Hot start issue m62tub44

[IsStupid]

M62TUB44 is cranking for ages when hot before it finally starts. Going to try and change a fuel pump and filter to see if that helps, anything else worth a shot? On m60s there's an ECU coolant temp sensor that causes similar issues? Worth changing on m62? Where is it?
Cheers

[Themoog]

Mine does that sometimes. It’s very intermittent. I put a new filter on which made no difference and I did buy a fuel pressure tester to see if the fuel supply is the issue ie non return valve but still haven’t got round to checking it. I’m also going to remove the crank sensor and give it a clean to see if that helps.

[Henn28]

Originally Posted by Themoog

Mine does that sometimes. It’s very intermittent. I put a new filter on which made no difference and I did buy a fuel pressure tester to see if the fuel supply is the issue ie non return valve but still haven’t got round to checking it. I’m also going to remove the crank sensor and give it a clean to see if that helps.

Same, both with the original 4.4 and now with the 4.6 in the car. Never been able to fix it, even with a new fuel pump, filter and cleaned/flow tested injectors. My fuel filter is the older smaller one which was only used for a few years, and doesn’t have the pressure regulator. My current hypothesis is that pressure occasionally leaks down at the rail, but not always, for some reason, rather than air or spark related.

So I’ve just gotten in the habit of getting in the car and immediately turning the ignition to run, then buckling up and then cranking the X. Has never happened when I follow this routine.

I have been chasing a very occasional fuel vent system code and wonder if fuel pressure could leak down through that system.

[andrewwynn]

Wife's would do this when the FPR failed. Technically just an o-ring. Test the gas pressure at the rail and let it sit overnight. If you don't have 10-20 psi these FPR is leaking back to the tank.


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[Henn28]

Originally Posted by andrewwynn

Wife's would do this when the FPR failed. Technically just an o-ring. Test the gas pressure at the rail and let it sit overnight. If you don't have 10-20 psi these FPR is leaking back to the tank.


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Thanks Andrew, you are definitely correct. I’ve put a gauge on it and it does leak down, occasionally. I’m just not sure how to fix it, or if there is anything to fix at all since the car doesn’t have a pressure regulator like the ones with the “newer” (larger) fuel filters do. I’m assuming that the fuel pump is supposed to keep the pressure from bleeding down on the cars with the older filter version, but it is only a year old. Hence my theory about the purge/vent system perhaps being the cause.

I asked my wife last night if she recalls it being hard to start when she drove the car daily (bought it new for her in 2002) and she said it’s been doing it occasionally for as long as she could remember.

[andrewwynn]

I had 01 with the large filter and FPR built in.

On realoem what does it show for FPR/filter? Yes got to have an FPR or it's not going to have the return line that feeds the siphon jet. Follow the return line to the left tank and see where it goes maybe the FPR is a separate unit on your car.

[80stech]

I thought the difference was weather or not the regulator was removable from the filter not that the regulator was at another location. Anyway, regulator is the least likely cause of fuel leak down.

[Henn28]

Thanks Gents. 6/2002 4.4i build car with fuel filter 16126754016. ( https://www.realoem.com/bmw/enUS/par...&q=16126754016 )

I've looked through RealOEM and the car, and can't find a stand alone FPR. Maybe it is built into the smaller filter. If so, then it definitely isn't the FPR that is causing my occasional hard start since the OE filter I put in last year has maybe 10k on it.

[IsStupid]

Just changed fuel filter with the built in fpr after having a complete no fire incident earlier, too much cranking killed battery so had to be jumped. When I removed old filter it was hot at least 45°c! Will see if that makes a difference before changing pump. Will keep you posted since battery is on charge now. Why did BMW put the fpr on the filter? Why not on the fuel rail like they used to? Means fuel filters are 5x the price than they need to be. Wtf bmw

[andrewwynn]

The filter and FPR can be replaced separately also the filter is good for half a million miles so they consider it "lifetime".



The o-ring on the FPR, however good for maybe 160-250,000.