[v12-engine] I have spark!

My no spark no fuel injector click / no start condition
has taken a step in the correct direction. After checking
all the wires and sensors I replaced the spark ecu unit. AND
SPARK was obtained. But still no fuel injector click or fuel
pump run when cranking. I had checked the air gap at the
flywheel for the spark ecu (.049) now I have to start
looking at the front sensor more as well as the fueling ecu
circuit. The relays a nd fuses will be the first target.
what are the common problems in this srea.–
DOZZER
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In reply to a message from DOZZER sent Sat 20 Jan 2007:

From what you are experiencing, and the lead up thus far, I’d
really take a close look at the connector that mates to the marelli
ECU, on the pin that is responsible for carrying the synch signal
to the fuel ECU (I don’t recall that pin number, off hand, but it
you need to know, I will look it up). Since you had water seepage
on that side of the car, that was responsible for the ECU being
toasted, I’d wager that you’ve got a corroded connection on that
particular pin, and perhaps others, too.

Note that if this signal is not getting to the fuel ECU, you won’t
get fueling. I presume you have either listened to the injectors,
or inspected the plugs after cranking to verify that no fuel is
getting there.

I can’t see, right now, why you would have multiple failures in two
separate systems (fuel and spark) contributing to your problem. I
suspect your fuel relay is functioning fine (you DO hear the fuel
pump come on and pressurize the rail when you roll the key to on
(not crank) don’t you? This can occur and the fuel ECU can still
not issue injector pulses, because these are tied to the marelli
synch output. No synch, no fuel pulses.

The connector housing on the Marelli’s cable can be opened
relatively easily; the pins are in there quite densely, though. In
fact, they are in there densely enough that it is easy for one wire
to break loose under strain; I want to recall the fuel synch pin is
located toward an end of the row…

Right now, my money’s on either a corroded connection, or a
corroded wire that has separated from the connector pin on the fuel
synch line.

Glad to see you are making progress!

Good luck,

Mike–
The original message included these comments:

all the wires and sensors I replaced the spark ecu unit. AND
SPARK was obtained. But still no fuel injector click or fuel


Mike, 1990 5.3 XJS Convertible, ‘Caterwaul’
Lakewood, OH, United States
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In reply to a message from DOZZER sent Sat 20 Jan 2007:

Checking the pcmf ( fuel ecu) I have no power to the number
3 pin. this is listed as fused 12 v supply. I have checked
the two large spade connection on the positive cable and
have power out of them. All my fuses show good. I figure
there is a fuse I missed or the wire is broken after the
fuse. Where is the fuse located and dose any one know the
wire color. I do have power to the number 22 pin with the
key on.

89 xjs v12 auto marrelli ignition–
DOZZER
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