i've got a 1967 f-250 with a 352ci FE motor in it. i recently bought the truck, so i'm not real familiar with the truck's history, but let's just say it's not pretty and not in great shape. it was, however, until last friday, running.

i was driving down the highway at 60 mph and all of a sudden the motor quit running. i put it in neutral and coasted to the side of the road. i checked it to see if anything real obvious could have been at fault. all seemed in order and the engine wasn't hot. if anything, it seemed colder than i had expected it to be, but i was 5 degrees outside.

so far i've looked into:

battery: the one on the truck was 8 years old and not putting out the CCA it was supposed to. when i tried to restart the truck on the side of the road the battery seemed low on juice and was having a hard time turning the motor over. i had it tested and they said it came back bad. i replaced the battery and the new one has no problem turning the motor over.
alternator: tested good
fuel pump: put a fresh filter in it and it's definetly pumping fuel
carb: don't know alot about how a carb can fail, but this one (600cfm holley, older model with manual choke) is still spraying fuel into the intake. just to be sure, i used a bit of ether to see if the engine would hint at running, and saw no improvement
coil: had it ohm tested and it passed with flying colors.
distributor cap/rotor/points: all of these checked out okay, not requiring cleaning or adjustment
spark plugs: i pulled several (but not all) of them and the ones i looked at were in good, average shape. no oil build up, not wet, good gap, etc. also, when rested on the block while the motor's turning, they are producing spark.
compression: this is an old, very worn motor. i expected compression to be shot to hell, but i'm not totally familiar with how to correctly test the compression. i do have a compression tester, and i tested a few of the cylinders. i hooked the gauge up and let the motor turn over a couple times and the cyliders all seemed to top out at 110 psi. from what i know, this is quite low, but not likely to have happened to all of the cylinders all of a sudden. so, though it's indicitave of lots of wear, it isn't the likely cause of my problem.

so i've come to these conclusions: i'm getting air, fuel and i'm getting spark. i may not be getting great compression but that was already the case before it died. that only really leaves timing, right? the distributor is in good shape and didn't move or twist, as it was tight and i found it right where i'd left it.

what are the chances that the timing chain's got enough slack that it could've jumped a couple teeth and now the crank and cam are out of time? are there any other things that i could look into? i'm looking to replace the motor in a few months and i'm hoping to limp this one along until then.

 

I would check the timing chain from what I've read on these engines they tend to wear and can jump teeth causing the timing to go out of whack if I remember right there's plastic gears in the timing system can someone clear that up for me if I'm mistaken?

 

not sure about the plastic gears, but the timing was about all i could think of that's left to check. this just confirms it for me. thanks!

 

its nylon gearing on the cam.metal on the crank. plastic would never make it.

 

When the engine died, did it stumble to a stop, or did die as of the the key was turned off?
Gene

 

did you actually verify that you're getting spark from the plugs or just inspect the components?

Don't forget about safety switches. Those little *******s have cost me many hours of troubleshooting.

 

when the engine died, it did not stumble at all, it just quit. just like if the key had been turned off. i considered the ignition switch, but other items that are powered when in the on position remained on. also, i did physically pull spark plugs and verify that there was spark jumping the gap, in addition to inspecting/testing the components. if the ignition switch were at fault, there would be no spark, as there would be no power to the coil, correct?

as far as safety switches are concerned, i'm not sure what exactly you're referring to. perhaps you could elaborate?

 

like the one that wont let my truck start unless the clutch is in. or wont let your car start in gear. I once spent 2 days trying to get a chain saw to run before I figured out it was the switch. Mowers too, like the one where you have to be sitting on the seat for it to run. AAARRGGH. I HATE safety switches!

Anyways, good luck with your truck man. Where you at? I've got a motor available.

