Ferrari Mailing List: Re: FI temperature sensor on the 328 ?

[Jeff Greenfield (coyote]

Rui - 

Several things to check  ...

First of all, there is always pressure behind the cold start injector. In
order to verify that the injector is not leaking, you need to remove it from
the plenum, and energize the fuel pump (pull off the connector on the side
of the air flow meter with the key on and the fuel pump should run). When
this is done, it should be dry with no signs of seepage.

That done, you need to verify that that the wiring to the cold start
injector is ok, and that it is not energized when it shouldn't be. AFAIK
there is nothing that controls this other than the thermo time switch and
possibly a relay. 

I believe that there is a pretty good wiring diagram of the fuel injection
system in the owners manual. This is easier to follow than the big one for
the whole car, but some of the wiring is still pretty convoluted.

There are two other temperature sensors. There is one in the bottom of the
coolant tank. This controls a vacuum switch that is somehow related to the
fast(er) idle when cold. 

There maybe another in your car, (I know your car is euro spec and as such
does it have an oxygen sensor in the exhaust? If not this may not apply to
your car) ... in the oil circuit, there is a 'T' on the bottom front of the
engine, and there is a temperature sensor there. This sensor tells the
system to go into closed loop operation and start using the oxygen sensor to
regulate the mixture.

Both the above sensors are open/closed type. I forget which way they go, I
think that the one in the coolant tank is closed when cold, open when warm,
and the other one in the oil circuit is open when cold and closed when warm,
but it is easy enough to determine if they are working with an ohmmeter when
cold and warm.

Make sure that the throttle switch is working too. There are three pins, you
should have continuity between two when the throttle is closed, there should
be no continuity between any pins when the throttle is opened slightly, and
there should be continuity between one of the same pins (when closed) and
another when wide open.

If your car does have an oxygen sensor, there should be an inline fuse
underneath the panel under the right side of the trunk where some of the
relays and the FI ECU is located.

If this fuse is blown, the whole system will not work correctly.

Lastly, again this depends on whether your car has an oxygen sensor, but if
it does you can get the fuel mixture close by measuring the duty cycle at
the frequency valve. They say it should be about 55% - 60%, but my car won't
run well until about 70%.

I went through most of this on my car a couple of years ago when it wasn't
running well, and found a whole bunch of problems.

LMK what you find and I'll try to help as best as I can.

Jeff


-----Original Message-----
From: Rui Gigante [mailto:rui.gigante [at] gmail.com] 
Sent: Saturday, June 09, 2007 5:28 PM
To: Jeff Greenfield
Cc: The FerrariList
Subject: [Ferrari] FI temperature sensor on the 328 ?

Hi listers,

after a hard period at work I've found some time today to play with and
drive the 328. Some of you might remember I suspected a problem with the
master brake cylinder, but it didn't happen again ... and the test suggested
by Jeff indicates that the booster is ok. I guess the master is just
starting to let go ...

So I've turned my attention to other matters, like the fuel injection. At
the beginning of the year I've replaced the thermo time switch because I had
a hard time starting the car when hot, and checked fuel pressures at a
certified Bosch shop. All was ok, and the car starts ok when hot, even if it
sometimes takes a bit longer than when cold.

When I came back from a very "animated" drive today, I've noticed that the
exhaust smell seemed to indicate a rich mixture. I've always been a bit
suspicious about the fact that when started cold, it never gets the rpm past
the 1,000, like I guess it should. It just idles at the same speed, cold or
warm. So I've decided to disconnect the auxiliary injector at the plenum
(engine warm), and voila, the rpm climbs to 1,400 rpm !!

That shouldn't happen, since I've checked that the thermo time switch in NOT
providing a ground path for the injector with the engine hot, but didn't
check if I had 12v at the injector ... So I guess one of two things might be
happening:

1- the injector is faulty and is always on, and someone in the past has
"tuned" the idle to compensate
2- I think there is a separate temperature sensor for the FI. If it's
faulty, then the electronics "think" the engine is always cold, and keeps
the injector on. I'm assuming in this case that the injector is actuated by
the electronics and not directly connected to the thermo time switch. And
the water temperature sender and gauge work perfectly ...

What do you guys think? Any ideias ? The car starts and drives great, but
I'm sure this is a problem I need to solve.

Rui
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