A4LD Crash/Disaster

[stfree]

I am in trouble here. Last week my troubled A4LD finally bit the dust in my 1990 Ranger 4.0. Big time. Fluid all over the road. Lurched as if locked up, then free wheeled. But that was expected really. I've been wanting to convert it to a manual and I've just now managed to find a donor tranny so good, right? Not really. In the course of destroying itself, the A4LD seems to have involved the engine too. It cranks.. fast, but no start. Fuel is present at the injectors, there is spark, there is valve train continuity (micro camera inspection inside the valve covers), the plugs all look good and the pistons all go up and down (by micro camera verification) as advertised. But zero compression on ALL SIX. In fact, it blows OUT the throttle body rather than sucks now. The only thing I can figure is that it has jumped time when the tranny momentarily locked up in such a fashion that no cylinder can build compression. I'm told that this is a non-interference engine so I'm not thinking a bunch of trashed valves. Anyone want to speculate with me about the timing being the problem? I've got a timing chain kit coming and I'll get into it in a day or so. Thanks.

 

[Dirtman]

Definitely sounds like it jumped time or broke the timing chain to me.

 

[RonD]

Yes it reads like the crank gears woodruff key got sheared off, when crank stopped but cam and chain didn't

Yes, 4.0l OHV is non-interference

But.............not too sure how hot bearings would react to the sudden stop, I assume the engine quit just after trans locked up?

You will need to pull the front cover off the engine, kit comes with new gears, chain, guide and tensioner, they are not expensive

Finding correct woodruff key may be a chore but its do-able
An hopefully crank didn't get damaged

 

[adsm08]

I'm with Ron. It has to have jumped time. I have seen exactly two instances of an engine blowing out the intake instead of sucking. One was a 5.0 that had the short block rebuilt over the course of 10 years, and the guy didn't do a valve job. #2 intake valve wasn't sealing properly. 20 minutes of diag, a tube of valve grinding compound, and a head gasket set later and it ran.

The other was an Intech 4V 5.4L that had been rebuilt by LKQ and they used 3V timing chains, which are actually about half a link longer, which allowed the intake valves to be open on the power stroke.

 

[stfree]

Thanks guys, it helps to have a extra vote or two on the diag mystery. I hadn't thought of the crank key shearing and then sticking to re-establish cam rotation. That would explain why the valve train is moving but wayy out of time. And obviously the chain is intact else the valves would not move. Yes, it quit almost instantly when the trans blew. It also issued a huge cloud of black smoke under hood at the same time. I thought it was on fire but no flames visible. Probably fired the last cylinder gas charge with the valves open and into open air. Quite dramatic.

 

[Snoranger]

I seen two 4.0 OHVs shear the cam sprocket tab (it's more of a tab then a solid key like the crank). I've yet to see the crank key shear.

 

[rusty ol ranger]

The pistons are moving aint they?

Long shot, kinda unlikely, but it coulda snapped the crank.

 

[adsm08]

The pistons are moving aint they?

Long shot, kinda unlikely, but it coulda snapped the crank.

Cam and FEAD won't turn while cranking if the crank snaps.

I heard a story years ago about an early 4.6 that snapped the crank while running. It kept running and didn't skip a beat until the guy shut if off, then it wouldn't start again because the starter turned the rear half of the crank, but not the front half, so the cams never got moving.

 

[rusty ol ranger]

Cam and FEAD won't turn while cranking if the crank snaps.

I heard a story years ago about an early 4.6 that snapped the crank while running. It kept running and didn't skip a beat until the guy shut if off, then it wouldn't start again because the starter turned the rear half of the crank, but not the front half, so the cams never got moving.

I seen a 351W crank snap once when a guy jammed the trans into reverse at 70mph.

Kinda acted how the OP described. I missed the part where he certified valvetrain movement.

 

[adsm08]

I seen a 351W crank snap once when a guy jammed the trans into reverse at 70mph.

Kinda acted how the OP described. I missed the part where he certified valvetrain movement.

He said valve train continuity, which to me means he stuck the camera in the oil filler and watched a valve or pushrod go up and down.