Is this distributor installed/aligned correctly?

7MGE for an '89 Cressida.

The factory manual advises to align to TDC compression which I've done as precisely as I'm able. Notch on the main pulley centered on the 0 mark, marks on the cam drive wheels lined up with the notches on the backing plate.

Then it advises to align the stamp on top of the distributor driven gear with the notch on the distr housing and install it with the bolt hole for the hold-down aligned with the slot in the hold down portion of the distr.

However, when installed like this, the alignment of the rotor ends up slightly ahead (oriented clockwise) of the contact for the #1. On the pic with the cap on, I've drawn a line showing the orientation of the rotor compared to where the #1 contact is. I thought it would be dead- center lined up.

I'm posting a link to some pics. Does it look like it's where it's supposed to be?

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Thanks for all input.

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Reply to
Doc
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It looks exactly as you say, but consider that your rotor tip is wide and it approaches the cap terminal before the axis line gets there.

Looks like you have an adjustable distributor holddown anyway. I would try it as is and check the timing. If you cant adjust it to spec, you may be off a tooth.

The most common mistake in stabbing a distributor is getting it 180 degrees off. All of us have done it before when we tried to rush things. Be sure you are on the compression stroke. The easiest way to know for sure is to take out the spark plug and hold your finger over the hole as you turn the engine. You can feel the pressure. At that point, adjust the pointer (if you have one) to the line on the crank pulley.

If you dont have an indexed crank pulley, there are other ways to find 0 TDC.

Reply to
hls

All that hls said, but I think you may be off a tooth. I looks a bit ahead, 153624 F/O. They normally don't make the distributor gear straight tooth, so sometimes it is hard to get it in correctly the first time. I would take it back off and double check all index marks, then re insert watching the rotor movement as you slide the distributor in to the engine. IMHO. Good pics Doc! Very helpful. Good luck.

Reply to
user

Don't forget the timing when the spark fires and you set the timing, it is normally several degrees 'before' TDC. This makes the rotor slightly past the post at TDC.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - G> 7MGE for an '89 Cressida.
Reply to
Mike Romain

Thanks. Yeah, definitely wanted to make sure it's TDC compression. TDC compression is the only point at which both the timing belt gear marks and the pully mark both line up with their respective center points. On this particular engine, you can also verify by looking through the oil filler cap. When you can see the cam lobe snout, you're just past TDC compression.

Reply to
Doc

No, that isnt quite right. The timing mark and the pointer ALSO align at 180 degrees off TDC.

If you can see both valves, you can use this as a reference to find TDC.

Or, you can use the pressure method I mentioned.

Be SURE you are working near TDC, not 180 out.

Now, as another poster alluded, the second most common error is getting the distributor stabbed one tooth off.

Reply to
hls

I find that the timing/harmonic balancer pulley goes around twice for every one complete revolution of the timing belt gears, so I believe it's correct that the only time both the timing belt drive gears and the timing/balancer pulley both line up with their marks is at TDC compression - this assumes of course that the belt drive gears were fixed on the correct TDC to begin with.

Reply to
Doc

So, for alignment should I use the centerline of the rotor or the leading end of the "T" shaped tip?

If I move the shaft/rotor back one tooth from what's shown in the poto, then the centerline of the rotor is slightly forward of the #1 contact instead of slightly past it as shown. I find there's no tooth that gives an alignment that places the centerline of the rotor even with the #1 contact on the cap when the base is aligned per the shop manual - i.e. with the slot centered on the bolt hole as shown in the photo.

Reply to
Doc

Try moving the shaft back one tooth from what is shown in the photo. When timing is advanced, the rotor should be in contact with the proper tower.

Reply to
Ray O

They are often a helical gear, so it will not be in the right position until it is properly bottomed out.

And if the bottom of the distributor shaft has a tang to drive the oil pump, odds are it is NOT going to hit bottom just by dropping it in. You have to roll the engine over until the oil pump tang lines up, and then the distributor shaft will drop the last quarter inch.

Reply to
Bruce L. Bergman

Absolutely correct in your observation. We may have a semantics issue however. For timing purposes, the TDC is when number one piston is at top dead center on the compression stroke.

That same piston will be at the top at a second point during the firing cycle, and the pulley mark and pointer will still be aligned, but the timing valves, belt, etc can be used to determine that this is not the correct point for distributor installation. Holding your finger over the spark plug hole is a simpler way to know for sure.

As I mentioned earlier, and others as well, you may be off a tooth in meshing the distributor gear with the camshaft gear...or you may not. You will know for sure when you try to time the car after it is running. If you have enough adjustment range in your distributor holddown slot, you can often time a car correctly even though you are a tooth off (and there is absolutely no adverse effect from doing this).

If your distributor rotor had a needle sharp pointer, I would say - from your photos- that you are a tooth off.

Reply to
hls

Like a couple of other posters mentioned, the distributor drive gear is helical so if you are lining up the rotor where you expect it to be it will probably move off that mark when it engages down below. I stick the distributor in the block, then turn the rotor 30 or so degrees opposite its rotation as I slide it down. Then when the gears mesh the rotor will turn to the exact position it should be in. Does that make sense? Anyhow, that works for me. Good luck. jor

Reply to
jor

That is because your timing is 'not' set, only your distributor is set.

When you set the timing, you set it at 'say' 10 degrees 'before' top dead center. (10 BTDC) Then the rotor hits the post on the distributor cap 'before' the engine comes to top dead center to make the spark.

This also means that the rotor will be 'past' the post at top dead center!

When you have the choice of before or after the post on the distributor cap, chose after for TDC.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile...
Reply to
Mike Romain

Exactly. Just stabbing the distributor in the correct configuration does not assure you of anything other than that you should have enough adjustment so that with a timing light, you can correctly adjust the timing with the engine running.

We used to adjust "static" timing by adjusting the timing pointer to the correct initial timing mark on the crankshaft, and then turning the distributor until the points opened to fire #1 cylinder. This sets initial advance pretty well.

Then with the engine running, we would check the timing with a strobe.

To see if the advance curve was correct (or desirable;>), it was easiest to use a distributor machine.

There are so many variations now on distributors, that it is hard to make generalities. Distributors dont often have "points" anymore, and the advance may well not be achieved by a combination of vacuum and centrifugal weights.

Reply to
hls

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