cold start problems

[joey79]

Every time I attempt to start the car cold, it has to crank for a very long time before it starts, if it even starts at all. Anywhere between 5-10, 10 second cranks. At the beginning of each crank, it seems to fire for a second, but it doesn't catch, and just turns over. After it eventually starts, it idles, runs, and starts again fine.

The FAQ says the most common cause of cold start problems is the WUR. I recently replaced fuel filter, all vacuum lines, intake boot, inspected WUR (looks perfect), tested aux air valve (seems to work fine).

I know it's getting spark. It seems like it's not getting fuel. Anyone have any suggestions?

[pommeree]

Visual inspection of the WUR can only verify the presence of the WUR.

First easy test would be: Is the cold start valve working?
With the engine cold, remove the cold start valve and point it into a jar.
Have a friend crank the engine and it should spray fuel.
Problems here would point to the CS valve itself or the thermo-time switch.

To test the WUR you'd need a fuel pressure test kit to verify cold vs. warm control pressure.

[epmedia]

On a few occasions, I've had to remove the CS valve completely, and smack the inlet end against the palm of my hand to dislodge any crap that may be in there. Also try to flush the inlet with some carb cleaner. And do not loose the little o-ring when you remove the CS valve.

Awhile back my CS valve was not working via stock wiring. I replaced the thermo time switch, and still would not work. I tested the thermal time switch - good test.

I recently bypassed the stock wiring to the CS valve with a momentary push button. Works great (like a manual/electric choke).

Also, I found that just 2-3 second starter cranks work the best for my '78 when it's cold. Fires right up by the second crank (knock-on-wood).

Robert

[goinstrong]

I had this issue, and found 2 things helped:

l. The positive wire on my alternator was corroded. I took it off, sanded it down, cleaned the threads on the alternator, put it back on, and sprayed it with a protectant.

2. The fuel line from the in-tank pump to the external pump/accumulator was in SSSSSAAAADDDDD shape!! Replacing this stopped that long cranking where it kicked like it would start, but took forever. Does the car start/run better with a full tank? If so, this might be the culprit.

Have you had the check valve and fuel filter replaced recently?
Hope this helps!
Tim

[joey79]

Well, I figured I'd just try disconnecting some lines and checking for fuel output. I jumped the fuel pump relay, and I'm getting lots of fuel from the main fuel line going into the fuel distributor. I get fuel from the line into the FD from the WUR too. I disconnected some of the lines at the injectors, and got no fuel. Would this indicate that something in the FD is blocked?

I havent tested the cold start valve, but I think it is working. I believe that's what's happening at the beginning of the cranking, where it fires for a split second, then just turns over.

[onesimo58]

. I disconnected some of the lines at the injectors, and got no fuel. Would this indicate that something in the FD is blocked?

To get fuel to the injectors you would have to lift up on the air flow metering plate with your finger (if they are long enough) or a screw diver.

[joey79]

Ahh yes, makes sense. Next chance I get to work on the car, I'll test the cold start injector, and maybe pull the fuel injectors to see if they're working properly. I did notice that while jumping the fuel pump relay, my frequency valve was quite noisy. Is the frequency valve supposed to be somewhat loud?

Anyone have any advice? I'll probably be tackling this again on the weekend.

[joey79]

bump

[pommeree]

After it eventually starts, it idles, runs, and starts again fine.

Your Injectors are fine!
Both your pumps are fine!
Your fuel distributor is fine!
Your hoses are fine!
Your frequency valve is fine!
Stop tearing all that $h1t apart, please.

If you're having cold start issues, why not address the components responsible for cold starting!?
Test the cold start injector.
Test the WUR.

[jrcook320]

On a few occasions, I've had to remove the CS valve completely, and smack the inlet end against the palm of my hand to dislodge any crap that may be in there. Also try to flush the inlet with some carb cleaner. And do not loose the little o-ring when you remove the CS valve.

Awhile back my CS valve was not working via stock wiring. I replaced the thermo time switch, and still would not work. I tested the thermal time switch - good test.

I recently bypassed the stock wiring to the CS valve with a momentary push button. Works great (like a manual/electric choke).

Also, I found that just 2-3 second starter cranks work the best for my '78 when it's cold. Fires right up by the second crank (knock-on-wood).

Robert

You may have a broken wire just off the TTS plug. Pull the boot back to check. I had that issue on my aux air valve, just resoldered the wire and it was good as new.

