1983 Ford F250 6.0L 460 standard tranny
Based at 8000ft elevation - drove it one day to 10000ft and parked at a trail head. Returned 40 minutes later and truck would not fire. Plenty of crank, but no ignition. I coasted it downhill toward town, popping the clutch as I went to no avail. Mechanic now has it and says low compression from ALL EIGHT cylinders. His theory: pre-existing oil leak caused low oil, so when I was cranking with the clutch, I was washing cylinders down with raw gas and that caused all the rings to collapse.
I wonder how all eight cylinders could do that. Plus, why didn’t the truck start if it drove me all the way up there in the first place?
Any ideas? Don’t want to buy an engine!
Craig
Was a compression test done on the engine? What were the results? (per cylinder) How many miles on the engine?
I’d get a second opinion. This sounds bogus to me. Low oil would not prevent the engine from starting.
In order for rings to ‘collapse’, they have to get red hot. If your oil pressure warning light works and it was not lit before you shut off the engine, I don’t expect that you could have done that much damage due to low oil level. Cranking with the clutch would still pump oil.
You definitely want a little more diagnostic detail before giving up on this engine, like specific compression test results and a leak down test to verify that the pressure is leaking into the crankcase rather than past the intake or exhaust valves. You have to have REALLY low compression for the engine to fail to start when spinning the engine with the clutch if that is the only problem. It would be hard to do that with leaking rings.
Low compression on all cylinders is quite often caused by a slipped timing chain and/or broken sproket. That could also be the reason why it refused to start. I think you need a second opinion. Is this shop the only game in town?
Mechanic says all eight tested at 58 pounds. Said normal is in the 130s.
I’m going to ask about timing - good idea. Thank you.
I’ve asked for the lead down test. He says 58 compression is definitely low enough to keep engine from starting. I just don’t understand why the truck gave no indication of trouble - no oil burning or coughing - and suddenly has no compression. I’ve also asked him to recheck the timing belt/sprocket. Thank you for your input.
Even 130 PSI is too low; it should be in the 150s and up depending on engine condition.
He is correct that cylinders around 58 PSI will not allow the engine to run at all.
What could have happened here is that your truck experienced a bad case of vapor lock. This means gasoline in the carburetor could have boiled over into the intake manifold and then into the cylinders after the engine was shut off. When you returned to the truck the choke is closed on a cold engine and this just adds more gas to the problem. Altitude and climbing mountains can make this problem worse; and this problem is not rare with this era of Ford.
Gasoline will wash cylinder walls down and cause a problem like this. As an example here, I worked for a dealer once who sent a Dodge Ramcharger back to the shop for a no-start condition. Gas to the carburetor, good hot spark, and it would not even cough when cranked over.
I determined this problem was due to his not very bright lot man whose favorite method of starting a vehicle during cold weather (if it did not bust right off) was to spray half a can of starting fluid (ether) down the intake tract.
The ether had washed the cylinder walls down and compression on all cylinders was right around 60 PSI each (V-8 engine). I squirted about a tablespoon of oil into each cylinder, reinstalled the spark plugs and within a couple of cranks it was running fine with never a problem again. This led to strict governance of ether use by the lot man.
Try the oil in the cylinder trick. This may fix you right up. (And no, the rings did not “collapse” on your truck.)
I would say you would have noticed reduced power if your compression was low all along, but with this big ol’ engine you might not!
The fact that all 8 of them are at 58 really makes me think that the timing chain’s slipped. Ring problems usually happen in degrees, with different cylinders being worse than others. Plus your mechanic should have done a “wet” compression test if he suspected rings, where he pours a bit of oil in the cylinder and then re-does the compression test-- if the problem is indeed rings the compression reading should jump back up.
To explain why it took you up, but not down, if the chain slipped while you were climbing the grade, a completely warmed up engine will often keep running even on low compression but won’t be able to restart once it cools down.
Where are you with all these high altitudes?
I’m in Colorado - outside Boulder. Mechanic did say he was putting some kind of oil into the cylinders when he first started working on it. Even let them sit for a night to try to get the compression back up. Says it didn’t work. Thanks for your input.
Something is missing here. You have a heavy Ford truck with a big V-8 that apparently makes it through the mountains all the time and was fine on the day you drove it an additional 2000 feet higher. Parked it and then the engine goes bad?
If this truck had very low compression to begin with (and it will not run at all on 60 PSI and would barely run on 120) then you would not have been pulling grades all along.
I’m real skeptical (putting it politely) about some of what you’e being told, including and not limited to:
The bogus “pre-existing oil leak leding to washing cylinders down”.
Collapsed rings - on all EIGHT cylinders?
And 58 PSI on all cylinders? Once in a blue moon maybe. Winning the lottery is a safer bet.
Added oil to the cylinders and waited overnight for the compression to come up?
You need to find another mechanic IMHO as the statements you’ve been given are way off the wall.
I still say give each cylinder a healthy squirt of oil, reinstall the plugs, and actually see if the engine fires up.
The only way I can see an engine quickly going to crap (debateable) like this would be if it suffered some serious overheating on the ascent up. If it were this severe then the engine would have been losing power and clattering on the way up.
What everyone has been trying to tell you is: have the truck towed to another mechanic. Current mechanic won’t like that? Tough! It’s still your truck, and you don’t LIKE the prospect of laying out several thousands of $ for an engine that WE (me) don’t think you need, and, that you could find some other use for.
Compression test? Was it done correctly? Was the gauge accurate? To me, doubtful.
Yes, Amen. Don’t go tell him what to check. The guy is leading you down the path. Just tow it out of there to someone else. Tell him you are taking it to your BIL or anything to get it out of there. A timing chain issue would do just that and can happen suddenly like that upon start up.