Date: Thu, 6 Nov 1997
From: "Mark Williams" <MCW627@worldnet.att.net>
Glenn,
I have a 1968 Volvo 142S, with the B18B, with the dual SU HS6's. I purchased it for $200, and have been restoring it for quite some time now. My problem is it stumbles at all speeds, and is worse on acceleration. I have rebuilt the distributor and the carbs, put a head gasket set on it, and a new timing gear. When I check the timing, it seems to have an intermittent misfire. The dwell is correct, but the timing always varies, and won't run at 5 degrees BTDC. I have sealed off the only vacuum leak I could possibly think of. I recently took the carburetors back off and cleaned and tuned them. It ran smooth for about the first minute then started stumbling again. I have no access to an ocilloscope.
Is there anything you can think of that might be causing this problem?
Thank you for your help,
Mark Williams
P.S. The valve lash is adjusted correctly.
Mark -
Whenever the timing won't hold steady, there probably is a loose mechanical fit somewhere that affects the timing. The timing gears would be the first thing I'd check. If you are reasonably sure you installed your new gear correctly and it is not loose, you should direct your attention to the distributor.
A loose distributor rotor could cause this problem. Check for looseness and an unusual wear pattern in the distributor cap. Also check for cracks in the cap. If these things look o.k., remove the wires (tag them first), and then remove the distributor from the engine block. Check the drive end for damage and excessive wear.
If the distributor drive end looks good, check for looseness in the drive gear, which should still be in the engine block. Check the teeth for damage. If you are confident in your mechanical skill, mark the gear's position and remove it. Check the bottom end of the shaft. If the end of the shaft is damaged, you should also check the oil pump for free movement using a long screwdriver as a substitute for the shaft.
When you replace the shaft, you must be sure it engages the oil pump and that it ends up in exactly the same position. Remember not to turn the engine while you have the distributor out.
I hope this helps. Let me know how you fare. -Glenn.
Glenn,
Thank you very much for your quick reply. I removed the distributor and inspected everything. I checked the compression and it is 155 psi across all four cylinders, and I also checked the vacuum at idle and it is at 20 hg, bouncing up 2 hg when it misfires, so I am sure it is not my cam timing. I inspected the distributor drive gear and it looked brand new, so I did not remove it. But I did notice that the points are prematurely burned. But I checked the dwell a few days ago and it was steady at 50 degrees. There is no shaft wobble, so I am thinking it might be the centrifugal advance springs. As I recall, my rebuild kit did not come with springs. Is there a way to check if spring tension is correct, without putting it on a distributor machine? Also, I noticed that the shaft has 1-2 millimeters of vertical endplay; is this normal? Thanks for all your help, I definitely feel like I am in the right direction now.
Thanks,
Mark Williams
Mark -
I don't have a book for the 142, but it seems to me the ignition settings should be comparable to the 1800 and 122. My Haynes manual for these cars says the timing should be between 10 and 23 degrees before top dead center, depending on the version of the engine. I get good results at about 17 degrees BTDC.
The dwell angle is listed at 59 to 65 degrees at 500 rpm. Points can get burned prematurely by setting them too close, which will also give a smaller dwell angle. If I were you, I'd try setting the points farther apart.
I've always used feeler gauges to set the points rather than a dwell meter, and experience tells me to set them a little wider than the minimum. I use a go-no-go pair of .017 and .020 feeler gauges. It's fairly easy to line up the rubbing block on the distributor cam by rolling the car forward or back by hand while watching the position of the cam. You need a manual transmission to do this, and have it in fourth gear. Don't roll over your feet!
This doesn't explain a jumpy timing setting, but it might make the engine run a lot better. If the timing jump is less than a few degrees, I wouldn't worry about it. I can't find a vertical play specification for the distributor shaft, but if the drive end looks good, it's probably fine. To check the advance springs, rev the engine while holding a timing light on the crank pulley. Look for a smooth advance and retard. If there's any doubt, replace the springs IF you can find a new set.
-Glenn.
Glenn,
Thanks for replying again. You're right, the springs are non-existent. The problem was bent spring posts on the shaft. Apparently, somebody lost one of the screws holding in the condenser, and put a longer screw in the hole, which bent the posts as they were coming around. Finding one of the shafts is going to be much easier than finding new springs!
By the way, I have an old Chiltons manual published back in '71, and according to it, you're right on the dwell setting, but on B18Bs with emissions equipment (California cars '68 and up, with PCV and heated intake), the timing should be 5 degrees BTDC @ 800 RPM. Compression should be at 170-200psi, although I think 155 across all four is quite impressive for 207,000 miles.
Best of luck with your page,
Mark Williams