CIS Experts - Cold Start Issue

[flat_6]

I have a '87 930 with a Black Fuel Head (930/66) and BL WUR. The car is running get once warm and the warm start is fine. My system pressure is 6.7bar and the cold setting is 1.8bar. This is a low as it will go? I have lot of adjustment still there but it wont go lower than this setting, so I increased the CP until it just starts to increase. With these settings it takes 3-5 sec. to get the car to start. I have the cold start valve disconnected as when its connected it wont start at all and you can start to smell the fuel so it flooding.

Over the summer I have verified the following to make sure I am getting enough fuel under boost, so I know these things are correct:
-tank filter checked and cleaned
-rewired both fuel pumps using independent fuses
-new Bosch 044 rear pump
-new fuel accumulator
-new fuel filter
-flow verified
-injectors cleaned and verified equal flow to each cylinder

I must have some type of restriction on the return? Is there any checks for the return line that I can do? Or is it the higher system pressure that is the issue?
Any advice is appreciated!

[DSPTurtle]

You can blow air through the return line and see if you hear bubbles in the tank.
You should be able to get the cold control pressure down more, what's your limitation?
Have you checked the timing?
I don't have my spec book with me but 6.7 sounds a little high for the euro head. I'll look it up unless someone chimes in first.

[flat_6]

Spec for that head is 6.2 to 6.4bar. I was running at 6.7bar because I did an injector flow test using multiple SP and CP and that setting flowed the most fuel under boost.
As for timing, the ignition timing is at 4 btdc. I used to use 10 but was advised to be closer to 0. Not really sure what stock is?
I can try the air in the return line as you said and see what happens. Thx.

[alwaysflat6s]

"I have the cold start valve disconnected as when its connected it wont start at all and you can start to smell the fuel so it flooding."

Not being an expert but with plenty of 930 engine experience, I don't see how you can expect a good cold start with this inop. Fix this and I have a hunch your issues will be resolved.

[BTW, just a quick squirt of gas before cold starting and see if it immediately fires- I would be surprised if it doesn't. This will answer any questions about cause.]

GL

[JFairman]

Do you have to have such lame idle speed timing to pass emission as in higher exhaust temps to heat up a catalytic converter? There's no other reason for that.

With the really low compression ratio and poorly atomized fuel from CIS at low speeds these things love idle timing up around 15-20 degrees btdc.
Anything less than that sucks and the car can't get off the line as fast as a child on a tricycle.

[flat_6]

Lol. I don't need the lame timing! I am emission exempt, '87 is the last year to receive exemption.
I can bump up the timing but don't think it will solve the fact that I can't get the cold cp lower than 1.8bar. I need some suggestion on why this is happening??
Thanks

[911nut]

In addition to fixing your timing, I concur that you should install a new cold start injector. Buy a genuine Bosch one too. The cheap ones are good for about a week (ask me how I know).

[T77911S]

i thought it was funny that you disconnect the CSV then complain it wont start when cold.
fix it.

setting the SP for 6.7 for the most fuel flow is NOT the way to set it up. you have the BL WUR, set the SP for stock and then adjust the WUR for AFR's. you dont need to do anything outrageous unless you are running big HP.

misture can also effect the cold start. check your AFR's.

[mark houghton]

The symptoms you've given are conflicting. She won't start at all when the CSV is hooked up (you smell raw gas as though flooded- and it probably is), but will start without the CSV....which tells me it's plenty rich (more than it needs to be) to support starting without the CSV. When you put the CSV back in line it's now way too rich to start because of the extra fuel being introduced on top of an already too rich condition.

Try raising your cold control pressure (thus leaning out the mixture) and hooking the CSV back up. Possible that your WUR is fubar. Also possible that your CSV (thermotime switch) is staying energized too long....it's supposed to time out after a couple seconds, and not actuate at all once up to temperature.

[flat_6]

Thanks Mark, i will try.

[911nut]

Another thing to do is to drop your system pressure down to the specification minimum. Running system pressure as high as you are will make the car run pig rich on-boost and no amount of fiddling with your BL WUR will correct it. Been there, done that.

[RarlyL8]

I agree with Mark, the cold start is too rich. It is probable that the ccp cannot be adjusted any lower due to the high system pressure. You don't need the ccp lower anyway so this should sort out once you find your new set points as they are no longer stock spec.

[flat_6]

Just FYI, my system pressure is high to try and get more fuel under boost as I hit <12 afr @ 5300 rpm. This helped a bit but not nearly enough as now I can get to 5800 rpm. Still need more fuel.

I will do as suggested and bring the SP back into spec and get the cold start sorted out. Then i guess its back to finding more fuel next season. I am thinking Water Methanol is the next step. My goal really isnt that crazy, I just want to run 1.0bar and get to redline with the afr =>12.0.

[Alan L]

+1 on the CSV advice.
Your WURsettings are not that far out of spec. Should be up to 6.7 or ideally around 6.4. I can't figure why you are short on fuel at boost - I have almost disabled my boost dump to get the AFrs up into the 12 range. You might like to check the CP on boost dump. You can do this manually by pressuring the WUR thru the manifold line to the WUR, with a mighty vac sort of thing, or whatever you have on hand. It is supposed to drop by about 0.5-0.7 bar at 5psi boost. You may have something screwy in your WUR.
Your 1.8 bar cold pressure is not out of spec - depending on your ambient temp. At 20 Deg C it would be correct.
Regards
Alan

[flat_6]

"Should be up to 6.7 or ideally around 6.4. I can't figure why you are short on fuel at boost" I wish i could figure this one out !!!

My boost CP = 2.1bar with SP = 6.7b. When SP = 6.4b, boost CP = 2.1b.

Also, my cold CP = 1.8b was @ 10 C.

[Alan L]

When you get 2.1bar boost CP, what is your warm CP?
Have you checked your fuel flow is within spec - maybe you have a lazy pump?
Regards
Alan

[flat_6]

I checked the fuel flow a year ago and was above the min. Spec. I also hooked up a gauge to pressure test the pumps and determined the rear pump was out of spec. I replaced it with a 044 pump.

So last night I reset the SP to 6.3b. Blew out the return line and set up the WUR
Cold cp = 1.65b at 13C
Warm = 3.65
Boost = 2.1
And connected the CSV.

Started it this morning and it is cold out !! Only 1C ....
Exact same symptoms; wouldn't start after 5sec of cranking. Started to smell like fuel, so I disconnected the CSV and then it started at 2sec. Of cranking??

So my thermotive switch must not be cutting out but it doesn't really matter since the extra fuel isn't helping it start. Now what??

[911nut]

Originally Posted by flat_6

So last night I reset the SP to 6.3b. Blew out the return line and set up the WUR
Cold cp = 1.65b at 13C
Warm = 3.65
Boost = 2.1

I think you are still way too rich.
I'm 3/4's of a whole point higher on warm cp (4.3) and boost cp (3.3) and I have a big turbo and SC cams.
What does the cold cp graph say your pressure is supposed to be at 13 degrees C?

[flat_6]

Cold cp graph calls for 1.2 - 1.6b. And 1.65 is the lowest mine will go. I agree that it has to be to rich but how ???? And how much should I raise the cp?

As for warm, my car has always run great at the factory set point of 3.65b. The is 14.7 most of the time but can fluctuate with ambient air temp changes. 14.5 - 15.2 afr.

[DSPTurtle]

Next time you try starting it, after your five seconds of cranking, pull both fuel pump relays and try to start it again. If it chugs to life, you know you're rich.