Distributor diaphram not working

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Nov 22, 2004
'77 w/ semi electronic vac retard system. Pulled the vacuum hose last night when I was checking my timing and tried sucking on the end. No change in timing. I'm assuming it's shot. Couple of questions:
1. Are these diaphrams still avail and if so where and how much $?
2. Could this be what is causing my slight pinging at hwy speeds when I floor it?
3. Exactally how does the vaccuum work going to the distributor? Is it coming off the vsv and does it turn on and off at certain rpm?

Thanks for all the help!
On my '77 I had the same issue. I purchased an OEM replacement. Not sure where you are located, but CDan can help you out of your local dealership doesn't deal.

So, to answer your questions:

1) Yes - IIRC around $50
2) Possibly, but check all sources such as timing, mixture, etc.
3) Mine was connected to a port on the base of the carb on the passenger side. BTW, IIRC it is vac. advance, not retard. The higher the RPM, the higher the vacuum, the higher the advance. Also, the vacuum ports on my carb were carboned/gunked up when I purchased my rig so check this as well.

1. If you can suck hard enough by mouth to move that advancer, you're in the wrong line of work!;p You need a vacuum guage to test it.

2. Pinging is caused by too MUCH advance, not a lack of it, so this points to the possibility that it IS working. Did you try driving around with it disconnected to see if the pinging stopped. That would confirm that it is making a difference, i.e........ WORKING!

3. IIRC, the diaphrams went obsolete several years ago.
I guess that raises the next question, both replies say I've got a vac advance, but I thought stock non CA USA was vac retard?
Mid '76 and later are vac advance.

Once I figgered out that the 1977 can could be used to change all the 75-76 trucks to vac advance, we bought every one in the country and then Toyota discontinued the number.


Users who are viewing this thread

Top Bottom