Engine won't start and turns over like it has no compression

My Mustang is running it's original 302W, no idea whether or not it has been rebuilt in the past at all.

Always been running fine, although the last couple of drives I noticed it wasn't idling as efficiently as it normally would.

Today I cranked it over, it fired up for a couple of seconds but wouldn't stay running, tried a second time, the same.

Tried a third time and it fired up then stopped very suddenly, and subsequently when I turn it over it won't even fire, and the engine now sounds like it is turning over without any compression, none of the normal engine cranking sounds, now sounds more like a free-wheeling whirring as the crank turns over.

I'm not really that savvy when it comes to engine diagnosis. I did check that the fuel pump is pumping ok and tried another coil but that didn't work, but the battery started to die so I've put it on charge and turned in for the night (Australia time).

Tomorrow I'll pop the valve covers off to see what the valves are doing when I turn it over, but it is the freewheeling sound that the motor is making whilst I am turning it over that has me quite nervous.

Anybody here got any thoughts? Might I have busted a timing chain or wrecked a camshaft perhaps?

With your "freewheeling" sound, my first suspicion would be the timing chain slipped. The OE cam gear had nylon teeth, which crack and fail over time. Remove your distributor cap and crank the motor over while watching the rotor. It should spin in time with the engine. Often when the can gear is stripped, the rotor will stop and start. If you turn the engine over to TDC on the balancer, the rotor should be pointing at the #1 or #6 plug wire. If it isn't, it's likely the cam gear.

Another easy test:
Pull a spark plug and with a remote starter crank the engine to verify pressure blowing out the spark plug hole. If yes you have pressure, then pull the distributor and check it's gear, maybe just a sheared distributor gear roll pin. If no pressure blowing out probably looking at timing gear as stated by HC previously.

Thanks guys, I did remove the distributor cap and the the rotor was turning, but I only looked at it for about one revolution - will check its orientation and proper function tomorrow.

Hemikiller said:

With your "freewheeling" sound, my first suspicion would be the timing chain slipped. The OE cam gear had nylon teeth, which crank and fail over time. Remove your distributor cap and crank the motor over while watching the rotor. It should spin in time with the engine. Often when the can gear is stripped, the rotor will stop and start. If you turn the engine over to TDC on the balancer, the rotor should be pointing at the #1 or #6 plug wire. If it isn't, it's likely the cam gear.

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Bingo!
At TDC the rotor is facing directly at no 4 cylinder, looks like the chain has slipped a tooth or three. Hopefully valves are still ok, though I am cautiously optimistic as this happened in my garage rather than while driving on the road. Time to pull the front cover off to take a look, thanks for the helpful advice, will post in this thread what I find out!

Flatback72 said:

Bingo!
At TDC the rotor is facing directly at no 4 cylinder, looks like the chain has slipped a tooth or three. Hopefully valves are still ok, though I am cautiously optimistic as this happened in my garage rather than while driving on the road. Time to pull the front cover off to take a look, thanks for the helpful advice, will post in this thread what I find out!

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Another issue could be you sheared the distributor drive pin. That would have it pointing the wrong place too.

When you pull it to do the timing chain verify the pin is good before you tear the front apart just in case.

Most likely the chain, but I did have a pin shear, too.

Flatback72 said:

Bingo!
At TDC the rotor is facing directly at no 4 cylinder, looks like the chain has slipped a tooth or three. Hopefully valves are still ok, though I am cautiously optimistic as this happened in my garage rather than while driving on the road. Time to pull the front cover off to take a look, thanks for the helpful advice, will post in this thread what I find out!

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There's no interference issue with a stock cammed 302. My first sporsroof's TC failed merging on to the highway on my way to work, swapped it out on the side of the road. That was 1992.

rcadd1ct said:

Another issue could be you sheared the distributor drive pin. That would have it pointing the wrong place too.

When you pull it to do the timing chain verify the pin is good before you tear the front apart just in case.

Most likely the chain, but I did have a pin shear, too.

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Good to know, I'm keen to change out the timing chain and gears anyway now, as I hate the thought that I might have a 50 year old gear in there with nylon teeth. I've ordered a crow cams gear/chain set from ebay (only $129 AUD which I think is great value) and also a gasket set. If the rotor doesn't move into the right position when I realign the cam and crankshaft then I'll pull the distributor then.

