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hello all and thanks in "advance" (a sad timing pun)
1984 f250 4.9l inline six manual tranny
recently posted with regards to a no-spark situation - thinking it was electrical, turns out it's mechanical (hence the subject)
i'm here to uncover as many hiddens as possible before taking on a repair which i have zero experience with.
i have not pulled the distributor out yet.
when the trucked failed, i was on the highway at cruising speed, and it just stopped running.
no noises, or loud bangs.
when attempting to start, motor cranks normal, no fast spin from mech timing failure
i cannot turn the distributor by hand (not loose)
i've read , that if the oil pump freezes, it can cause the distributor to fail (retaining pin failure?)
so, i'd like to know as much as possible before proceeding, as a precaution, and to increase efficiency of the repair
(once i start, i'd like to push through and finish)
my initial questions are:
if the dizzy can't be turned (loose), does this mean anything in particular?
if something has broken-off, are there ways (tricks of trade) to retrieve or pull out loose parts when i pull the dizzy out?
is there a way i'll be able to determine if the oil pump is frozen?
what other possibilities might i consider?
Put the #1 piston at TDC on the compression stroke. Mark the distributor housing and block with a scribe line or sharpy, so that after reinstalling the the distributor the base ignition timing will be very close to what it was before as far as that goes. Pull the distributor. It sounds a little bit like the roll pin that aligns the distributor gear on the shaft has sheared. At least that would be the best of the bad possibilities. The question is, why did it shear?
Could be the oil pump is locked up. If you determine the oil pump is OK, and have replaced the roll pin, then for re-installation of the distributor you'll have to hold your tongue just right, and drop the distributor fully seated and at the same time get the rotor to align with the location of the #1 terminal of the distributor. Because the gears are helical, the rotor has to start out with some windage, almost leading the end point desired by a whole terminal spacing. When you remove the distributor you'll see this in reverse.
If the distributor housing is aligned with the mark made previously, and the rotor is aligned with the #1 terminal at TDC compression, it should start right up again without any drama. Again though, the question is why did the roll pin shear? (Assuming this is the fault)
if i may, would there a way to determine the status of the oil pump? and, can the roll pin just wear out, and fail?
if the oil pump is driven (turned?) by the dizzy shaft, would i be able to get to it and would it turn if otherwise ok, kinda thing?
thanks again!
If the roll pin on the dist gear has sheared off you are going to have to pull the gear off to drive out the piece in the dist shaft . Once the gear is off drop the dist back in the hole and see if you can rotate the rotor. there should be some resistance turning over the pump if not then the pump drive shaft could have sheared. Hopefully it is just the roll pin and not the pump drive shaft or pump.
"Writing" out loud... you said in your first post "no spark" issue. So it sounds like you confirmed no spark? (sorry I haven't seen your other thread) If you haven't, you could take the distributor cap off and have someone bump the starter to see if your rotor moves at all. I'm guessing from your situation that the rotor won't rotate when the engine is cranking - but could be an easy check before pulling the distributor.
If the rotor isn't rotating, it has to be the gear, right? Shearing of the hex shaft (intermediate shaft) would have no impact on spark, only oil pressure.
Technically, the rotating assembly of the distributor could have sheared - but how and why would it? It has nothing "resisting" it's rotation - unlike the oil pump, distributor gear, and intermediate shaft combo. And this would be easy to check because you could spin the rotor freely by hand with the dizzy still installed.
Bottom line - if your rotor isn't turning when the engine is cranking, you'll have to pull the distributor to find out what the issue is. Here are a couple pictures to help.
Oil pump. The intermediate shaft (hex) below is inserted into the oil pump to drive the pump. Intermediate Shaft (hex). Goes between the distributor and oil pump. Distributor. The intermediate shaft (hex) is inserted into the bottom of the distributor. Closer look at distributor gear and roll pin
