Warm start issue

Goaltender46 · #1 09-10-2014, 09:59 PM

My car 2003 Bmw X5 3.0 Manual trans with 262,000 miles

I have been suffering from a warm start issue. The SAV starts up fine in the morning and if its been sitting for several hours. When it sits for about 20-45 minutes is when it takes a few seconds to start up (around 10 seconds)
Replaced parts; Spark plugs (original NGK 4 prong) MAF meter, Fuel injectors and o rings, Crank position sensor,Fuel filter and fuel pump. The issue popped up 2 weeks after the fuel filter change. Originally I was chasing a set of p2098 p1093 and p0313 codes. Those codes went away after the fuel injectors were replaced only to come back 2 weeks later. Of course the car runs great other than the warm start issue. Strangest thing is if I leave the key in the on position for a few seconds it starts right up which is why I changed the fuel pump thinking it was check valve. But the issue is still there. I'm stumped hopefully someone has some insights on this one.

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upallnight · #2 09-10-2014, 11:25 PM

There's a vacuum hose that is connected to the fuel pressure regulator with the fuel filter. Either someone didn't install the hose correctly or you have a vacuum leak or the hose has developed a leak.

Goaltender46 · #3 09-10-2014, 11:48 PM

Does the regulator on the fuel filter serve as a check valve? I was under the impression that they only regulated pressure under high throttle conditions. I will take a look at the vaccum hose first thing tomorrow AM!

upallnight · #4 09-11-2014, 09:36 AM

When their is no vacuum to the regulator that's is when the engine is normally at WOT. At WOT the engine is using more gas so the DME commands the injector to stay open longer. For a cold engine a rich mixture is essential for it to start and run. For a warm or hot engine (Yes even after 20 minutes the engine is still hot) less gas is require to start the engine so the injector should be closed for a longer period of time.

It starts right up after you leave the key on for a few second because the fuel pump is switch off by the DME if the engine hasn't started within that period. It will keep the fuel pump off until the engine starts.

You can try this the next time you try a warm start. Before starting the car, push the accelerator pedal all the way to the floor and hold it there. This will tell the DME that the engine is flooded and to not start the fuel pump. Start the engine, does it start right away?

n_sievers · #5 09-12-2014, 08:12 AM

I had this same exact issue pop up after I did a list of preventative maintenance including fuel filter replacement. I too replaced my fuel pump initially thinking that was the concern but did not resolve. I ended up finally diagnosing it as a faulty regulator that was integrated in the new fuel filter (ordered from an aftermarket supplier) so replaced with a new one directly from BMW and problem was immediately resolved!

upallnight · #6 09-13-2014, 11:37 AM

This is why I don't use aftermarket parts.

Goaltender46 · #7 09-15-2014, 11:55 PM

So I tried holding the gas pedal to floor while starting it several times and that did not change anything it still took a while to start. So my next approach will be to swap out the fuel filter. I used a aftermarket Hengst filter. I will get the OEM unit this time. I'll update with the result.

Goaltender46 · #8 09-16-2014, 12:17 AM

Quote:

Originally Posted by n_sievers

I had this same exact issue pop up after I did a list of preventative maintenance including fuel filter replacement. I too replaced my fuel pump initially thinking that was the concern but did not resolve. I ended up finally diagnosing it as a faulty regulator that was integrated in the new fuel filter (ordered from an aftermarket supplier) so replaced with a new one directly from BMW and problem was immediately resolved!

Thanks for this post! I'm swapping out the aftermarket part for the OEM filter.

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