Hemikiller said:

There's no interference issue with a stock cammed 302. My first sporsroof's TC failed merging on to the highway on my way to work, swapped it out on the side of the road. That was 1992.

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Ok, that makes me let out a sigh of relief! Pretty sure mine has a stock cam. I'm assuming if the chain and gear have been quite worn that with a new set the engine will run slightly more efficiently?

One more query, do I need to remove the water pump from the timing cover when I take the cover off, or can I leave it attached to the cover without fear of a leak after reassembly? I replaced the water pump only a couple of years ago so I know the pump is in pretty good shape.

I'd replace the water pump gaskets while you have the timing cover off. They "should" be okay, but better safe than sorry.

Lots of times when the plastic gear fails, parts of it end up in the oil pan. So, consider that as well. Others may have relevant experience with this. When my 400M failed, the gear was in pieces.

Here in Australia we can often be heard to use the word "cactus", which in our regional colloquial idiom can refer to something as being "dead, broken, ruined, no longer working".

So I can emphatically and without any exaggeration say that the cam timing gear in my car has been found to be totally and utterly CACTUS.

It was quite amazing that the car was running at all, and I can be quite thankful that the final chain jumping failure occurred in my garage and not out on the open road in the middle of nowhere.

When I put the harmonic balancer back on so that I could manually turn the motor, the amount of backlash at the balancer diameter is around 3/4 of an inch, or around 13 degrees backlash. Needless to say that I am expecting my car to run somewhat better than before when the new chain and gears are installed.

Thankful for Hemikiller pointing me in the correct direction with the diagnosis!

Yeah, that one is totally "cactus", and it'll run much, much better with stable timing.

As the others noted, the nylon bits from the gear are now in the oil pan. The "best" way to handle this issue is to pull the pan, clean it and the oil pump screen out. The reason for this is Ford used a screen with an open grommet in the center, with a metal strap covering the hole. I believe it was designed like that in case oil sludge plugged the screen, it would still allow oil to flow. Unfortunately, it also lets pieces of nylon through, which jam the pump, snap the driveshaft and the engine continues to run without oil pressure.

When I turned wrenches for a living, timing belts were becoming common and failures were frequent. I came to know the distinct cranking sound in short order...some were pass-through, some were not....pretty expensive fix on those that were not.

you certainly received some great advice in this thread. I have been traveling, so missed your original post until after the flurry of suggestions. It may be too late for me to offer my thoughts to be of any help, and they would be largely redundant re: looking for evidence of a timing chain that jumped, dropping the oil pan and cleaning the oil pickup screen and oil pan to get rid of all the nylon/plastic tooth coating that failed, and replacing the water pump while you have the car apart anyway. I will add this, which I did not see in my cursory skimming of comments...

I suggest you get a high quality double roller design for the new timing chain and gears. And, in order to prevent the camshaft gear teeth from shelling nylon/plastic coating, I recommend using all steel teeth, no nylon or plastic coating, The all steel gears are a little louder than the plastic coated gear teeth designs. But, it will last you much longer. I hope you did not suffer any engine damage with pistons hitting valves open at a bad time. I have (also) heard the older 302 engines are a non-interference design, but I never bothered to look that up to find out for sure, until now.

It looks like the answer re: the 302 being an interference engine or not is a definite maybe, where a lot depends in whether or not the engine is stock, and if its valve timing was retarded for emission control reasons. One quick way to see if there was any kissing of valves and piston heads is to remove the spark plugss and use a bore scope to look for any "witness marks" indicating a collision with valves and pistons. If you are lucky you will see no such damage, otherwi$e you are in for some fairly significant money. If you ever remove a set of heads for any reason, it is a good opportunity to have them magnafluxed to see if they are cracked or damaged.

**** my wife called me a cactus just yesterday!

And here in Tucson, AZ, we grow cactus, just like my profile picture!

mrgmhale said:

I suggest you get a high quality double roller design for the new timing chain and gears.

