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I NEED SOME ADVICE ON AN ELECTRICAL PROBLEM I’M HAVING ON A 1990 28 FOOT CONQUEST MOTORHOME WITH A FORD 460 7.5 LITER GAS ENGINE. A FEW WEEKS, AGO, IT WOULD NOT START AND I FOUND A SQUIRRELS NEST INSIDE THE ENGINE ON THE LEFT SIDE.AFTER TAKING THE NEST OUT, I FOUND THAT THEY HAD EATEN THE WIRES THAT GO TO THE IGNITION COIL RIGHT UP TO THE PLUG.I PURCHASED A NEW PLUG AND A NEW COIL AND REPAIRED THE WIRES. THE ENGINE STILL WOULD NOT START DUE TO NO SPARK. THE RED AND LIGHT GREEN WIRE THAT GOES TO THE PLUS SIDE OF THE COIL AND ALSO TO THE RADIO CAPACITOR IS HOT WHEN I TURN THE KEY ON. THERE ARE TWO DARK GREEN AND YELLOW WIRES THAT COME OUT OF THE MINUS SIDE OF THE COIL, ONE GOES TO THE TFI IGNITION MODULE AND THE OTHER GOES TO THE IGNITION SUPPRESSION RESISTOR ACCORDING TO THE WIRING DIAGRAM I PURCHASED. I HAD THE TFI IGNITION MODULE CHECKED AT THE AUTO STORE AND FOUND IT TO BE O.K. I’VE BEEN UNABLE TO FINE THE IGNITION SUPPRESSION RESISTOR. ALL FUSES IN THE FUSE BOX SEEM TO BE O.K.
I’M NOT SURE IF THE MINUS SIDE OF THE COIL IS BEING PROPERLY GROUNDED WITH THOSE TWO DARK GREEN AND YELLOW WIRES OR DOES THE COIL GET GROUNDED BY BEING MOUNTED TO THE ENGINE BLOCK. ENGINE WAS RUNNING GREAT BEFORE ALL THIS HAPPENED. DON’T KNOW WHERE TO GO FROM HERE. JOHN

John, (You asked) DON’T KNOW

Submitted by Big Block 409 on Sat, 12/10/2011 - 16:27.

John,

(You asked) DON’T KNOW WHERE TO GO FROM HERE.

Take a second (and if necessary) a third look at what you are asking in terms of spark delivery, and then correct (any and all) mistakes.

How are you testing for spark?
Is the method you are using accurate?
Is there spark but is it NOT reaching the plugs?
Is there no spark from the coil (and or distributor)?
Is there a "PIP" signal?
Is FUEL reaching the plugs?

(You said) ALL FUSES IN THE FUSE BOX SEEM TO BE O.K.

Are there any blown "Fusible Links"

HI, FIRST OF ALL I'D LIKE TO

Submitted by johnandjoanner on Sun, 12/11/2011 - 08:59.

HI, FIRST OF ALL I'D LIKE TO THANK YOU FOR THE HELP!
I USED THE SCREWDRIVER TO CHECK FOR SPARK WHILE RESTING IT AGAINST THE ENGINE BLOCK, I ALSO USED A TEST SPARK PLUG THAT I GROUNDED TO THE BLOCK AND HAD NO SPARK AT THE CYLINDERS OR AT THE COIL WIRE TO THE DISTRIBUTOR. I CHECKED FOR FUEL TO THE CYLINDERS AND FOUND IT TO BE OKAY. I FOUND FOUR FUSIBLE LINKS AND CHECKED BOTH SIDES OF THE LINKS AND FOUND THEM TO BE OKAY. COULD YOU TELL ME WHAT THE PIP SIGNAL IS? JOHN

John, You’re welcome my

Submitted by Big Block 409 on Sun, 12/11/2011 - 09:41.

John,

You’re welcome my pleasure buddy. With a voltmeter or test light check to see if the coil has power with the key in the on position. Next thing is to see if the coil is getting a ground signal trigger. You do this with a test light hooked up backwards. Hook the alligator clip of the test light to the positive battery terminal. Now take the tip of the test light and touch it the signal wire of the coil. The test light should blink when cranking over the engine if its getting a signal. The (PIP) Profile Ignition Pickup sensor is a hall effect switching sensor located inside the distributor or behind the crankshaft harmonic balancer. It’s a three-wire sensor that creates a pulsed voltage signal. If you were to look at the signal on a scope it would appear as a square wave that switches between 0-12 volts. The PIP signal is first sent to the module, and from there it gets sent to the ECM. The ECM creates a (SPOUT) Spark Output signal from the PIP signal. The PIP’s trailing edge signal turns on the primary ignition circuit. The SPOUT signal’s leading edge turns off the primary circuit to fire the coil. The SPOUT signal has additional timing adjustments from the ECM and is visible as notches in the waveform. If the PIP sensor is black in color, it needs to be replaced. The black sensors are used with open bowl distributors. When they fail, they turn into silly putty in the area of the ignition module connector. These sensors should be tested hot while tapping on them lightly. Below is a helpful link.

http://351winsor.com/joel/Ignition_Systems/tfi2.html

I'LL GIVE ALL OF THIS A TRY

Submitted by johnandjoanner on Sun, 12/11/2011 - 11:08.

I'LL GIVE ALL OF THIS A TRY AND SEE WHAT HAPPENS,BUT IT MAY TAKE ME A FEW DAYS TO FIGURE ALL THIS OUT.
I'M PRETTY GOOD AT BASIC AUTO REPAIR BUT NOT AS KNOWLEDABLE AS YOU ARE. BUT I'LL GET BACK TO YOU!
JOHN

John, In my experience with a

Submitted by Old Pete on Sun, 12/11/2011 - 17:50.

John, In my experience with a no spark problem on a 460 it has always been due to a failed ignition module, tfi module, or pick up coil (pip). As you can see 409 is a very thorough professional and posted everything you need to know to check all three. The only thing I can add is that you shouldn't buy or replace any parts yet. Your problem could be nothing more than a wiring or connection problem due to the squirrel's nest. Check all the wiring first. Make sure all the wiring is in good condition and if splicing is necessary you should solder all connections and use shrink tubing instead of black electrical tape. Then check the wire connections at the ignition module, tfi module and pickup coil. Make sure all those connections are on tight and clean and are free of all dirt rust and corrossion. The next thing is are there any error codes? Don't go by the check engine light either. Just ignore the light. Do a scan for error codes even if the light is off and then if there are codes you should post post them here.