348 fusebox wiring diagram

I can't say I've specifically seen a pinout for the rear side of the fusebox. You may have to get the details from the regular wiring diagrams. They show the internals, but you would have to refer to all of them to get a complete picture. Do you have a 2.5 or 2.7 engine management system?

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Do you have a specific issue which requires the opening of the fusebox?

 

The changeover date to 2.7 was 1990, so you definitely have a 2.7.

Here's the 2.7 wiring engine management diagram:

https://www.dropbox.com/t/MU5fywqGEcn2tTq7

The diagram includes a decoder for the relay and fuse lettering/numbering.

The pumps themselves share a common ground. Not sure where that is on the 348, but I doubt they are far away from the fuel tank. Pump power is controlled by the onside engine ECUs, so it seems strange that both would fail. For info: The ECUs control both the power and ground to the pump relay coils. Power for the relay coils comes from the same side/bank injector relay (which is controlled the respective ECU). The coil earth/ground comes directly from the ECU.

When you say the pumps aren't running when cranking, do you mean there is no fuel pressure at the rails or can you actually hear the pumps (not) running when the engine is cranking?

 

Can you monitor the voltage on the fuel pump fuses? They are downstream of the pump relays. Note that the fuel pump relays also control power going to the O2 sensor heaters. Maybe you could also monitor the voltage at the O2 heater fuses? (fuses #9 & #20).

 

As Ian informed, each fuel pump has its own relay which provides the +12V to the pump. The ECU does not ground the pump (the pump is always grounded) but provides ground to the Pump Relay to engage it and the relay will then send +12V to the pump. The Pump Relay will engage if:

1. The Injection Relay is first engaged which provides +12V to one side of the pump relay coil (the Injection Relay is engaged by the ECU at ignition "on", if I remember well)
2. The ECU grounds the other side of the Pump Relay coil (when the ECU gets signal from the crank sensor showing that the engine is turning)

So, basically, you have to have the Injection Relays operational and a command from the ECU for the Pump Relay to be engaged. I suggest you first do the following simple tests for each pump:

1. Remove the fuel pump relay and verify that you have +12V at either socket 30 or socket 87 (see drawing below, it is as looking at the relay socket); you don't need to switch the ignition "on" for this test
2. Plug two wires (with male spade terminal at one of their ends) into the pump relay sockets 30 and 87; touch the other ends of the two wires together and see whether the pump runs (you will also notice a fairly strong spark on connection of the two wires together if the line to the pump, and to/through the pump fuse, is good)
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Hi please help ferrari 348 left hand fuel pump 5 to 8 wont pump when trying to start but will if i put 12v to pump. the relay has power at 87 but no earth at 30 swaped ecu still the same also swaped the relays no joy ps there is spark at 5 to 8

 

Did you try to jumper the pump relay sockets as described under point 2. above the relay drawing in the post #7 above? Did you check the pump fuse?

 

HI yes the wire behind the fuse box had gone a green colour i cleaned it up and running on both banks now but engine hunts on both sides now its a 1991ts with no cats thanks for your reply

 

The banks are mechanically linked to each other. I can’t see how one side would hunt.

When the rpms dip, does the engine nearly stall? What is the rpm range when cold and hot? By the way, if you disconnected the battery during your electrical checks, did you do an ECU relearn?

 

no both sides hunts when cold and hot

 

Understood, but I wasn't sure why you would say "both sides". Hunting is a change in overall engine rpm. Left and Right Engine banks can't run at different speeds (AFAIK).... unless there are some serious mechanical issues

 

Hi found my problem with the hunting it was the fuel regulator on bank 5678 fuel was coming of the vacum pipe new on order

 

Hi just fitted fuel pressure regulator to my 348 ferrari runs a lot better but erratic at tick over but if i disconect air mass regulator it runs nice. i have swapped them over still the same ps no cats on car early 1991 model please help

 

What is an “air mass regulator”?

Mass airflow sensor? (MAF)
Idle air controller?

If you’re talking about the MAFs, if one is faulty and you swap them over, there should be no change in overall engine behaviour. If you disconnect a faulty MAF, it forces the car to use other parameters to operate the engine.

It sounds like the MAF you disconnected is faulty. Which MAF did you disconnect?

Try using specialised MAF cleaner from your local auto store. Use liberal amount several times. Let dry.

 

The right bank run erratic if i take off the connect plug it runs good i have cleaned them both with a maf cleaner. also taken left bank sensor and put on right same result.Cant understand it

 

I don't understand what you are trying to say. How do you know only one bank is running erratically?

 

bank 1234 exhaust makes unevan
running but dead smooth with maf disconnected

 

So when you swapped the MAFs, the problem remained on the RHS? Did you pull the plug on the "new" RH MAF again to see what happened.

 

yes same result

 

Interesting. Doesn't make sense to me, either, unless the MAF connector wiring is faulty. Sometimes the pins are corroded/dirty.

Do you get the same exhaust behaviour when you raise the rpms? Can you explain in better English what the exhaust is doing? Is it pulsing? Does it smell rich?

 

No revs ok maf connected . exhaust note goes up and down maf connected at idle

 

Could you elaborate? I'm having difficulty understanding what you are saying (in the absence of details and punctuation).

No what? And when? Revs ok when MAF connected? Do you mean the engine idles well with the RH MAF connected or disconnected? Or when you say "revs ok", do you mean it responds well to accelerator input?

Do you mean in frequency or volume (or neither)? I still don't understand how two mechanically linked banks can create fluctuating exhaust notes on one side only. Is this fluctuation simply more noticeable on the RHS due to the colour of the exhaust?

 

. exhaust note goes up and down maf connected at idle. Disconnected from maf idle ok ff sake