Rebuilt 400i runs, then dies

Has anyone experienced this? Any ideas?
We have a Ferrari 400i, just rebuilt, with JE forged pistons, .003" clearance.
Injection units have been rebuilt. All the usual stuff with a rebuild.
When it was first started it ran for about 15 minutes before getting a little rough
and stopping. It has been run a number of times since, and each time it seems to run longer
from cold before dying. Injection primary and control pressures are in spec. When it dies,
if we try to restart immediately, the starter tries but cannot crank the engine. If we wait
perhaps 15 seconds, it starts again and will run for a shorter time before dying again.
From cold we're out to about 45 minutes now before it dies. This is my first experience
with FI. We're suspicious of the FI (hydro lock?) or, heaven forbid, not enough piston
clearance. Would an engine recover from piston seizure this quickly? If we turn off the key
after running for a while, but before dying, it seems to stop more quickly than if we
turn it off earlier. Please tell me it's not the pistons!

 

I have no idea for sure, but I would definitely be suspecting the fuel supply. I have heard of the fuel pumps getting clogged up from deteriorated rubber because of the use of the wrong hoses. Once the rubber has settled the car runs okay, but then as the rubber gets sucked into the pumps again the car dies. I don't know if that is the problem you are having, but as I said, I would be checking out the fuel first.

 

Start it up cold. Let it run until it dies.

Immediately spray in starter fluid via the air filter. Restart. If she starts right back up (of course, it will just be brief before the starter fluid is burned off), then you've identified a fuel supply problem.

If she doesn't start right up but rather needs to still cool further, then you've got to worry about mechanical problems (e.g. piston seizure - though less likely).

 

The fact that it seems to bind up does make me suspect that the pistons are expanding and seizing.

Hydro-locking really can't happen when pistons are moving and valves are opening/closing. If that happened you'd probably have to remove spark plugs to turn it over.

Did you remember to put oil in? It's a lot more than 5 quarts (18-19 IIRC). If so have you verified oil pressure? I have seen motors seize from no oil and restart later (after refilling) with no apparent trouble.

 

Is there any sign that one bank of cylinders is more effected than the other? The 400i has two totally separate fuel systems from the separate pickups in the fuel tanks to the injectors. Something floating around should shut down one bank of cylinders but doing both would seem odd.

Al

 

.003 should be enough, although it is on the low side of the JE spec. Are you sure it was measured correctly? If so, there shouldn't be enough piston expansion to cause what you are seeing. There's a pretty big margin of safety, and if you are get seizure due to the pistons after only 45 minutes of idling, my guess would be that the clearances are MUCH tighter than you think, probably more like .001 or even less. One common horror is the machinist getting confused between the desired spec and the actual piston size, or an individual unfamiliar with tapered pistons to measure in the wrong place, like at the piston top, instead of just above the skirt.

 

well, I guess I'd recommend pulling all plugs and bore scoping the cylinders top to bottom by rotating the crank manually lthrough full cycles ooking for any signs of scoring. It would seem odd that you would recover from a piston seize but something is causing the starter or crank to bind. I suppose if you had several grossly over torqued connecting rods you could get a seize but again, I don't think you would recover from it. If the engine was idling normally and the plugs aren't drenched I can't really see how you could get enough fuel into a cylinder to cause a condition similar to hydrolock. And if you really hydrolocked I'd think a) you probably would have developed that deep knock resulting from destroyed bearings or b) a really bad case of milky oil. When the engine stops, does it do so quickly (abrupt stop) or just kind of slowly die and/or cough like fuel starvation?

hummm, just had a second off the wall thought. about 2 years ago I had a marine engine that wouldn't crank. Thought for sure it was the starter but it turned out I had water leak (salt water) on the back side of the crank mounted water pump that after the engine sat unused for a while, actually had sufficient rust build up that the crank mounted pump was binding and preventing the engine from turning over. Now that's pretty unlikey but what's wrong with a little out of the box thinking?