1986 740 GLE B230F Ignition Timing Issue

[Kmaniac in California USA]

Took the car out for a drive tonight to warm it up. Still seems to run fine. Anyway, after all the disconnection and reconnection of sensors the timing is still at 40 BTDC at idle (950 rpm by tach). I then disconnected the vacuum sensor and restarted the car to see what happens. The idle to 1200 rpm (no doubt a system default) but the idle timing did not change. Cracked the throttle and the timing advanced as expected. I'm thinking that the vacuum sensor is not the issue.

I think my next step will be to remove the distributor and have a look inside.

[Kmaniac in California USA]

I have some questions about distributor removal on my B230F. Do I have to remove the valve cover to remove the distributor or do I simply unbolt it and slide it out the back? (Not much room between the cap and the firewall)

Does the distributor shaft fit into a slot in the camshaft, and if so, how many ways does it fit? Example; My big block MoPars have a rectangular key that fits either correcting or 180 degrees out in a slot on the drive gear. It fits only two ways. Are the Volvo distributors similar??

Any "heads up" before I start would be appreciated.

[billofdurham]

To remove the distributor you need to remove the cap first - 3 screws which are captive so won't fall out and disappear wherever good screws disappear to. That gives you slightly more room to work.
Remove the rotor arm and dustshield.
Remove the two retaining bolts.
Remove the distributor from the cylinder head.

When refitting there is no problem of being 180 out as the drive is offset.

Bill.

[Kmaniac in California USA]

Hi Bill:

Thanks for the step by step.

Well, I removed the distributor tonight and that was a lot easier than I thought it would be. Good thing I am 6-feet, 4-inches tall, that made reaching across the engine compartment a "piece of cake". I feel sorry for any short Volvo mechanics.

I found a little engine oil seepage into the distributor. Is there a replaceable shaft seal to prevent this? I also observed some type of "crud" on the Halls Effect sensor. Could this have an effect on the timing?? The Halls Effect sensor is mounted like I would expect without any sign of looseness or movement. The wheel that spins inside the sensor is rigid, too. So upon visual inspection, everything appears as I think it should.

The cap and rotor have been in service for 38,000 miles according to the latest service record. They show some wear so I'm thinking of replacing them while I have it apart.

There is no record on the age of the Halls Effect sensor. Would you recommend replacement out of general principle or do you think I should try cleaning it up first and try again?

Any knowledge you can pass along regarding the distributor would be appreciated.

Cheers!!

[billofdurham]

Light at the end of the tunnel, perhaps?

I feel sorry for any short Volvo mechanics.

I know one who has to stand on a step to change the plugs.

VADIS shows two oil seals on the shaft, one large and one small. FCP Groton also shows them.
http://www.fcpgroton.com/category-exec/ ... y_year/36/

It is possible that yours have deteriorated allowing oil into the body of the distributor.

I don't know how much the crud would affect the timing but it definitely should not be there. As everything else seems to be sound with the Hall Effect sending unit I would clean it and give it a try.

A new cap and rotor seem to be called for. Again, they are often overlooked during servicing as "they looked OK".

Keep at it before someone switches off the light at the end of the tunnel.

Bill.

[Kmaniac in California USA]

Yes, there is a light at the end of the tunnel. ....just my luck, it's the TRAIN!!!

Well, I cleaned out the distributor with electrical cleaner. I even cleaned the contact points on the cap and rotor. I put it back together again and set the distributor at full retard of the adjustment. The engine started and ran. The timing mark is now less advanced than it was, but still off the scale by about 20 degrees advance. At idle the timing mark stays at the same position whether the engine is cold or hot. Could this indicate a bad temperature sensor??? My only other thought is the possibility that the impluse plate has shifted on the shaft, but I don't see how that is possible.

Any other thoughts out there??

[vegasjetskier]

Is the distributor driven by the camshaft? How many degrees would one tooth on the camshaft equal?

[Kmaniac in California USA]

The distributor attaches directly to the rear end of the camshaft on this engine. I previously inspected the position of the cam sprocket timing mark and the timing belt is installed correctly, with no evidence of skipping a tooth. Good call on your part, but I already eliminated that possibility.

Side note: I did remove the manifold vacuum sensor and associated hoses last night and found them secure, without vacuum leaks. Running the engine with this sensor disconnected raised the idle from 950 to 1200 rpm but had no effect on the ignition timing at idle.

[vegasjetskier]

Are you absolutely sure you are looking at the correct marks for the ignition timing?

[Kmaniac in California USA]

Well, I tried another experiment. The engine has a coolant sensor that reports to the ECU. As my Haynes manual states and another poster confirmed, this sensor advances ignition timing by approximately 15 degrees when the engine is cold and is supposed to retard the timing once the engine is hot. As a test, I disconnected this sensor and started the engine to see the effect. With this sensor disconnected, the engine started at 700 rpm, then slowly climbed up to 1300 rpm. The timing mark at idle was now higher than it was with the sensor connected. I reconnected the sensor and the timing retarded back to where it has been. Plus, the timing at idle is the same whether the engine is cold or hot. I think this sensor may have failed and is telling the ECU that the engine is cold continuously. Does anybody have any thoughts on this??

Note to VJS: Yes, I am absolutely sure I am looking at the correct timing mark on the crank pulley.