Long crank to start (fuel delivery) - drainback valve?

Just recently started having an intermittent (approx 80% of cold starts, 10% warm) problem w/the engine cranking longer than normal to start. Thinking it's a fuel delivery problem b/c once in a while there will be a gas smell once it starts. Have traced the fuel lines under the car and no leaks are present as best I can tell. Plugs, cap & rotor are fairly new and it runs great once it starts, and it cranks strong just takes longer than it should.

Thinking there's probably a drainback valve in the fuel pump as there are on most vehicles, and guessing it's on the in-tank pump but hoping somebody can confirm before I go parts shopping. Any suggestions?

My second thought is the PCV valve might be sticking, not generating a vacuum at startup. Will replace that today and see if it helps.

Thanks,
CR

You are probably correct on not holding pressure in the line. Turn the key forward and wait about 4-5 seconds before engaging the starter, this will diagnose if the problem is drainback or some other issue

Check your external pump.

Hey thanks for the suggestions guys, had set this thread to send me an auto email if there were replies, but never got one! Glad I checked

Reading more in the Bentley I did find reference to the fuel pressure being held by two devices - the drainback valve in the external fuel pump AND the fuel pressure regulator on the fuel rail. Mechanic buddy of mine said that if the regulator was bad, the vacuum line would have gas in it (makes sense, if it goes bad the diaphragm leaks and then fuel is pulled into the vac line). After running a while the vac line is dry as a bone, so I'm pretty sure it's the fuel pump.

Ordered the external pump Friday from BavAuto, it was $180 or so on their site but $150 when I called to place the order, always a nice surprise! And just for sh*ts, I'm doing the pressure regulator also, for $60 it can't hurt to cover all bases. Probably about due for a replacement anyway, 22 yr old rubber won't last forever!

Will post up when I get it solved, but thanks again for the confirmation that the drainback is on the external pump. Kinda strange, expected it to be on the low pressure pickup in the tank but I guess it makes sense to hold it at the external.

Final note for anybody replacing their fuel pump, was told it's a good idea to replace the fuel filter w/the new pump to avoid mucking it up. Have one of those in the garage already, good excuse to put it on

Thanks again!

CR

Originally Posted by Just Bryce

You are probably correct on not holding pressure in the line. Turn the key forward and wait about 4-5 seconds before engaging the starter, this will diagnose if the problem is drainback or some other issue

Meant to mention, my fuel pump doesn't prime when the key is turned one click short of start. Is that normal? I'm sure it doesn't prime, at least it's not right now -

The check valve in the fuel pump goes bad over time. When the valve fails, it allows all of the fuel in the injector rail and supply line to drain back into the tank causing longer cranking times. A dealer can order a repair kit which consists of a new section of rubber hose with an imbedded check valve. It costs about $5 and takes only a fuel minutes to install.

The fuel pump does not run if the engine isn't turning. That's a safety feature BMW built into the system.

Excellent idea on the check valve, I should be able to rig that up myself. One of those "Doh!!" ideas when ya hear it mentioned!!

For what it's worth, replaced the fuel pressure regulator yesterday and that seems to have fixed the problem - 5 out of 5 starts it fired right up, one after it had sat all night

Thanks for the comments and ideas!

CR

Originally Posted by mike b

The check valve in the fuel pump goes bad over time. When the valve fails, it allows all of the fuel in the injector rail and supply line to drain back into the tank causing longer cranking times. A dealer can order a repair kit which consists of a new section of rubber hose with an imbedded check valve. It costs about $5 and takes only a fuel minutes to install.

The fuel pump does not run if the engine isn't turning. That's a safety feature BMW built into the system.

That is incorrect

The fuel pump engages when the key is turned to the forward position just before cranking. If the system is holding fuel pressure then it may just be for a split second but it does indeed energize at that point.

Originally Posted by mike b

The check valve in the fuel pump goes bad over time. When the valve fails, it allows all of the fuel in the injector rail and supply line to drain back into the tank causing longer cranking times. A dealer can order a repair kit which consists of a new section of rubber hose with an imbedded check valve. It costs about $5 and takes only a fuel minutes to install.

The fuel pump does not run if the engine isn't turning. That's a safety feature BMW built into the system.

Damn stealership didn't know anything about it...figures

edit:

Think I found the part number in Google: P#16 14 9 068 988
Just ordered one from the dealership, will be here in about a week. Suggestions on where to install it (at the tank or just upstream of the ext pump?)

Update, installed the check valve (what a deal, $3.20!!) and it still takes longer than it should to start, so it's gotta be the cold start valve or fuel pump. I don't have a pressure gauge and am not gonna buy one right now, so the pump is going back to BavAuto and I'm gonna live with the extra cranking. It only takes about 5-10 seconds, which really isn't much longer than it took before, so the heck with it for now

Thanks for the tips though, that check valve is a steal - tempted to pick up a few more of them, they'd be handy on any old vehicle!!

my car does the same but when a take my car a just turn the key to on put my seatbelt on, push the check and den a start the car