I need some troubleshooting advice. No start issue.

[JustinS1219]

So, I recently swapped out a 91 m20b25 for an 88 or 89 (still waiting for confirmation) m20b25 on my 91 325i vert. I replaced quite a bit of stuff on my new motor and it's now resting in the bay of my car. All belts are installed and tensioned properly, the fuel pump is pumping, spark plugs are getting spark, the CPS is plugged in properly and the main engine ground is installed and tightened! However, the engine isn't turning over. It cranks but won't actually turn over.

When my original engine took a poop could it have messed up my ECM? Are the ECM's from 88/89 325i's different from 91 325i's? The fuel rail that was on the new engine's intake manifold is different from the one that is on my old engine's manifold...would that make a difference?

If anybody has any advice or troubleshooting ideas please let me know! Also, if anybody needs more info please just ask questions and I'll answer them to the best of my abilities!

Thanks in advance!

[BigBillions]

id check the fuel rail connector diagram for both yrs to see if they are compatable. one guy did a swap and the wire harnees in the 88 was different from the 91 or reverse. anyway they were different and fried a wire in the harness that controls the coolant temp.

[Gregs///M]

Make sure the fuel inlet and return lines are not swapped. Easy to do that when swapping engines or fuel rails.

[jlevie]

As mentioned the first thing to check is to see if you have the fuel hoses crossed.

FYI: If the engine is cranking it is turning over. In this case it isn't firing.

[JustinS1219]

had the fuel lines mixed up...DOH! fired right up once they were switched!