So I'm making some good progress on the rebuild. The previous post is linked here. I just recently rebuilt the power steering pump and got it back into the car, that thing is a beast to get out. That's not a job I'm looking forward to doing ever again, so I'm happy to have that behind me. I've also got the radiator back in the car and refilled with new coolant. The AC compressor pulley was damaged in the accident, so now with the power steering pump back in the car, I've finally been able to get the AC compressor replaced. Afterward, I was able to vacuum down the system and get the moisture evacuated, so I'm at the point where I need the engine running to recharge the AC. When I got the car, the notes from Copart had said that the engine didn't stay running. I had assumed that was probably due to the driver-side MAF and airbox being destroyed in the accident, and there was probably a short somewhere causing the engine to stall, however, I don't think that's the case now. When I start the car, it'll fire up but it will immediately die after a second. I'm not getting any useful errors from the Foxwell, and the live data from the OBD isn't saying anything telling.

The only thing I could think of is that the throttle body maybe isn't responding correctly for the car to idle, it's also making some strange electrical sounding noises that I'm not sure if is normal. So I took the intake off and videoed the throttle body response with the car on, but not starting the engine. You can see that the throttle is moving, but I'm not sure if I'd say it's healthy. I can't say I've stared at a lot of fly-by-wire TBs to say if that's normal behavior or not. I did take the TB off and clean it, and opened it up to see if there was any noticeable damage, but everything looked fairly normal. It made slightly less noise afterwards, but still similar, however, the intake manifold did smell like there was a decent amount of fuel in there. Not sure if that's from EGR or something I should be looking into further.

So long story short, does anyone have any leads on what to look into that may be causing this behavior?

 

could be anything. the ECU can start and stop the engine at will depending on how it's programmed (assuming there are no hardware problems). the TB noise could just be the ECU startup routine. i guess you'd have to compare to one that is known to be working.

but if i had to guess (and i am) and it starts and stops like that consistently with the same run-time interval i'd be thinking the ECU is finding something it doesn't like and is stopping the spark intentionally. just a wild guess, of course.

 

I was wondering that as well, but hoping I could find proof of it somewhere. I was able to record the live data supplied via the OBD using the foxwell, it looks like when the engine shuts off the cylinder #1 spark advance goes from 25deg to 9.5deg. I'm not sure if 9.5 is what it should be at during a cold start, or if that's low enough that the ECU is killing the engine that way. Unfortunately, the foxwell only logs data in 1 second increments, so I can't get a higher fidelity on what's actually going on. Everything else looks fairly normal, fuel pressure goes from 75 psi to 58 during startup, but I'd expect that to drop initially while the fuel pump catches up.

 

if it stops within one second on a consistent basis (as is implied by the previous post) then i would lean towards the ECU finding something drastically wrong and shutting it down on purpose. if so, it's possible that some special ECU snooping software/hardware is in order.

i suppose to test whether fuel is the problem, it would be possible to spray some starting ether or whatever into the throttle body while someone starts the car and see if it gets a few more revolutions before quitting. if not, it's most likely the spark that's missing and would point to the ECU intentionally shutting down the engine.

if the ECU is cutting off the spark, i would look for particularly important sensors (cam position sensor for instance, or security issues, etc.) that the ECU might find to be critical, particularly in the areas that received damage and double check that they've been reconnected and wires are not damaged.

i would also check out the foxwell (i have one, but know diddly-squat about it) for system test/check menus that may be of service.

 

I shot some carb cleaner in the intake, it did boost the RPM a bit on startup, but the engine still cut off after a second.

Next I checked on the spark advance through the start up, it doesn't go through any crazy values, but maybe it's still possible that the ECU records an advance value while cutting the spark entirely.


Any other thoughts on what sensors to check? I'm seeing RPM, so I don't think it's that one. Is there another sensor relative to the clutch that the ECU would read as critical? I've confirmed with the previous owner that the engine started acting like this immediately after the accident, so I would think that it's something to do with the crash. I've check the ECU data and it says that 'crash mode' is not currently active, so it would have to be something else that it's seeing that it doesn't like.

 

assuming that the ECU is intentionally shutting down the engine. i would probably start scouring the internet for cars with similar problems. and jot just aston martins.

whether manual or automatic i would try different combinations of clutch/brake/gear/e-brake, etc. when starting to see if it makes any difference. you never know.

and i'm assuming you've seen this: and ones like it:
10 Causes of a Car That Starts Then Dies Immediately (And How to Fix It) (oards.com)

good luck

 

Normally faults that stop a running engine just after starting will be a lack or incorrect feedback and the ecu stops the engine to prevent damage. The ignition and timing circuit and fuel circuits are the ones I would look at first. What is likely in the damaged area of the engine, is it a camshaft position sensor?

 

I'm beginning to wonder if I just can't get enough information from the Foxwell, because according to it, all of those sensors are good. I'm seeing an engine RPM (CKP value), and I'm seeing that the crank/cam synchronization is good for the 1 second the engine is running. None of the CID (cam sensor) values are indicating a failure in the live data or throwing a DTC. Fuel pressure is showing what I assume is a good pressure at 75 psi at key on, and 58 psi during start. It doesn't run long enough to see if that's sustained though, but I haven't been able to visually identify any damage to the fuel lines. After it runs, the exhaust does smell a bit like fuel, but maybe that's normal for a cold start?

As for what would be likely to have been damaged in the accident, that's where I'm really struggling. The only piece of the engine that was damaged during the accident was the AC compressor pulley was dented. I rebuild the power steering pump while I had it out because I noticed it looked like it had been slowly leaking oil for a while. The rest of the damage was in front, concentrated around the driver-side headlight. So the driver-side airbox and MAF were destroyed, and the PDC wiring loom was ripped apart along with some minor damage to the headlight wiring loom, both of which have been fixed and the MAF replaced.

 

for the engine to start, it is absolutely necessary that the air filters are connected as well as the MAF, otherwise, it stalls like on your video

 

because just about everything attached to the car (interior and exterior) is controlled and monitored electronically now, either directly or indirectly, and in turn is connected to the ECU, it's very easy for designers to decide to stop the car for just about anything that they deem to be unacceptable. and they do.

for instance, they could stop the car because the radio doesn't work, or the trunk lid is not closed, or the tires are too low (or too high), like i said, just about anything. so concentrating on issues involving the engine may be too restrictive. a close reading of the user's manual may (if it hasn't been already) be helpful...

 

I was wondering the same thing, but here's a video of a guy rebuilding a Vantage and he gets his to start up with no issues without using air filters.

 

Mine 4.7L engine don't work without air filter, I have tested.
On video, is an 4.3L, it's an another gestion motor work

 

Perhaps a long shot, but I recall another member having a similar issue that was caused by the crash sensor. I know your scan tool seems to be saying it's fine, but it may be worth a)unplugging and plugging back in, and b) potentially replacing it with a known good unit.

 

Have you gazoline on injectors?

 

yes, fuel pressure is reading 75 psi at key on, and drops to ~50 psi when the engine starts. I've tried jumping the fuel pump relays so that they're powered at all times and that doesn't seem to have an effect on the issue, it still cuts out.