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windwaiver
Joined: 08 Feb 2009
Posts: 69
Location: reno, nv
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 Posted: Mon Nov 23, 2009 10:47 am Post subject: Hot start, Wur diagnosis |
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Ok heres what i know. 82 924 NA
I did the cis pressure tests on the unit. Starts fine cold, pressure is limited to 1.5 bar then increases to 3 to 4 once heated up. Holds almost 2 bar for 20 minutes after shutdown.
Will restart without problem for about 20 minutes. After the fuel pressure bleeds off, starting it like it started before i replaced the warm up regulator.
This unit is different from the one I pulled off. It had a vacuum port on it, nothing connected but it was there. Looked stock since the bolts are different lengths. I replaced it with one from an 81 that doesn't have the port. Once it cools down and pressure drops, the wur doesn't restrict, are there different temperatures for these 2 units?
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81 924 na (great parts car)
82 924 NA
87 944S this is gonna cost
00 K1200LT
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Ozzie
Joined: 12 Mar 2005
Posts: 4448
Location: Townsville, Qld. Australia
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| Posted: Mon Nov 23, 2009 11:25 am Post subject: |
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the vacuum port on some WUR is used to vary the control pressure with demand.
Control pressure is reduced when demand is high, eg WOT to allow more fuel to the injectors.
As per poor starting. they are all a cow to start when warm. some people are lucky and everything is spot on.
you only have to have something slightly off, eg, rest pressure, ambient temp, and problems will happen.
.
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Its AUTO and its BLACK
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Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
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| Posted: Mon Nov 23, 2009 10:20 pm Post subject: |
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This is recommended in the owners manual - it works for me and several others..
If it doesn't start on the first try, before touching the key for a second attempt, press and hold the throttle pedal to the floor, then turn the key. Continue holding the pedal to the floor until the engine fires. -And of course let off the gas as it starts to avoid over-reving.
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'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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924RACR
Joined: 29 Jul 2001
Posts: 9071
Location: Royal Oak, MI, USA
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| Posted: Mon Nov 23, 2009 11:10 pm Post subject: |
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| Ozzie wrote: |
As per poor starting. they are all a cow to start when warm. some people are lucky and everything is spot on. |
Sorry, don't agree with this. Means the tuning or some such are still not right.
Even our racecar is stupid easy to start at any temp above 40 degrees F, unless the mixture's adjusted wrong.
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'79 924 #77 SCCA H Prod racecar
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Slam
Joined: 07 Jan 2005
Posts: 1689
Location: Wainwright, Alberta, Canada
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| Posted: Tue Nov 24, 2009 3:30 am Post subject: |
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^+1
Check your fuel accumulator maybe?
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windwaiver
Joined: 08 Feb 2009
Posts: 69
Location: reno, nv
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| Posted: Tue Nov 24, 2009 4:18 am Post subject: |
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i've replaced and tested the accumulator ($220.00 for the accumulator) no leaks and the pressures are within specks for the timing. Removed the fuel pump check valve and tested it as well. With the pressures within specs it says both the accumulator and injectors are ok.
No one seems to think its the change out in the WURs?
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77.5 924 NA
81 924 na (great parts car)
82 924 NA
87 944S this is gonna cost
00 K1200LT
If i had a nickel for everytime I screwed up....... |
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D Hook
Joined: 02 Nov 2002
Posts: 3158
Location: Omaha, NE
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| Posted: Tue Nov 24, 2009 5:44 am Post subject: |
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I may be wrong but for some reason I thought the WUR with a vacuum port is for the 931 and early 928.
I don't recall having a vac. port on my '80.
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Slam
Joined: 07 Jan 2005
Posts: 1689
Location: Wainwright, Alberta, Canada
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| Posted: Tue Nov 24, 2009 7:16 am Post subject: |
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CSV or thermo-time switch?
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'84 944 - kid blew motor
'83 944 - resting comfortably. For 12 years
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'80 924 - gone
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windwaiver
Joined: 08 Feb 2009
Posts: 69
Location: reno, nv
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| Posted: Tue Nov 24, 2009 11:49 pm Post subject: |
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ok help me out here what is the csv?
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77.5 924 NA
81 924 na (great parts car)
82 924 NA
87 944S this is gonna cost
00 K1200LT
If i had a nickel for everytime I screwed up....... |
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pocketscience
Joined: 23 Apr 2006
Posts: 1650
Location: Sydney, Australia... mate!
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| Posted: Wed Nov 25, 2009 1:20 am Post subject: |
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Cold Start Valve
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Slam
Joined: 07 Jan 2005
Posts: 1689
Location: Wainwright, Alberta, Canada
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| Posted: Wed Nov 25, 2009 3:59 am Post subject: |
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Sorry, my bad. I should have been more explicit.
The 5th injector at the back of the intake is the CSV. If it doesn't shut down after warmup you'll get a constant rich condition. Sometimes simply unplugging the electrical connector on it will tell you if it's the culprit. It's controlled by the thermo time switch that sits below it. The switch is supposed to shut it off after warmup.
