Occasional ignition followed by stall

tropikchiken · Post by **tropikchiken** » 05 Aug 2019, 06:24

I've tried searching this but with no luck, so my apologies if it has been answered before.

I have a 2004 XC70 w/ 145k that runs flawlessly other than occasionally, when starting it up, it sounds and feels good but immediately dies. When this happens, almost always, the next attempt is successful and the car runs without incidence.

One time about a month ago, though, I had to do this 4-5 times before the car would start, and when it did, the "Low Engine Performance" light was on for a couple minutes (though the car felt like it was driving normally).

If it matters at all, I've noticed this tends to be more prevalent on very hot days - that could be entirely coincidence, though.

It's not a major problem now, but I don't want to ignore signs of something that could end up being a bigger problem and leave me stranded.

Any ideas what would cause this behavior?

Post by **jimmy57** » 05 Aug 2019, 07:10

Fuel pressure check would be my first effort with that symptom set. The fuel pump assembly has a pressure relief valve and the pump itself has a non-return check valve. If either fails the fuel leaks from the line up to engine. If the fuel pressure is not held to a minimum of about 2 bar(29 psi) for 20 minutes that indicates a problem. Usually a fail for this test is a continual drop in pressure once ignition is switched off and the pressure goes to zero in 2-3 minutes. That same issue will partly drain the fuel line up to engine and the pump will pressurize line but with a big air bubble in line. Once the fuel in injector rail on engine is gone then some extended cranking will be needed to cycle injectors enough to purge the vapor out through injectors before liquid returns and the engine will run.
There might be fault codes that would lead to another diagnosis so reading the codes need to be done also.

chris11211 · Post by **chris11211** » 05 Aug 2019, 11:28

Check for any air leaks from MAF to the throttle body.

Post by **E Showell** » 05 Aug 2019, 20:52

If you smell fuel, could be bad engine coolant temperature sensor. Have experienced that with P80s. Next time it happens, hold gas pedal to floor while cranking. If it starts relatively easily, then I'd say bad ECT.

tropikchiken · Post by **tropikchiken** » 10 Aug 2019, 11:31

jimmy57 wrote: ↑05 Aug 2019, 07:10 Fuel pressure check would be my first effort with that symptom set. The fuel pump assembly has a pressure relief valve and the pump itself has a non-return check valve. If either fails the fuel leaks from the line up to engine. If the fuel pressure is not held to a minimum of about 2 bar(29 psi) for 20 minutes that indicates a problem. Usually a fail for this test is a continual drop in pressure once ignition is switched off and the pressure goes to zero in 2-3 minutes. That same issue will partly drain the fuel line up to engine and the pump will pressurize line but with a big air bubble in line. Once the fuel in injector rail on engine is gone then some extended cranking will be needed to cycle injectors enough to purge the vapor out through injectors before liquid returns and the engine will run.
There might be fault codes that would lead to another diagnosis so reading the codes need to be done also.

Thanks for the advice

I ordered a fuel pressure gauge and left it hooked up for about 20 mins after turning engine off and was around 35psi.
I was going to try and repeat the test, but the junk tool was broken already - basically the entire inner assembly of the screw on nozzles was falling apart. So maybe it wasn't very accurate to begin with...

Sometimes I go for long periods without this issue - it has been probably at least a month since it last occurred. Maybe I shouldn't worry.

Georgeandkira · Post by **Georgeandkira** » 12 Aug 2019, 12:36

Your step #1, while encouraging, was compromised by the cheap/broken gauge. Get a better gauge. Maybe there's good one you can borrow from an auto parts store (tool loaner program)?