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Join Date: Feb 2007
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930 to much fuel

Hi, I recently removed the old 3.0 turbo and replaced with a later 3.3 turbo. The car starts but has a lot of black smoke from the tail pipes, I have spoken to porsche shop and they have advised me that it is overfueling, don't really know what to check.

The other problem I have is that the rear fuel pump will not come on. If I run a live directly to the pump it will kick in and the car will start. If I then turn of the ignition and then restart, the front fuel pump will not start up unless I remove the live that is going directly to the rear pump.

Once I have removed the live the front pump will start, I can then reconnect the live back to the rear pump and the car will start up again. Any thoughts on where I go from here would be greatly appreciated as I am now at a complete loss. If I had the funds I would put the car into Porsche and be done with it but I dont.

Old 02-10-2007, 02:39 AM
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Crotchety Old Bastard
 
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Did the 3.0L run well before the swap?
You may have more than one problem. What fuel components were kept and what ones were swapped?
Did the 3.3L engine run well befor the swap?
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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 02-10-2007, 10:18 AM
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The car originally had a 3.0 turbo and ran great before the swap.
The 3.3 turbo came from another car I owned and also ran great before removal. I replaced the fuel lines and 3.0 spark box and repalced with the 3.3 turbo ones. The wiring in the multi plugs was exactly the same so nothing needed changing there. The car fired up virtualy first time but oozed black smoke when cold. The smoke does subside a bit when warm. I spoke to porsche shop they seemed to think everything regarding transplant was ok, but questioned the fueling and pump relays. Just after some second opinions.
Old 02-10-2007, 01:26 PM
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Crotchety Old Bastard
 
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The relays would explain your no start unless manually powered situation. I don't know about the over fueling though.
What boost are you running? Is it possible that a boost spike has blown the diaphagm in your WUR?
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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 02-10-2007, 09:29 PM
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Is there anyway of testing the WUR?
Old 02-11-2007, 02:43 AM
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Use CIS pressure testing gauges. They're about $100 from Pelican or your local good auto parts store.

Sounds like your fuel pressure is too low. It would start easy but then run rich.

The WUR increases fuel pressure to lean the system as the engine warms up.
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Old 02-11-2007, 06:30 AM
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Crotchety Old Bastard
 
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A blown diaphagm would result in fuel seaping around the WUR.

How long did your car sit during the swap?
Did these problems occur immediately upon starting the new engine?
How many miles have you put on the new engine?

It could simply be that you have gotten some crud in your fuel system when the lines were cracked; CIS is very sensitive to contamination. If the car was down for a time the fuel head piston may be sticking as well. Have you taken it out and ran it hard?
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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 02-11-2007, 06:46 AM
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Replaced the relays today with some sucess, now both fuel pumps work great without manual live to the rear, I can hear both fuel pumps working but will not start, she fires as soon as cranked but sounds like the pumps are switching off as soon as she fires up.

2 steps forward 1 step back
Old 02-11-2007, 10:25 AM
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Thanks so far for all your help, I have now replaced both the red relays and replace one of the rubber relay holders, I have the baby firing, she is still giving out some black smoke but not as much. I took her for a road test and as soon as boost comes in she starts bucking as if fuel starvation, does this look like a bad fuel pump?

Any further advice would be much apreciated.

Thank you in advance
Old 02-14-2007, 04:40 AM
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A bad fuel pump is possible, but there are many things on the CIS system that could cause this. I wouldn't replace parts until a fuel check is done. Some checks are: fuel flow (volume per time), unregulated fuel pressure, cold fuel pressure, and hot fuel pressure. Fuel flow can be checked with a measuring cup and the pressures are checked with a CIS gauge set.
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Old 02-14-2007, 06:33 AM
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