Startup problem after letting it sit for a while

[Unispeed]

The car does this only when its hot out and I have left it sitting for a few hours.

I start the car and it acts as if its not getting enought fuel for about a full second. During that "second" the engine is hunting for idle. After that the idle goes to normal. I also noticed that if it sits for a while the car cranks a bit more before it starts, not much but I can hear the difference. If I shut it off and try restarting it it starts crisp (2 cranks and idle goes where its supposed to).

On the other hand, if the car has been sitting and its been cool outside (less than 50 degrees) it starts crisp. It seems to be temperature related...

Yes, I pressure tested...

Any thoughts?

[The_Jerbel]

Sounds like the fuel system is not holding pressure with the car off, so once the pressure has dropped off, the fuel pump has to run for a second or two before the pressure is high enough to crack open the injectors and fire the car up.

[Unispeed]

Hmmm, so how do I go about fixing this? and why is it happening only when its warm out. It starts just fine when its cold.....

[The_Jerbel]

Could be a bad FPR. Could also be a bad fuel pump check valve, etc. The best way to fix it is to use a fuel pressure gauge on the output line of the fuel pump while turning the ignition to the "on" position. If pressure is in spec, then try it after the FPR.

[Unispeed]

Update... today it was 85 degrees out.... after letting the car sit for 5 hours it took about 4 seconds worth of cranking for it to start. Temperature really effects the situations for some reason.... do you still think its a fuel pressure problem? Also, what fuel guage do I buy? any links? and where and how do you hook it up "to the outup line of the fuel pump" ? Any pictures? Also, where and how do you hook it up after the FPR?

Pictures of the locations would be helpful.

Thanks

Could be a bad FPR. Could also be a bad fuel pump check valve, etc. The best way to fix it is to use a fuel pressure gauge on the output line of the fuel pump while turning the ignition to the "on" position. If pressure is in spec, then try it after the FPR.

[The_Jerbel]

fuel pump is in the trunk under the black plastic circular cover. There are arrows on it which show which way the fuel is flowing either into or out of the pump. The FPR is on the driver's side of the y-pipe and is a little aluminum cylinder. Hook up the hose of the gauge to the output nipple on the pump as well as the FPR.
The gauge will have two hoses coming off of it and will enable you to hook it up inline with the fuel system. Any gauge will do as long as it's this style.

[rms-s4]

since they are about 20 dollars and fuel pumps are way more, get a coolant temp sensor and try that. when those start to shit the bed you can get extended crank and rough running. check for a MIL or see if any codes are pending but not stored yet for Coolant temp sensor

[damnthemansam]

fuel pump is in the trunk under the black plastic circular cover. There are arrows on it which show which way the fuel is flowing either into or out of the pump. The FPR is on the driver's side of the y-pipe and is a little aluminum cylinder. Hook up the hose of the gauge to the output nipple on the pump as well as the FPR.
The gauge will have two hoses coming off of it and will enable you to hook it up inline with the fuel system. Any gauge will do as long as it's this style.

i thought that was where the evap canister was.. ?

[The_Jerbel]

i thought that was where the evap canister was.. ?

What are you referring to? fuel pump or FPR?

[Unispeed]

You mentioned the fuel pump check valve... where exactly is this located? Is it part of the fuel pump itself or is it a separate piece... would anyone know the part number of the "fuel pump check valve"? I replaced the fuel pressure regulator with a 4.0 bar from Vast but it hasnt really made a difference.

EDIT: I should also add that the cluster displays ungodly hight outside temperatures.. for example when its 80 degrees outside it thinks its 140 degrees. Might the sensor that is reading outside temperature have anything to do with how long the engine takes to crank? Or running in general?

Thanks

Could be a bad FPR. Could also be a bad fuel pump check valve, etc. The best way to fix it is to use a fuel pressure gauge on the output line of the fuel pump while turning the ignition to the "on" position. If pressure is in spec, then try it after the FPR.

[nizmosx]

install a check valve like this drawing i made and your problem should go away. im guessing you have a walbro fuel pump?



the check valve should be sitting just like how it is, but inside the red circle.

[Unispeed]

I have the stock fuel pump, but I dont understand what you mean by check valve... is this something thats oem or a modification that was done by you.. also what kind of checkvalve would I use.. dimensions and where you bought yours would be useful.

install a check valve like this drawing i made and your problem should go away. im guessing you have a walbro fuel pump?



the check valve should be sitting just like how it is, but inside the red circle.

[quicksilver_S]

Hows your battery? battery level has affect on temp and when you start the car?

[BastardS4]

the built in check valve on your fuel pump has most likely failed. Its possible the FPR is dumping pressure as well but less likely.

Its really not a big deal. I have no check valve at all on my 044 pump and aside from it being a little harder to start, it really has no impact.


Another possibility, is that the pressure feed line from fuel pump to the top of the tank (6 inch clear plastic line) has a hole in it. But again, not very likely.

[Unispeed]

Ehhh?

hows Your Battery? Battery Level Has Affect On Temp And When You Start The Car?

[Unispeed]

I already replaced the FPR.. a small hole eh? Ill check it when I get a chance... if there was a hole there though woudnt I have gas all over the trunk? Or at least in the area where the pump is?

the built in check valve on your fuel pump has most likely failed. Its possible the FPR is dumping pressure as well but less likely.

Its really not a big deal. I have no check valve at all on my 044 pump and aside from it being a little harder to start, it really has no impact.


Another possibility, is that the pressure feed line from fuel pump to the top of the tank (6 inch clear plastic line) has a hole in it. But again, not very likely.

[Unispeed]

How do you inpect the "pressure feed line"? Do I have to take the pump out? If so what are the steps in taking the fuel pump out?

the built in check valve on your fuel pump has most likely failed. Its possible the FPR is dumping pressure as well but less likely.

