UPDATE: SOLVED: ''pop" sound and stall

1986F150six:

Dang, if my truck had not been at that shop  I would not have given up on fixing it myself so easily, I wish I had seen this post before I dropped off the keys today!  I'm just not the type to tinker for hours for free when the owner of the place is trying to make their bread and butter.   Well I guess he ended up with bread butter *and* jam after working on both my trucks🙂

Welp, it was most definitely the rotor.  The pin/tab had busted right off💀.  Less than a year old, should I be buying a more specific brand or changing more often? I doubt I put 10,000 miles on it last year.

Lessons learned.  Never assume newish means working... And check your sources of ignition before jumping to conclusions about fuel.

Also, now I really want to save up for a DS2 conversion.

All in all she does run better now.  I'm hoping mpg improves as well.

Since I don't have the hybrid setup I hope I am correct to be timed at 10 degrees tdc right?

Thanks all, much appreciated as always.   Let's see if the picture loads 








The General:  1985 F150 4.9/1bbl Carter/CA emissions, manual w granny gear

Hey all,

I had a stall-n-die yesterday:  I was driving at highway speed and heard a pop or something under the hood and immediately stalled out and could not restart even after letting it sit until cooled down (2 hours).  The only thing I can think of is a fuel pump relay , as that would actually explain the intermittent rough running that can't be traced to anything else yet.  But I could be totally wrong.  EDIT:  maybe I fried my PCM?

Only prob is I can't find it, unless the parts store sold me the wrong relay.  (I received a black 5  blade relay)  I have looked through the forum and seems like it should be on the firewall by the brake booster, or else fuse panel driver's side, or in the passenger side cab floor area, but I can't find it.  Is it actually a 4 blade relay, right there in the middle of the firewall??  At a loss, and the diagrams (or more likely my reading of them) didn't help.  Having a hard time with the Chiltons as well, do I even HAVE a fuel pump relay with an EEC or do I have a mechanical fuel pump?   Hm, boy do I feel ignorant right now.

relax. not knowing is no sin. if you have the 4.9l with the yf single barrel carb then you have a mechanical pump. no relay or ecu involved. some have an ecu for timing advance as an early hybrid system with a tps on the front of the carb. if you don't have a tps, single wire o2 sensor, and have a distributor with ds2 then you have no ecu on board. that is a great thing yet no one but us select few know anything about it.
that does not say anything about the pop though nor about it stalling out.

Let's see:

I DO have a TPS (replaced it during smog battle)
DO have a single wire O2 sensor
Distributor is a new (reman actually I think) NAPA, not a Duraspark.  I replaced it right away, before I learned about the more desirable ds2 conversion (Not super clear on why it's better tho) but if you put the Duraspark in there you have to run different wires or something?...


ls this (TPS/ O2) because it's CA emissions, or is my truck setup even more obscure than that?

The auto electrician (highly reputable) I was at for my *other* truck (The General died as I was just showing up to meet the tow truck) had access to a pretty big database of wiring diagrams and he said it pulled up the 5.0, the 4.9, and the diesel all as the same diagram--the 5.0.  It showed that there should be an inertia switch somewhere in the passenger footwell area, which 1.) I thought those were only for EFI? and 2.)  wasn't there.

I am rechecking the Chilton's tonight.  I swear I only have the fuse panel under the steering wheel, and there are no relays up by the brake booster.

There is a black 4 blade relay looking thing right in the middle of the firewall, right next to a round black Thing I Don't Know, but it looks like it is riveted to the firewall.

Thanks for the fast reply today, I appreciate it..

