As the title says, I have a 2011 V8 Vantage that *sometimes* has a hot start issue. Cold starts after sitting for a long time haven't been an issue. However, sometimes when hot it'll rev to maybe 1,000-1,500 rpm at start and then immediately die. It's annoying to not start on the 1st attempt, but its really really annoying when it doesn't start on the 2nd, and the 3rd, or the 4th attempt. Also, sometimes in parking maneuvers it will die. At first I thought since this is a new car to me that maybe I was stalling it, but for sure I've had it die with the clutch all the way to the floor while parking. Otherwise it seems to drive fine. After a few failed attempts to start it will throw a check engine light. It doesn't always do it in the same way, but the most common code is P2111

Previous owner thought it was the key module in the dash, I replaced that, didn't change anything. Redpants was having a sale, so at the same time I bought and replaced the clutch position switch and the ambient air temperature sensor. Still has the problem. I've also cleaned the throttle body and the MAF sensors. I'm thinking it's either throttle or fuel related. I plotted the throttle response on my code reader, I also plotted the throttle response on a 2017 Jeep Wrangler JK 3.6l V6, and a 2022 Jeep Grand Cherokee WL 5.7l V8 to compare. When I look at plot on the Aston there is a weird blip at the end. Like the throttle closed too much and then it needed to open a little to be in the correct position? Any thoughts??

 

https://www.6speedonline.com/forums/...e-light-3.html

 

May want to have that car scanned. I am having a similar problem with my 09 Vantage. The car starts right up until I get the car to operating temperature shut the car off and try to restart it. It takes three or four times to start the car. My repairman says I have a fuel rail pressure problem. And I also read that a lot of the Aston Martin's have a defect in the gas tank with a hose separating and not supplying adequate pressure to the fuel rail. You may want to check that out

 

Interesting. The fuel rail pressure sensor is another thought I had. I can pull up fuel pressures on my scanner, but I don' know what good/bad numbers are. And if the sensor is bad, then it's kind of moot. Looks like you also have a roadster. All the videos I've seen have been for a coupe. Do you know how to get at the fuel tank? I'm guessing the top need to be 1/2 way up?

 

I beleve you have to get to the gas tank fuel lines from the top

 

Hello @DK570 ,
Another item that comes to mind with a hot start issue, is the crankshaft position sensor.

Johnny

 

That's a good thought, I'll keep that in mind, but I have yet to see any codes related to crank position sensor. Most common one is P2111 which is throttle position, another I've seen is P115B which is 'check fuel system'. I've also had the LCD screen in the tach display 'check fuel system'. I agree a bad crank sensor could cause those, but then I'd expect at some point to see a code like P0335. I've searched for other cars (not Astons) that have my same symptoms and I found a post on a Volvo (another former Ford Premier Group brand) forum that seemed to match my problem exactly. In that case the culprit was very worn plastic gear teeth inside the throttle on a car with 200k. I opened mine up and saw a little wear, but seemed fine. Those gears don't rotate 360* so I spun the big gear 180* when I put it back together so completely unworn sections would be in contact. I doubt it'll change anything, and I won't know until spring when I can drive it again.

 

If the car is telling you to "check fuel system" then check the fuel system. The fuel pressure relief valve in the tank is a common source of issues. It can stick open and bleed off fuel pressure instead of holding it when the engine is off. Hook up an obd scanner and monitor the fuel pressure when you first turn the key on. The system will prime and should hold pressure and very slowly bleed off over the next several hours. If it quickly drops then you have your culprit.

That same pressure relief valve can cause fuel starvation under load and high rpm and will throw your fuel trims out of whack.

See my DB9 fuel pumps thread. I had hot start and cold start issues with "check fuel system" errors as well. After resolving the issues in the tank I haven't had a single fail to start. Vantage is similar to DB9 in the tank, but only one pump instead of two.

https://www.6speedonline.com/forums/...uel-pumps.html

 

I believe Rich at red pants also had an issue with the hose or pump in the fuel tank. It’s on his website somewhere.

 

Right, I think there's a good chance it is pump related. I wish I could find info on what acceptable numbers are. I did check this a while back and took pictures on the scanner display, but now I can't remember if the pics were before or after starting etc. I seem to remember it did not drop off quickly after shutting down. This would be something I could check again while the car is parked for the winter. Did your problem occur on cold start, or only on hot start? In my mind (I could be wrong) I'd think a bad valve would affect cold start more after there's been a chance for the pressure to bleed off? But it could be something else wrong with the pump, not a valve. I was also thinking maybe fuel pressure sensor is bad.

 

For me it was both hot and cold. The first pressure valve to go was so bad the pump couldn't even hold full pressure at idle. The pressure valve and check valve keep fuel in the system at all times. Hot starts are also affected if the fuel vaporizes due to excessive heat that pushes all liquid fuel back into the tank. Fuel pressure sensor could be something to look at, but there are plenty of things to check before swapping parts.

The Vantage fuel pressure is ~40psi while running and 50psi after turning the key off.

 

I checked fuel pressure today during a cold start (remember it's January in WI, so won't be able to drive it and get hot start for a while). Fuel pressure started at basically 0, climbed to 55 psi while running, and then dropped down to basically 0 again after shut down. That's probably not good. There seems to be some disagreement between Redpants and Bamford Rose as to what is normal, but both agree that quickly going to 0 psi is not good. Bamford Rose says that a drop that quick after shut down will trigger a CEL, but I've not had a light unless it fails to start a few times, and never the code that they say should be expected for low fuel pressure.

 

Fuel pressure should remain after shutdown. Your problem us that the check valve that prevents fuel pressure from bleeding back into the fuel tank is defective. Most modern cars have the check valve integral to the fuel pump. That's where your diagnosis should start