Ahh yes, makes sense. Next chance I get to work on the car, I'll test the cold start injector, and maybe pull the fuel injectors to see if they're working properly. I did notice that while jumping the fuel pump relay, my frequency valve was quite noisy. Is the frequency valve supposed to be somewhat loud?

Anyone have any advice? I'll probably be tackling this again on the weekend.

The frequency valve is very noisy, that is normal. The injectors should not spray until the sensor plate is lifted.

A visual inspection of the WUR is pointless. Did you even take it apart? Even looking inside the aluminum case is pointless. This is probably a simple issue of your cold control pressure being too high. Best bet is to remove it, take it apart and clean it with carb cleaner (meaning clean the internal valve body and inlet screen, not the inside of the aluminum case).

1) Test your cold start injector
2) clean the WUR
3) Test the cold start again

If there is no improvement, you can try the next 2 things:

1) re-set your base mixture to make sure it is set correctly. See the faq for a basic guideline on how to do that. Before you do that, I would ask how the car runs once it's warmed up?

2) If adjust the mixture doesn't help, you can adjust the WUR blindly. Give the small 5/16" diameter recessed plug a quick rap with a hammer and drift. Moving it a few thousandths of an inch inward will lower just your cold control pressure which will increase your fuel mixture only when cold. Use caution here, since you're going blind you will have test after each adjustment. While testing, unplug the WUR so the heating element doesn't raise your control pressure before you're done. If you go too far you may have to pull the WUR, take it apart and tap it back out from the inside.

3) Better yet, you can make your cold control pressure externally adjustable by drilling and tapping this plug and so when you go too far with the hammer and drift you can pull it back out with a nut and bolt. If you are not comfortable doing this I can do it for you for $20.

4) Better still, buy a pressure test kit from jc-whitney for $50 and make your cold control pressure adjustable as outlined in the faq. Now you can test ALL your fuel pressure specs (system pressure, cold and warm control pressure, and rest pressure) and set the WUR back to spec.

[joey79]

I'll check the TTS plug. I did take apart the WUR, and inspected the valve surfaces. They looked flawless. No rust, spots, pitting, nothing... pefectly clean bare shiny metal. I'll tear it apart again and soak it in carb cleaner if that might possibly help though.

The car runs fine, and starts up again easily once it's warm.

Thanks for the replies everyone.

You may have a broken wire just off the TTS plug. Pull the boot back to check. I had that issue on my aux air valve, just resoldered the wire and it was good as new.


The frequency valve is very noisy, that is normal. The injectors should not spray until the sensor plate is lifted.

A visual inspection of the WUR is pointless. Did you even take it apart? Even looking inside the aluminum case is pointless. This is probably a simple issue of your cold control pressure being too high. Best bet is to remove it, take it apart and clean it with carb cleaner (meaning clean the internal valve body and inlet screen, not the inside of the aluminum case).

1) Test your cold start injector
2) clean the WUR
3) Test the cold start again

If there is no improvement, you can try the next 2 things:

1) re-set your base mixture to make sure it is set correctly. See the faq for a basic guideline on how to do that. Before you do that, I would ask how the car runs once it's warmed up?

2) If adjust the mixture doesn't help, you can adjust the WUR blindly. Give the small 5/16" diameter recessed plug a quick rap with a hammer and drift. Moving it a few thousandths of an inch inward will lower just your cold control pressure which will increase your fuel mixture only when cold. Use caution here, since you're going blind you will have test after each adjustment. While testing, unplug the WUR so the heating element doesn't raise your control pressure before you're done. If you go too far you may have to pull the WUR, take it apart and tap it back out from the inside.

3) Better yet, you can make your cold control pressure externally adjustable by drilling and tapping this plug and so when you go too far with the hammer and drift you can pull it back out with a nut and bolt. If you are not comfortable doing this I can do it for you for $20.

4) Better still, buy a pressure test kit from jc-whitney for $50 and make your cold control pressure adjustable as outlined in the faq. Now you can test ALL your fuel pressure specs (system pressure, cold and warm control pressure, and rest pressure) and set the WUR back to spec.

[epmedia]

You may have a broken wire just off the TTS plug. Pull the boot back to check. I had that issue on my aux air valve, just resoldered the wire and it was good as new.

A busted wire?
NO WAY, It's only 31 years old!
lol - hmm... I forget if I even tested the wires.
Thanks Josh, that makes perfect sense.
Too late now though, cause I cut them . Robert

[joey79]

I tested the cold start injector, no fuel came out. Tested voltage with a multimeter at the csi plug, 0v. Tested voltage at thermo time switch plug, nothing.

