Engine confusion

Good afternoon folks,

After using the search, mr google and the service book. I still can't figure out what's going on with the truck. I have a 1996 dodge ram 2500 with the 360 gas engine. After having the compression test done, and it reading 80 on all but 2 cylinders. I had changed the motor out and it really needed a new heart anyways.

I got a 360 from the same year Indy truck. Good clean low mile engine. It went in with minor difficulty. The issue now is, when I try to start it, it'll start up just fine run for 10 or 20 seconds and die. While it runs the generator light comes on. I've double and triple checked the wiring diagram as well as, but can't figure it out. While I had the motor out, I replaced the crank sensor, wires, cap,rotor. pcm was reprogrammed 6 months ago. But with it being a different engine but same size do I have to get it reprogrammed?

Have you checked alternator output? The gen light comes on with no alternator output I believe. Or pcm power input from the gen. Idr if the pcm was the voltage regulator on those trucks or not


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Forget the battery light for now, the engine wouldn't start at all if the battery was dead, and battery can run the engine for a while without gen output.

The issue is the truck stalling after 20-30 seconds. The PCM if from 96-97 will work from either the 5.2 or 5.9 engine, but it won't run right unless its from the same size engine.

If it runs at all then we can rule out a lot of things that would cause it not to start in the first place such as the crank and cam sensors (they can cause stalling but usually they won't restart right away). When it is running does hitting the gas allow it to run longer or does it have no effect? What happens if you try to fire it up right away after stalling? Does putting it in gear change anything?

Make sure you're getting good fuel and that the IAC motor on the throttle body is functioning as it should.

Sounds like a fueling issue to me. If you've got the nifty Schrader valve on the driver's side fuel rail, stick a fuel pressure regulator (rated for fuel injection, of course) on it and watch it while the engine runs. It should read 45 +/- psi continuously while the engine is running. If it drops while the engine is running, you've got a pressure leak somewhere. Could be from a lot of places but the most likely place to cause such a drop while the engine is running is the fuel pump.

You say that your low compression prompted you to replace the engine. It's also possible that weak fueling may have aided the problem as well. I've learned that when it comes to old vehicles, there are often multiple weaknesses that augment the same issue.

As long as we're on the issue, are you using the fuel injectors from the old engine or the injectors on the new engine (assuming you got the new engine with injectors). It's entirely possible that the owner of the new engine swapped the injectors with "upgraded" variants, which, especially in a stock engine, is all a bunch of ballyhoo and will cause issues without very specific tuning.

Yeret said:

Sounds like a fueling issue to me. If you've got the nifty Schrader valve on the driver's side fuel rail, stick a fuel pressure regulator (rated for fuel injection, of course) on it and watch it while the engine runs. It should read 45 +/- psi continuously while the engine is running. If it drops while the engine is running, you've got a pressure leak somewhere. Could be from a lot of places but the most likely place to cause such a drop while the engine is running is the fuel pump.

You say that your low compression prompted you to replace the engine. It's also possible that weak fueling may have aided the problem as well. I've learned that when it comes to old vehicles, there are often multiple weaknesses that augment the same issue.

As long as we're on the issue, are you using the fuel injectors from the old engine or the injectors on the new engine (assuming you got the new engine with injectors). It's entirely possible that the owner of the new engine swapped the injectors with "upgraded" variants, which, especially in a stock engine, is all a bunch of ballyhoo and will cause issues without very specific tuning.

Click to expand...

The engine still has the same injectors that came with it. They were just installed with new o rings. The engine ran fine from the video that I was shown prior to purchase. It's unknown to me on if they were changed out for bigger or not though. I'll get a pressure tester tomorrow and have a go at it again.

dodge dude94 said:

Make sure you're getting good fuel and that the IAC motor on the throttle body is functioning as it should.

Click to expand...

Fuel was good, and the IAC seemed to be working well. But that's one other thing I can check out as well.

dudeman2009 said:

Forget the battery light for now, the engine wouldn't start at all if the battery was dead, and battery can run the engine for a while without gen output.

The issue is the truck stalling after 20-30 seconds. The PCM if from 96-97 will work from either the 5.2 or 5.9 engine, but it won't run right unless its from the same size engine.


If it runs at all then we can rule out a lot of things that would cause it not to start in the first place such as the crank and cam sensors (they can cause stalling but usually they won't restart right away). When it is running does hitting the gas allow it to run longer or does it have no effect? What happens if you try to fire it up right away after stalling? Does putting it in gear change anything?

Click to expand...

I had checked both the driver's and passenger side of the block, and it has 1996 cast into the passenger side and 360 cast into the driver's side. So that would lead me to believe that it's the same year and size of motor. When it stalls out, it starts right back up but still won't continue to run. I have to keep my foot into it to keep it running. When I put it into gear, it kinda chugs a bit then dies when I come to a stop to shift directions from reverse to forward.

crazykid1994 said:

Have you checked alternator output? The gen light comes on with no alternator output I believe. Or pcm power input from the gen. Idr if the pcm was the voltage regulator on those trucks or not


Sent from my iPhone using Tapatalk

Click to expand...

I can't keep it running long enough to get a voltage reading. But the battery is only 8 months old and it gets the positive disconnected each time I leave it for longer than a few days And gets a bump up charge after a month of sitting. I keep the negative hooked up. I had read that if you run it for 20 to 30 minutes, the pcm relearns? The last time I was out and working on the mule, I sat in the seat for almost 40 minutes and now it'll pop once in a while, but still won't stay running. It only "pops" while in gear.

I thought that the pcm doesn't relearn and make proper (or any) adjustments until and unless you're driving it around
'introducing it to variables' so that it can begin to make adjustments to all the different inputs received such as the increased flow into the air intake fluctuates as the coolant temperature rises all while the input from the up to four oxygen sensors are changing constantly. I thought the pcm (when new or rebooting) starts off in limp mode, then as it receives new , updated versions of information begins gradually upgrading itself to 'crawl, walk & finally RUN !!!! ) for lack of better metaphors . This was how it was the last two times I've replaced the 'brain'. Also, not sure about the Rams , but I last replaced the pcm in an '06 T&C van with 3.8L and manual told me to reset PCM by removing both terminals of battery,wait 30 seconds and touch leads to each other to 'reset' for just such occasions as an engine swap etc. NOT SURE IF YOU WANT TO DO THAT WITH A RAM TRUCK W/O ACTUALLY READING THIS IN THE MANUAL OF SAME !!!

Same procedure here

Kpearson said:

Good afternoon folks,

After using the search, mr google and the service book. I still can't figure out what's going on with the truck. I have a 1996 dodge ram 2500 with the 360 gas engine. After having the compression test done, and it reading 80 on all but 2 cylinders. I had changed the motor out and it really needed a new heart anyways.

I got a 360 from the same year Indy truck. Good clean low mile engine. It went in with minor difficulty. The issue now is, when I try to start it, it'll start up just fine run for 10 or 20 seconds and die. While it runs the generator light comes on. I've double and triple checked the wiring diagram as well as, but can't figure it out. While I had the motor out, I replaced the crank sensor, wires, cap,rotor. pcm was reprogrammed 6 months ago. But with it being a different engine but same size do I have to get it reprogrammed?

Click to expand...

Do you have your old motor still? You can salvage the IAC, Map/maff sensor, etc. from it and try replacing the parts on the engine. You might salvage the injectors, too and have them cleaned and new seals. Your pcm doesn't need reprogramming, the 318/360 engines are interchangeable between years--the pcm doesn't care when the engine was born and as long as everything plugs in, it should be okay. Is the CEL lit? Have you checked the OBD2 for codes?