Vacuum Advance timing question. (1 Viewer)

[Burl6085]

I'm in the process of getting my 1984 FJ 60 smogged in Fresno CA. I just got the carburetor back from Jim Chenewoth and it seems to be running really good. I have replaced all the vacuum lines so I believe there shouldn't be any leaks from old vacuum lines. My question is when setting the timing to 7*btdc, which tubes do I pinch shut or remove and plug to make sure the vacuum advance isn't altering the timing any. I have tried multiple combination's of plugging and pinching off and the timing always seems to stay at 7*btdc and doesn't advance when the vacuum lines are released or reconnected. Is this normal or might there be something else wrong? I copied the vacuum line routing from a guy off the Marlin Forum who had a 60 and his passed smog consistently, so I believe the lines are good. Any additional help and advice would be much appreciated, because this is my first 60 and want to put fj40jims rebuild to good use.

Thanks

 

[2mbb]

There are two vacuum lines that connect to advance diaphragms mounted on the distributor. The correct procedure is to remove and plug both lines. I think it is important to remove the lines, not just pinch them, because you need to release any vaccum that might be contained within the diaphragm body. As described below, there may not be any observable advance at idle, but it is still good practice to disconnect and plug the lines when adjusting the timing.

One diaphragm (the outer one) is for the High Altitude Compensation, which advances the timing a set amount when the truck is at high altitude (above 4000ft). This diaphragm should not be activated at lower elevation levels.

The inner diaphragm is connected to the advancer port on the carburetor. This provides a varying amount of advance depending upon the position of the throttle and the venturi vacuum being created inside the carburetor. As the RPM/load increases the vacuum and therefore the advance should also increase. There could very well be no advance at idle. If you increase the engine speed and watch the timing mark with the light (it's hard to do by yourself on the 2F setup), you should see the timing mark advance. If not, something is wrong. There is a temperature switch (BVSV) which only allows advance when the engine is warm. If you never get vacuum to the advance diaphragm, this may be bad or the vacuum delay valve (VTV) may be clogged. Or your advance diaphragm may be broken.

If you haven't done this already, you should get a copy of the emissions manual. There are procedures for testing all the components. This manual is a MUST HAVE for california smog legal trucks.

 

[trd55]

The vacumm diaphram might be in operative. My main advance does not work, but the high altitude does. Put a vacumm pump on the diaphram and see it it holds a vacumm.

 

[lehiguy]

Once warmed up, only the vacuum advance signal from the carb is operating. That is a ported vacuum, so it should not be present at idle. You should see the timing jump when cracking the throttle. And as trd55 said, the diaphrams on the distributor can and will die in their old age. Test it; just, well, suck on it.

 

[Burl6085]

Thanks that makes sense

I was just looking for a noticeable change in the timing because when I bypass the the computer on my efi 4Runner the timing and engine change noticeably. I'll post what happens whith smog tomorrow.

Thanks for the replies.

 

[lehiguy]

I was just looking for a noticeable change in the timing because when I bypass the the computer on my efi 4Runner the timing and engine change noticeably. I'll post what happens whith smog tomorrow.

Thanks for the replies.

That's an animal of a different color; they do change pretty wildly when you disconnect the timing from the computer's control, carbed things aren't like that.

 

[Burl6085]

Passed smog and registered

I passed smog with minimal emissions today. What a relief, I was beginning to think my investment in the 60 was going to be futile. Thanks fj40jim you do legit work.

 

[cruiserfj45]

Glad to hear it. I just finished with my fire academy and now have time to work on my Cruiser. I needed to smog it back in Dec. One of my problems was that the vac advance had some rust (other problem that was fixed). A little of WD-40 and all is good now. We should get together some time and go wheeling.

 

[Butt Ugly Chuck]

I passed smog with minimal emissions today. What a relief, I was beginning to think my investment in the 60 was going to be futile. Thanks fj40jim you do legit work.

Congrats!

 

[Burl6085]

Glad to hear it. I just finished with my fire academy and now have time to work on my Cruiser. I needed to smog it back in Dec. One of my problems was that the vac advance had some rust (other problem that was fixed). A little of WD-40 and all is good now. We should get together some time and go wheeling.

Yer Jake from marlin as well right? If so I still have those fj 60 bumpers and pushbar combo if you want them.

 

[deltapine1]

Correct timing question

I had noticed some detonation recently in third under load. I first thought it was some bad gas but since I have put 2,300 miles on my 60 this last month I thought I would check the timing just to rule it out. I followed the manual and 2mbb's instructions and disconnected and plugged both vac. lines to the dizzy. Using a timing light I verified the pointer is at the round dimple.

I have a question. The manual tells us the pointer should point to the round ball or dimple. As I am sure 99% of us don't stand on our head in the engine bay and get intimate with the starter we don't actually line the ball or dimple up directly with the pointer. If you line up the pointer witht he ball as I do from an overhead view at about a 45 degree angle from the top of the fender the ball or dimple is actually below the pointer. This is because of angle required to view the timing window and pointer while leaning over the fender well.

Does it really matter or should we be standing on our head to get the pointer and ball lined up?

I think if I were looking at the pointer level the ball would be above the pointer.