Tech Forum : Cold start problem.

svn2002s

Posted Friday, Apr 29th 6:16am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 11

Walnut Creek, CA
79 323i, 69 2002,71 2002, 03 330i

My car (79 323), takes forever to start when cold. When warm, it starts at the first try. So, I am ready to spend the $$ and buy whatever I need NEW, I just had it. Does NE1 has a list step by step what to check. Is just the cold start valve?

chad

Posted Friday, Apr 29th 8:22am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 104

saskatchewan, canada
79 320i, 82 320i

it could be the check valve in your fuel pump, i believe bmw sells an external check valve that u can put inline after your fuel pump, that way u dont have to replace your pump if its still good.

Tricord

Posted Friday, Apr 29th 7:09pm [Edit] [Quote] [IMS] [View car]

Administrator
Post nr. 811

Belgium, Europe
323i Baur

Could be a faulty cold start valve or because the fuel system is losing pressure over time due to a faulty fuel accumulator.

Of course, I'm assuming your timing is correct.

jrcook320

Posted Tuesday, May 3rd 10:01am [Edit] [Quote] [IMS] [View car]

Junior Member
Post nr. 1

Van Wert, OH
'81 320i

Loss of rest pressure usually causes warm starting problems, but this could still cause hard cold starting as well. Places where you lose rest pressure are the fuel pump check valve, the pressure regulator, WUR, a leaking cold start injector, and the accumulator as tricord said.

The check valve threads into the fuel pump and can be replace without replacing the pump. This is where the bango fitting is. I have read this is the most common cause of the most common K-jet symptoms. Its about a $15 USD part. To help solve a leaking pressure regulator, remove and clean it. To check for a leaking accumulator, remove the fuel drain line off of the back of the accumulator, if it leaks you will know it.

Check the cold start system: check that the 5th injector sprays when you try to start the motor, if not, check that the thermo time switch is working, if so, check for voltage at the injector when cranking.

It could also be a dirty or misadjusted (or leaking) WUR. First take it apart to clean it, and check the inlet filter for junk. If that doesn't work you may have to tune it. Here is a good link I found on one way (and probably the best way) to tune the WUR.

http://www.landsharkoz.com/tt/ttwur.htm

DHoang

Posted Wednesday, May 4th 9:57pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 235

Texas USA
323i, e39 528i, Maserati Spider, Tundra LTD V8 p/up

svn2002s wrote:

Does NE1 has a list step by step what to check. Is just the cold start valve?

Get this book:

plus
Kjet pressure gauge

In one afternoon, you'll become a Kjet expert. I guarantee it.

MayanArch

Posted Sunday, Nov 4th 4:07pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1431

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

OK, I am reviving this thread because I am having serious cold start problems on my 323i (not the Baur).

Where is the cold start valve?

I have a pretty seasoned BMW mechanic tell me that I should jump the electronics so the fuel pressure starts going as soon as I turn the key on ACC. He said it is wired the way it is from the factory so the fuel pump will stop in case of an accident.

I typically trust whatever this guy says, as he is an old timer BMW guy from the 2002 days and on....but this sounds wrong.

This post seems to think that the cold start valve is the problem, and just cleaning it or replacing it will cure the problem.

Please help by pointing me in the right direction......starting with the location of all these parts. Photos are definetly appreciated.

ArnZ

Posted Monday, Nov 5th 2:47am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 126

Qld, Australia
BMW 323i

cold start valve is under the inlet manifold near the crankcase ventalation tube, there should be some wires connected to along with a fuel line.

the warm up regulator (WUR) can be found near the ignition distributor, as jrcook320 said they sometimes need a clean, and if that doesnt help then you can make them adjustable.

another problem with cold starting could be the air slider valve which lets more air in for cold starts, this valve can sometimes become stuck and stay closed/open. this can be found under the inlet manifold too

anyways heres a link to a site which will give you a better understanding of k-jet

http://www.auto-solve.com/mech_inj.htm

MayanArch

Posted Monday, Nov 5th 5:25am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1432

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

ArnZ wrote:

OK, so how do you go about cleaning the WUR? Tips? Problems? Precautions? Do I need to buy replacement seals to put it back together?

What do I clean it with? Techron? Brake Cleaner?

Please help.

Does the Cold Start Valve need to be cleaned or serviced?

MayanArch

Posted Monday, Nov 5th 5:36am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1433

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

Where is the check valve to the fuel pump? What does it look like?

wayfast

Posted Monday, Nov 5th 5:26pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 13

Belleville, Michigan
81 323i

nvm someone already posted it

ArnZ

Posted Tuesday, Nov 6th 6:14am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 127

Qld, Australia
BMW 323i

MayanArch i dont know how to clean the WUR and air slider valve but ask jrcook320, pm him and ask him about cleaning a WUR.

ive personally never cleaned one before. so im not too much of help, sorry

MayanArch

Posted Wednesday, Nov 7th 3:14am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1437

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

chad wrote:

it could be the check valve in your fuel pump, i believe bmw sells an external check valve that u can put inline after your fuel pump, that way u dont have to replace your pump if its still good.