[epmedia]

I tested the cold start injector, no fuel came out. Tested voltage with a multimeter at the csi plug, 0v. Tested voltage at thermo time switch plug, nothing.

What makes the csi valve difficult to tshoot, is that it's only suppose to work when the engine is cold, while cranking, for only several seconds.

I failed at tshooting mine, that's why I ended up bypassing the stock wiring with the push button. I believe the problem was a loose bundle of ground wires attached to the "dipstick tube support bracket". Or possible busted wire like Josh mentioned earlier.

EDIT: I believe the thermo time switch supplies V-, don't quote me on that though.

So check out those wires, Robert

[pommeree]

I tested the cold start injector, no fuel came out. Tested voltage with a multimeter at the csi plug, 0v. Tested voltage at thermo time switch plug, nothing.

You're definately onto something.
Appears to be wiring.
TT-switch is boss of the cold start valve.
Even more importantly, you're getting 0V at the CSV.

I believe that Robert is right:
Two contacts on TT-switch are 12v for the bimetallic strip and -V for the cold start valve.
If the bimetallic strip is warm, circuit is open and no cold start valve.
If the bimetallic strip is cold, circuit is closed but only for 20-30 seconds until +12V heats the strip and shuts off the CSV.

Get a second opinion as it's been awhile since I went through the same thing.

Also, collectively here on the forum, there's probably now fewer than 873 people with spare TT-switches and cold start valves handy but it appears to be a wiring/fuse problem.

[epmedia]

Ok, I pulled some specs from the Haynes:
To test the Thermal-Time-Switch:
Connect a test light between "batt+", and "terminal W" on the TTS.
It should illuminate the test light brightly when engine is below "95 deg F" for NA models, and below "59 deg F" for others. And this is only for 8 seconds folks (probably only when cranking engine will apply?).
There is also a stamp on the side of the TTS for it's specs.
I also imagine an ohm meter could suffice for testing if no test light is readily avail.
It's no wonder why the system is so darn hard to troubleshoot...

Robert

Anyways, heres a quick sketch from '78 320i:

[joey79]

I'll make it known that these readings were taken with a dying battery. I charged my battery, and I'll repeat these test tomorrow, but I don't think anything will change. I also jumpered my fuel pump with the csi fuel line disconnected, and got a torrent of fuel.

[epmedia]

Welp Joey79 - If you checked your grounds, and all good -
Worst case will be bypassing the stock wiring with a momentary switch.
It's failsafe as far as electrical goes (unless the CSV craps out, or gets clogged).
I'll try to back-trace the wiring incase you have to resort to this.
Need about 20' 18g/16g wire, momentary switch, a place to mount the switch, soldier tools, shrink wrap, 1 eye connector. Took me about 3 hours to plan and implement.

Test the CS Valve also: If you have test leads/aligator clips: pressurize the fuel system (listen for the fuel pumps to turn on), put 12v +/- to the CS Valve and see if it squirts fuel (into a container) - NO SPARKS DAMMIT !! Have a fire extinguisher nearby.
Robert

[fo0manchu]

I just found that my wire off the csi is broken, and looks like its been that way for awhile. However, the car starts right up first time everytime. I just have to let the fuel pump build some pressure in the lines and then crank.

I'm assuming you have checked timing, spark plugs, fuel pressure, and vacuum pressure?

Did you check the voltage at the plug of the CSI while cranking? If you just check the voltage of the injector, it will be 0v.

You need to check the injector for ohms not voltage.
Check the voltage on the harness while cranking.
you should always disconnect the coil wire and fuel pump fuse while testing.

[joey79]

Welp Joey79 - If you checked your grounds, and all good -
Worst case will be bypassing the stock wiring with a momentary switch.
It's failsafe as far as electrical goes (unless the CSV craps out, or gets clogged).
I'll try to back-trace the wiring incase you have to resort to this.
Need about 20' 18g/16g wire, momentary switch, a place to mount the switch, soldier tools, shrink wrap, 1 eye connector. Took me about 3 hours to plan and implement.

Test the CS Valve also: If you have test leads/aligator clips: pressurize the fuel system (listen for the fuel pumps to turn on), put 12v +/- to the CS Valve and see if it squirts fuel (into a container) - NO SPARKS DAMMIT !! Have a fire extinguisher nearby.
Robert

I actually thought about a momentary switch. I'd like to get the stock wiring working though. Could I run 12v from somewhere else to the TTS? Is there a fuse or relay that could be bad? The wiring to the TTS looked good with the rubber pulled back. CSI wiring looked good too.

