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Jeff NJ's Avatar
 
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suddenly cranking longer to fire up

So Ive been driving the 930 a bunch lately and it has been running great. However, the other day after sitting for about 4 hours, I turned the key and it cranked over for a couple seconds before firing, and then started slowly and then came right to idle. I thought it was weird. On the drive home, it ran great, AFR's were all in line with what they were prior. No loss of power at all. The next couple starts, the same thing happened. Cranked for a couple seconds and then ran. I do not give it throttle to start it.

This morning, I listened for the CSV giving the shot of fuel before I hit the starter and it sounds as it always does, but it did the same thing with the long crank. Tonight, I turned it to ON and then off a few times to make sure I had enough gas in there for a cold start and it still took longer to start.

I have been monitoring AFRs throughout the range and they are fine and unchanged. Power comes on strong and all the way to redline, so no power loss at all.

Hot start fires right up the one time I did that, so it seems its just cold or almost cold that takes longer to fire.

Up to now, when cold, at the very first crank it would bark to life every single time.

I haven't touched anything at all for a while.

Anyone have this issue? Any ideas? If something is starting to fail, I want to catch it before I get stranded somewhere.

Thanks!
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1988 930 Venetian Blue
Old 09-21-2017, 07:09 PM
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Turbofrog
 
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Accumulator, bad batch of fuel, leaking injector, WUR cold start (are the atmo temps same?).

Try half throttle to see if its too rich?
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79 930: HX40S#16, MS3pro+ID1000+044+E85, Ignition: 123/TUNE/MSD6A, True split BB, 2*turbosmart38,
99 Audi S4: RS4 engine/E85/K24brids, KW3, Movit+RS6 discs
Old 09-21-2017, 08:50 PM
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Hmm. I did fill up literally on the way that day and the first time it happened was the first restart after the fill up.

Temps are similar. Been warm here for a bunch of days now and is very much like summer weather.
When you say try half throttle, you mean at cold start?

Hopefully its just fuel. I'll add some seafoam to see if that helps.

Thanks for the ideas!
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Old 09-21-2017, 09:02 PM
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I am dealing with this issue RIGHT NOW.

on a hot-start it cranks for a few seconds then fires on 4 cylinders and picks up the other 2 in a few seconds then runs great.

This is caused by a loss of fuel pressure in the lines. remember these cars are constant injection systems and need every bit of pressure to fire on all 6.

90% of the time the culprit is the fuel accumulator (also called the fuel pressure regulator, etc) behind the fuel filter

it can ALSO be (as stated before)

a leaky injector

OR

the check-valve on either of the fuel pumps. (these can be replaced without buying the entire fuel pump).

I had hoped my accumulator was bad.

just my luck? its one of the others so I have to do more diagnosing.
Old 09-21-2017, 09:54 PM
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Turbofrog
 
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Quote:
When you say try half throttle, you mean at cold start?
Yes, more air to ignite fuel incase some or all cylinders are too rich to ignite with idle air. Could also be the AAR? air valve is sticky as it should be open when cold to help cold starts.
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79 930: HX40S#16, MS3pro+ID1000+044+E85, Ignition: 123/TUNE/MSD6A, True split BB, 2*turbosmart38,
99 Audi S4: RS4 engine/E85/K24brids, KW3, Movit+RS6 discs
Old 09-21-2017, 11:43 PM
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first off you are not hearing the CSV if you are just turning the key to ON,
the CSV fires ONLY when in start.
what you hear are probably the fuel pumps. they run for about a second with the key on.

you need to check control pressure cold first off.
you can also check for air leaks. an air leak effects cold starts more than hot starts.
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ [__] RUNNING: [__] NOT RUNNING:
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[] RUNNING:[_] NOT RUNNING:__2000 MER E320 WAGON [_] WRECKED:[]RUNNING:
Old 09-22-2017, 03:54 AM
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CSV on 930 does not activate above 45F.
Hot start is fine.
Cold start is sluggish. Most typically that is the WUR beginning to fail. Verify by checking you cold control pressure. It should be in the middle to lower end of spec. Upper end of spec is more lean and can cause hesitation.
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Old 09-22-2017, 04:46 AM
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So it's been a couple weeks and I ran through that tank of fuel and refilled from a different gas station when almost empty. Cold starts still crank for a bit.

