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Richard930's Avatar
 
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Running rough after service

So, after installing my new RarlyL8 headers and muffler, a BL WUR and doing a major service including new wires, plugs, filters, rotor, cap and valve adjustment, with great anticipation we fired it up.

Sounds like a VW Beetle and makes about the same power - not what we were expecting. Injectors were cleaned and serviced as well while everything was apart, and it seems that cylinders 1 and 3 are not firing. Checked for spark and that's fine, swapped the injectors to other cylinders and the problem remained with numbers 1 and 3.

So, my tech thinks the fuel distributor is the problem. I don't mind getting it overhauled if it really is the problem, but I'd like to make sure that we haven't overlooked any other probable causes before doing this. I don't think there's anywhere local that can do it, and sending it to the US will probably mean I won't be driving it for the next 3 weeks which I would be very unhappy about having waited this long to get my new exhaust system installed.

Car was running fine except for a relatively minor warm start issue where it would run rough (like on 4 or 5 cyls) for a minute or two before clearing up.

Any suggestions? Also may need a suggestion for somewhere to send it or to buy an overhauled one if this is the problem.

Thanks in advance,
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Richard
1982 930, K27-7200, Ruf wheels, Leask WUR, Tial WG, WEGO IV AFR, RarlyL8 headers & single out muffler, TK I/C
2011 R350 winter beater
2004 BMW R1100S

Last edited by Richard930; 05-07-2010 at 10:41 AM..
Old 05-07-2010, 10:37 AM
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Crotchety Old Bastard
 
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Well that totally sucks Rich.
As you know I offer fuel tuning as part of my performance packages. You probably didn't know that I keep rebuilt WUR's and fuel heads in stock. If you are sure this is the problem I can ship one out to you today. I will need your rebuildable core which you can ship back to me in the same box.
Shoot me an e-mail or phone call and we'll work it out so your down time is minimized.
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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 05-07-2010, 10:52 AM
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Take all 6 injectors out and stick them in 12oz ribbed plastic bottles.
A 6 pack of bottled water is a good source for the plastic bottles.

Now turn on the fuel pumps and press down on the airflow sensor plate and look for fuel spraying into the plastic bottles.
Push it down all the way to get maximum flow from the head and injectors.

This is so easy to do, and there's no other better way to check the fuel head and injector(s) flow on the car.

I can't believe your "tech" would suggest going to the expense and time waiting for a rebuilt or replacement fuel head. If he wants to do that without this simple test all I can say is he doesn't have a clue and go to someone else.

Sitting for a couple few months will not likely do a thing to your fuel head like clog one of the 6 differential valve ports or orifice's but messing with all those ignition parts you mentioned could easily cause the probelm your having.
Old 05-07-2010, 02:25 PM
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Infidel
 
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I have a complete euro fuel head and metering plate assembley, mint condition, no idea what it's worth but willing to part with it? Maybe it's something you want to take off me Brian if you keep this stuff in stock?
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Jonathan.
87 930, 993 turbo engine, RS Tuning 520PS/515lbf-ft, Arrow Rods, ARP hardware, Solid lifters, G50-50, RS Flywheel, 890nm Sachs clutch, RSR coil overs all round, 993 C4 calipers front, 930 fronts on the rear, Ruf Speedlines.....
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Old 05-07-2010, 02:33 PM
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beancounter
 
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Have you checked, double checked and triple checked that the firing order is correct? You say new wires and new cap and rotor...pretty easy to screw that up and it will run like poopy. Check the most obvious things before you suspect a faulty fuel head.

reordering the wires is WAY cheaper to fix than a new fuel head too.
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Old 05-08-2010, 05:04 AM
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Crotchety Old Bastard
 
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If you recall in my headers thread I had a similar situation. "While I was in there" I did the same refresh of plugs, cap, wires, clean the injectors etc. and had the same result of 2 dead cyliders. Turned out to be leaking injectors combined with a lean idle mixture. The leaky injectors were caused by fuel lines that do not like to be disturbed and were likely overtightened sometime in the past. Lean condition was due to the headers. There was also air in the lines. All combined the car ran horribly.
I went through this with Rich so hopefully he will post results of those checks as well. Absolutley agree that you don't want to buy a fuel head you don't need - and I won't sell you anything you don't need.

