1999 Volvo XC70 No spark

Tiny
BOBSEPE
  • MEMBER
  • 1999 VOLVO XC70
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 193,000 MILES
5 cylinder 1999 XC70. Cranks, but will not start. B+ to each of the coil packs but weak trigger voltage to each coil. Hence no spark or weak spark at plug.

I changed timing belt and used Volvo cam locking tool to hold twin cams in place. Placed tension on Variable Timing unit to hold it in place during timing belt installation. Timing is "spot-on."

I had to remove and replace the exhaust cam sensor to gain access to cam shaft for locking tool.

Fuel pump cycles when ignition switched is turned to the "start" position.

Ideas?
Tuesday, June 30th, 2009 AT 6:21 PM

4 Replies

Tiny
JIS001
  • MECHANIC
  • 3,412 POSTS
If you have a weak spark then first thing to check is the condition of the battery and make sure that it is fully charged and your cables are clean with no corrosion because that could cause a weak spark. Also did this problem happen after you replaced the timing belt? If it did then recheck all your timing marks. Also you mentioned nothing about the crank mark? Was that on it's mark as well? You will need to remove the crank pulley to chek the crank mark. On the inside of the crank sprocket look for a small notch towards the engine block. Some have notches on two of the teeth and some have only one. If only one then line that notch of the inside groove to the notch on the engine block. If the sprocket has two notches then line the middle in between the the two notches to the notch on the block.
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Thursday, July 2nd, 2009 AT 1:35 AM
Tiny
BOBSEPE
  • MEMBER
  • 3 POSTS
Thanks for the reply. The battery is fully charged and the timing is 100% correct. Engine has compression 185-200 psi. No electrical cables corroded.

There is a very weak to no trigger signal condition to pin 1 of the coil pack. I have measured 12V at each of the coils at pin 4, pin 3 is ground and pin one is for the trigger signal from the ECU. Pin 3 is not used.

I removed the cam sensor to engage the cam locking tool on input and exhaust cams when I changed the belts.

Can the cam sensor have gone bad? How do you test it? Is it possible that the clearance between the cam sensor and the stator on the end of the cam is misaligned? If so, how do you set/measure the propoer clearance?

What is the role of the crankshaft sensor on the flywheel? Again, how would you test it?

Thanks,
bob
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Thursday, July 2nd, 2009 AT 6:17 AM
Tiny
JIS001
  • MECHANIC
  • 3,412 POSTS
If the cam sensor were to g bad your car would still start but would set off the engine light. As for misallignment of the stator it only goes one way just like the cam locking tool you are using so you cant mess that up. The sensor in the back at he flywheel is the RPM sensor and if you get metal particles then that can interfere with the signal causing a no start. You can remove and inspect the sensor. If you have metal then clean it up. But if there is metal then you need to replace the starter and the flywheel. Now on pin #3 did you check for ground? Make sure you hve good ground also. And also did the car start fine before you replaced the timing belt?
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Saturday, July 4th, 2009 AT 6:01 PM
Tiny
BOBSEPE
  • MEMBER
  • 3 POSTS
I solved the problem. I replaced the cam sensor, the car started and the engine ran on 3 cylinders with cylinders 2 and 4 not firing. Replaced the coil packs for those cylinders and it now operates on all 5 cylinders.

Apparently coil packs fail without warning. The check engine light did not illuminate despite the secondary circuit in the coil pack had failed. Perhaps the ECM incorrectly believed the engine was firing on all cylinders. Yet I could smell raw gas exiting the exhaust pipe. This was my clue to check the coil packs. When I swapped the coil packs for cylinders 1 and 2, cylinder 2 began to fire and cylinder 1 was dead.

As soon as I replaced the bad coil packs, the engine ran on all 5 cylinders. Very smoothly.
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Wednesday, July 15th, 2009 AT 2:25 PM

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