Well, my car does what I am about to describe roughly once or twice a year but there is no clear pattern.

You see, today after doing about 20 minutes of highway driving at about 65 mph, I pulled over into a carwash to get a wash. I got in line, but the line was standing still since there was an obscenely muddy F-150 that was trying to get clean. This somewhat irrelevant, but the point is that in this line I idled for about 10 minutes and then shut the car off for another 10 minutes since this truck was taking so long. Then, when the line starts to move, I reach for the key, and with my foot NOT touching the accelerator and the car in neutral and the clutch pushed in, I try to start it. The car sputters a lot and tries to run but cannot go past about 500RPM, shakes greatly, and dies about 10 seconds later. About half way through this, I realized the car was struggling and gave the car about 3/4 throttle but with no avail. I then attempt to start it again with about 1/4 throttle but again with no success, just sputtering no matter what I do with the accelerator. So, embarrassingly, I had to push the car out of the line and tried to start it again, but still the same. I consulted my grandfather who has a lot of experience plus was there to witness what the car was doing and said the car was getting starved of fuel because it was either having vapor lock or a fuel pump issue. My dad, on the other hand, insists the car was flooded, despite the fact that the tailpipe did not smell like gasoline. Can these cars flood, or is this more likely vapor-lock or some other issue?

So, we leave the car in the parking lot for about an hour and come back to start it. My dad gives it about 3/4 throttle and it starts on the first try.

I'm at a loss. Now the car runs and starts fine, like it always does 99% of the time. This is the third time this car has done this, all under similar hot-start conditions. The car had a full tank of gas, new spark plugs (but it had also struggled the previous two times on the old plugs) and it was about 95*F outside. I tried as much as I could on the spot like taking the gas cap off, also checking the air filter as well as unplugging/inspecting the sensor on the air filter box. Someone please give me a suggestion to the cause of this mystery!

Thanks VERY much in advance!

 

According to Joe Namath, Vapor Lock is the third most common cause of engine stalling.

 

What???

Anyway back on topic.. Could be anything from a faulty maf, to a bad fuel pump, to a cracked vac elbow...

When it has this problem have you ever tried tapping the fuel pump to see if it starts?

As far as the MAF with the car HOT, unplug the maf and see if there is a change.

 

Agree with what Matty said (esp the "What???") but really could be any number of things; some that occurred to me (in addition to Matty's advice) with those symptoms are faulty fuel pump relay, engine speed sensor, cam position sensor, etc.

Heat soak appears to induce the problem (apparently, though that could be a red-herring too..); that's maybe why it started for your Dad w/o issue, it had just cooled down enough. Unfortunately you're going to need to do some diagnosis when the problem is happening. If your interested we could give some things to try... are you a DIYer?

BTW: I don't agree with either your dad or grand-dad; unless you monkeyed with the fuel line routing (and most likely even if you did..) fuel injected engines don't suffer from vapor-lock. And if it was flooded, it would have started for you when you held the throttle open.

 

Joe Namath on The Simpsons - YouTube

Anyhow, in my case I have had similar symptoms on two occasions with two causes. The first time, I found the air pump's exhaust valve was stuck open, as well as the airbox thermostat bypass was stuck open drawing air off the manifold. In the middle of summer. The ECU did not care so much for these things.

The second time, the coolant temp sensor was throwing intermittent low temps, causing the ECU to flood the plugs. I could not start it by holding the throttle open either, when it was messing up. But I could dry the plugs by pulling the fuel pump fuse and cranking it.

Either way, it's not vapor lock. All old guys blame everything on vapor lock.

 

Fuel injection is pretty much vapor lock proof. Vapor lock is from the fuel boiling inside the fuel line and causing the pump to starve or take an extremely long time to bleed the vapor out and get fuel back into a carburetor. Since the pump is submerged in fuel it can't really vapor lock. The reason fuel injected cars shouldn't be able to vapor lock is that most have a return line and fresh fuel is pushed up to and past the engine each time before you start it. That way if any fuel vaporized in the line it get's pushed past the injectors back to the tank. That and the engineering is much better and they keep the fuel lines out in the open where air can cool them or insulate them if they are close to heat sources. Lastly there is the higher pressure, at least 10 times what a carburetor-ed system runs at that also hinders vapor lock from occurring.

Old guy (like me) thinking, if you can't see it or don't understand it, it must be vapor lock

To unflood a vehicle you need to hold the pedal all the way to the floor. The ECM recognizes the WOT and the low RPM and cuts fuel drastically way below what the sensors tell it would be the normal amount to start. If you're holding it at 3/4 pedal that ECM should be dumping a ton of fuel in there. In that case you're not helping to start a flooded engine but adding fuel to a starved engine. Maybe the pump or pump relay is cutting out?? Have you changed the fuel filter recently??

You can easily flood a fuel injected engine because it is electronically controlled and senses what it needs to start when you turn the key. If you put your foot on the throttle and open it at all you are adding extra fuel to the amount of fuel the ECM projected the engine needs and can easily flood it. The further you're into the throttle the more likely you'll flood it before it has a chance to start. Other than if you have your foot all the way to the floor.

From your description it sounds more like it's not getting fuel instead of your "helpers" thinking it's flooded. Just my guess. I'd be inclined to point at a fuel pump relay that's heating up and won't close but it would be nice if it would just break so you could find the problem.

 

I read on here at some point that you can bypass the fuel pump relay by connecting port 15 and 85A (I think). Now, I hate to sound stupid, but where are these ports?

Also, where is the fuel pump relay?

Thanks for the help!

 

The fuel pump relay is red (or green) and numbered 103. The Volvo part number for the relay is 9434225. To gain access to the 103 relay, you have to take the top cover off of the fuse box that is in the engine compartment. Remove the four #25 torx screws. Once the torx screws are out just lift the lid and you will see the relay.

Using a paper clip to jump between the socket positions associated with pins 15 and 87 on the relay is the procedure to bypass the relay itself. If the car runs OK the relay was bad, if you still have no fuel pressure then the fuel pump itself is likely bad. There should be a diagram of the pin numbers on the side of the relay.