I just found that my wire off the csi is broken, and looks like its been that way for awhile. However, the car starts right up first time everytime. I just have to let the fuel pump build some pressure in the lines and then crank.

I'm assuming you have checked timing, spark plugs, fuel pressure, and vacuum pressure?

Did you check the voltage at the plug of the CSI while cranking? If you just check the voltage of the injector, it will be 0v.

You need to check the injector for ohms not voltage.
Check the voltage on the harness while cranking.
you should always disconnect the coil wire and fuel pump fuse while testing.

Timing is good, plugs are brand new and getting spark, I haven't actually measured fuel pressure, but I get lots of fuel from the fuel line when jumping the fuel pump relay. Haven't measured vacuum pressure either, but I recently replaced all vacuum lines and intake boot. I'm 99.9% sure that vacuum is ok.

Yes, I checked voltage at the plug, not the terminals on the injector. Checked voltage at the TTS plug as well, and got 0v. (while cranking)

[epmedia]

I actually thought about a momentary switch. I'd like to get the stock wiring working though. Could I run 12v from somewhere else to the TTS?

I wanted to keep mine stock as well.
I don't believe you want to do that permanently. V+ is supplied only when the engine is cranking. V- is supplied only when engine cold, for 8 seconds max when cranking.

Is there a fuse or relay that could be bad? The wiring to the TTS looked good with the rubber pulled back. CSI wiring looked good too.

Don't take my word on this, I never tried it:
The Haynes calls it a "changeover relay" my fusebox-cover calls it a "choke relay" with terminal # 87 on it? And on fuse #16 is has choke listed with other stuff. I'm not certain on this, especially for newer models. The wiring diagram is pretty haywire in this area for me.

I tried troubleshooting with my Haynes, and gave up - but maybe you will have better luck. I even swapped relays, and it still did not work.

************
I believe the engine does not have to be running for testing #1, and #2:
1) when engine cold: remove connector to the TTS, verify -12V is on the "W" connector, or better: near 0 ohms to ground.
2) when engine cold: remove connector to the CSI, verify -12V is on one of those wires, or better: near 0 ohms to ground.
3) if -12V is good on #1, and #2, then I would imagine that the relay is bad, or has bad +12V connections, or fuse.

Hope that helps, It's the best way i can esplain it .


Robert

[joey79]

Alright, I have power now. First off, I tested the CSI and it sprayed perfectly. Then I looked around a bit, and just happened to find a second unused brown plug tucked away under the intake manifold. I put the multimeter on it, turned the key and got ~12v. Plugged it into the TTS, plugged in the CSI, cranked, and it sprayed. I then reassembled everything, and the car started perfectly after about 3 seconds of cranking.

I don't know why there are two brown plugs, but one of the previous owners must have mixed them up at some point. I have a spare blue plug as well. Maybe I'll just cut them off to eliminate future confusion.

Thanks to everyone who took the time to help me out!

[pommeree]

I don't know why there are two brown plugs, but one of the previous owners must have mixed them up at some point. I have a spare blue plug as well. Maybe I'll just cut them off to eliminate future confusion.

Thanks to everyone who took the time to help me out!

That's part of the "North America Warm Start Fix" It's a timer and a parallel harness that's designed to run the CIS when hot, too, in order to overcome a supposed hot starting problem.
Do not cut but instead trace everything carefully and remove intact.
Many owners have remarked on improved performance after they've removed all that.

[epmedia]

That's part of the "North America Warm Start Fix"...

Interesting. That makes it even more difficult to tshoot.
I'll stick to the manual override on my '78 for now .
****
Glad you got it going again.
I was running out of ideas. Robert

[fo0manchu]

Alright, I have power now. First off, I tested the CSI and it sprayed perfectly. Then I looked around a bit, and just happened to find a second unused brown plug tucked away under the intake manifold. I put the multimeter on it, turned the key and got ~12v. Plugged it into the TTS, plugged in the CSI, cranked, and it sprayed. I then reassembled everything, and the car started perfectly after about 3 seconds of cranking.

I don't know why there are two brown plugs, but one of the previous owners must have mixed them up at some point. I have a spare blue plug as well. Maybe I'll just cut them off to eliminate future confusion.

Thanks to everyone who took the time to help me out!

Nice! Glad you found the problem.