82 SC RoW - Possible bad WUR
 

I'm having an issue with my 911sc. Ever since I've owned it (last few months) I've had surging idle on startup that evened out when the vehicle got warm. It shut off on me once during startup a few months ago. A few days ago, I went to start it and it wouldn't hold idle. When I hold the throttle it will stay running. We ran a few tests and here is what we have so far:

Smoke Test through airbox = Passed
CIS Fuel pressure = 5.3 Bar
WUR cold pressure = 1.3 bar 22c
Resistance on the heating element = 37 ohms

We are suspecting a bad WUR, does that sound correct?

Thanks!

Identify your WUR......
 

What is the Bosch ID number on the WUR? Do you have a US or ROW spec motor? You might have the wrong WUR installed in your car (?). Keep us posted.

Tony

RoW - 089.

Describe your hunting in more detail. Idle around 1500 immediately at start and settling down to after a few minutes to 950 range is normal. Surging between those points or dropping to 400 and then coming back up isn't as normal. My 83 Euro tends to drop after 15 seconds to 400 if the AFR setting is on the lean side. It always returns to 950 range without touching the gas peddle. The drop is virtually eliminated when the AFR is a little richer. I have no surging or what I would think of as hunting at idle.

I believe your WUR pressure is in range assuming you had vacuum applied.

CCP s/b 1.7 bar minimum at 22C. System pressure a smidgen too high. Frankly, neither one bothers me too much if you transition to WCP in a few minutes.

37 ohms seems to be a high number but I don't know. I would think that would lean it out quicker if it's supposed to be 25-ish like the 090 US WUR.

Post your WCP numbers and when.

http://forums.pelicanparts.com/uploa...1506643186.jpg

Well, I went to start the car today and it started up, hunted for about 20 seconds, and started idling right at 900. Went to drive it and it decided to stall again as soon as I let off the gas pulling out of the lot. The car seems to be running REALLY rich solely based on the smell from the exhaust and I've ordered a wideband, but it still seems like its an issue with something failing. I just don't see why the car would just start running rich one day without anything being changed.

What was the temperature at your location? It was chilly in Ohio this morning. That can make the car run more rich.

1.3 Bar @22*c
1.6 Bar @30*c

System Pressure is 5.3bar.

It idles fine after it warms up but dies completely after blipping the throttle OR getting off of it in between lights. It also will try to die in between shifts when off the throttle.

It's had the same symptoms ranging from 60* up to 82-85* F

Control fuel pressure data...........
 

Yahh,

When you get a chance, measure your cold control pressure versus time @ 30 sec. intervals:
a). Fuel pressure test without running the engine until the CCP stabilized to WCP.
b). Same fuel test with the engine running but do this in a different day. You want to do both tests when the engine is stone cold and note of the ambient temp.

Each test should not last more than 5 minutes from start. The data would sufficient to get a good picture of how your WUR works. If you have any question, just ask. Your CCP is out of spec. and the WCP could be too (?).

Tony

Hey Tony,

Thanks for reaching out. I haven't measured it in intervals but we did do cold/warmer engine temp:
1.3bar @ 10*c
1.6bar @ 30*c


Is this still something I should do?


Here is an updated troubleshooting report:

-Car was bought as non-running car form a customer of ours that brought it in yearly for SI and oil services. The car had maybe 150 miles added yearly.
-Tested the starter and found out the ignition switch was failing so we replaced it alongside the battery.
-Dropped motor to do a valve adjustment/ fix whatever oil leaks we could without rebuilding and found 5-6 broken headstuds.
-Broke the motor all the way down, new bearings, piston rings, all new seals, RSR cam seals, Supertec Head studs, VR gasket kit, and carrera hydraulic tensioners. The heads went off to the machine shop, checked, and new guides installed/valves ground.
-Set timing, drove the car daily with surging idle at warm up (summer temps in VA)
-The vehicle was running fine with a fluctuating idle for about 2k miles after top/bottom end refresh.
-Shut off once after starting about 1k miles in but started right up and ran.
-One day after a 3 mile trip to the grocery store, it started but wouldn't hold idle and immediately died.
-Brought it in and started troubleshooting
- Wouldn't hold idle, had to hold throttle and started measuring pressures
- After sitting overnight, the car started to hold idle after 30 seconds (nothing changed)
- Once throttle is applied and you let off the car immediately shuts off


Smoke Test through airbox = Passed
CIS Fuel pressure = 5.3 Bar
WUR cold pressure = 1.3 bar 22*c
WUR warm pressure =1.6 bar at 30*c
Resistance on the heating element = 37 ohms ; Spec is 24 ohms

WUR casting........
 

Yahh,

Take a good look at the top of your WUR and find out if you have:

a). "Germany".
b). "France"
c). Blank.

Keep us posted. Thanks.

Tony

I can see the letters ECN without removing anything so it appears to be FRANCE.


Thanks!

CIS Flowtech...give Larry a call. The only Bosch authorized WUR/Fuel head rebuilder in the US and gets the fine little parts no one sells.
If you buy a rebuilt one 99% chance he did it.

He rebuilt my 89 Euro WUR and now the CIS works as it should (euro AFR controlled by the wur).

No affiliation with Larry but he does great work.....the indy shop I go to in Phx send all of their Bosch stuff to him....never had a return.

Just did test A.

62*F
BAR Seconds
.8 0
1.1 30
1.4 60
1.5 90
1.7 120
1.8 150
1.9 180
2.0 210
2.1 240
2.2 270
2.25 300
2.3 330
2.35 360
2.4 390
2.42 420
2.5 450
2.5 480

Test results.......
 

Yahh,

The reason I asked about the markings on your WUR was to determine if you have "Germany @ 30 Ohms" or "France @ 36 Ohms". These are the average resistance values I find between these WUR's (G or F).

Next, is to gather the data for same test but with engine running. This initial data shows your WUR is working but out of calibration. Your next data would be totally different so do not be alarmed. Just collect and record data without prejudice. Thanks.

Tony

I would set the CO and RPM to specs - anything else is just a guess. Sorry I don't know what the specs are for a 911 Euro SC- could be underside of engine lid or engine decal.

Porsche Factory spec manual... 800-950 rpm... CO... 1. - 2.0 for 930-10 82/83

Just to confirm: are you applying vacuum to the wur for your pressure readings? The chart posted shows results with vacuum, I believe. Tony will help you solve it but the little details like this can make all the difference in troubleshooting.

This is a test result without VAC applied. It is a slow riser that is for sure. Also the max bar reached is too low. But that could be down to only applying 12 V or less.
The bimetal gets 13.X when the car is running and that could make a difference.

I would say that at 1.3 bar at 22 celcius with 37ohm resistance start-up should be fine for a 089. But if it climbs that slow you will sure stall when you lift the throttle.

See what the run test suggested by Tony tells us.

When a bimetal rises that slow usually the wire around the metal is still ok but the insulation has cracked.


http://forums.pelicanparts.com/uploa...1508249612.jpg