QuestionQUESTION: Hi Roland,
You were a great help to me before. I have another problem. My wife was driving home from the store last week and the engine of our 1999 Chrysler LHS (3.5L) just turned off while she was driving down the road. I think it might be the timing belt because I have over 150,000 miles and it has never been replaced. Is there an easy way to diagnose my problem, or at least rule out other possible issues like fuel delivery and spark? When I turn the key, the engine cranks, but doesn't start. I don't see any way to view inside the valve cover to see if the lifters are moving when the engine is cranking and I cant find the schrader valve on my fuel rail to check fuel pressure. Any thoughts?
ANSWER: Hi Darin,
Did you check for fault codes using the ignition key:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time? Then watch the odometer to see if the reading changes to show any 4-digit fault codes.
A way to check the belt would be to check for compression at one of the cylinders. If it sounds like it always sounded when cranking it over the chances are good it is not the timing belt.
Usually when it simply dies, the cam or crank sensor has failed, and those would be a 0340 and 0320 code, respectively.
On fuel, just listen for the fuel pump, which should run for about a second or so when you turn the key to the run position, the sound coming from within the fuel tank.
You can of course check for spark by removing a plug with its coil and then ground the shell of the plug and have a helper crank while you observe for spark.
But the code search is the first place to start.
Roland
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QUESTION: Okay Roland, I did the fault code check with the following results. 1684, 0700, 0703, 1391, done. What do you think?
ANSWER: Hi Darin,
It apparently is not the timing belt.
The 1684 means that sometime in the past 50-100 key cycles the power to the pcm was disconnected. If you can't recall disconnecting the battery then check the battery cables and the ground points of the - clamp wire.
The 0700 says there is a specific transmission code also stored, which apparently is the 0703, which means the brake switch is stuck on or off, or the sensing circuit that monitors it is not working, so check the brake light function. It has nothing to do with the no start.
The 1391 means EITHER the cam or the crank sensor is intermittent, but doesn't say which. I would suggest that you check the voltage pulsing of both sensors to see if one ot the other isn't as expected. The easiest place to do that is at the pcm plugs, where if you will probe through the insultation with a fine straight pin you can connect with the wire proper and then clip your meter to the pin. The common sensor ground wire is on pin 43(black/light blue) while the cam sensor pulse would be measure between pin 43 and pin 33(tab/yellow) while the crank pulse between 43 and pin 32 (gray/black). Turn the ignition key to 'run' then with a socket and ratchet on the crank pulley bolt turn the crank by hand and watch for voltage to pulse betweee 5 and 0.3V several times per revolntion. Ideally one or the other of those reading will not show the pulse so that would be the sensor to change out.
Roland
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QUESTION: Hi Roland,
I am back working on this problem with my LHS. I went ahead and replaced both the cam and crank shaft sensors, with no change. I thought maybe it could be the ASD relay, so I switched it with the Windshield Wiper relay, but it didn't help either. I am stumped. If it was my timing belt, wouldn't I hear some banging of the pistons and valve stems? Any thoughts?
AnswerHi Darin,
I would believe the cranking sounds would be much different if the belt were broken.
The 1391 code speaks of there being intermittent sensor output signals. I would be inclined to do the measurements that I proposed in my last answer. All you need is digital voltmeter and some straight pins to pierce the insulation and contact the wires. That way you will know if the sensors are putting out pulses or not.
Of course you could also check for spark which is an indirect test. If you have spark then the sensors are good and the timing belt is working.
But if you only show a 1391 I would be inclined to check the sensor signals directly which if you found them would remove that code as the cause of the no start.
No start with no codes but having spark would suggest a mixture issue such as an inaccurate MAP sensor or an egr valve that is sticking slightly ajar.
Please let me know what you learn.
Roland
