Hi I have a 98 Dakota 5.2 recently replaced motor with same motor from a 97 ram 1500. I have checked my asd relay everything was good there have power where I’m supposed to relay tested good on my relay tester. The issue I’m having is I have no power to my ign coil which is giving me a no spark no run problem. I’ve replaced my crank POs sensor and fixed any bad wiring. Tried a test pcm from a 98 Durango 5.2 no change in problem. Checked all grounds and replaced main grounds at battery. Replaced power wire from fuse box to battery. Replaced lock cylinder and ign switch. Have fuel pressure at schrader valve on ds rail. Inspected harness from pcm all the way to the ds firewall. Can shoot either to it and get it to run momentarily but after either runs through motor she dies. Fuel gauge and oil pressure battery gauge works but that’s it no rpm. Engine temp is into die to bad sensor but that won’t stop from running. No lights in dash scan tool communicates properly. When engine was replaced the original motor blew #7 connecting rod cap off so I swapped all engine accesories onto my donor motor as well as the intake manifold since the connectors were different. Battery is a brand new interstate I’ve load tested it and charged it every time it’s been out more than a week. Read the cam shaft POs sensor could be a problem or pcm. If it was a pcm though wouldn’t the truck run with my test pcm or does that have to be exact pn/sn to work? Also haven’t rechecked timing but even if timing was wrong the truck should still run just run rough I would’ve thought. I am a heavy diesel mechanic and this is my first gas job motor swap I’ve done and it’s really humbled me haha. Any helpful insight or tips to fix this is much appreciated. Only light coming on in dash is Check gauges scanner showed a p0320 code before crank POs sensor was replaced but no codes since then. Motor was swapped back in nov 2023 and I’ve been tinkering on this truck on my free weekends when I’m not on a mobile repair call. Thanks in advance.

Original pcm

Test pcm from durango 98 v8

Test pcm from 99 Dakota v6



Vin

What truck started as

Truck currently

 

You will only have power at the coil for about 3 seconds at initial key on, and then when the PCM sees the engine turning. Does the fuel pump prime?

 

yes fuel pump has fuel bled fuel system at rail multiple times until there were no bubbles or aeration in stream. Truck has fuel pressure and compression. Truck will run long enough for either to pass through engine and has healthy engine turnover when cranking

 

Truck will run long enough for either to pass through engine

What does that mean???

 

If I spray either in the intake it will run long enough for the either to make the engine create combustion and then will die back off to not running just crank.

same way anyone sprays a shot of either on an engine that is hard to start.

 

You have a fuel problem then. Verify fuel pressure with a gauge, should be able to 'rent' one from your local parts store. While you are there, 'rent' their noid lights as well, to test and see if the PCM is actually pulsing the injectors.

 

The fuel issue will cause my spark plugs not to spark? I have physically removed one and held it to the d/s head while someone crunk it and saw no spark.

 

It runs on starting fluid, but not without it, that's a fuel problem. It's entirely possible you have more than just one problem though.

 

I’ll have to check my injectors this weekend according to my scan tool fuel pressure was good I have a pretty in depth scan tool I normally use on road tractors but it works on cars and trucks as well.

 

Should be ~45 psi of fuel at the rail. As mentioned, the ASD relay only provides power to the fuel pump, injectors, and coil for 3 seconds at key-on, and again above about 100 RPM. If the engine is spinning over and it's not sparking, then it's not getting a crank signal. But of it runs on starting fluid/ether, then it's getting spark of some kind to light off that fluid.

The other option is a grounding issue for the heads themselves preventing spark. The back of each cylinder head should have a 3/16" wide braided ground strap or a 10AWG ground wire that goes to the firewall. Without those, the engine is not grounded since the rubber engine and transmission mounts are not conductive. Likewise, the head gaskets aren't conductive and the head bolts are only barely conductive, so grounding the block doesn't do much. Heads themselves have to be conductive to ground to complete the spark path.