1996 Dodge Ram 1500 Full size van will not run
#1
09-14-2007, 12:40 PM
1996 Dodge Ram 1500 Full size van will not run
Ok, this thing has me stumped. I hope you can give me some insight.
Background -- 1996 Dodge Ram 1500 Full Size Van 3.9L automatic and about 60,000 miles. I left a job site and pulled out and while accelerating the engine died. No hiccup or jerking - just 100% quit. I have a Chilton's manual as a guide for the engine elctrical.
I have a Chilton’s book for the wiring and it seems to be accurate. I have a computer diagnostics software package and OBD2 adapter to check for codes and read sensor outputs - plugs right into the OBD2 plug just like any reader or scanner. I also have a logic probe for checking any digital signal outputs or digital circuits. And a volt-ohm meter of course. I have pressure and vacuum test equipment as well.
I have tested as follows -
Absolutely no codes (DTC's) of any type.
No blown fuses - under hood or in dash.
The engine will fire and run for about 1-2 seconds then shuts down if you crank for maybe 5-10 seconds at wide open throttle. If you continue cranking it is almost like it is just on the verge of running but just will not. I hold the throttle wide open to do this. I can not get it to fire unless I use wide open throttle. There is an output from the throttle position sensor (TPS) using my computer software. There is 5 VDC as supply power for the sensor.
Found low fuel injection pressure - Changed fuel filter in tank (not an easy job) and have 45-48 psig while cranking. Pulled injectors also to be sure they were not plugged. All 6 injectors firing and nice even spray of fuel. I am convinced it is getting fuel.
Checked crank position sensor and found completely open from 1-2, 1-3, and 2-3 contacts and a very small bare spot on one of the wires. Replaced this sensor. Still will not run. I thought this was the problem as I believe the engine starts on the cam sensor but runs off of the crank and cam sensor. I later on bench tested the crank sensor with a 5 vdc power source and logic probe and the sensor removed is working. So a working old sensor and a new one have been tried. Unplug this sensor and you get a code.
Checked cam position sensor and it seems to be ok. Unplug it and you do get a code. 5 VDC as power supply. Also note that the engine will fire - see above. Testing with a logic probe on the engine shows it is outputting a pulse.
The coil test ok for primary and secondary resisitance with volt-ohm meter. Distributor cap, rotor, and secondary ignition wires all look ok - did not do any testing with any type of test equipment. I have no way to bench test the coil. Using a gap type spark tester it does produce a spark.
MAP and TP sensors test ok. Removed the MAP sensor and bench tested it. Has 5VDC as power when on the engine.
Auto shutdown relay tests ok - switched it anyway with the horn relay.
Checked voltage to the primary side of coil while cranking -- about 10.4 volts - not 12 but should be ok and the engine will fire and run for about 1-2 seconds anyway. Also unplugged the O2 sensors as they are heated and on same circuit as the ignition coil. Spark plugs are firing and it seems to be a reasonable spark and engine does run for 1-2 seconds. The 10.4 volts while cranking is still there with the O2 sensors unplugged. I am not sure if this 10.4 volts is a problem because it does fire and run for a second or so. See above. I figure it is due to the power drain from the starter.
Have not checked the idle air control.
Have not checked for sync between cam/crank etc. as I have no tool.
I have not removed or disturbed the distributor in any way except to remove and replace the distrbutor cap after this problem occurred.
With only 60,000 miles I would expect the engine compression would be OK. It has not shown any difficulty in starting until this problem.
Questions -
Can these engines get out of SYNC without the distributor or crank sensor being removed? Engine has a metal timing chain - not a belt.
Is there a way to do a cam/crank sync without a DRB tool or some other expensive piece of equipment ??
Any thoughts on anything else I might check or have overlooked.?? I am thinking it must be electrical.
I realize it may be the computer ... but I want to be sure everything else is done before that step.
9-13-07 I received a used PCM (engine computer) today. I installed it and still the exact same problem.
Thank you,
DB <------ Dumb Butt