Its really not a big deal. I have no check valve at all on my 044 pump and aside from it being a little harder to start, it really has no impact.


Another possibility, is that the pressure feed line from fuel pump to the top of the tank (6 inch clear plastic line) has a hole in it. But again, not very likely.

[nizmosx]

the check valve is a bmw part from a bmw 7 series i believe. you just buy it and put it where the picture shows. if your factory fuel pump check valve failed your car will hold no pressure in the fuel lines resulting in you having to crank the car a few times to pressurize it. install this check valve and it will keep some fuel in your line for the next start up. 7 dollar part from bmw. i dont remember part numbe.r

[Unispeed]

Alright, so the consensus is that the car is not getting enought fuel right off the bat, but why does it only do this when its hot out? Cause when its cooler it starts good everytime, but as soon as it gets hot it cranks more and starts very weak and then picks itself up.... I'm confused

[RuS4ty]

Mine is doing pretty much the same thing too, I ordered another crank position sensor to see if that fixes anything...
If that doesn't work Ill try the check valve.

Let me know how the check valve works out and ill let you know the like about the crank position sensor.

[Unispeed]

honestly though, if it was a checkvalve it would do it all the time.. If I park the car in the garage (about 75 degrees) and come back 2 days later to start it it starts just fine. On the other hand if its hot out all it takes is a couple of hours and it just sits there and cranks and starts weak... It also seems to be related to how hard I drive the car before I park it.... If I floor it here and there, and then park it... come back after 2 hours to start it = crank heaven. EGTs were next on my list of things to do.... Idk, but I am thinking they are reading wrong on startup and the car is actually dumping too much fuel...idk.... someone correct me if my assumptions are wrong.

Again, the car has had the following done to it:

Giac x
Baileys
AWE IC
Milltek turboback
New fuel filter
New timing belt and water pump
New front o2 sensors from Vast
New coolant temperature sensor
OEM plugs gapped to .25
NO CODES
ALREADY PRESSURE TESTED

[BastardS4]

we have told you what to try first. stop over analysing it and try these simple things first.

[Unispeed]

What simple things, you mean installing a check valve? If it was a check valve problem then my question is "why is this not happening when its cold out and why does it seem to get worse if the time before I stomped the throttle a few times". You also said that the pressure feed hose is probably not it so I didnt delve at all into that one, plus its the 4th and I doubt I can go to the dealership to get a new one. I am just trying ot find an answer that makes sense, thats all. Now, my question is: "Would faulty or on their way out EGTs cause longer crank times? Temperature and weather I heatsoaked the engine the time before seems to have alot to do with this...

we have told you what to try first. stop over analysing it and try these simple things first.

[The_Jerbel]

No.

[Unispeed]

Jerbel, welcome back! So, you still think its fuel pressure related even after what I said about heat affecting the situations so much? I was thinking it was a sensor of some some sort because of that. What do you think I should do next?

[The_Jerbel]

I would install the check valve. Well, in all honesty I would get a cheap fuel pressure tester and check the pressure to be sure of what's really going on. That way you can either determine it's a fuel problem, or completely rule it out.

[Unispeed]

Ok, i'll probably end up doing that.. I noticed when I was looking at the fuel pump today that the output and return lines are made of plastic... or a harder rubber, not exactly a good spot to T a fuel pressure gauge... where is the best place to put it? If you have access to it maybe you could post a picture. Thanks

Edit: The fuel pressure gauge I'll buy will probably be this one: http://www.ecstuning.com/stage/edpd/...productID=5701

So I need an 8mm ID hose that I can T this into. I was thinking of putting one before the fuel pressure regulator and one after. What would be some good T points? Again, a picture would help immensly

I would install the check valve. Well, in all honesty I would get a cheap fuel pressure tester and check the pressure to be sure of what's really going on. That way you can either determine it's a fuel problem, or completely rule it out.

[The_Jerbel]

It depends on the connectors that the tester uses, but if possible, I would put the tester right where the fuel line comes into the fuel rail.

[Unispeed]

Yeah, that would be ideal, but I dont think the fuel gauge I posted about will work there. How did you do yours?

It depends on the connectors that the tester uses, but if possible, I would put the tester right where the fuel line comes into the fuel rail.

[Unispeed]

Ok, upon looking at it better I noticed on the top of the airbox there are 2 fuel hoses. One of them goes directly to the passenger side of the fuel rail. The other one goes directly to the fuel pressure regulator wich in turn plugs into the fuel rail. Wich one of these is providing fuel to the engine and wich one is returning it to the tank?

[The_Jerbel]

Feed line hooks up to the passenger side of the fuel rail.

[Unispeed]

You said its off a 7 series.... I called the bimmer dealer and he asked my what year car I had and all the other stupid questions that went with it. I told him what I wanted but he said I wasnt giving him enough info. I was wondering if you had any other info on this checkvalve.. maybe the year of the car.... the make you mentiones is the 7 series, but year, that I am missing. Or better yet, since you seem knowledgeble about this valve, maybe a part number?

install a check valve like this drawing i made and your problem should go away. im guessing you have a walbro fuel pump?



the check valve should be sitting just like how it is, but inside the red circle.

[RuS4ty]

Update??

[Unispeed]

Ok, so Installed the check valve thats talked about on this site:

http://forums.roadfly.com/forums/bmw...1711019&page=2

and I have to say that the problem has gone away... thanks bmw!

[RuS4ty]

So I ordered the part from BMW early last week and they said it would be in saturday. I went in today to pick it up and they inform me that BMW no longer sells/makes this part... hmm...

where did everyone else get theirs?
This is kind of an inconvenience since I leave this weekend to drive across the country...

[golf#1]

Update with anyone that has had this issue?