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Crotchety Old Bastard
 
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The data is a bit confusing. Low CP should correspond to a rich condition.
Typically a weak fuel pump will result in a drop of system pressure which transfers to a rich condition. That rich condition switches to a lean condition on boost as the pressure/volume is too low to support healthy AFRs on boost.
What you are reporting is an intermittant lean condition during non-boost events coupled with low CP.
Verify the fuel pumps are getting 12.5V each while running and that system pressure is in spec. Do a volume test as suggested if you can. Have you looked at the fuel head? Do you have access to a known good -037 FD? These symptoms sound like your fuel head is having a stroke. Every component plays a part though so all must be checked.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'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 01-24-2014, 05:10 AM
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i was thinking the FD but i went back and saw he had it rebuilt. (dont know anything about who did it).
CP is going hi-lean when he hits the gas.

"I tried to rev it the CP goes from 3.2 to 3.4 as I hit the throttle, then as it settles down it goes to about 3.1 and then steadies back at 3.2."

dont know if he is setting the mixture with it at 3.2 bar. i know when i tried to run mine at 3.1, it drove fine except on boost really sucked. even with AFR at 13 at idle.

CP should be stable. pressure regulator? fuel head.

air leaks. they can do weir things. check the intake bolts. mine kept coming lose.


one other question. the line from the top of the FD to the WUR, is it the original line or does it have one of those fuel dampers on it?
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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 01-24-2014, 07:12 AM
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Crotchety Old Bastard
 
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Good idea to check the intake bolts. They are an often overlooked vac leak source. Cracked blocks as well.
We've rebuilt plenty of WURs and FDs that were previously rebuilt. Lot of hacks out there using Asian Internet parts.

Last edited by RarlyL8; 01-24-2014 at 09:36 AM..
Old 01-24-2014, 09:33 AM
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"FINALLY!

about time alan. i regulate my air down to around 15-20psi and pressurize the WUR. you can also do this on the dist to check boost retard."

Sorry for absence - been out of country for 6 mths, and limited internet.
ANY small airleak will affect the AFR range most/worst at low throttle openings - because the air leak is a greater proportion of the air intake at that point, compared to WOT or inbetween. So you need to be sure there are no leaks - as Brain says - intake/injector blocks etc. They often crack over time/heat. Or the seals under them. Would pay to spend a bit of time assuring yourself theses do not exist - cracked vac hoses etc.
Dropping the CP (richening) covers a multitude of sins, but doesn't solve the original problem.
As Brian says, it would be really useful to see the CP when the issues arises. It may be the CP is floating high when the WUR heats up - heat soak when sitting would describe your last posted experience.
This problem is really frustrating to deal with. My SC even has a slight issue like this. I suspect in its case it is a slight imbalance in an injector - ie one running slightly leaner than the others. That is another thing you need to check - that all injectors are closely matched. There are threads on this, but on the 930 it really is worth spending a bit of time synchronizing them. If you have one or two flowing slightly low(er) than the others, bring them up to same flow. If you have one or two high(er) bring them down - and leave the others alone. The manuals generally talk about 10% tolerance. I think this is too wide for the 930 and really you can get it to 1-2% with patience.
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 01-25-2014, 06:49 PM
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Thanks for the replies gents. Found a small vacuum leak (finally) coming from the gasketed area of the crankcase breather. Tightened those nuts and it seems to be gone.

However, the car still runs like *****. When fired it up cold it will run and rev ok. I don't dare take it around the block anymore, as once it gets warm it will go super lean to the point you can't raise the RPMs past 2600 while stationary. My mechanic is pretty good at this CIS stuff and he is running out of ideas.

Yesterday we replaced the forward fuel pump (the later one is pretty new and still showed 140psi) as a trial, as well as the fuel filter. And cleaned, inspected every fuel fitting as well as checked all hoses, checked for more vac leaks, etc.

I think I am going to have to replace the fuel head with a known working one, even though this one was just gone through. Now it seems like something is failing once it gets warm (hence the fuel pump trial) as the car has gotten worse, meaning that I cannot even drive it around the block anymore.

Will keep you updated.

Thanks
Old 01-26-2014, 06:50 PM
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I can't help thinking you are going down the wrong track here - replacing fuel head at this point. The issue you have is a relatively common one. I come back to Brians initial suggestion - compare the warm CP before it behaves like this, and after. That will help quite a bit in trying to pinpoint the issue.
It is simply leaning out too much when hot. Hard to think why the fuel head would do this when it is capable of running fine when in warm up (richer) phase. So I come back to air leaks, CP settings and injector performance.
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 01-26-2014, 08:56 PM
  Pelican Parts Technical Article Directory    Reply With Quote #46 (permalink)
 