HTH
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'84 944 - kid blew motor
'83 944 - resting comfortably. For 12 years
'87 944 - sideswiped by trucker
'80 924 - gone
'78 924 - gone
'77 924 - rusting comfortably |
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9XX Girl!
Joined: 20 Sep 2009
Posts: 1617
Location: Cornish Riviera SW England
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| Posted: Wed Nov 25, 2009 10:07 am Post subject: |
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| Slam wrote: |
Sometimes simply unplugging the electrical connector on it will tell you if it's the culprit. It's controlled by the thermo time switch that sits below it. The switch is supposed to shut it off after warmup.
HTH |
 Hmmmm..... even if the thermo time switch doesn't switch off, the CSV will only fire when the engine is cranking. The CSV gets its positive feed from the key switch that brings in the starter motor solenoid. It gets its negative feed via the thermo time switch.
So when the engine is cold, the thermo time switch is closed and grounds the cold start valve regardless of the ignition being turned off or on.
you then turn the ignition on and start cranking. this puts +12v on the the other side of the cold start valve, the cold start valve fires, squirts fuel, and shuts off the second you stop cranking.
When the engine is hot, the the thermo time is open and the cold start valve never gets grounded, so when cranking the +12v on the the other side of the cold start valve does not cause it to fire.
When warm, the thermo time switch (TTS) is closed and grounds the cold start valve but... if it carries current for too long, it will open as it contains a bi-metal trip with a heater coil warped around it and a set of contacts. if it carries current for too long it will open itself to stop you flooding the engine.
Once the engine has started, removing and replacing the plug on either the CSV or TTS will do absolutely nothing! 
The problem is that Bosch had problems and could never manufacture the TTS at a consistent quality or reliability. if you replace it with a new one (not a used one) it should help, for a bit! (couple of years) unless you get lucky and get a real good one. Do the hot start fix and you will have control over whether it fires during starting or not yourself.
as for the warm up regulator. the one with the vacuum port is preferable as it will work harder at full throttle giving you that extra little bit of zoom.
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924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
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Slam
Joined: 07 Jan 2005
Posts: 1689
Location: Wainwright, Alberta, Canada
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| Posted: Thu Nov 26, 2009 2:58 am Post subject: |
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Good post. Funny thing, though, that in two cases now where we've had cars running rich, disabling the wiring to the CSV has fixed them. Must have been the TTS in both cases. But if that was the case, how'd they get power if the CSV is only energized while cranking? A leaky CSV will cause trouble, too.
_________________
'84 944 - kid blew motor
'83 944 - resting comfortably. For 12 years
'87 944 - sideswiped by trucker
'80 924 - gone
'78 924 - gone
'77 924 - rusting comfortably |
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9XX Girl!
Joined: 20 Sep 2009
Posts: 1617
Location: Cornish Riviera SW England
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| Posted: Thu Nov 26, 2009 5:06 am Post subject: |
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| Slam wrote: | | Funny thing, though, that in two cases now where we've had cars running rich, disabling the wiring to the CSV has fixed them. Must have been the TTS in both cases. But if that was the case, how'd they get power if the CSV is only energized while cranking? |
Someone has changed the wiring?
When you turn the ignition key to the III position,"Pin 50" of the ignition switch goes live, this feeds "Pin 17 - Plug E" on fuse board via a Red/Black 4mm wire. "Pin 17 - Plug E" connects to internal "Track 50" of the fuse board.
This track then leaves the fuse board via "Pin 10 - Plug A" and connects to "Pin 50" of the Starter Solenoid via another bit of Red/Black 4mm wire.
"Track 50" also, leaves the fuse board via "Pin 10 - Plug C". Two wires are crimped into this Molex connector (10-C), one is 1mm Red/Black and goes to Pin 50 of the Fuel pump relay (this is the latch signal that sets the delay-off of the timer), the other is a 0.5mm Red/Black wire that goes to the CSV. The other side of the CSV is connected to the TTS via a Green/White 0.5mm wire. The other side of the TTS goes to "Ground" via a Brown 0.5mm wire on a 6mm crimped eyelet next to the Aux Air Valve.
The only way the CSV can get a live feed is if there is a major fault in the fuse board or someone changed the stock wiring.
| Slam wrote: | | A leaky CSV will cause trouble, too. |
Yes, but this is not due to an electrical fault. It is just leaky and would leak regardless of whether the plug was on it or not.
I'm afraid, Bosch were too ambitious with the TTS and did not realize it was unreliable until after 2/3 years of production. It was only used between 78 and 84 and then phased out.
Hot start fix is the way to go.
Read Chapter 3 Fuel Emission Exhaust - Part 2 - Hot Start Problem Fix http://www.924.org/techsection/technical.htm
I used a switch on the Throttle Body to ground the CSV during hot starting. Just depress the throttle ((like it says in the handbook), this closes the switch and grounds the CSV), then turn over the engine and it will fire.
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924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY |
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9XX Girl!
Joined: 20 Sep 2009
Posts: 1617
Location: Cornish Riviera SW England
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| Posted: Thu Nov 26, 2009 5:11 am Post subject: |
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It may pay for you to look at this current thread too
http://www.924board.org/viewtopic.php?t=30733&postdays=0&postorder=asc&start=0
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924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY |
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