Jump to content

5.2 Dodge Won't start


Recommended Posts

I have a 2001 Dodge Ram with a 5.2 that will not start. I have changed out the PCM, coil, plugs, distributor cap, cam sensor, rotor. It is also not showing on the Solus scanner any oil pressure. Replaced the sensor still no luck. Hooked up a gauge to the port shows 45psi cranking. Somethings missing but I don't know what, does anyone have any suggestions? ASD and fuel relays are testing good. Any help will be greatly appreciated!



Oh boy... Hmmmmmmm,


Do you have test equipment? Such as but not limited to:


Scan tool? If so which ones...


Spark tester?




Test light?


Fuel pressure gauge?


Propane enrichment bottle?




Pressure transducer?


Compression gauge?


Also do you have an information system to look things up? If so which ones...


It's Saturday. I am at the shop are you?


Ball in your court. I'll check back later. cool.gif

Link to comment
Share on other sites

Oh boy... Hmmmmmmm,


Do you have test equipment? Such as but not limited to:


Scan tool? If so which ones... Snap On Solus and Vantage, Auto Ingenuity


Alright then... When you hooked any of them up on a Chrysler product look to see if you have any codes. If so which ones? I don't like when Chrysler has a code they will put in a value for the PID that has to deal with that code. In other words the value being used is shown and NOT the true value. For example if you had a coolant temp DTC say open circuit. On any other vehicle but Chrysler I would expect to see -40F. With a Chrysler it will look at the IAT and mirror it during start up. Or you might see a value of 115F to maybe 140F.


With that said as an example I would like a PID scan. If there is a DTC that PID may not be real. Key on engine off before you even try to start the truck and if you have no DTCs then look at all values and compare to what you would expect to see. Some things would be the temperature. If this is in your shop and it is 60F then the IAT and ECT should be close. Another would be the M.A.P. I would expect something around 29 or 30 kpa. If you see something less I would be concerned.


Now if all those are good. Crank the engine. Do you see a rpm reading?


Hopefully you get the idea of what I would like to see.


Spark tester? YES


Good. Did you use it? If so did you have spark every other revolution of the engine. Not just spark when you turned the key on or off.



In this day and age you need one. I have many. DVOM's come with different options on different model. You need to be able to measure voltage, voltage drops, ohms, amps. and more. I would look into Fluke. If you want a couple different models I would be glad to recommend some depending on the use.


Test light? Duh...


Should I take that as a yes? If you are poking fun at me just be ready for the kick back. wink.gif


Fuel pressure gauge? YuP

Good and I see from your response to Jeff you used it. It's just when you started this request for help you failed to give us all your test results so we could make a decision on a path to try and help you. All I saw was a lot of parts thrown at this and it didn't help. It seemed to me(with all due respect) you didn't do testing, didn't have the equipment to do the testing, didn't have the info to know what you had in front of you, wasn't trained for testing and/or had a tech that was lazy in testing.


Do you have anything else you would like to share that you tested?


Propane enrichment bottle? NO


I would suggest getting one. Great test tool! You could flow a little propane into the intake to see if this would lite up for a second. In place of it some carb cleaner or silicone spray could do the trick. Be CAREFUL!


Labscope? VANTAGE


It'll do. Have you used it much?


Pressure transducer? ?? For the oil I used a manual gauge, if thats what you are asking


Nope. I was asking as I use one for doing compression testing. I can actually see the intake and exhaust valves opening during the compression test as well as I use it with the engine running in the spark plug hole for a running compression and snap throttle compression. We don't need it just asked to see if I wanted to see something. No biggie.


Compression gauge? YES


Good, did you happen to check any of the cylinders? If you didn't I wouldn't head there yet unless you said the engine cranks fast and easy.


Also do you have an information system to look things up? If so which ones... ALL DATA

Good. I don't have AllData but at least you have it for looking up specs. Does it cover the year of this truck?


It's Saturday. I am at the shop are you? NOPE closed shop for Thanksgiving


You posted on Friday and I read it on Saturday. Hope you had a good Thanksgiving! I would of been glad to help over the weekend.


Jeff- Fuel pressure is good, I have not checked the sync, but will let you know.




Looking forward to you updating with your test results. Hopefully I gave you some things to think about.



Edited by Spence
Link to comment
Share on other sites

Nothing yet to report, have not had a chance to get back on it.


BTW I do have a DVOM, didn't recognize the acronym, it is a Fluke.

I also have a Power Probe it is awesome for troubleshooting electrical issues.


I really appreciate you checking back


Thanks for not letting us hang.


Kinda figured you had a DVOM. Which model of Fluke?


I check in once or twice a day. If you get some test results I would look forward to hearing about them.


For starters do you have spark? Not only at the coil wire but at the spark plug too.


What is the cranking vacuum reading with the throttle plates closed?


Talk to ya later



Link to comment
Share on other sites


Here is the complete history, I did not include it because I felt it might cloud the issue.

The 5.2 in question has been installed in a 1990 Jeep Wrangler. We rewired the harness to integrate the OBD1 and OBD2 systems, since at the time of this swap no one was making a harness.


Ugh! I don't think it would of clouded the issue at all. If anything it might be some of the issue. I would of preferred you been more up front in the beginning.


The Motor is out of a 2001 Dodge Ram 1500 2x4, it was recently rebuilt and has about 50,000 miles on it. It was running fine when we removed it from the donor vehicle.


Ok... You have a good engine. That's a good start.


I am not showing any oil pressure on the scanner, but I can manipulate the sensor and prove it works fine. I also installed a manual gauge to verify there was oil pressure.


Good that you verified oil pressure. You know you are not good to hurt the engine. It's now an electrical issue. It shouldn't keep this from firing up. Do you think it will keep it from starting? If so why?


We have spark verified from the coil to the plug, it will pop off every once in a while like its trying to start, but thats it. If you add a shot of either/carb cleaner it does nothing.


Have you pulled any of the plugs to see if they are flooded?


What is the cranking vacuum with the throttle plates closed. This next step I want is important you follow it if you are going to use rely on the results. Keep cranking it for 15 seconds and what is the vacuum/pressure reading at the end of the 15 second cranking period?


We verified that the signal was coming from the crank sensor and replaced the cam position sensor. Today I am going to check for sync between the two.


If you had spark your crank signal is working.


I am also going to test for high resistance readings on the ground circuit, to see if our harness has any issues.


Do you know how to do voltage drop tests? If so check your grounds that way.



I do a lot of engine swaps. Ones that mate an engine that was never in a vehicle to a different one. Instead of trying to cross between two different fuel/ignition systems we install a stand alone PCM. We then do our own programming. You may want to consider that.


In the mean time which computer are you using. The OBD I or the OBD II? Which sensors are being used and are they of the system that the PCM uses?


Thanks for the update.






Link to comment
Share on other sites

  • 2 weeks later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Create New...