QuestionQUESTION: Hi Roland.
The car cranks but won't start. I think I've gone through all the checks suggested in the book and have run out of ideas.
CEL only shows recently disconnected battery. A friend just checked the codes with his OBD reader and said it didn't show any.
What I've found is that there's no spark on the No. 1 cylinder (and No. 4, which use the same coil). The coil tests OK with a meter. A test light shows the connector from the PCM is not grounding the red wire. (The Haynes book says red is 3/6, but 3 and 6 are sparking, so I assume it's an error in the book.)
I moved all the relays around with no effect.
The camshaft and crankshaft position sensors test OK. At least I get 0.3V and about 5V when I turn the engine. The wires from the sensors to the connector on the computer look to be OK. The terminal numbers shown in the Haynes book don't match what I've found, but each of the sensor wires has a connection to the computer.
I think it's getting enough fuel. You can smell it in the exhaust pipe.
If four cylinders are getting a spark and there's fuel, why would it not run on those four? There's not even a hint of it wanting to start. So the spark is at the wrong time? Reading through some of your answers, I wondered if it's not a timing problem but an air/fuel mixture that's preventing the other cylinders from firing.
I found that the insulation on the wires at the crankshaft sensor was mostly gone. The wires were in contact and I suspected that was the problem. But I corrected that and it didn't make any difference. The sensor apparently wasn't damaged, as it shows 0.3 volts and 5 volts as expected when I turn the engine by hand.
I had the water pump and timing belt changed last week. I drove it four days, 150 miles, no problem. Parked the car Thursday night and Friday morning it wouldn't start.
Also, I put 10 gallons of gas in a nearly empty (1-2 gal) tank Thursday night. But it drove home, 25 miles, OK.
I think that's all the clues I have. Hopefully this gives you some ideas.
Mike
ANSWER: Hi Mike,
I assume this is an LH body vehicle.
The '94 Chrysler manual does show the red wire on pin 18 of the pcm (which changes to red/yellow at the spark coil pack) does fire plugs 3/6. The black wire at pin 19 of the pcm fires plugs 1/4. So I don't understand how you can not have 1/4 firing when 3/6 wire is apparently the one not being grounded. It is possible but doubtful that the wiring colors changed between '94 and '97, but I think that unlikely. The primary winding of the coils should be 0.45-0.65 ohms, and the secondary winding should be 7,000 to 15,800 ohms (In the absence of codes I do agree that it could be a fuel/air ratio issue (and that for some reason you also aren't getting spark on 1/4).
My favorite candidate for a no start/no codes situation is the exhaust gas recirculation valve being stuck slightly ajar due to being gummed up where the stem enters the valve body. So take a close look at that valve and try spraying some WD-40 on the valve stem where it enters the valve body, then move the stem back and forth with the tip of a screwdriver inserted in the slot of the valve stem. The internal spring-action should shut the valve to a dead stop.
I suppose it could be that the cam sensor is not sensing the slots for the one and four cylinder location points but the sensor itself is OK. That might be due to the tip not being in close enough contact with the surface of the cam. You might try a new paper spacer on that sensor tip and then push down until it contacts, when reinstalling it.
Let me know if this is helpful.
Please read the PS below and respond to it.
Roland
---------- FOLLOW-UP ----------
QUESTION: Yes, the coil resistances checked OK.
The 1 and 4 cylinders definitely show no spark, and the black and white wires definitely receive the ground connection. I'll look at pins 18 and 19. I don't have my notes here, but want to say I traced pins 2, 3, and maybe 11 from the PCM to the coil.
I've never looked at the EGR valve. Not sure I even know where it is. I'll find it in the book and do as you suggest. Perhaps it's two unrelated problems coincident.
LH body? I'll confirm.
Thanks Roland. This gives me a few more things to try tonight.
ANSWER: Yes, pcm 19,17,18 are to sparks 1,2,3. The egr is at the rear of the right cylinder head and has a small diameter exhaust pipe that runs to it. It could be contributing significantly to the no start. The LH is the New Yorker/Intrepid/Concorde/LHS/Vision.
---------- FOLLOW-UP ----------
QUESTION: The diagram in the Haynes book agrees, 19, 17, 18. But when I traced 1, 2, 3, at the coil connector back to the PCM they went to 11, 3, and 2, respectively. But in any case still no spark at 1/4.
After moving some things out of the way I could view the EGR valve. Due to the location, I didn't remove it, but did apply vacuum to the hose from the EGR transducer and the valve moved freely every time. I don't know if that means it's fully closing, as you said. There's power to the connector at the transducer. Out of curiosity I took the transducer apart. The large rubber diaphragm is fine. There's 35 ohms resistance across the solenoid terminals.
What would you suggest next?
Could the timing belt have jumped during start-up? I'm wondering if it's coincidence that this happened days after having the belt changed. And how much could the belt move without things hitting? So perhaps that's not an explanation.
Mike
AnswerHi Mike,
It appears that the pcm pin assignments for the coil driver wires were changed in the '97 model (and possibly the '96 as well). Does the pcm have 2 40-pin plugs or 1 60-pin plug?
But if you show continuity for the 1/4 coil wire but get no spark on those plugs then presumably the sensor is not picking up the slots on the cam sprocket is all that I can suggest or the 1/4 coils are bad. Try sensing the output voltage from the cam sensor and be sure you see (1,2,3,1,2,no) pulses in that order as you turn the engine crank 2 full rotations. That should cause all 3 coils to pulse properly if that is the case. You might see the coil driver wires ground out momentarily (at the coil plug) while you turn the engine by hand as a check on whether the 1/4 driver circuit is working, but that may require an oscilloscope and cranking over with the starter motor?
On the egr, just be sure that the internal spring action is indeed driving the stem to a dead stop, not to a point slightly less that dead stop if you can get the tip of a screwdriver into the slot of the valve stem.
I hope one of these tests will reveal the cause of your no start.
Roland
