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

Hi Matt can I just check a few things with you....?

If you remove the brake fluid reservoir cap in the frunk when you switch on the ignition to the 1st setting can you see the fluid go down (as the accumulator is being charged with fluid)?

NB. I had been messing with the brakes already so it did it quite quickly after switch on but if you have not used the car for a day or 2 this can take about 30 seconds or so as the accumulator loses pressure and the reservoir refills with the fluid.



As above if you have your foot already pressing the brake fluid before switching on do you hear the pump buzzing and then feel a vibration in your foot on the brake followed by a slight drop in the pedal just as the ABS light goes out?



And view of just the pedals - you should feel a slight tremor in the pedal as it runs the test followed by the pedal relaxing slightly



Have you thought about just buying a new orange relay to 100% rule it out?

Is the test fuse (my UK car is shown so may be the other way round but it's the 5amp one above the relay with a white spot) NOT in - pic here shows it in place but that is not the norm - should be removed unless testing.

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Did you know that if you have the test fuse in as per pic above you read flashes on the dash that tell you of any stored fault codes?

Have you definitely got a 348/355 ABS CPU installed and not one from another car (people do do that)?

Just so I understand right once you've started the car (and the engine running) but not driven anywhere the abs and brake failure light both extinguish then after driving and breaking a couple of times the brake fail (or is it the ABS light) comes on? Or both?

Might be worth posting a video of ypur startup sequence of lights and also a pic of the lights you get when the problem occurs.

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I just bought a used USA Brake Light Test/Seat Belt&Door Buzzer Module for U$27. I'll run some tests on it to see if is more than just a relay (brake-wise).

If it's easy to get inside, I'll take some photos of the internals.

I didn't realise it was fitted to so many different Ferraris... 328's, 348's, 355's, Testarossa...

 

Checking volts at the orange relay socket (with the relay pulled) should prove that the fault is elsewhere. The relays are not cheap ... USD90 + P&H.

 

I don't think the mystery has been solved just yet.

There shouldn't be any current flowing through the starter when the car is running.... unless the start system is set up like the F355.

@m.stojanovic Miro, doesn't the 348 have some kind of system to cut out heavy current devices like headlights and windscreen wipers during start? I can't find a relay for this in the wiring diagrams (at least not in the 2.5 diagrams). On the F355, there is a special relay that shuts down the heavy current devices during start. The relay is de-energised during start (by putting voltage on both sides of the coil). When the relay is energised, allowing power to the headlights and windscreen wipers, the start relay solenoid/coil becomes part of the earth circuit for this special relay. Because the current goes through two coils, it's not sufficient to energise the starter. I think you or some other electrical guru explained this to me previously.

Well, that's the simplified explanation. On my F355, you can pull the lead off the starter and the special relay coil still manages to find an alternate path to earth. e.g. through the coil of the Brake Test Module.

 

The mystery is about what is keeping some "floating" voltage on the "START" line. Since it is not the Test Device, there must be some other device connected that needs the "START" signal. Anyhow, since everything works well (including the Test Device ?) with the Starter Relay removed, there is probably no need to investigate why there is that weak floating voltage on the line to the starter solenoid (possibly caused by a kind of relief relay that could be present on 348-s for some markets). The following drawing explains why the Orange Relay is held "on" after the key is released back from the START position.
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Left Drawing: When the Starter Relay is not present, the START current is applied to the starter solenoid and the Yellow Relay - both are switched "on". When the START current is switched off (the engine has been started), the starter solenoid coil, which has very low resistance, represents a grounding point to the "+" side of the Orange Relay and the relay is instantly switched "off". At the same time, any "floating" voltage/current on the START line is also grounded via the starter solenoid coil and will have no effect on the Orange Relay. So, in the factory setup, the START line is +12V with the key in START and it is ground when the key is released back to "RUN".

Right Drawing: Wen the Starter Relay is installed (inserted), the grounding effect of the starter solenoid is removed and we have two relays connected to the START line which carries the mysterious floating voltage. This voltage/current is obviously not strong enough to switch "on" the two relays otherwise it would cause the starter motor to engage before the key is turned to the START position. What is happening is that, after the key is released back from START, the Starter Relay will go off (maybe with some delay) but the orange Relay will not. The reason for this is because the holding voltage of the Starter Relay happens to be higher so the weak floating voltage will not hold it but the Orange Relay is probably more sensitive (efficient) so the weak voltage will still be enough to hold the relay "on". The holding voltage of standard relays is usually some 5-7 volts.

If you still want to have the benefit of the Starter Relay, do not use any of the standard car cube relays (~90 Ohm coil resistance) but a motorcycle starter relay (this is what I have on my 348). These relays are also quite compact but their coils have much lower resistance (some 5-10 Ohm) which will "eat" (channel to ground) the floating voltage almost as well as the starter solenoid coil. There are many types of motorcycle starter relays. You can go for a genuine (Honda, Kawaski etc.) or for an aftermarket one. Some examples:

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Sounds possibly like a bad ground some where. You know, like when you have a bad ground on a tail light and the instrument lights glow lights because the voltage is back feeding trying to find a way to ground. (2002 Toyota pickup problem. )

 

Please let us know what you find out because there a number of us that have that starter switch installed. Glad you found what was causing the problem.