I then adjusted the CCP lower and watched the AFR's over a few days of cold starts and got it down to about 10.5 AFR (eye watering), and made minor adjustments up to where it is today in the high 12's. All cold starts did the same thing after each micro adjustment- longer cranking than it used to be, so it seems to me that the CCP is not the issue as all adjustments made no difference to the time it took to start it when cold. It definitely runs better cold where it is now - high 12's at cold start, but still cranks a while to kick.

Holding the throttle down halfway doesn't change it.

I wouldn't think the accumulator would be an issue because that would affect hot starts, no? If it sits for 12-24 hours between starts, wouldn't the accumulator have lost all pressure anyway?

The car runs strong and smooth once it starts, restarts are fine - hot, warm, doesn't matter. I get full boost, no hesitation at all and break the tires free when I try. No engine misses at all.

Unless you guys can suggest something else to try, I am not sure what to do and will just keep driving it until something else happens to expose any issue (if any).
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Old 10-05-2017, 09:48 AM
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Crotchety Old Bastard
 
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Could be you are developing a vacuum leak. If so it will get progressively worse and you'll need to chase it down. Loose or cracked phenolic injector blocks are notorious for this.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 10-05-2017, 05:36 PM
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air leaks.

how is the ignition system
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ [__] RUNNING: [__] NOT RUNNING:
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[] RUNNING:[_] NOT RUNNING:__2000 MER E320 WAGON [_] WRECKED:[]RUNNING:
Old 10-06-2017, 04:47 AM
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Thanks guys.

I'll go through the usual suspects with regards to leaks. I have the aluminum injector blocks, so they aren't cracked but I'll check to see that they're all tight. I've replaced all the hoses over the past couple years, so they are unlikely to fail, but you never know.

I went through all of that last year when I was tracking down a miss, which I solved. That turned out to be an injector that wasn't screwed tightly into the injector block, allowing air to pass by.

Ignition seems good. New plugs, wires, cap and rotor over the past two years. Coil is original.
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Old 10-06-2017, 07:40 AM
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miles..cap rotor and plugs.

pull a vacuum on the brake booster hose and booster to test for leak.
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ [__] RUNNING: [__] NOT RUNNING:
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[] RUNNING:[_] NOT RUNNING:__2000 MER E320 WAGON [_] WRECKED:[]RUNNING:
Old 10-06-2017, 09:41 AM
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Quote:
Originally Posted by T77911S View Post
miles..cap rotor and plugs.

pull a vacuum on the brake booster hose and booster to test for leak.
Probably less than 4000 miles on the cap rotor and wires. Less than 2000 on the plugs.

I will check that line and pull a vacuum on it with my mitivac. It was good before, but I have not replaced it, so maybe that failed. Would the brakes be affected if it was bad? Their feel and power hasn't changed.
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Old 10-06-2017, 09:49 AM
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I get this sometimes when I don't trickle charge. you can test fuel pumps in isolation but when you're asking the car to start it's got two fuel pumps, starter motor, ignition circuit and a few more that go live. Then maybe a few grounds that aren't completely clean. it's an easy one, I try that first. good luck
Old 10-08-2017, 07:51 AM
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Some one already mentioned AAR. Presuming you still have it. It is the other part of your cold start equation. Regulates an extra bit of air to help with the rich start/CSV. It does over time get gunked up, or broken circuit. You can check by pulling hose off and looking down with torch/mirror. At cold you should see a gap - some have odd shaped T type slots, others, half moon thing. But at cold it should have these open. When warmed, engine off, look again. Should be closed.
Regards
Alan
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Old 10-09-2017, 01:20 AM
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I have been experiencing similar problems at cold start and after searching for a while came across a possible cause.Could be the ignition switch.This was a fix for me.Try jumping the starter when cold.Pull yellow wire on starter,turn key to on then jump at starter.Good luck,
Old 10-09-2017, 01:55 PM
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Turbofrog
 
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I wanted to save my ignition switch so I installed one start button to the dash and one to the trunk. Here is the schema copied from tech forum.


https://photos.app.goo.gl/kNzsX0RAcVvqH0DF3
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79 930: HX40S#16, MS3pro+ID1000+044+E85, Ignition: 123/TUNE/MSD6A, True split BB, 2*turbosmart38,
99 Audi S4: RS4 engine/E85/K24brids, KW3, Movit+RS6 discs

Last edited by smurfbus; 10-10-2017 at 03:08 AM..
Old 10-10-2017, 03:04 AM
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