Cold start issue (only occurs when sat overnight)
 

Hi all,
My Torslanda (B200F) has developed an odd starting issue, when it's been sat overnight it will often take prolonged cranking to get it to fire up. Sometimes 20-30 seconds. Once started, it will run perfectly all day and stop/start faultlessly.

I suspect a fuel issue, I haven't changed the fuel filter or underbody pump since I've owned it and I'm curious as to whether it might be suffering from a partial blockage or weak pump which means the car is struggling to make sufficient pressure at the rail for the first start of the day.

Does that sound right, or am I barking up the wrong tree? I've had hot starting issues with the B200F in my 744 which were cured by changing the coolant temperature sensor. Could that be the cause of this issue, despite the problem being the other end of the temperature scale?

I'm keen to diagnose it properly rather than fire the parts cannon at the car as money is a bit tight at the min. Huge thanks in advance for any and all help!

i would connect a fuel pressure gauge and watch it when someone cranks it in the morning , it should go up quickly as soon as you crank , does it prime for a second or two when you put the ignition on?

Yes I get a couple of seconds of fuel pump buzz when I turn the key. The underbody pump is noisy in general, it runs perfectly right down to the bottom of the reserve so I don't think the in-tank pump is faulty, but I suspect the underbody pump may be weak or the fuel filter partially blocked, causing the cavitation noise.

It's a really good shout to check the pressure at the rail, I have a pressure gauge so will ask my partner to crank it whilst I check the pressure, thanks for the tip!

My car did this and it was moisture getting in under the distributor cap. When I dried the cap inside it would fire right up. Sometimes it’s things like this that you never really think of.

Try turning the key to make the pump prime about 25 times then try and start it.

My guess is that if the pump is struggling then you’d notice issues at high rpm after it was up and running.

Cheers

I'm still none the wiser with this. Changed plugs, leads and dizzy cap/rotor arm which seemed to help but it still does it from time to time.

Also, the rev counter is intermittent...could this indicate that the CPS is on the way out, I wonder?

There are some basic things to check before spending any money:

Clean fuses 4 and 6
Clean the main bettery earth connection, hidden on the inner wing behind the battery.
When it won't start, join fuse positions 4 and 6 together to make the fuel pump run by-passing the relay.

I would think that the CPS would be a full time problem and not a starting only.

Another thought is the check valve on the main pump that holds pressure to the rail may not be doing it’s job and allowing the pressure to die off over night hence the fuel supply being lower upon first startup…

It is quite ok for the pressure to die off overnight , volvo only stipulate that the pressure should hold for 20 mins after shut off to prevent the fuel boiling in the lines on a hot day , causing long cranking on a hot start ....

I had very similar issue with another car in the past. It turned out to be the pump. Basically, this car had a fuel system with one rail and the fuel pressure regulator was on the pump itself. So it would keep the pressure of fuel at bay, and if it got too much the extra fuel would drain back in tank right at the pump.
Well, something started to give up, whether it was the pump or the regulator is still unknown, but they were replaced as a unit (couldn't separate one from another) so regardless of the culprit the result was the same.

What did help, though, was to turn the key to pos1 to hear the pump prime, then when it stops turn the key off and back on to pos1 to prime again. It would do this only two times, if I went for the 3rd priming cycle it wouldn't do it. But with 2x priming it would fire right up even after standing still for 2 days, while with only normal (one) priming it would need long cranking to start after the night.

I don't know how the fuel system is on your car, but the logic is the same of course - there is a pump, pressure regulator and either 1 or 2 fuel lines, so it might be worth checking it out. Fuel pressure gauge should point out if it is the pressure problem, and if so then you just have to figure out if it's the pump or the regulator.