 

For info, there are no diodes (in the brake light circuit) of the Euro version of the Test Module. I'll see if that's the same for the USA version when I get it.

I didn't physically open the module to look for diodes. The module case looks hard and brittle, so I didn't want to risk opening it. I just did external resistance checks on the module pins. i.e. the coil is around 78 ohms.

 

As Matt informed, the "floating" voltage was still present on the Start line after unplugging the Test Device so it does not seem to be the cause of the issue with the Orange Relay (when using the Starter Relay).

If it is not the Test Device, then there could be a so called Relief Relay connected the the Start line. These relays are usually connected between the "Ign 12V" and the Start line and their normally open (NO) contacts are used to switch certain things off while cranking the engine. This is usually the high consumers like heater blower, radiator fan(s) etc.
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Ignoring the Orange Relay for the moment:

With the factory setup (left drawing), the Relief Relay gets +12V at ignition "on" (RUN) and has ground through the Starter Solenoid (which has just about 0.3-0.4 Ohm). So, at RUN key position, the Relief Relay is switched "on" providing power to the mentioned consumers. With the key in START position, the Start line gets +12V and the Relief Relay, having +12V on both sides of its coil, goes "off" cutting the power to the consumers. When the key is returned to RUN, the Relief Relay is switched back "on".

With the Starter Relay installed (right drawing), its coil, having resistance of some 85 Ohms, does not provide good ground for the Relief Relay and this may cause, in some cases, the Relief Relay not to switch "on" at all. Furthermore, the current flow through the Relief Relay may cause the Starter Relay to stay "on" after the key has been released from the START position causing the engine to continue cranking until the ignition is completely switched "off". This is because the Relief Relay and the Starter Relay coils are connected in series between "Ign 12V" and ground which results in about 6 volts on the Start line (the relay coils act as a voltage divider, 2 x 85 Ohm).

With the Orange Relay included in the "equation", we have 85 Ohm on one side of the Start line (the Relief Relay) and 42.5 Ohm on the other (2 x 85 Ohm in parallel of the Starter and Orange Relays). This voltage divider, having 85 and 42.5 ohms, will cause about 4 volts to be always present on the Start line (when the ignition is "on"). Even though quite low, the 4 volts seem to be enough to prevent the Orange Relay from switching "off" after it has been energised during cranking of the engine (just read that some standard car relays will not go off until the voltage on their coils is reduced to less than 2 volts). And the "divided" voltage can be higher if the Relief Relay happens to have somewhat lower coil resistance than the other two relays.

I once had a problem on my BMW E30 when I installed a standard cube relay as the Starter Relay. The E30, as I discovered, has two Relief Relays (2 x 85 Ohm = 42.5 Ohm) connected to the Start line (resulting in 8 volts on the Start line from the "voltage divider") and they caused my Starter Relay to stay "on" (and continue cranking the engine) after I released the key from START. Installing a motorcycle starter relay solved the problem.

 

Yep... Just for info for future (different) problems.

I was looking for these devices earlier. On the 355, 550, 360 etc... there is a specific relay, but I couldn't seem to find one in the relay list the 348 or in the diagrams.

 

Then Matt should reconfirm that, after unplugging the Test Device, the Orange Relay was still not switching "off" after cranking, i.e. that the ABS Pump was still not operating after the engine has been started.

It is also possible that a Relief Relay (or a relay for some other function) was an additional installation on Matt's car by the PO or dealer.

Matt, if you are going to experiment with other standard cube relays as the Starter Relay, be prepared for the possibility of having your engine still being cranked after you release the key from START. If this happens, just turn the ignition key to "off".

 

Do you have an aftermarket alarm/immobiliser (or the remnants of one removed) somewhere in the start circuit?

 

The holding voltage (release voltage) of some 12V relays can be even lower than 3 volts. For example, Tyco V23234 Series car relays will release only when the voltage on their coils drops to 1.5 or 1 volt (depending on the version):

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I'm running a WR-1 relay which I bought as a kit - the relay in that one is a Bosch 0 332 019 150

I will say though that my ABS light is a bit temperamental but I suspect that's not to do with the relay though as it's slow to go out if I haven't used the car for a few days but does go out if I use it like a daily driver.

I'm not sure how you do the test but if you post some clear instructions/pics up I don't mind trying it for you


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Why use WR relay for hard start, why not solve the cause as opposed to mask it?

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I think addresses an issue of poor design - similar to the "slow windows"

 

Isn't the point of the relay to shift the heavy current devices from the cabin to the engine bay? i.e. no solenoid current going through the ignition lock contacts or relay panel.

 

Perhaps you can do the following test: Disconnect the "Start" wire from the starter solenoid; connect a suitable extension wire to this wire, long enough so that you can bring it around and inside the car; unplug the orange relay; switch the ignition "on", keep on touching the ground with the extension wire and listen to any clicking.