Can?t start my '96 minivan: no starter action

QuestionEdit

QUESTION: Hi, Since a couple of days i can?t start my 1996 plymouth. radio, lights, heater etc. all goes on, but engine won?t even crank. I have replaced the starter relay, no good, I have connected battery + to pin 87 of the relay socket, engine cranks OK meaning the starter is OK? I have disconnected the battery with no result. I have checked every fuse and those are OK. i have done a visual check on the cabling behind the steering wheel, all OK... I have no idea on how to proceed... any thoughts are much appreciated. `Best regards, Magnus from Sweden

ANSWER: Hi Magnus, May I ask the model of Plymouth and the engine size (L)? And do I understand correctly that the engine starter motor will not activate in the normal manner, and also that even if you by-pass the starter relay and jump the starter motor solenoid switch that the engine will not 'catch' and run, and of course that you have the ignition switch in the 'run' postion when you do that jump? Also can you tell me the vehicle indentification number so that I can verify the official model year and other aspects of the vehicle. Roland

---------- FOLLOW-UP ----------

QUESTION: Hi Roland. Thank you for a very swift answer! The model is : CHRYSLER GRAND VOYAGER (is does say plymouth on the back) it?s a 3.8L engine. I must confess, i did not test the jump with the ignition switch in the run position. I suspect, since the starter is trying as normal the engine would start... although that is still to proove. To the point is that my 2 year old son climbed up the driver seat while my wife unpacking the car. The key was not in the car, engine was shut off but nevertheless after that event this started... what could he possibly have done to cause this??? (a bit embarassing I must confess) ID number is : 1P4GP54L5TB159953 also, before this the "service engine soon" lamp was lit, now it isnt... Thank you for your time and effort,

ANSWER: Hi Magnus, Let us assume that the issue is purely related to the starting circuit and straighten that out first. The power that the starter relay controls comes out of fuse 5 (40 amp) in the power distribution box and so you should find there to be 12V on pin 30 of the relay socket. The power to control the relay's actuation coil comes from a solid state fuse (positive temp coefficient device) #10 located in the fuse box that is under the dash on the bottom row. It should show 12V when you turn the key to the start position. The actuation coil is grounded by the engine control module when it receives digital information that the key is in the start position and that the gearshift lever inside the transmission is in either park or neutral position. It is possible that the shifter in the cabin is slightly out of adjustment so try moving it to either side of the P or N position to test that possibility. If the shift position sensor in the transmission is in the P or N position and the ignition switch is moved to the start position then you should hear the relay close. So have your wife do that while you touch/listen to the relay to see if it clicks or not. Have her move the shifter off-center slightly on either side of the detent positions. The ignition switch start position voltage output depends upon fuse 10 in the box under the hood and a regular fuse 2 in the box under the dash. Its output goes to the transmission control module which then combines that with the trans range sensor position and send the "ok" to the engine controller to ground the starter relay coil. Let me know what you find from checking over the fuses/voltages/shifter. On the check engine light, try to get a fault code readout using the ignition switch:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the check engine light, which should remain 'on' to see it begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat the process to be sure that you have an accurate set of flash counts. Let me know those counts and I'll let you know what the code is and what to do about it. When you disconnect the battery the fault code is erased so that may explain why it is no longer 'on' when you are driving the van. But it will come back when/if the controller sense there to be a fault. Do the readout then. Roland

---------- FOLLOW-UP ----------

QUESTION: Hi Roland, thank you for your detailed answer. I have tried to follow your instructions and yes, I have 12V on pin 30 in the relay socket. The relay also do a distinct "click" when i turn the ignition key to start. although, what I find a bit strange is that I cannot measure any volts through the fuse no 10 (ignition) under the dash. it looks OK but I changed it anyway, no result. It does not change when I move the shifter slightly. As for the check engine light, the code it gives is 1255, I have repeated the procedure 4 times just to be sure. however I cannot find the 1255 when I google it... Any help is very much appreciated.

AnswerEdit

Hi Magnus, I just noticed that when you asked the question in the beginning that you said the starter motor was turning over the engine when you jumped to pin 87. Now it doesn't. Now you have replaced the relay, and the relay is clicking which is just like a jump to 87, and as well you have verified that there is 12V on pin 30 of the relay which provides the voltage to 87 when the relay clicks. It may be that the battery is too weak to turn the stater motor. But since we are pursing the situation with the wiring of the starter motor let us finish this part of the troubleshoot. The 12 and 55 codes are unremarkable: the 12 means the battery was disconnected sometime in the past 50-100 key on-off cycle so only it that hasn't happened would I be concerned about that. The 55 means that all the codes have been shown. If the relay is indeed clicking then fuse 10 is ok, it would only show 12V when you put the key to the start position so that would explain why you didnt get volt reading. The next step is to go to the starter and verify that the brown wire there shows 12v when a helper turns the key to the start position which would verify that the relay is indeed passing through the 12v from pin 30 to pin 87 of the relay and then on the brown wire to the starter brown wire at the starter. If it is then you would expect to hear a loud click from the starter solenoid/switch. If you don't, then I would believe that the starter solenoid is not working. That solenoid is what applies the high current coming down the red wire to the starter motor proper to make it rotate. If you do get a loud click from the solenoid switch but no action from the starter then I would believe that the brushes inside the starter are not making good contact with the commutator inside the starter. You could try tapping on the side of the starter with a hammer while the helper does the start key positon to try and 'jar' the starter to make contact at the internal commutator/brush interface and start to work. If that doesn't happen despite the loud click then I would check to be sure that the fat red wire is in good condition at the + post battery clamp and at the other end at the starter motor attachment point. But don't do anything with that wire until you disconnect the - post clamp from the battery to be safe from accidentally shorting the red wire to ground which would put you at risk to a burn. If the red wire is good, the solenoid clicks, and the hammer doesn't do the trick, then the starter motor has gone bad and needs new brushes and a commutator refurbishment, something typically done a rebuild shop, OR the battery is now too dead to operate the motor as it did when you jumped to 87. Roland