Fuel Pump Sound With Ignition "On" 308 QV

Is the safety switch on the airflow meter plugged in? It's something a mechanic might unplug during his normal duties and forget to plug back in.

There's no "intelligence" in the fuel pump electrics -- if you're in a mode (for whatever reason) where the fuel pump runs, it should stay running as long as you are in that mode.

 

Some are very noticable.... others not so much , but once they are 'on' they are 'on'...they do change note as the carbs pump up.....

 

On an '83 Mondial it's between the air filter box and the fuel distributer, pointing to the rear and angled up. Blue connector with 2 wires. Very noticable as its the only electric connection on the fuel distributer. Should be in the same place on the 308.

Hack

 

Here:
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it's probably just cruddy pins in the connector given the intermittent behaviour. However, if the pins/socket look ok, peel back the black boot and check the wires.

if that's ok, follow the wiring back to the main harness and see if there's an problem there (not likely, but that's where the fault is on a friends 308. Until I get around to fixing it, I suggested that if she does roll over the car, the engine stalls, and a fuel line ruptures, she may want to considered hopping out first and combing her hair later.

if the switch itself is squirrelly, I've never changed one so can't babble about that.

 

back through the return line to the tank. Fuel is constantly circulating through the system and some is diverted to the injectors when the metering plate goes down.

the fuel pump is not supposed to run with the key in the on position unless the engine is running (which as steve said depresses the metering plate and opens the safety switch). The safety switch is bypassed with the key in the crank position so the fuel pressure comes up without needing to crank for a while.

 

What wolftalk said. There is a pressure regulator in the fuel distributor which returns fuel back to the tank in order to maintain constant system pressure.

BTW, the fuel pump isn't the only thing buzzing in a K-Jet Lamba system. The ECU will be driving the frequency valve (located near the left side of the fuel distributor) based on the oxygen sensor reading, and that should be buzzing away as well.

 

The downside to doing this isn't on the fuel side, as Phil explained, but on the electrical side. The FP draws a significant current (like 9~11A), and, if the FP is "on", so are a bunch of other things as Jeremy noted (ECU, FV, WR & O2 & AAV internal heaters, etc.) so the total current draw might be something like ~15A -- without the alternator working, that puts a big strain on the battery. A few seconds = no problem, but a few minutes = not a good idea to do this regularly IMO (although your FP shouldn't be running with the key in Pos II if the engine isn't really running).

 

Check if the frequency valve is running as well as the fuel pump. You can just put your finger on it and feel if it's vibrating. If it is, it's almost definitely the safety switch which is bad.

 

Wish I had a picture, but... It's strapped to the fuel distributor, on the left side. But only if you've got a K-Jet lambda system (i.e. if you've got a euro model, don't bother looking for it). I think the quick way to tell, correct me somebody if I'm wrong, is that the fuel distributors for the lamba systems were black, where as the other ones were silver.

 

I dont have my books available, but assuming the CIS on the Ferrari is the same as other cars, normally the pump should "cycle" for 5 seconds and stop whenever the key is turned to the on position. There generally are two fuel pump relays, one has a timer.

The fuel system operates at very high fuel pressure, over 80 psi, through a regulator. When the pump is running, the pump is flowing a minimum of a liter of fuel every 15 seconds, and what the engine does not use is returned to the tank. There is an inline pressure accumulator that contains about one liter of fuel at full line pressure, to balance out fuel pressure changes or pulses.

The 80 plus psi line pressure is regulated down further within the fuel distributor, to around 65 psi control pressure. The injectors themselves are simply pressure relief valves, that will only release fuel through them when the pressure reaches some 60 psi.

I have never done it but have read that the pump can exceed 200 psi if a blockage or pinched line were to stop the output of fuel from the pump. I once measured almost 2 liters of fuel in 15 seconds (almost 2 gallons per minute) while the pump maintained a system pressure of over 75 psi. Its quite a high flow pump. That volume of fuel is constantly being cycled back to the fuel tank.

Being you mentioned changing coils, its possible you may have either missed a wire, or have a bad connection in that area. IIRC, the fuel pump relay with the timer needs a signal from the ignition that the car is NOT running, in order to shut off the fuel pump.

 

I believe the pump has a pressure limiting safety valve that will open up at around 115 psi and shunt the gas back to the inlet, to avoid such situations. Course, if the safety valve is blocked somehow...

 

Also refer to Section 3 of your OM -- it has good illustrations showing/locating the fuel injection system components:
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Perfect! Thanks Steve. In pretty much any overhead engine shot, the damper blocks the view of the FV.

 

bad assumption. There's no timer operating the fuel pump.

nothing you do over at the coils or ignition ecu can affect the fuel pump circuit.
the fuel pump is controlled only by:
1] ignition key position
2] airflow safety switch
3] the fuel pump relay
4] and depending on where you look and who was translating that day - the "start valve relay" aka "relay for cold start injector" aka "fuel injection delivery pump starting relay". This relay actually closes the fuel pump relay depending on the state of [1] and [2].

trying to figure it out from the qv owners manual schematic is somewhat less effective that trying to get drunk on coors, so snag a 1989 328 owners manual and look on page 73 for a slightly more useful diagram (note that there are some differences to the earlier cars, but not the fuel pump part). It helps a little to know that wire KL 50 is powered when cranking, and KL 15 when key is in the on position (and maybe when cranking too). Also, on bosch relays, terminal 30 connects to 87 when the relay is powered, and 30 connects to 87a when it's not powered.

also, just to add a different spin to steve's comment about the heating elements on the AAV and WUR being powered when the fuel pump is running....that means if you sit there long enough to close the AAV and disable the WUR cold start enrichment, the car will likely run badly when first started. You haven't flooded the engine...just the opposite - you're too lean... and you have no fast idle. Misfires may result in unburned fuel smell, though.

 

I'm almost certain that a few miles with one bank not burning fuel would not harm your Hyperflow cats, unless you noticed an obvious smell or a ridiculous amount of heat as you walked by the rear of the car. If your cat was serious damaged, it would not flow properly as you noted on higher rpms.