Coldstart vs warmstart
11-20-2018, 11:25 AM
#16
Rennlist Member
11-20-2018, 04:19 PM
#17
Rennlist Member
Thread Starter
- Thermotime switch
- cold start valve
- aux air valve
easy to test.
Ofcourse when I found the culprit, I will need to recalibrate the CO mixture.
I'll keep you posted
11-20-2018, 04:58 PM
#18
Rennlist Member
How do you plan on re-calibrating your CO? You need either the an exhaust analyzer, wideband C02 sensor or the original gas/test tube thingy to do correctly. Otherwise you are just flat out guessing and the CO mixture is SUPER SENSITIVE. A small turn either way could move you 1 point off your ideal stoichiometric 14.7...
11-20-2018, 11:50 PM
#19
Rennlist Member
Thread Starter
How do you plan on re-calibrating your CO? You need either the an exhaust analyzer, wideband C02 sensor or the original gas/test tube thingy to do correctly. Otherwise you are just flat out guessing and the CO mixture is SUPER SENSITIVE. A small turn either way could move you 1 point off your ideal stoichiometric 14.7...
11-21-2018, 09:56 AM
#20
Rennlist Member
ok good. I presume you have no cats on the car then??
11-23-2018, 01:12 PM
#22
Rennlist Member
Thread Starter
Hi Brad, I was able to do some tests :
- I tried to start the car (temp outside is about 2 °C (35°F )) : car started for about 2 sec and died
- I tried to start the car with AAV bypassed, so I replaced it by a tube so that enough air could pass : car started for about 2 sec and died
- I then measured the voltage coming from Thermotime switch during start : about 9V, so Thermotime switch is giving signal/power to coldstart valve
- I then checked if coldstart valve/injector is spraying fuel during start : affirmative, so coldstart valve is working fine
- I checked the sparkplugs after start : they are not really wet, but they did smell like fuel
WHat now ???? Could it be the WUR ?? Or is there something else I can check ??
- I tried to start the car (temp outside is about 2 °C (35°F )) : car started for about 2 sec and died
- I tried to start the car with AAV bypassed, so I replaced it by a tube so that enough air could pass : car started for about 2 sec and died
- I then measured the voltage coming from Thermotime switch during start : about 9V, so Thermotime switch is giving signal/power to coldstart valve
- I then checked if coldstart valve/injector is spraying fuel during start : affirmative, so coldstart valve is working fine
- I checked the sparkplugs after start : they are not really wet, but they did smell like fuel
WHat now ???? Could it be the WUR ?? Or is there something else I can check ??
11-23-2018, 06:16 PM
#23
Rennlist Member
Sounds like its only running on cold start injector. We need to see fuel pressure at WUR - system(65-75psi), and control(cold <20psi). Sounds like cold control is too high - blocked WUR? Have you tested delivery rate ~ 1350cc/30 secs? Do the injectors spray when air plated is deflected (or when cranking)? Try loading tank with oil (like berrymans, Marvel Mystery), bridge fuel pump relay and let fuel circulate for a few hours, this can clean out sludge sometimes.
jp 83 Euro S AT 57k
jp 83 Euro S AT 57k
11-23-2018, 06:44 PM
#24
Rennlist Member
Thread Starter
Sounds like its only running on cold start injector. We need to see fuel pressure at WUR - system(65-75psi), and control(cold <20psi). Sounds like cold control is too high - blocked WUR? Have you tested delivery rate ~ 1350cc/30 secs? Do the injectors spray when air plated is deflected (or when cranking)? Try loading tank with oil (like berrymans, Marvel Mystery), bridge fuel pump relay and let fuel circulate for a few hours, this can clean out sludge sometimes.
jp 83 Euro S AT 57k
jp 83 Euro S AT 57k
I knocked the pin (to which bimetallic plate is attached) deeper inside the WUR to lower the pressure.
This worked a while till I added a new fuel accumulator
Perhaps it influenced my control pressure again.
I will need to check again my pressures, I believe
11-23-2018, 09:38 PM
#25
Rennlist Member
You need to thoroughly clean the insides of the WUR before playing with moving the pin IMHO. The brass screens can clog badly - best clean is to burn off the lint, the way Riyadh barbers burnt the fluff off my ear lobes. I got some pressure improvement by blowing carb or brake cleaner backwards through the WUR.
jp 83 Euro S AT 57k
jp 83 Euro S AT 57k
12-02-2018, 09:23 PM
#26
Rennlist Member
Thread Starter
You need to thoroughly clean the insides of the WUR before playing with moving the pin IMHO. The brass screens can clog badly - best clean is to burn off the lint, the way Riyadh barbers burnt the fluff off my ear lobes. I got some pressure improvement by blowing carb or brake cleaner backwards through the WUR.
jp 83 Euro S AT 57k
jp 83 Euro S AT 57k
i adjusted my mixture & idle by using the basic setup of a Kjet :
Turn the mixture screw closed (CCW) , then open it 9&1/2 turns.
BUT IN ORDER TO BE ABLE TO START MY CAR AND KEEP IT RUNNING, I HAD TO DO 14&3/4 TURNS!
THUS VERY RICH FUEL MIXTURE (measured CO was 10% instead of between 1,5 - 2,5 )
I tried to leaner the mixture but then my car does not keep running,
So does this mean my fuel pressure (control) is too low??
12-02-2018, 11:07 PM
#27
Rennlist Member
You should be able to get a gauge and fittings kit from ROger - 928srus - and do it properly. You CANNOT properly tune a CIS car without knowing the pressures are in spec.
jp 83 Euro S AT 57k
jp 83 Euro S AT 57k
12-04-2018, 01:28 PM
#28
Rennlist Member
Thread Starter
Pressure reading cold and engine not run (bypass fuel relay) : 3,6 bar (52psi)
This is way too high : should be between 0,9 and 1,6 bar (13 and 23 Psi)
12-04-2018, 05:20 PM
#29
Rennlist Member
In that state (3.6b), crack open the outlet of the WUR - (carefully, with extinguisher handy!) - if very little fuel comes out, and gauge barely drops, WUR is blocked. If gauge drops a lot, much fuel sprays out, blockage is further along the circuit. Note that 3.6 is higher than a good hot pressure should be - mine hot is 45psi(3.1b). If you have power on the wiring into the WUR it will heat the bimetallic and start lifting control pressure, so cold test is best done with connector removed.
Checked the return line at the tank for fuel flow ?
jp 83 Euro S AT 57k
Checked the return line at the tank for fuel flow ?
jp 83 Euro S AT 57k
12-04-2018, 08:27 PM
#30
Rennlist Member
Thread Starter
Good thinking there to check where my system is blocked.
I will check and provide feedback.
Returnline is never checked. Perhaps I can also disconnect Returnline at the engine and put line into a large bottle.
If situation improves I know something is wrong with my return line
But I will first check my WUR
Btw European 928S has warm pressure (according to Porsche specs for M11/12 engines) at 3,6 +- 0,2
I will check and provide feedback.
Returnline is never checked. Perhaps I can also disconnect Returnline at the engine and put line into a large bottle.
If situation improves I know something is wrong with my return line
But I will first check my WUR
Btw European 928S has warm pressure (according to Porsche specs for M11/12 engines) at 3,6 +- 0,2