 

to check the timing chain aling the 0 deg timing mark on the harmonic dampner and the timing pointer. your #1 cylinder should have both valves fully closed, and the rotor (under dist cap) should be pointing to the lug for the #1 spark plug. Now the crank shaft turns two revolutions for each revolution of the cam, so if the rotor dosent line up turn the crank 360 deg and check it again. Also if it is a timing chain that has jumped a tooth or so you compression test would be invalid. hope this helps

 

First, I'd check that you have voltage at the coil and points with key turned on, not cranking it over. You said your getting spark while cranking. If timing jumped while going down the road at 60 mph it would have been poping back or some type of back firing...
Not just go died out without a fight to keep running. Try hot wiring it.
Put a jumper from the+ battery terminal to the +side of coil terminal.
Then try cranking it with key switch. Remember while you turn the key to the start mode it bypasses the run mode and gives it higher voltage to start then 7-9 volts in the run mode which may have a broken wire inline to the coil.
That my 2cents.
orich

 

it's an automatic trans, so no neutral safety switch. the safety switch that requires it to be in park to start is functioning, as it won't even let me turn the motor over if the truck's not in park, and it currently turns over.


i figured that timing being off would make compression low, so i was a bit suspicious of how low the results i saw were. thanks!


the wiring supplying power to the coil reads 12V when the key is in the run position. there's an external resistor that is attached to the same terminal of the coil that the power wire is, and when the voltage is read at that terminal with the key in the run position, i get 6-8V. disconnect the power wire and check it all by itself and i've got 12V. not sure if this is how it was originally supposed to be, but this is how it was when it died. just to check, i removed the resistor and tried starting the truck, to no avail. any reason that this wouldn't have the same effect as hot wiring as you've described?

as far as how it died, i did find it odd that some sort of partial mechanical failure in the timing could result in such a smooth shutting-off of the motor. at least if it were only off a tooth or two. if it instantly jumped several teeth maybe, but i've never heard of that happening and the chain remaining intact. i'll have to pull the timing cover and maybe the valve covers and take a peek. maybe some time when it's not 5 degrees outside.

i live in the SE corner of WA.

 

out of curiosity.... everything else being equal, how low would compression have to get before lack of compression would cause a motor to quit running? when it turns over, there's at least enough compression to make the appropriate noises in the exhaust pipe. and how many teeth would the timing have to jump to make the motor not run at all? i was thinking that 1 or maybe two teeth and it would still run, but run horribly and probably require some change of ignition timing. while trying to crank it, i tried rotating the distributor a good 20 degrees each way, to see if that would help. even with all of this, the motor never so much as stumbled. and through all the testing and trying i've done, it hasn't stumbled once. not since it shut off has it even hinted at running.

 

I would think if your getting fuel spark and air you should atleast get some back firing even if the timing is out did you try spraying starting fluid in the carb or dumping some gas in it? Maybe try this and see what happens just to rule it out and get you one step closer to finding the problem.

 

I tried to make a 2300 4 cylinder run with the belt one tooth off--no soap.

Looking at your rotor (cap off), rotate the engine. Once it moves, reverse the rotation. Note how far you have to rotate the crank before the rotor moves. 5 degrees or more is a lot of slack in the chain and it should be replaced, jumped or not. If it is just loose and not jumped, your engine will phase in and out of tune--a good idle will slowly deteriorate, then snap back to good, for example.

So far, timing chain still sounds like the most likely culprit. My 289 didn't make a sound when it jumped.

 

You can get an idea of what kind of shape the timing chain is in by pulling the dist cap off and turning the crank until the rotor moves, and then turning the crank in the opposite direction and seeing how far you have to turn it until the rotor begins to move in the opposite direction. You shouldn't have to turn it much, just a quarter turn or so.

Some of the original timing gears were coated with nylon to make them quiet, if the nylon disintegrates then the remaining gear becomes much smaller and lets the timing chain loosen up so much that it becomes easy for it to jump teeth.

I really doubt the motor would just lose compression as you're driving down the road unless something else happenned. If the timing chain jumped teeth then the compression readings would be off because the cam would be opening the valves at the wrong times.