Riddle me this - No compression, then compression.

[AlexGSi2000]

Had an interesting situation in work a few weeks ago that I am still scratching my head over.

Was sat at my desk in work when a colleague pops in and asks if I can take a look at their car, as it wasn't starting.

I wonder over, turn the key to hear the sound of no compression. I initially thought the starter may not have been engaging with the flywheel, however the auxiliary belt was spinning.
I've been around many engines with little to no compression and had the same sinking feeling I usually get when I cant hear any pulsation/strain on the starter. The car / exhaust also stunk of unburnt fuel.

This person is not a car person by any stretch of the imagination, so without wanting to break any bad news just yet, I take a look at the vitals, starting with the oil.
The dipstick was dry.
I asked if there were any issues or anything amiss when driving to work that morning or any warning lights on the dash - all was normal supposedly.

I advised that from my experience, it didn't sound good and if they had breakdown cover - I was confident the car wasn t going anywhere.
I mentioned that the oil looked like it was very low, and that it probably wouldn t change things, but for the sake of a few quid suggested we go to the local motor factors and buy some oil.

I returned a little while later and poured in about three litres before the dipstick looked happy.

Turned the key again, sounded like there was no compression after a 10 or so second crank.

At that point I think I broke the bad news and told them it sounded like the engine had seen its last.

For the sake of it, I thought there was nothing to lose, so decided to try another crank - After around 10 seconds the starter changed tone, not the same tone as a battery losing charge, but that of some load being placed on it.
Over a further 10 or 15 second crank, the starter motor started pulsing, one cylinder, two, closely followed by three and four - then the engine started.

When the engine started, it ran like nothing had happened - as smooth as you like.

I turned it off after 30 or so seconds, turned the key and it fired straight up.

I told them to go and buy a lottery ticket and book it in for a service.

The car in question was a 2016 Huyundai Tucson petrol 1.6.

Ive been trying to fathom what may have happened, the only thing I can think of are the following;
- Oil starvation to hydraulic lifters - perhaps not actuating the valves?
- Oil starvation to some kind of VVT so the cam timing was incorrect?
- Oil starvation to the underside of the pistons meaning the cylinders/rings were washed with fuel and not sealing?

Its been a few weeks and the car still drives as if nothing had happened.

[Martin350]

If it was that low on oil my money would be on the hydraulic lifters.

[FiF]

Funnily enough had a slightly similar situation years ago, mid 80s. Wife had a phone call from her sister who was stranded in town with her boyfriend. His car wouldn't start and she said it sounded different. Called us for help.

Car was Sierra and the story was that he had got out of the car, engine still running, somehow he'd planted his foot on the gas getting out, engine revved apparently really screaming. He'd shut it off and now it wouldn't start.

Turning it over, clearly no compression. Cam belt in place no obvious damage, oil level ok-ish. Likewise said this doesn't look good, and as the car couldn't be left where it was towed him to the in-laws house as nearest sanctuary.

Couldn't get it running, at which point the boyfriend announces he'd better call the AA. Bit my tongue as to why he hadn't called them in the first place thus avoiding the ruination of my Saturday evening.

AA arrived, tried all the things I'd tried, also said it didn't look good, then announced he'd try a trick he'd heard about. Removed the plugs, put a generous squirt of oil in each cylinder, replaced plugs and leads.

As soon as it turned over there was compression and fired up first pull. Ran ok for years after.

Pass.

[Stu R]

Pretty sure they run solid buckets so highly doubt it was the lifters.

I'd wager cam timing and/or phasing went wonky because of the low oil pressure affecting the tensioner. Cranking it got the pressure up (fnarr), cylinders just caught depending on fuel and timing.

[BuyaDuster]

That sounds like one tough engine to me! Impressed.

[Sardonicus]

Sounds like it maybe was flooded excess fuel bore washes inc the pistons rings and ring lands and compression is lowered significantly seen this more times than I care to remember with well/worn used engines , once the fuel evaporates you can get some kind of result from the residual oil and thus ring seal is resumed once it fires then the bore are once more splashed in oil and full function is resumed , shunting a car from here to here without letting the engine warm up is a prime candidate for this behavior IME especially in colder weather for obvious reasons

[stevieturbo]

Hard to say...but strange.

I did have a similar encounter one day with my old 1.7cdti Combo van.

Messing about with OpCom one day and I decided to hit "reset", thinking this would just clear some ste in the ecu. Well yes...it did. It reset Immobiliser data, VIN data....etc etc not quite what I expected.

Flashing immobiliser light on dash, and when I cranked, it spun, but zero attempt to start. And even more bizarre, especially for a high compression diesel.....it just spun over pretty fast with no sound or feel of compression, which really freaked me out at the time.
I'd just wrecked my new van lol

Eventually I figured out how to recode the various parts in the ecu, and everything started and ran as normal. Even cranking until start sounded normal again.
Weird.

[Sardonicus]

stevieturbo said:

Hard to say...but strange.

I did have a similar encounter one day with my old 1.7cdti Combo van.

Messing about with OpCom one day and I decided to hit "reset", thinking this would just clear some ste in the ecu. Well yes...it did. It reset Immobiliser data, VIN data....etc etc not quite what I expected.

Flashing immobiliser light on dash, and when I cranked, it spun, but zero attempt to start. And even more bizarre, especially for a high compression diesel.....it just spun over pretty fast with no sound or feel of compression, which really freaked me out at the time.
I'd just wrecked my new van lol

Eventually I figured out how to recode the various parts in the ecu, and everything started and ran as normal. Even cranking until start sounded normal again.
Weird.

Yep even the experienced get thrown a curve ball every now and then I had something similar years ago on a silvertop Zetec MK1 mondeo the owner had a cambelt kit fitted at another garage they also changed his oil and fitted Castrol 15 50 weight oil (should be 5/30) this caused the hyd cam buckets to jack up when cranked in the cold weather and hence no compression got towed in took me a while to work that one out, blowing off the MAP sensor pipe was a helpful hint during cranking rang the garage to go over the work then they gave me the oil detail BOOM I would of laid money on the fact they'd fked up his valve timing or bent valves due to when it first came in but No

[hidetheelephants]

How did you get that sorted? Was it just a matter of changing the oil and then a lot of cranking with the plugs out? Hydraulic lifters don't usually exchange their oil very quickly.