I went to change the cap n rotor on my 93 f150 4.9L and while pulling the rotor the whole distributor shaft came out...is this how the distributor is built or do I have a problem? This may seem like a silly question but I've never encountered such working on gm... 😂

 

Suppose I'll put some background info. I have a 93 f150 4.9L, 4x4 with manual trans. About a month ago my truck sorta lost all power. It struggles to reach 50-55 mph and seems to not go over 3k rpm with the pedal to the floor.

 

Pictures would help a lot here - they're purportedly worth a thousand words. Lacking those words, or a picture, it is hard to interpret what all is going on here.
- Normally to remove the shaft from the distributor body, a roll pin has to be driven out of the gear, and then the gear pressed off of the shaft.
It sounds like you're saying that the distributor body remained bolted to the block while you pulled the shaft up and out (assuming along with the vane plate) which would leave the gear behind (maybe still in the general area, prevented from falling into the oil pan by the shaft that drives the oil pump). It doesn't seem possible that the truck could have run at all if the gear had been this loose, so maybe this interpretation is wrong.
- Maybe the shaft broke above the gear and what was removed is just the partial shaft; again, it doesn't seem possible that the truck could have run at all in this state, so maybe this interpretation is wrong.

So, what exactly came out, what exactly remained behind?

 

Alright so that was fairly vague description, my apologies. The distributor housing remains bolted and attached to the block but I can grab the circular piece that the rotor slides onto and remove it from the distributor housing I believe the the part that I can pull out goes from the piece that the rotor slides onto down to the shaft that goes into oil pump. I won't have a picture to show until tomorrow.

 

Sounds like the roll pin sheared off and now the engine is trying to run out-of-time. Prolly best to let it sit until you get a replacement.

 

My fear now is that when I go to remove the distributor, is anything going to fall into the oil pan...? I'll have a picture later today

 

Yes it dose sound like the roll pin sheared and the gear is now spinning on the shaft.

Yes your fear is vary true at this point in time.
Not knowing how far out you pulled the shaft that the gear stayed in place and the shaft went back thru the gear.
With a wish & prayer when you undo the hold down and you pull the dist out any grim build up on the shaft will hold the gear to the shaft and will come out with the dist.
If it stayed in the motor and stayed there and did not fall you might be able to take a magnet and fish it out.

Other wise you can go 2 ways from here.
1- if it went all the way down in to the oil pan just leave it there as it should not move and get a new gear and roll pin for your dist.
2- drop the pan to get it out. I here on 4x4 you can drop the pan with motor in truck a 4x2 you can not.
Dave ----

 

 

Gear stayed inside

 

Well, that's not something one sees every day. So before just replacing it, why did this happen - are there any upstream problems?

The distributor itself typically places very little load on that gear - it's mostly along for the ride while the main load is the oil pump. So there might be something going on down there that caused this failure.
With the parts now in hand (the bare dist shaft without a gear + the oil pump drive shaft, seen still attached to the dist shaft in your second photo), you can turn the oil pump by hand and see how it feels (or that it even turns at all, let alone smoothly).

Some other considerations:
Any history of oil pump issues, maybe replacement at some point? Maybe a high-volume oil pump put in (high volume = high load)?
Is it an aftermarket distributor, possibly with a chineseium roll pin? If so, new or rebuilt?
How many miles on the engine (or on the oil pump, or dist if it was replaced)?
Was the PIP pickup replaced in this dist at some point (which would require messing with that roll pin, likely reusing it)?
Looking down into the dist's mount hole on the block, how do the camshaft's matching gear teeth look?

It would be useful to get a look at the dist gear if possible; maybe fishing it out with a magnetic or claw pickup tool. For example, the cast vs steel issue -- where the gear and camshaft materials get mismatched (if that's even a 4.9l issue, as it is with the V8s*) - might have led to a badly worn dist gear, eventually leading to the pin shearing. Other clues as to what happened might be on that gear.

* See the photos here: https://www.ford-trucks.com/forums/1...l#post21205147

 

Well, as Dave mentioned, if the (now disconnected) drive gear falls into the pan, it's not a game stopper. It's too big to be sucked up into the oil pickup. I'd guess it's still meshed with the cam gear and it might be worth your time and effort to see if you can't fish it out (which may involve you becoming very creative with fabbing a tool for that). If you are able to fish it out, you can get a new roll pin and re-use that distributor.

However, you might have another issue as BWNG mentions. Why did that roll pin shear? It would suck to have the same thing happen again in a few months or so. There's no way to determine if the oil pump is high-volume without looking at it. So, you'd have to drop the pan (which involves jacking up or removing the engine in a 4x2 truck) to verify that. It's hard to tell if the roll pin was defective from the pic posted. It sure looks like it sheared completely, there wasn't an existing crack/fracture which ended up expanding & failing. I wonder if real thick oil might have contributed to the pump becoming hard to turn...?

 

The truck ran very well when I got got it, kept great oil pressure. The only thing I've done to it mechanically was clutch/master/slave and release bearing. I am concerned as to what could have caused the pain to sheer off. The problem that led me to discover the distributor broken was the fact the truck had lost power, struggled to reach 55mph with pedal to the floor and couldn't rev past 3k. Could that just have been due to the pin/gear issue? I do believe the distributor is not original (there were some stampings on the distributor housing which includes a QR code lol) I got my hands on a stock distributor I may toss in today and see what happens. Truck is a 4x4 so dropping pan may be an option so I can inspect things a bit better.
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I ran the part number and it's an AutoZone dura last gold distributor

 

Yes, when the gear starts moving on the shaft, your timing goes off based on the amount of spin from it's original position, just like turning the dist. when setting the timing.

Did you get the old gear out? I would DEFINTELY see if you can spin the oil pump before you go any further, something caused that pin to shear...

 

FWIW, I recommend getting a hold of that missing dist gear for analysis before putting in what will be at least the third distributor to go into that truck. I'm not the soldier in the field, so that opinion isn't worth all that much.

Is it undamaged?
I haven't worked on a 4.9l dist, but have disassembled too many 5.0/5.8l dists of that era, and those gears have to be pressed on and off - there's no way that (yes, without the pin) that it could be slid off by hand. You should see some of the Youtube videos of clowns trying to get it off via various ad hoc wrong-tool methods (hammers, torch, &c.). Did it maybe crack? Is it in one piece? How could it still be intact if it's not still press-fit onto the dist shaft? The whole gear won't get sucked into the oil pump, but small enough slivers might.

Since that was not an OEM dist, did the steel vs cast dist gear problem occur? Again, I don't know enough about 4.9l dists to know if that is even a problem with them like it is with 5.0/5.8ls.

When a problem has been successfully diagnosed, all of the weird symptoms usually get explained (or identified as irrelevant, or some that had been thought irrelevant turn out to be related - in any case, a whole bunch of mystery gets cleared up). Maybe just having been a poor aftermarket dist is enough to explain everything. Even if so, there's still one thing that doesn't make sense: that the gear was loose enough to slide right off implies that it would have probably similarly spun on the dist shaft when in operation (as a normally working oil pump would supply more force than that), in which case it would seem that the engine would not have run at all. As that contradicts what's been given, that in turn implies that there's still some data missing. Maybe the missing gear will supply that.