348 Brake Pump Runs before startup but won't run AFTER startup!

Removing power from a relay coil (or any coil of wire) will cause a voltage spike which could damage the circuits. The diodes help reduce the spikes.

The same components and power seem to be used for pressure control with the car running or not. The only time that the pump is commanded off (other than the pressure being ok) is when the orange relay energises during engine start. I can't see how this can be an issue unless vehicle vibration is affecting the relay in its relaxed position. Doesn't seem likely though. You can always disprove this by jumpering the orange relay (pins 30 and 87a)

Back to @m.stojanovic

 

Then wouldn't this mean the orange relay is faulty? Or do you mean the pump ran continuously?

 

(EDIT: Sorry.. I made a second post, but deleted it. I'm still trying to wrap my head around the logic).

If your pump is behaving normally with the orange relay jumpered, is it possible your Test Module is sticking in test mode after start? (Item 102 in the diagrams)

https://www.dropbox.com/t/GwpoH2OH33Zo8yWo

Supposedly, the start-up test lasts 7 seconds, and since cranking shouldn't go for 7 seconds, there must be some kind of delay circuit in the test module to keep the test running. Having said that, I don't know if the orange relay is held in for the full test period.

Jumpering the relay should bypass the effect of the module on the orange relay.

 

Can you put your test light on the orange relay socket coil pins (sockets 85 & 86) to see if it is being energised when it shouldn't be?

Note: I don't know how smart the ABS ECU is. I don't know if it will generate a fault message/light if the resistance of your test lamp doesn't match the coil's resistance.

 

I just realised that the test module is only powered when the key is turned to start. I don't see how the orange relay could be held in for even 7 seconds.

 

That's the confusing part. If it wasn't returning to the normally closed position, it wouldn't work the next time for start.

Not sure. It's shown in the parts manual in cabin electronics diagram, but it could be anywhere.

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I'm still trying to determine its function. Maybe I'm misreading the WSM and it's only there to turn on the light.

 

I just realised this module is not as shown in the parts manual above. On N. American cars, it includes seat belt buzzer functions, similar to the USA F355's.

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Your understanding about the Orange Relay is correct. The relay is "off" (contacts closed) all the time except during cranking the engine when the relay is switched "on" opening its contacts to disable the Pump Relay. The fact that the Pump Relay remains disabled after the engine has started means that something is keeping the Orange Relay still energised ("on") after the key has been returned back from "start" position. A couple of possibilities:

1. The diodes inside the Orange Relay have blown. When bench testing this relay (12V to pins 85 & 86), it should switch "on" only with "plus" on pin 86 and not with opposite polarity.
2. Certain fault in the Test Device is keeping the Orange Relay "on" (current backflow from the Test Device) after the engine has been started.

I don't think the Test Device has function in the operation of the ABS Orange Relay but I may be wrong. I would first test the Orange Relay as mentioned under 1. above and, if the test shows that its diodes are good, I would try with the Test Device disconnected.

 

(EDIT: crossposted with Miro)

Here's a graphic I have for the F355

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Ignition power (START) comes in on pin 8. I don't see any time delays. The module looks like it is only a basic relay (with respect to the brake warning system). The pink wire goes to the brake light.

On the 348, the test module just seems to be a convenient splicing point for power coming from the ignition key (during start).

How long does the brake light normally remain illuminated after engine start?

 

Just to confirm... did you say the BRAKE warning light came on not the ABS light?

I did misread the manual. The time delay referred to the ABS light, not the brake light (and was 7 milliseconds for each control valve).

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The 348 manual is mixing the usage of terms "START" and "MARCIA" (RUN) for the key positions. The word "START" in the line "a - when key..." under "2 - ABS..." should read "MARCIA" (RUN, i.e. ignition on).

 

Is this on your car, Miro?

This is confusing. According to the wiring diagram, the ABS system isn't hooked up to the RUN position at all. How does it know that the key is in RUN?

And is your car Euro or US? I forgot.

 

Is your key fully returning to the RUN position after start?

Maybe the spring mechanism is broken or the lock simply needs lubricating.

Not sure how similar the F355 and 348 are with regards to locks, but ...

https://www.ferrarichat.com/forum/posts/149135677/

 

Did you find the Test Module and disconnect it as Miro suggested?

Maybe there are diodes in that, too?

Apparently it's above the driver's left knee (LHD car)

https://www.ferrarichat.com/forum/posts/138035163/

 

Old electricians rule: If in doubt, go to the last modification.

 

Is brake failure supposed to generate a sound on the US 348?

Even if there were diodes in the USA/CAN/JAP style Test Module (with seat belt buzzer circuits), I couldn't see how a diode failure could keep power on the orange relay coil.

Theoretical circuit:

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I was thinking that there may be brake warning wiring in the module linked to the buzzer circuit (for the seat belts). Anyway, if you can find the module, it can easily be eliminated as a "suspect".

Did you see if there were any diodes in that?

 

My comment was merely on what is written in the manual:

"2 - ABS warning light (2, Fig. 24)
This comes on according to the following
sequence:

a - when key is turned to START position,
it comes on for a few seconds
while the control unit checks
all connected circuits.

The warning light then goes out if no
faults are found."

The underlined actions are normally performed when the key is turned to MARCIA (Ignition ON or RUN) position and should not be while the engine is cranked. Anyhow, this is not really important for solving the Matt's problem.

 

Your issue with ABS Pump is most likely caused by the added starter relay. Disconnect it temporarily and reinstate the original connection to the starter solenoid.

The inserted starter relay may be causing the problem you described because there is some partial fault in the Test Device. Before disconnection of the starter relay, you may first try disconnecting the Test Device.