No Start problems

[fdfbuilds]

Have a no start condition with my 2000 Dodge Ram 2500 Quad 4x4 Cummins Diesel (approx 545k miles I think...been a while since it was running).

 

Went through the “BLUE CHIP DIESEL – NO START TESTS”. Truck started when I hot-wired the VP44, which stunned me! 

 

But before the hot wire: initially had 12.7v on pin #7 of VP44 plug (with respect to battery…had the charger on the batteries) in “run” key position, dropped down to 12v while cranking (“start” position). Testing between pin #6 (ground) and pin #7, had 12.7v with key in “run” position…then in “start” voltage dropped down to 6v and fluctuated between 6v and 11v not coming back up to 12v until key was back in “run” position.  With negatives of both batteries disconnected, Fluke Mod 325 meter didn't register any resistance between #87 at the Fuel Pump relay and pin #7 on the VP44 plug (but in no-load condition...don't know how to do that).  

 

Had the ECM re-built by Car Computer Guys in November 2023.  I was having troubles with my PureFlow lift pump (RP-100). Subsequent to the ECM re-build, PureFlow replaced the lift pump on warranty.  Since my lift pump difficulties, fuel mileage dropped significantly (trips I was getting 19.5-20 mpg barely achieved 15 mpg).

 

The blue wire with red tracer was already cut & capped.  Even though I don’t remember doing it, makes sense I may have done that back in September 2013 while diagnosing another no start…turns out I had a bad Crank Shaft Position Sensor. 

 

I replaced the VP44 with a rebuild in August 2013 at 325k miles. 

 

Probably have more than one nail in my tire...so perhaps new VP44, injectors (they have 545K, original equipment), and???

Don’t know what to do next.  What are the next tests I should do?  Some helpful advise would be greatly appreciated!

 

[Tractorman]

I would double check Pin #6 (ground) test.  This test should produce a steady voltage.  I would use a test lamp with an incandescent bulb, if possible.  This will place a small electrical load on the circuit being tested.  Pin #6 is connected to Splice #168 which splices into two ECM grounds and an engine block ground.  Splice #168 has been know to be troublesome.

 

So, try retesting Pin #7 to Pin  #6 with a test lamp - ignition on for the first test, engine cranking for the second test.  The lamp should dim slightly, but remain steady for the engine cranking test.  If the test fails, then keep one lead of the test lamp on Pin #6 and connect the other lead to a battery positive post.  Note the results of the test.

 

Are there any DTC's stored?   If so, knowing what they are could help with troubleshooting.

 

Your high mileage injectors should be replaced.  The injectors are not the cause of your no-start, but you have gotten a good service life from them - time to replace them.

 

Using a multi-meter to check resistance at connectors is a common practice, but it has its limitation, i.e., a single strand of wire in multi-strand wiring maybe the only connection, which can falsely indicate that a circuit is good.  This is why I use a test lamp whenever I can - to place a small electrical load on the circuit during the test. 

 

- John