My 1997 850 Volvo won’t start in the cold until I spend a good 30 minutes reving it. I’ve changed the spark plugs and cam sensor. Could it be the fuel pump or something else? I’m in desperate need of help.
How can you “rev” it, if it won’t start ?
Do you mean, the engine turns over but doesn’t start?
That’s quite a battery that can crank the engine that long and not lose its charge. You are putting a lot of wear on your starter motor.
Possibly the engine loses fuel pressure overnight. Try the “key dance” - turn the key to Run (not all the way to Start.) The fuel pump(s) should run a few seconds. You may hear this. Turn to Off then back to Run. Each time, fuel and fuel pressure are being brought up to the engine. After a few steps of this dance, turn the key all the way to Start. The starter motor should turn the engine over and, if low fuel pressure was the problem, the engine should start fairly quickly.
Good luck and please let us know.
This actually did work! Does that mean it’s the fuel pump?
Maybe, but a weak fuel pump is more likely to show itself when you are accelerating hard, using lots of fuel.
Losing pressure overnight has two causes I can think of: 1) the anti-drainback valve, probably located in the fuel pump assembly, leaks. So the fuel pressure that is built up in the line to the engine is not held, and the fuel dribbles back into the gas tank, and you have about zero PSI fuel pressure in the line from the fuel pump to the engine. 2) A fuel injector is leaking. The fuel dribbles into that injector’s cylinder. No fuel pressure in the AM, and a flooded cylinder that may delay the engine’s startup. Holding the gas pedal to the floor while cranking should clear this up in a few seconds.
My 1999 Honda has exhibited this problem a few times, especially when the amount of fuel in the tank is low and the temperature has fallen. My wife and I know the key dance and do it on those rare occasions when the engine does not fire right up in the AM. A new fuel pump with anti-drainback valve would probably solve the problem, but so does the key dance.
If the key dance solves the problem, that usually is a problematic fuel pump one-way anti-drain valve. If I had this problem however, before replacing the fuel pump I’d do a fuel pressure hold test. I’d also check the fuel pressure regulator, if your car uses that device. If the hold test confirmed the fuel pressure was dropping rapidly after the key was turned off, and no other explanation, I’d pony up for the fuel pump. The other cause of loosing fuel rail pressure is a leaky injector, but that’s a good deal less common.
When the fuel pressure leaks into the intake manifold through a leaky injector it often causes a difficult to start problem when the engine has been up to normal operating temperature, then stopped, say to go into 7-11 for a Big Gulp. Upon restart the engine acts like it is flooded. Do you have that problem?