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Thanks for your advice mrgmhale. I do have a Crow Cams double gear-set on order, not sure if it is a roller type though. But one thing comes to mind - wouldn't the extra gear width mean that my harmonic balancer will stick out further and stop my drive belts from lining up? Or does the double gear have a counterbore in it so as to retain stock width?
Edit: double roller gear set arrived today, width of the gears are the same as stock width, harmonic balance will sit in the same position and the stock fuel eccentric and oil flinger will both have clearance, so all good!

Always good to close out a mechanical problem forum thread with the final fix solution, so here is the update on the wrecked timing gear. I actually completed this job within a couple of weeks after the first post.

As detailed in the original posts I tried to start my car in my garage and the engine turned over but then stopped extremely suddenly, and subsequent attempts to start had the engine seemingly freewheeling as it turned over.

Hemikiller responded with the probable diagnosis as being a slipped timing gear and subsequent disassembly proved this to be totally correct - stretched timing chain and a timing gear with teeth worn down to the nubs with the final spectacular failure spinning the crank almost half a revolution out of timing gear alignment.

So I ordered a nice chunky new Crow Cams double roller gear and chain set which arrived in the mail fairly promptly.

Hemikiller advised that the "best" method to remove any broken teeth from the sump would be to remove and clean out the oil pan. However I lacked the equipment (and the confidence) to do this so I set about doing what I guessed might be the "second best" method.

I emptied the sump of oil and then placed a clean oil catchment tray under the sump with a small kitchen sieve clamped onto the inside of it.
With the timing cover removed there is a decent sized open gap between the front of the oil pan and the cylinder block, so I jammed a funnel into the gap and then dumped a gallon of clean kerosene into it, which came straight out of the open sump plug bringing pieces of timing gear flotsam and jetsam along with it, the pieces being caught in the sieve. With disquiet in my mind at the thought of a piece of gear breaking my oil pump I must have done this flushing about 25 times, each time moving the funnel around a bit to get the flushing to flow through the sump in different directions.

Eventually the bits and pieces stopped coming out and I used a boroscope camera to peer all around inside the oil pan and was confident that I had cleaned out all the pieces, but I couldn't see under the oil pump pick up so I bent up a strip of tin sheet and slid this in through the gap at the motor front and moved it back and forth under the pickup to make sure the were no gear pieces jammed in the between the pick up and the pan. Checked again with the boroscope, nothing showing, did another couple of flushes and was satisfied that I had got everything that could be got. No doubt the mesh on the oil pickup has some bits jammed in it still, but I'll see that as an acceptable risk.

The timing gear has obviously been wearing out and falling apart for years and years and I assume most of those small bits have been flushed out of the engine during oil changes or ended up in the oil filters over the years. All of the bits'n'pieces that I managed to flush out of the pan are consistent with the final abrupt failure of the gear when the chain jumped. Photo below of the bits that came out, including a couple of black plastic mystery pieces that aren't a part of the gear.

Everything reassembled ok, the distributor was waaaay out of position with the new gears so I reset that.

So how does it go with the new timing gear set? Well Hemikiller said my engine would run much much better. Well I would add an extra "much" to that that statement !

My car always idled somewhat roughly - now it idles super-smooth at 600 rpm.

My car has always been gutless, I have owned it for 15 years and all during that time I had bought into the idea that by 1972 the Ford 302 had hobbled the horsepower to comply with emission standards, and that's just the way the engine was supposed to be. It is only a three-speed car with a stock-spec engine (apart from a Holley 570 4bbl carby) and it will never be a rocket, but now when I get up into the higher rev range this thing really accelerates along very nicely, and I'm not only now easily keeping up with the traffic but I'm also finding myself jumping down on the gas pedal at every viable opportunity. And the car even runs quieter too.

The lack of power my car had was the only disappointing piece of the picture that was stopping me from enjoying my car to the fullest, but now that has been totally solved for me!

Pretty amazing what proper cam timing will do for how your engine runs?! I have a cheapo Amazon borescope and it's a tremendous tool for automotive use.

You'll gain a little more with a performance curve in the distributor and a bit more initial timing.

I get scared when I see this timing chain post. Mine has been unseen within the original engine...tick tick tick... But thanks for the update.