Where can I source this check valve? Does BMW still carry it?

MayanArch

Posted Monday, Jan 21st 11:15pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1497

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

I wanted to see if you could hep me with my WUR.

I took it off today, but didnt take it apart. It seems that someone already modified it with an adjustment screw at the top. I think this has to be giving me problems since the car runs fine until it gets cold for more than 4 to 6 hours.

I thought it was the distributor, but I t has been cleaned twice, and the car still gives problems. It runs like a beauty once started, but needs 8 to 10 cranks, if not more, if left to sit for a while.

I did notice that the inlet and outlet valves hold liquid. I dont knoow if they are supposed to, but I sprayed some carb cleaner in there and it stayed. It did not seep in.

Is it supposed to do that cold, or is that a sign that the mesh and outlet holes are dirty?

aussie323i

Posted Tuesday, Jan 22nd 3:51am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 609

australia
1979 323i

Also check your 'temperature time switch' this is the brown plug on the thermostat housing.

My car was taking ages to start, and I thought the system pressure was leaking out while the car was switched off, but on closer inspection it was just that the temperature time switch had come off! I plugged it back in and there was no more problem

jrcook320

Posted Wednesday, Jan 23rd 12:30am [Edit] [Quote] [IMS] [View car]

Junior Member
Post nr. 1

Van Wert, OH
'81 320i

I'll post what I emailed you for the benifit of others since you asked the same question here:

If it only has 1 screw close to the electrical plug (on a recessed hole) then it has been modified to adjust cold control pressure, which could effect cold starts and cold running if the pressure is incorrect. Do you have a fuel pressure test kit? If not you can buy one from jcwhitney for $60. This will tell you if your cold control pressure is off. From your symptoms I would guess that your cold control pressure is slightly high, causing a lean mixture when cold and thus a hard cold start.

It is normal for the WUR ports to hold liquid. The valve inside requires fuel pressure for it to open enough to flow fuel. Once fuel pressure drops below a certain point it is designed to close so that rest pressure stays above 22 psi for 20 minutes.

Have you verified that your cold start injector is functioning? This depends on the thermo time switch to work properly and is very important for cold starts. Pull it out and insert it in a jar, pull your coil wire (put it somplace it won't spark) and have someone crank the motor while you check for fuel spray.

The fuel pump check valve can be bought from bavauto.com or most other vendors that sell bmw parts. It just threads into the outlet of the fuel pump. Like I said above, a failing check valve usually causes warm start issues due to a loss in rest pressure. A loss in rest pressure is less of a problem with cold starts since control pressure is lower (for a richer mixture) and the cold start valve sprays. So if the car starts fine within 1-4 hours of being run, then it's not likely you have a loss in rest pressure.

jrcook320

Posted Wednesday, Jan 23rd 12:34am [Edit] [Quote] [IMS] [View car]

Junior Member
Post nr. 1

Van Wert, OH
'81 320i

Here is one of my posts in the faq thread on bimmerforums, I thought it may be helpful even though some of the info has already been posted. The fuel presser data isn't correct for a 323i, can anyone post that information?

First off, if you’re trying to trouble shoot a problem or are just asking a question, knowing what each component is and what it does will be a big help to you and to us as we try to answer your questions. Read and study the links below to learn what things are and what they do. There are a few components that often go by different names. The Control Pressure regulator (CPR) is the same thing as the Warm up Regulator (WUR). The Air Flow Meter (AFM) is also called the Lift Plate or Sensor Plate. The auxiliary air valve is also called the Idle Air Valve. I generally refer to the fuel distributor as the FD, the air flow meter as the AFM, and warm up regulator as the WUR.

Mechanical Fuel Injection

CIS trouble shooting:

If you’re having CIS problems, the most valuable book you can buy is “How to tune and Modify Bosch Fuel Injection” by Ben Watson. If you buy this book, you’ll also need to get a CIS pressure test kit. For only $60, JCWhitney sells them for less than half the price that Bavauto and other BMW suppliers do.
CIS pressure test kit

The most common 2 problems I see being asked are hard cold starts and hard warm starts, these 2 questions get posted over and over again.

