Allpar Forums banner

1 - 14 of 14 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
Just changed fixed a broken timing belt and now the car won't start. Getting fire, compression is 95 on cylinder #1, timing is dead on, sprayed starting fluid in the air box..all with no success. Found several posts and videos of measuring the voltage in the cam sensor pigtail. I have 5V, Gr, and 4.95V with the ignition on. The voltage does not change when cranked. Most posts say 8-10V on one of the tabs. Am I looking at a new computer since the voltage is so low? Thanks for any replies.
 

·
Registered
Joined
·
4,683 Posts
Just changed fixed a broken timing belt and now the car won't start. Getting fire, compression is 95 on cylinder #1, timing is dead on, sprayed starting fluid in the air box..all with no success. . . .
95 lbs compression on cylinder #1 is low. You mentioned a broken timing belt which means dual overhead camshafts probably got out of synchronized time and there was valve collision. Now you have at least one bent valve. But that is NOT keeping the engine from starting.

Cam position sensor is a Hall effect device. Follow this link to a similar problem on a 2005 PT Cruiser. See post #8 dated Jan 28, 2020 at 1:12 AM and the discussion about testing a cam position sensor. You do not need a new engine computer.

P0340 no start 05 pt cruiser (at https://www.allpar.com/forums/threads/p0340-no-start-05-pt-cruiser.224653/ )
 

·
Super Moderator
Joined
·
21,398 Posts
Early cam and crank position sensors ran on 8 volts, the rest of the sensors ran on 5 volts.
By the mid-'90's(?) all sensors ran on 5 volts.
There is a 5 volt supply wire. The cam signal return wire that switches between 0 and 5 volts and a sensor ground return wire. It shares power and ground with the crank sensor.
If you sweep a magnet across the face of the sensor, you may see it toggle between 0 and 5 volts. Same toggle by cranking the starter.

Any fault codes? The wiring harness connectors for the ign coil pack and cam sensor were the same style early on and could be inadvertantly swapped. They could reach either component. This would cause a no-start.
They changed this later on so that only the correct plug could be connected.
I have also heard of cam sensor target magnets cracking and unable to send a signal.
 

·
Super Moderator
Joined
·
32,051 Posts
You cannot detect the proper voltage transitions with a digital multimeter, if you're using that. You either need a good analog meter or a scope.
 

·
Super Moderator
Joined
·
21,398 Posts
Agree. You can't tell anything with numbers jumping around. An analog meter pointer will wiggle to show the Hall Effect toggling, but a scope is the preferred method. A nice square wave pattern with no noise.
 

·
Registered
Joined
·
8,096 Posts
I'd suggest going back over the timing marks and making sure it's EXACTLY lined up. It's very easy to get one of the cams off a tooth or two and cause nightmares. Pretty sure 06PTElectricBlue has an excellent shot of how the timing marks HAVE to be aligned. I've been looking on the PT forum and can't find the one I'm thinking about. Rick has a much better memory than I do!
 

·
Registered
Joined
·
2,981 Posts
Make sure one of the cam sprockets isn't 180 degrees off. I did that once. I didn't pay attention to make sure the arrows were pointing up. There are position markers on both sides of the sprocket, so if you have the arrow pointing down, you will still be able to align cam marks; but one of the marks will be the wrong one.
 

·
Super Moderator
Joined
·
21,398 Posts
Yes both sprockets at 2.4L FRONT and ⇧UP⇧.
Since it is difficult to get a good head-on view of the cam timing marks from above, I use a small dental mirror and straight edge across the bolt centers. Then roll the crank over 2 turns and make sure that the cam marks stay aligned. Sometimes the belt will 'settle' and a mark may move out of alignment.
The front cam is monitored by a cam sensor, the rear cam is not.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #11
Thank you for the replies. Turns out that the rings were frozen. Had 1-90, 2-10, 3-35, 4-185 compression per cylinder. Poured some good ole 30W oil in the spark plug holes and turned the motor over about 15 times. Installed the plugs, and it fired right up. So glad I did not have to tear down that beast again. Cheers!
 

·
Registered
Joined
·
1,133 Posts
Thank you for the replies. Turns out that the rings were frozen. Had 1-90, 2-10, 3-35, 4-185 compression per cylinder. Poured some good ole 30W oil in the spark plug holes and turned the motor over about 15 times. Installed the plugs, and it fired right up. So glad I did not have to tear down that beast again. Cheers!
How long had the car been sitting before you changed the timing belt?
 
  • Like
Reactions: Doug D
1 - 14 of 14 Posts
Top