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EricFromCT
EricFromCT, Ford Lincoln Mercury Senior Master
Category: Mercury
Satisfied Customers: 3697
Experience:  ASE, Ford Lincoln Mercury Senior Master, Diesel, Kia Professional Elite
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2006 mgm 4.6 pcm controls fuel pump, fuel injectors, but no

Customer Question

2006 mgm 4.6 pcm controls fuel pump, fuel injectors, but no ignition cop coils. fuses ok, ckp ok cps ok, no codes, no problem with pats, no spark.....
JA: Sometimes things that you think will be really complicated end up being easy to fix with a Mercury. The Mercury Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so he can help you best.
Customer: i just did
JA: Are you hoping to fix this yourself?
Customer: yes
JA: Great! What have you tried so far?
Customer: i just told you
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Customer: idk
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Submitted: 1 year ago.
Category: Mercury
Expert:  EricFromCT replied 1 year ago.

Hi. Do you have power on the red wire at the coil connectors with the key on?

Customer: replied 1 year ago.
Expert:  EricFromCT replied 1 year ago.

Are you getting an rpm signal on the tachometer, if equipped, or on a scan tool when cranking?

Customer: replied 1 year ago.
perfect
Customer: replied 1 year ago.
pcm controls fuel pump, fuel injectors, but no ignition cop coils. fuses ok, ckp ok cps ok, no codes, no problem with pats, no spark.....
Expert:  EricFromCT replied 1 year ago.

Did you check the ground side of a coil connector while cranking and see if the pcm is grounding the coils?

Customer: replied 1 year ago.
with led tester very weak blink, with noid light nothing, i did checked battery power on pcm switched powers and grounds ... all ok
Customer: replied 1 year ago.
noid light on injector perfect
Expert:  EricFromCT replied 1 year ago.

Maybe you should try to light a bulb from the red wire at the coil connector to a ground. You may have high resistance on the power circuit to the coils. That circuit is common to all the coils. Obviously, each coil is grounded seperately to the pcm.

Customer: replied 1 year ago.
just did tail lamp bulb .........bright...ok
Customer: replied 1 year ago.
i replaced pcm, programed pats and same situation, pcm controls injectors and fuel pump but something is disabling or downgrading the coil drivers in pcm
Customer: replied 1 year ago.
isnt there something like on gm when you open wide pcm turns of injectors or mercedes when recognize misfire turns off coil...?
Expert:  EricFromCT replied 1 year ago.

Yes. Ford cuts out injectors at wide open throttle. Also the crank sensor is the main input for spark on Ford as well.

Expert:  EricFromCT replied 1 year ago.

What does the theft light do? Prove out after 3 seconds or blink rapidly?

Customer: replied 1 year ago.
goes off after three seconds no codes
Expert:  EricFromCT replied 1 year ago.

Ok. How do you know the crank sensor is good?

Customer: replied 1 year ago.
fuel injector are pulsing, rpm on dash moving, rpm on scanner showing about 200 +- and scope showing wave form while cranking.
Customer: replied 1 year ago.
what are those diodes for pcm for?
Expert:  EricFromCT replied 1 year ago.

They are so voltage can not travel in the opposite direction. I have had a diode not let a fuel pump run intermittantly before. So you could swap it and see if it helps.

Expert:  EricFromCT replied 1 year ago.

Was any work done to this? What caused the no start?

Customer: replied 1 year ago.
guy came to gym and after that no start
Expert:  EricFromCT replied 1 year ago.

Have you tried for the heck of spraying some starting fluid into the engine see if you get something?

Customer: replied 1 year ago.
i am flodding i can smell fuel and i got on extra test coil no spark.........
Customer: replied 1 year ago.
what could possibly separately disable the coil drivers
Expert:  EricFromCT replied 1 year ago.

Possibly a CHT sensor?

Expert:  EricFromCT replied 1 year ago.

Although according to the workshop manual if the cht is reading too high the pcm cuts the injectors.

Customer: replied 1 year ago.
i have good grounds on c175b pins 10, 47 to 50 and switched power on pins 35 and 36 and power at 44
like i sad injectors are not disabled
Customer: replied 1 year ago.
CHT normal reading
Customer: replied 1 year ago.
can't look at exactly pcm wiring diagram to see what exactly is affecting the ground, functionality or performance of coil drivers?
Customer: replied 1 year ago.
can you? :)
Expert:  EricFromCT replied 1 year ago.

You already tried a pcm. If you replaced it then that is not the problem.

Expert:  EricFromCT replied 1 year ago.

I can get you all the workshop manual info you need. I can convert it to pdf format for you to have. But there is an additional fee from the website to have the pdfs.

Customer: replied 1 year ago.
I am master ase and i am using alldata but seem to me as unsufficient source of informations........
Customer: replied 1 year ago.
what bios data would be able to disable only ignition?
Customer: replied 1 year ago.
is it even possible by hardware or software? i feel stupid......
Expert:  EricFromCT replied 1 year ago.

I do not know every bit of strategy built into the pcm. You got a good one. I know wires chaff on those cars in the harness that runs around the left front frame area and over the left front fender well splash shield.

Expert:  EricFromCT replied 1 year ago.

Does the motor sound like it cranks normal? Did it jump time and the cam and crank correlation is too far off?

Customer: replied 1 year ago.
yeah, sounds pretty normal......trying something
Expert:  EricFromCT replied 1 year ago.

THe electronic throttle body can cause a limp mode or engine shutdown.

Customer: replied 1 year ago.
in one point we ve had spark on test coil,,,,,rest of coils unpluged.....
Expert:  EricFromCT replied 1 year ago.

You could try disconnecting the little capacitor on the engine in case that has done something weird. It is wired directly to the power circuit for the coils. I have seen alternators cause interference. COuld try disabling that.

Customer: replied 1 year ago.
to be continued........
Expert:  EricFromCT replied 1 year ago.

yup