308qv, won't rev & popping, wur?, CIS expert needed

I think my 328 was around 30-50psi when I checked a month ago.
cold pressure depends on ambient, so alaska would be the place to go for really low values.

higher control pressure makes for a leaner mixture. The airflow plate in the metering head is lifting up a piston with slits in the sides of it. The higher the lift, the more slit area is exposed, and more fuel can flow through the slits.

the pressure from the wur is pushing the piston back down, making it harder for the airflow plate to lift the piston. As the wur pressure increases, less fuel is delivered for a given volume of air. Hence larry's comment about the airflow plate...if it's not positioned correctly, then the air volume measurement is wrong.

the green wire is an output from the O2 sensor to the ecu. If you unplug, the ecu side won't show anything.

0.5v means the mixture is correct. Less voltage is leaner, more voltage is richer.

when the car is warm, it should be running in closed loop and the ecu will try to adjust the mixture via the frequency valve to get the O2 output to 0.5v. In practice, it will overshoot, so watching the O2 output will show it oscillating around 0.5v.

if you just leave the o2 sensor disconnected, then how does the car idle/run when warm? In theory it should be worse since the lambda system is not compensating for the higher wur pressure.

 

huh...if you leave the wur heater disconnected, the wur would take a long time for engine temps to raise the control pressure. That would richen the mixture for a while, but is doesn't seem like it's off enough to really cause that big a problem.

did you fill up the tank before coming back from monterey? maybe it's just a load of bad gas.

if it's not the gas, does the problem only happen when moving from close throttle to open throttle? In other words, does it maintain open throttle rpm just fine, and rev ok from say 2000-3000? If so, the throttle switch or a couple relays on the injection ecu plate come into play.

 

the control pressure can be too high if :

1] the wur has a problem
2] the fuel return line to the tank has a restriction
3] there's a blockage in the system pressure push valve chamber (the fuel returns from the wur and enters the push valve chamber on it's way to the fuel return line)
4] too much fuel is getting sent to the wur due to a bad restrictor in the fuel distributor.

to test #4, you disconnect the fuel line to the wur and let it pump into a container. The probst book says typical is 160-240cc in 60 seconds. I don't know the ferrari spec.

for #3, you'd probably need to remove the push valve. You might be able to get away with disconnecting the wur return line and letting it pump into a can while you measure the control pressure, but you'd need to plug the hole in the fuel distributor.

for #2, the system pressure would probably be too high also

for #1, if you disconnect the wur heater and run the car, the engine will be warming up while the control pressure stays low. At some point, the car should be running fine, and then too rich. If your symptoms correspond, then the wur needs some attention.

if you have air in the fuel lines or the gauges, the readings could be off.

also, try unplugging the frequency valve. That should cause the system to go full lean, which will give the symptoms you are seeing. You said the FV is buzzing, but maybe it's not working or is blocked. Unplugging it should make a difference.

 

phil i just uploaded the bosch page with the ferrari specs on it. supplement '84~'87. lists the specs for '81 on.

the other is checking the WSM but i'm not sure if it's in there.

 

Sometimes it’s good to manipulate things to help with isolating problems.

You can simulate a rich O2 sensor signal by applying a "AA" battery 1.5 volts to the ECU green wire where the O2 sensor is connected. Unplug the green wire pictured in one of the posts. Put the + end of battery on the wire (Toward ECU--not O2 sensor) and connect the other to ground--your system will run max rich. If you ground the wire from the ECU, the system will run max lean.
These tests are described on page 22 of Probst book and they should help you isolate the problem.

You can also manipulate the WUR by applying vacuum to the fitting.

Mark

 

larry i uploaded the ferrari specs to phils site last night.
but here's a quick view,
control pressure cold

with applied vacuum 460~600mbar
10* = 1.7~2.0bar
20* = 2.0~2.4bar
30* = 2.4~2.6bar
40* = 2.6~3.4bar

temps are in celcius

control pressure warm
without vacuum 2.5~2.9bar
with vacuum 510~550mbar 3.3~3.7bar

system pressure 5.0~5.6bar

 

Hi again Larry,

Certainly sounds as something's amiss in the fuel circuit, but just to clarify (since ignition issues are the most common on 308/328): you did verify spark on all plug wires (inductive timing light)? If one isn't firing the fuel injection will sense a "rich" mixture (via O2 sensor) and attempt to correct by "leaning" the system (i.e. ignition faults can drive FI system to limit of parameters)

Best,

Carl