of the plastic sensor. We reinserted the wire and FINALLY we had SPARK !
Thanks for your help.

Thanks for posting back, glad you found it…With electrical problems, 90% of the time it’s a bad connection…