To be clear, in case it helps, this was actually an Oregon truck from birth on.  The original owner's dad was a Ford dealer up in Medford area-- they chose CA options when purchased new.

often dealers which are in border states of California will opt for cali emissions due to salability.
the round thing in the middle of the firewall sounds like the wiper motor and has a plug with four or five wires going to it. but it slightly on the driver side.
you have no fuel pump relay.
 this is a new diagnosis now. does it have fuel? does it have spark? a "pop" sounds like a backfire. a backfire can blow off vacuum hoses and caps and even gaskets in some cases. once they do, it's now a major vacuum leak and will definitely cause rough running or even a failure to start.
sadly, enough mechanics today don't even want to know more than what their autel or modis tells them. I have three of the next generation in the family and one who is a mechanic. and I try to be an available mentor to any of them who will ask.

not sure about the fuel or spark but I am heading back over today.  

The thing is, it died AT a shop, so the guy has been super nice letting me mess around with it in his parking lot, but I don't feel right doing much more investigating before I hand over my keys for a diagnosis.    

I have looked all over and don't see any vacuum line issues, even the vacuum tree on the manifold and the ...little row of vac lines covered up by the black casing back by the PCV valve.  The pop did sound like it could have been a backfire out off the carb, but I mean I looked behind me as well to see if I lost a part or something because it was so unexpected and maybe not quite a backfire sound (I didn't see anything)

I have:  solid crank but zero turnover as if no fuel.
            my relatively new throttle cable has more play than it should
            no apparent gasket leaks
            no oil/ water leaks
            no loose/cracked plugs
            no loose nuts at carb base


           

Remove the distributor cap and have someone turn the key as to start the engine. Doe the rotor move?

While you're in there, make sure the bolt that holds down the distributor is tight. I have to wonder if the sudden pop, plus the no-start condition, couldn't be the result of the timing slipping in a major way. That could easily fire a spark plug while the intake valve was open, leading to everything in the intake manifold igniting. Then of course the engine would die, and not restart, due to the timing being so far off.

Mat is right on no fuel relay, as the fuel pump is mounted to the left front of the motor.
The truck should be a feed back system after 83, so has a computer to lean out the carb and adjust timing.
A computer going bad "should not" stop the motor from running.

Now if I get this right you were driving at speed and you got the pop and it stopped running.
At first I would say timing chain but the 300 six motor uses timing gears.
Could they strip? Yes but almost never heard of so I would kind of count that out.
Even more so if the motor cranks over at normal speed as a bad chain / gears it cranks over faster than normal most of the time.

Now it was posted to pop the dist. cap and see if the rotor spins and this is a good start but not a tell all.
If the dist. pin broke, this has been posted to happen more times than not, the timing could be off and why the pop sound but the rotor could still spin when cranking the motor over.

What needs to be done is pull #1 plug and get the motor to TDC and see where the rotor is pointing to.
Just note the TDC mark on the crank will come up 2 times before #1 is at TDC.
Now if you have it at TDC and the rotor is pointed 180* out then I would say you might be ok but turn it till at TDC.

If the rotor is not 180* off or at TDC then the dist. needs to come out (mark dist. to block and cap for #1) and the pin holding the gear to shaft checked. Dont just look at it because when they shear it looks like the pin is still in good shape as you see the ends of the broken pin. Try to drive the pin out to make sure the pin is good.
If pin is sheared you will need to try turning the oil pump shaft to make sure it is not jamming up and caused the pin to shear.

Oh yea before getting into all this check for fuel & spark.
Good luck
Dave ----

rotor button failure! bingo.  when in doubt about whether you should be using one brand over another, the answer most always is "MOTORCRAFT". as close to factory as available.
 on the timing adjustment, it seems that you do have the "hybrid system" as in (I was hybrid when hybrid wasn't cool). you have what is referred to as a thick film distributor. that is due to the thick film ignition module being mounted directly on the distributor. there is a "spout" plug wired into the harness about 6" from the distributor, it is usually a male/female combo of black plastic, that should be disconnected while setting the base timing. after base timing is set and distributor tight then turn off the truck and reconnect the spout plug. now the eec/distributor will adjust the advance as needed

Good to here it was something easy and is running again.
Dave ----