Finding TDC

[matthewb0051]

Was about to take off my MFI pump to have it worked on and noticed that when getting to TDC the rotor did not align with the mark but the mark on the pulley was aligned. The dizzy rotor had not come around to the mark on dizzy. I am stumped here. Followed all the steps to get to TDC but marks not aligning at same time. I know I need to do this and then rotate some more to have pump marks aligned.

It is not on cylinder 4 (180 degrees out) It is running behind the marks on pulley. As an example, if the dizzy alignment mark were 12 o'clock the rotor is at roughly 10 or 11 o'clock when Z1 comes up on pulley.

Why would the marks not align? How can I fix?

Car is 1969 911E. Frustration and thoughts of selling creeping in...

[ManniB]

It might be that a PO has mis-aligned the distributor by one or more cylinders and then compensated by plugging in the plug wires accordingly. Hope this makes sense to you.
Identify the cylinder no. 1 plug wire and see where on the distributor cap it is connected. Does the rotor lign up with that position when the pulley is on TDC?

- Manfred

[James Brown]

at TDC #1 (your positive) and the dissy is not correct, where is #1 plug wire? does it line up with the rotor position at TDC? the dissy can go in anywhere so it might have to be re clocked.

[kidrock]

Matthew, you have a PM.

[Joe Bob]

There was a recent thread where the PO...at least claimed by the newbie that the dizzy was 180 off.

The PO, supposedly just redid the plug wires. The newb, had backfiring thru the intake when he changed plug wires and hooked it up as per the SC diagram......

Always trust....but verify.

[GaryR]

When #1 is TDC the Z1 mark on the pulley should be aligned, the rotor should be on the Z1 mark on the dizzy, the #1 piston should be at the top of it's stroke, and both #1 valves should be "relaxed" (closed) with the proper rocker arm clearance. If any of these are not true let us know, else all is well. Of course this is regarding an SC but I can't imagine Porsche changing basic timing parameters.. or did they?

[T77911S]

not really.

depends on how the igntion timiing is set.
if it is advanced at idle say 8 degrees, it will NOT line up with the mark on the dist body when the crank is TDC.
line the rotor up the the dist mark. look at the pulley. is that about where your timing hits with the timing light?

one thing about the 911 dist. as said above. the dist can basically be put in in any position, you just have to move the plug wires around to line up to where #1 is at TDC.

on my 930, i line up the magnetic "ploes" for #1. my rotor is pointing who knows where. it does not matter as long as #1 is the one firing. i do know my rotor is off from the mark on the dist.

i think all you are concerned about is making sure TDC for #1 is on the compression stroke and that you need to line up Z1 for that. dont worry about the rotor

[911pcars]

There's really no reason to complicate the basic mechanical relationship with other compensation procedures when it involves the crank pulley, no. 1 piston, rotor position and other engine timing requirements. It's like when my Dad created his own paper filing system to maintain job security. He alone knew where things were, but it really wasn't ideal for others in the office if he weren't there. However, for a one-man office staff, it was fine.

An 8º static timing setting measured at the crank pulley is only a 4º difference in the distributor. Thus, the rotor shouldn't be that far out of alignment with no. 1 cylinder at TDC, end of compression. On early 911s, the rotor rotates in a CW direction and should be near a dash line on the dist. housing when pointing to the no. 1 spark plug wire when it fires.

Sherwood

[GaryR]

Originally Posted by 911pcars

There's really no reason to complicate the basic mechanical relationship with other compensation procedures when it involves the crank pulley, no. 1 piston, rotor position and other engine timing requirements. It's like when my Dad created his own paper filing system to maintain job security. He alone knew where things were, but it really wasn't ideal for others in the office if he weren't there. However, for a one-man office staff, it was fine.

An 8º static timing setting measured at the crank pulley is only a 4º difference in the distributor. Thus, the rotor shouldn't be that far out of alignment with no. 1 cylinder at TDC, end of compression. On early 911s, the rotor rotates in a CW direction and should be near a dash line on the dist. housing when pointing to the no. 1 spark plug wire when it fires.

Sherwood

Sherwood, that's correct, and once you have messed with any of it you should run a timing gun on it. To me it's nuts to have the dizzy off by a cylinder when all you have to do is set the engine to Z1 (with #1 at TDC), pull dizzy and point the rotor to the Z1 mark on it, then drop it back in! Put wires in correct firing order, set timing where you want and done.

T77, I understand what you are saying and you are correct, but that is a minor timing correction. I am baffled by the dizzy's with modified plug wire arrangements when it's such a simple fix to set right.

[NoYouRelax]

I had the same problem. Just remove the distributor and rotate it to the notch while pully is at TDC. Reinstall it and rewire it with the #1 wire in its proper position and follow sequence with 2 through 6. My PO's work baffles me sometimes, and I am just and engineer with too many tools.

I suspect that the previous mechanic put the distributor in 180 degrees out and did the correction at the dizzy cap.....yes, even though it is notched.