1986 740 GLE B230F Ignition Timing Issue

[vegasjetskier]

I don't knowm much about these cars, but if it has a mechanical advance in the distributor, it could be a weak or broken spring that is causing the problem.

[Kmaniac in California USA]

Thank you for the input. Problems with either mechanical or vacuum advance mechanisms was considered early on. However, this car has neither, with ignition timing controlled solely by the computer. Still, a good call on your part.

[billofdurham]

The B230F is a non-interference engine. The timing belt should be changed every 48,000 miles or 4 years, whichever comes first. I think you should change it, even though it won't harm the engine if it breaks, but you may well be stuck in the wide blue yonder if it goes. There is no recommendation by Volvo on replacing the tensioner except "Spin the tensioner roller and check for roughness or shake, renew if necessary". At that mileage I would think it may be due a change.

Is there a way to check the timing marks on this thing without tearing the front of the engine down to bare belt?

Yes. The top half of the timing belt cover can be removed to expose the timing marks on the camshaft pulley.

The slots in the distributor are for adjustment but are a real pain to get to. I would check first to see if the belt has slipped as that distributor should never need adjusting and I don't think it would move far enough for the timing reading you have.

Bill.

[Kmaniac in California USA]

Hi again Bill:

Greetings from across the pond!

Thank you for the timing belt replacement schedule. That's the first time I have seen or heard this. I will check to see if the top of the timing cover can be removed easily. I was leaning towards doing this as my first step. I will replace the timing belt and tensioner, especially if I find the cam timing off.

I will post my findings later, after I get my hands dirty.

[billofdurham]

Thank you for the timing belt replacement schedule. That's the first time I have seen or heard this.

My computer is full of Volvo trivia.

This is how it comes apart - 3 bolts to get the top section off. It's a pity Volvo didn't do this on all of their engines.



Bill.

[Kmaniac in California USA]

Hi Bill:

Thanks again for the additional trivia. But now I'm even more confused, not with your information, but with what I found this morning.

I rotated the crank to TDC and loosened the timing belt cover enough to pull it forward and view the cam timing mark. The cam mark is right where it should be, on top. So clearly, the cam and crank are timed correctly. Now for my next question:

Is there a crankshaft or camshaft sensor on this engine that guides the computer?

By the way, the outer surface of the timing belt has numerous surface cracks in the rubber, so I know it's time to replace it, that is if I can figure out why the distributor timing is off so much.

Again, any thoughts, given this new information, would be greatly appreciated.

[billofdurham]

There is no crankshaft nor camshaft sensor on this engine. The distributor has a Hall Effect sending unit which sends signals on engine speed to the ECU. In addition to receiving the engine speed info the ECU receives engine load info from the intake manifold. This is a vacuum system. Speed and vacuum signals are monitored by the ECU to control spark advance and dwell angle. The manifold vacuum signal is also used by the ECU to control the ignition timing. Check the vacuum pipes for leaks etc.

As this is something that did not go wrong on my B230 engines I am also on a learning curve here. My research has found this:

http://www.brickboard.com/RWD/volvo/382 ... ments.html

The year, model and problem are the same and there could be some advantage in checking.

Bill.

[Kmaniac in California USA]

Hi Bill:

Thank you for the lead and the information.

First of all, I don't think my problem is the vibration damper. the reference post describes the timing mark just walking around the scale. In my case, the timing mark is static, but approximately 30 degrees advanced of where it should be. Plus, when I crack open the throttle, the mark advances as I would expect it to when it is in its proper position and I can see it retard when the knock sensor operates. Then the mark returns to the static position again when the throttle is closed. It seems to me that the whatever engine position sensor has somehow slipped from its proper position. Also, a slipped pulley on the balancer would not account for the tailpipe emissions measured during the smog test. If the pulley only had truly slipped, the emissions would be normal and only the timing mark would be out of place.

I inspected the ECU under the dashboard. The ECU in my car does NOT have a vacuum port like the one shown in my Haynes manual. I guess some models have the direct vacuum port and others do not. Again, my Haynes manual refers to a vacuum switch that is suppose to report to the ECU, but I cannot find this under the hood.

I was only able to find four vacuum ports from the intake manifold. One for the power brake, one for the fuel pressure regulator, one for the crankcase ventilator and one for the vent control switches. I could not find any feed for an ECU sensor or any sensor bolted directly to the manifold. I'm not sure how the ECU monitors vacuum. Any help here would be appreciated.

Since there is no crackshaft or camshaft sensor, is it possible that the halls effect sensor in the distributor has somehow slipped from its proper position, causing this anomoly?? I'm not thrilled with the prospect of removing the distributor, but that may be my next step if I cannot find or rule out a vacuum sensor for the ECU.

Again, anyone's thoughts on this problem would be greatly appreciated.

[Kmaniac in California USA]

...arghhh!!!!!!

Sometimes when you are so focused trying to find the forest, you get frustrated when the trees block your view.

In other words, if that vacuum sensor for the ECU was a snake, it would have bit me, not once, but many times. I guess I got confused seeing the tap to the plastic intake pipe and missing the second tap to the intake manifold.

Once I put the interior back together, I will inspect this device and the supply hoses for leaks.

I will keep you all posted.

[vegasjetskier]

Since there is no crackshaft or camshaft sensor, is it possible that the halls effect sensor in the distributor has somehow slipped from its proper position, causing this anomoly??

Or maybe the vane wheel moved on the distributor shaft? Or the distributor moved in the block?