5.2 crankshaft position sensor
#1
03-11-2005, 04:38 PM
5.2 crankshaft position sensor
Hi,
My '99 Ram Van 5.2 does not seem to pick up a signal for each window in the flywheel flex plate. If I put an oscilloscope on the sensor it shows an irregular train of pulses. Likewise a timing light on the coil output shows irregular flashing. Engine runs but lack power and is rough.
If I touch the flexplate surface and crank the engine the feeler moves in and out indicating an out or round flex plate. Dealer mechanic says replace the flex plate. Any other ideas?
Thanks,
Tom LaMers
My '99 Ram Van 5.2 does not seem to pick up a signal for each window in the flywheel flex plate. If I put an oscilloscope on the sensor it shows an irregular train of pulses. Likewise a timing light on the coil output shows irregular flashing. Engine runs but lack power and is rough.
If I touch the flexplate surface and crank the engine the feeler moves in and out indicating an out or round flex plate. Dealer mechanic says replace the flex plate. Any other ideas?
Thanks,
Tom LaMers
#2
06-25-2006, 10:31 PM
RE: 5.2 crankshaft position sensor
Problem has been researched and corrected. Removed old CKP sensor and mounted on a lathe with 5 volt supply and a flex plate in the lathe chuck . Ran lathe at about 1000 rpm and observed output of the sensor. At about .025 inches clearance the outpout would start to break up. Checked another sensor and it broke up at about .050 inches.
After talking to the Wells tech rep, Jim, found the normal clearance height is about .035 inches. and I knew my flex plate was runnng out about .010 inches. Purchased a new style Wells sensor SU3026 with the all plastic nose (no metal magnets showing) and measured its reading distance as .105" and installed it in the Van. Engine fired up perfecly. now runs on a 8 cylinders and has lost tendency to backfire when cold and make premature downshifts.
Clearly the old sensors were occasionally missing a few cylinders and failing to both inject and spark. Engine ran but without pep and was rough. This pumped excess air into the cat causing other cyls. to run lean or rich depending on open loop or closed loop. Also the CKP sensor pulses set the trans pressure regulator point so was causing early downsifts. There is apparently no built in diagnostic for this condition in the PCM but the factory diagnostic manual does give a test to be performed checing the number of CKP pulses per CMP pulse and this should always be 8 for the V8 and 6 for the other.
Tom LaMers
After talking to the Wells tech rep, Jim, found the normal clearance height is about .035 inches. and I knew my flex plate was runnng out about .010 inches. Purchased a new style Wells sensor SU3026 with the all plastic nose (no metal magnets showing) and measured its reading distance as .105" and installed it in the Van. Engine fired up perfecly. now runs on a 8 cylinders and has lost tendency to backfire when cold and make premature downshifts.
Clearly the old sensors were occasionally missing a few cylinders and failing to both inject and spark. Engine ran but without pep and was rough. This pumped excess air into the cat causing other cyls. to run lean or rich depending on open loop or closed loop. Also the CKP sensor pulses set the trans pressure regulator point so was causing early downsifts. There is apparently no built in diagnostic for this condition in the PCM but the factory diagnostic manual does give a test to be performed checing the number of CKP pulses per CMP pulse and this should always be 8 for the V8 and 6 for the other.
Tom LaMers
#3
06-26-2006, 12:07 PM
RE: 5.2 crankshaft position sensor
The situation you describe "to backfire when cold and make premature downshifts" sounds like what my RAM is doing when it is cold. I have a '96 5.2 4X4 RAM. It never does it when it is warm. In my situation, it would down shift when I'm acceletate quickly. It seems change gear normally, shift into fourth for a few second then suddenly down shift to third for a couple second then shift back up to fourth. I'M not noticing any backfiring. Maybe it is not related.
Pascal
Pascal