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Thanks Alan. I have done some tests with the WCP. Right now it is at 3.5. I have lowered it to 3.2 and again to 2.9 and it still behaves about the same, though it seems to run better for longer. I could try lowering it again tomorrow, who knows. Also concerning is that right now, it idles at around 12 AFR, if I lower it, will idle around 10 or so and I can never get it to idle where folks say it should, 13-14. I could potentially try lowering WCP lower, to maybe 2.5 or so and see but that seems very low per everything I've read.
Old 01-26-2014, 09:07 PM
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When the car gets to the stumble point is the CP still at 3.5, or over time is it drifting higher? Is it stable when you rev it to 2-3000 rpm (you mention hitting the wall at 2600).
What condition are the injectors in?
It sounds like it is running worse now than before?
What did you change?
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 01-26-2014, 09:18 PM
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Yes, CP is still at 3.5. When you rev it, it will go up a bit to around 3.6, then fall when you let off the throttle, then settle back to 3.5.

Injectors have very few miles on them. When cold the car idles perfectly and throttle is snappy and it starts every single time, almost no matter what cold pressure is which makes me think injectors are good.

It is now consistently running worse than before. But, it had done the same thing to me before, where it wouldn't rev. But then I had a host of other issues, shorting alternator which burned up 2 MSD boxes, etc.

Since it's been running consistently badly I last was messing with the fuel pressure in the fuel distributor, trying to lower and raise overall system pressure. But, I changed it all back to how I found it, so the system pressure is back to 6.2 bar.
Old 01-26-2014, 09:26 PM
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You swapped over/or had fuel head rebuilt - do you know if the 6 ports are calibrated to match?
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 01-26-2014, 10:33 PM
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I am not sure about that. I just had them do whatever they do, this is a local fuel inj company who does a lot of porsche stuff for a local supplier, so I assumed whatever they did was correct. But I wanted to swap in another fuel head because now I'm questioning their work.
Old 01-26-2014, 10:44 PM
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It is hard to know where to throw the resources - time and money. Always a bit of a trade off in terms of possibilities. But eventually you have to start eliminating everything.
You can tune/check the injectors yourself. If the shop did not have the working motor when they set the fuel head up, you may still have an issue there. Impossible to know. But one or two mismatched/bad injectors could cause the issue. A morning (2-3hrs) work would eliminate that possibility. Compared to what else you have had to pursue, it may be worth a shot. The 930 is a bit easier than the SC in that the injectors unscrew. Release the fuel lines at the injector (hold the injector in a spanner while you do it). Then remove each injector and hook up again the fuel line (12& 13 mm spanner from memory). Place a small (100ml) container under each one. Turn key on and I think you have to pull the airplate switch at back of air intake. For this test you want to depress airplate with finger a small amount (since it is low throttle opening that is the issue) . Collect the fuel for about 30 secs - until you have enough to measure (50-70 mls is good). Then either weigh each amount or measure it in a graduated measuring cylinder. If you do this, post results and we will tell you where to go from there.
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 01-26-2014, 11:37 PM
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Thanks. This is an interesting test and I will gladly do it. Probably not tomorrow but hopefully Tuesday. Will post results here afterwards.
Old 01-26-2014, 11:50 PM
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it sure sounds like you still have an air leak.

i have done everything you have done plus a lot more. figure it has to be the dist or the FD.
found an air leak on #3 and maybe #2 intake. not sure if this my only problem, but it is a problem.

i dropped CP's down to 2.8 at one point. finally i concluded the car should not have to run this low and set everything back to stock settings, except idle AFR, and started looking for the real problem. i was running in the 11's and 12's.

i found that my return line to the tank was being pinched in the back left of the engine bay where it runs under a "clamp". i just rearranged all the hoses that run thru there and cleared it up. i was thinking it was making my CP's change.
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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 01-27-2014, 02:39 AM
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Ok, so I've been waiting to get 6 graduated cylinders to try the injector test, they should be here today.

In the meantime I had some time so I just swapped out my "in-spec" -016 fuel head with a running -037 from a 77 turbo. I've kept everything else the same, still running the -022 WUR and the car seems to be running much differently, and better. It's not as smooth or balance feeling (idles rougher) as before but the AFR's are doing what they're supposed to, kind of opposite of what they did before. Idle is about 12, cruising is around 13-14 and when I hit boost it goes right down to 10. I haven't driven it extensively but have taken around the block several loops at different temps and the AFR never goes about 15 and I can not make it do the lean tip-in thing at all, ever. So, that's where I'm at now... Need to venture further with it and actually take it up the street, but so far it's looking like a big improvement.
Old 01-30-2014, 03:33 PM
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Crotchety Old Bastard
 
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Be careful with the metal fuel lines when you do that test. If you bend the lines or over tighten and the feruled end does not seat properly when re-attached to the injector the ball seat can oval out and it will leak. There is no fix for that except a new line and you sure don't want fuel spraying undetected in your engine compartment.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'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 01-31-2014, 05:06 AM
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