More 1992 B230F Timing Questions

[haroldburbank]

Somehow the timing belt jumped the sprockets a hair while I was spinning the cam sprocket (and timing belt) on the car. Full tension on belt at all times. I moved #1 piston (via crank pulley) to TDC, and checked this against proper rotor position (at plug wire for #1 piston). Then I released the timing belt tensioner, removed the timing belt from the cam sprocket only, moved the cam sprocket backwards a hair to align the sprocket timing mark with the timing belt cover mark (at about 11 o'clock), and reinstalled the belt and tensioner.
Car will not start. Apparently no compression, indicating timing is pretty far off.

Please advise how to correct without pulling the crank pulley and repositioning the timing belt entirely. Believe I read when the cam is moved out of position it must be rotated a full 360 deg. to assure proper valve sequencing before alignment with timing mark. Cannot see why crank pulley and belt must come off altogether on these facts.

HB

[Kmaniac in California USA]

Hi Harold:

By reading your post, it appears that you indexed the crank using the timing mark on the crank pulley only, but did not remove the crank pulley at all. This is NOT the way to properly index the crankshaft for proper valve timing, since this method assumes that your vibration dampener has not failed with age. Let me explain:

The crank pulley is also a vibration dampener. The center hub is connected to the outer pulleys (which contain the timing mark) by a molded rubber donut in between. When (not if) the rubber donut deteriorates, the pulleys (with the timing mark) will rotate on the donut and move the timing mark with respect to the center hub, most likely advancing the mark relative to its proper position. There is no way to test the condition of the vibration dampener or verify proper timing mark position without removing the crank pulley and comparing it to a new one.

When I replaced the timing belt in my 740 last month, I too, used the crank pulley only to index the crank. When I put it back together, it would not start (sound familiar?). I took it off and put it on several times with the same result before I considered that there might be a problem with my crank pulley. Fortunately, I had an independent, discount Volvo parts supplier in a nearby town, which had a new crank pulley/vibration dampener in stock. So I took my crank pulley to the shop, laid it on top of the new pulley, lined up the keyway slots in the hubs and found my timing mark was off from the new pulley by 48 degrees in the advance direction. Naturally, I bought the new pulley. NOTE: Some people might recommend buying a used pulley from a junkyard. I do not recommend this, because you might be buying another failed pulley and you have no way to check it.

To properly index the crank, you first line up the timing mark to TDC before disassembly. Once you get the crank pulley off, you must verify that the keyway slot in the end of the crankshaft is aligned with a rib on the crank seal cover at approximately 11 o'clock. If the crank is not aligned with this rib, move the crank until they are in line. Only after the crank is indexed in this manner can you accurately index the cam and auxiliary sprockets and install the timing belt correctly. NOTE: This indexing procedure in not clearly explained in my Haynes manual. But using the pictures there and my explanation, you can figure it out.

If you find that the crank slot is not aligned with this rib, your timing mark on the pulley has shifted and the pulley must be replaced. You can verify this by comparing your pulley to a new one like I did.

My suggestion to you is to remove the crank pulley and lower timing cover and index the crank as I described above. Then you will see how far off the cam timing truly is. Then remove the timing belt, index the other sprockets and reinstall the belt. While the belt is off, check the condition of the tensioner pulley and replace it if it spins rough.

As a side note, please review my post titled “1986 740 GLE B230F Ignition Timing Issue”, if you haven’t already done so. I have been planning to post my revelations with the crank pulley once I get the car smogged, which it hasn’t passed yet due to other issues. Note, too, that if your timing mark has slipped as mine did AND the ignition timing was reset in this condition, it’s probably not running as well as it should to begin with, since the ignition timing would be retarded. There is a special tool available to use to hold the crank while loosening and tightening the crank hub bolt. The Volvo parts dealer I use loans this tool for free when he sells a timing belt. See if you can get use of one of these tools to help you remove the crank pulley.

The issue I encountered with the crank pulley/vibration dampener is probably more common than most people, even Volvo mechanics, might think. I am sure that many a car has been junked as a result of this “weak” design flaw that went undiagnosed.

Please let us know what you do and what you find. Let me know, too, if you have any questions.

[billofdurham]

Chris,

Thank you. When I read the post I thought of how to refer HB to your problem and solution. I didn't think it would be so easy.

Bill.