A hard cold start accompanied by a rough idle when cold is often caused by an incorrect mixture when the motor is cold, which is often due to a dirty or misadjusted WUR. The first thing to do is check for vacuum leaks. The next thing I recommend doing is to clean your WUR.
How to clean your WUR

A hard warm start is often due to an internal system leak causing a drop is rest pressure. The culprits for this are a leaking fuel pump check valve, leaking system pressure regulator, WUR, or cold start injector. The most common is the check valve which costs about $15. Sometimes cleaning the system pressure regulator and/or WUR can solve leaks in those components. If the cold start injector is leaking it will need replaced.

CIS Pressure Specs:

For those that have a pressure test kit and just need to know the pressure specs, here they are for the 80-83 e21:

Fuel pump delivery (as measured through the fuel return line): 750 cc's/30 seconds

Cold control pressure:
50 deg = 17 psi
75 deg = 26 psi
100 deg = 35 psi

System Pressure:
65-75 psi

Warm control pressure:
39-45 psi

Rest pressure (leak test): above 22 psi for 20 minutes

injector opening pressure: 45 psi

Injector flow test: Pull the injectors and put them each in a jar or graduated cylinder and spray for 10-20 seconds. Check for good spray pattern out of each injector, total volume delivered should be equal

How to tune the WUR:
You should never have to buy a new WUR unless yours is corroded or the heating element is broken. You can make the WUR adjustable, this link is a good start but I consider it incomplete so I'll write my own DIY when I get a chance:
How to tune your WUR

Here's a diagram I drew up on how to make both cold and warm control pressure adjustable. This is how my WUR is set up.

MayanArch

Posted Wednesday, Jan 23rd 11:04pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1500

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

I am going to clean the WUR. See if that helps.

I was told the cold start valve pressures were checked cold and were fine. My only reason to doubt their word is that the problem persists.

Maybe they are right, the distributor has gone bad.

They also charged me for a new accumulator, which has the check valve inside it....so I guess that has been checked also.

My WUR has been modified by someone already, but they only did half of the job. They put in that 8mm screw that is pictured on the left of your schematic.

Is it safe to play with that adjustment, considering that it will only be doing half of the adjusting needed to the plate?

jrcook320

Posted Thursday, Jan 24th 3:49am [Edit] [Quote] [IMS] [View car]

Junior Member
Post nr. 1

Van Wert, OH
'81 320i

It is worth trying. A very dirty or clogged WUR will have the effect of raising control pressure and thus leaning out the mixture. It stands to reason that this could have the greatest effect when a cold motor needs a lower control pressure because blockage could become a greater restriction than the valve itself (and thus control pressure is higher than it should be). As the motor warms up control pressure goes up as the WUR begins to restrict flow naturally, so the blockage may no longer be the bottle neck restriction.

With the DIY you can't go wrong as long as you're careful.

The accumulator does not have the check valve inside it, the fuel pump does. I don't htink that is your problem though.

I would not recommend adjusting the cold control pressure without a pressure gage since you will be tinkering blind, but if you are very careful and have the time you could probably still get it right by trial and error.

If you decide to do that, you want to lower your cold control pressure to enrich the mixture, so knock the post inward with a hammer and drift. I would suggest only one hit for every time you try to start the car to see if your condition improves. Make sure you unplug the WUR so the bimetallic strip doesn't heat up. If you go too far you can easily pull the post back out to raise control pressure in a very controlled fashion by tightening the nut.

jrcook320

Posted Thursday, Jan 24th 3:49am [Edit] [Quote] [IMS] [View car]

Junior Member
Post nr. 1

Van Wert, OH
'81 320i

whoops.. posted twice.

MayanArch

Posted Thursday, Jan 24th 6:57am [Edit] [Quote] [IMS] [View car]

Member
Post nr. 1501

Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978

I am going to try to clean it first.....and would rather just make it fully adjustable if I am going to try adjusting.

The problem when cold sounds like there isnt enough gas for spark. At first you only hear the starter. At the second or third try you hear the starter going, and the engine trying to turn every once in a while....but it doesnt. The next try it tries to turn more often, especially if you hit the gas pedal....but doesnt. It will do this a lot until after a lot of tries the engine will turn and fire, and stall........which means it is finally going to start. It starts after that.

One thing that happens in some of these attempts at starting is that you hear a deep throttly sound after the failed crank.

It sounds like the exhaust clearing...but feels like it is comming from the intake boot or flapper for some reason. You also get a puff of smoke and the smell of gas from that general vicinity when that happens.

melloh

Posted Thursday, Jan 24th 9:13pm [Edit] [Quote] [IMS] [View car]

Member
Post nr. 642

California, USA (San Jose)
1980 320is, 1991 318is

svn2002s - I just realized you were the original post. If you need a k-jet pressure guage, you're welcome to borrow mine. You can come down to SJ and pick it up, or I can drop it off on my way to the meet Ken posted in the general forum. Let me know and send me an IMS.

[Mayan, i'd of course lend it to you but with the shipping cost from CA you may as well buy one.]