Jon - shipping is likely prohibitive but I can take a look at that. Most typically I just swap cores with the client so no down time. I do get a cracked core every now and then which cannot be rebuilt. I hate giving that news to folks ...
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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 05-08-2010, 07:25 AM
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If the fule checks out (per Jim's test) I would go back to ignition. I also had mis-fire woes after a bunch of while-I'm-in-there stuff.
Down and dirty, put your old cap and rotor back on the distributor and see if those 2 exhaust tubes start getting hot. After that try an old plug wire on those cylinder(s)... then an old plug.

I found out (again) that new isn't always good...
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Old 05-08-2010, 09:26 AM
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Thanks for the suggestions - I`ll go visit the car tomorrow and make sure that all the obvious and simple things have been triple checked. He`s a very experienced mechanic and trained on the production line at Porsche back in the sixties and early seventies before being a head technician at the dealer for a long time, so I`d be surprised if he was wrong on this - but you never know. Its just too much of a coincidence to have changed a bunch of parts and then have this problem and I`ve read too many threads where people have changed 30 year old plug wires only to have issues with the brand new ones!

I`ll definitely get him to do the injector into the bottle test if he hasn`t already done it.

Brian - good to know that you`ve got rebuilt fuel heads available I`ll let you know if I definitely need one.
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Richard
1982 930, K27-7200, Ruf wheels, Leask WUR, Tial WG, WEGO IV AFR, RarlyL8 headers & single out muffler, TK I/C
2011 R350 winter beater
2004 BMW R1100S
Old 05-09-2010, 07:06 AM
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Crotchety Old Bastard
 
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I've got one Euro head that should be your part number; I'll put it to the side until we know for sure.

I have a plug wire issue right now. Replaced the original wires with a set of Magnacore. Extremely dissapointed in them. Fitment is terrible. They are loose on the plugs and too tight in the cap. Bad enough to cause a constant miss at idle. I'll be looking for another brand ...
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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 05-09-2010, 09:35 AM
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Did the flow test and there was nothing coming from one of the openings (just disconnected the lines on top of the head), and very limited flow from a second one. We tried out a used fuel distributor from a local dismantler and it had the same issue, albeit on different openings. System and control pressures have checked out perfectly (fresh BL WUR so they should!).

I still find it very strange that it seemed mostly fine a few weeks ago when it went in, and somehow completely crapped out while the other work was going on but I guess that's better than having a problem on a trip or at the track. Hopefully this was the cause of the occasional warm start issue I was having, and may also explain the leanness I saw when on the dyno a month or so ago. If it was the cause of these two issues, I guess I should just be happy I didn't hole a piston at some point.

So, thanks to Brian I should have a rebuilt fuel distributor in a few days and be back on the road next week. Then I'll be posting about my driving impressions with the new exhaust.
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Richard
1982 930, K27-7200, Ruf wheels, Leask WUR, Tial WG, WEGO IV AFR, RarlyL8 headers & single out muffler, TK I/C
2011 R350 winter beater
2004 BMW R1100S
Old 05-10-2010, 07:36 PM
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If all you did was disconnect or loosen fuel head banjo fitting lines while on the engine you didn't test anything. That was a waste of time and a fire hazard.

The 6 individual fuel distributor differential valves need the high opening pressure resistance of the CIS injectors to do their final step in the fuel metering.

good luck...
Old 05-10-2010, 08:09 PM
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The injector lines were reconnected to the borrowed fuel head and the problem moved to 2 other cylinders which would seem to confirm that the injectors and lines are OK. ie cylinders 1 and 3 weren't firing or getting fuel from my fuel distributor and cylinders 5 and 6 weren't firing or getting fuel from the borrowed one.

Agree about the fire hazard though with all that fuel burbling out of the fuel distributor - not something I'd try at home, but it does look to me like its definitely the fuel distributor.
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Richard
1982 930, K27-7200, Ruf wheels, Leask WUR, Tial WG, WEGO IV AFR, RarlyL8 headers & single out muffler, TK I/C
2011 R350 winter beater
2004 BMW R1100S
Old 05-11-2010, 04:50 AM
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