Starting problem

90DYNASTY502

MEMBER
1990 DODGE DYNASTY
6 CYL
FWD
AUTOMATIC
156,000 MILES

I have a 1990 3.3L Dynasty. Two weeks ago it died, started, died, started. Etc. Finally made it home and it would not start back up. Next morning it started up fine. As soon as the car got warm. It did it all over again.
Replaced Battery and alternator because they were old. Next tested my coil and sensors, which all need replacement. Replaced the cam sensor, crank sensor, ignition coil pack, wires and spark plugs. Inspected all ignition wiring and sensor wiring and found no damages.
Car ran and started great for about a day. Now the temp outside has dropped and been in the 20's all week and car starts and runs great. Oil pressure starts dropping after an hour of driving but car stays running fine. No engine check light has come on thru this whole thing but now car will not start till next day after started up and driven all day. I have checked the fuel pressure at the rail, checked for faulty fuel injectors and checked fuel pump, but all are fine. Engine is due for an oil change, vacuum lines are hooked up but car will not spark at all until the next day (roughly 8-12 hours). Other than replacing the computer or an already new (but possibly faulty) part listed above, where do I turn next? Possible relay problem? Please help. Tight on money at this point and we have only one car and a new born. Engine and transmission have both had full rebuilds within last 30,000 miles. Dont kno where to turn. Please ANSWERS!
Thanks,
Alex

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

Hi Alex. Welcome to the forum. The lack of spark is the first clue, but the ignition coil circuit is not responsible for most no-start problems. That falls on the trigger circuit, the cam and crank sensors. The next time you have a no-start with no spark, use a test light or an inexpensive digital voltmeter to measure the voltage on, (I believe) the dark green / orange wire at the coil pack or at one of the injectors. You can also test for that voltage on the two small terminal nuts on the back of the alternator. You will find voltage on all of those points for just one second after turning on the ignition switch. What's important is that voltage must come back during engine rotation, (cranking or running). If it does not, you would normally suspect the cam or crank sensors but since you already replaced them, you should be aware that the air gap of the crank sensor is critical. The new sensor had either a thick paper spacer or a thin plastic rib molded on the end to set the gap. If the gap is too large, the engine CAN start and run fine at times and stall with no spark, no injector pulses, and a dead fuel pump at other times.

The direction to go next depends on whether you find voltage on the dark green / orange wire during cranking. If you find it is missing during cranking, check for 5.0 volts feeding one of the wires to the cam and crank sensors. That feed wire will be the same color and stripe at both sensors. The 5.0 volts should be there anytime the ignition switch is on.

Caradiodoc