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Ask fordtechsuzukitech25 Your Own Question
fordtechsuzukitech25, Ford Technician
Category: Ford
Satisfied Customers: 98
Experience:  master ase certified,senior master ford certified
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F150: i have a 2005 5.4 f150. it has compression spark and

Customer Question

i have a 2005 5.4 f150. it has compression spark and fuel pressure. what could be wrong. my solus computer says 75psi fuel but its not reading an engine rpm. all the cam sensors and crank sensors are homing and working correctly
Submitted: 2 years ago.
Category: Ford
Expert:  fordtechsuzukitech25 replied 2 years ago.
rpm signal comes from crank sensor only, cam sensors r for fuel(when to open injectors) if crank sensor is good, then its either a broken wire from sensor to pcm or the pcm itself. there r two wires from sensor to pcm so it should not be too difficult to do a ressistance test(ohm's test)
Customer: replied 2 years ago.
It ohms out at the plug on the computer. If the pcm was bad Would it still have fire? Will it still have fire if the crank sensor was bad?
Expert:  fordtechsuzukitech25 replied 2 years ago.
its possible but not likely, if there is fire,fuel and compression the only thing it needs is timing. it should definetly be setting codes if there is no rpm signal. And if it has spark then it has a crank signal to the pcm, which is rpm signal. So when I run into goofy readings like this I make sure powers and grounds to PCM are good. And do a reset(disconnect negative battery cable for 10 min. and then touch it to the positive terminal and see what happens
Customer: replied 2 years ago.
I have compression on each cylinder. I've tried everything. Do you know of anything else to check?
Expert:  fordtechsuzukitech25 replied 2 years ago.
when u pulled plugs were they wet with fuel, or black with carbon, I do no there have been injector problems with those, have u tried holding throttle pedal to the floor while cranking it over and see if it tries to start
Customer: replied 2 years ago.
They were wet. I'm replacing plug on the morning just to try something else. No I haven't held the pedal to the floor
Expert:  fordtechsuzukitech25 replied 2 years ago.
when u hold throttle pedal to the floor and crank the engine, the pcm will not open the fuel injectors, so if you would hold the pedal to floor and crank engine and it starts or tries to start that means it is getting fuel from a leaking injector or multiple injectors, also if the engine is flooded, it will stop fuel and clean out cyl. and start