Will a bad ground fry a coil?

Little Red Zuk · Jul 19, 2011

So my 88 F350 is giving me some issues. Last week, she wouldn't re-start at a gas station. Had it towed to Auto Truck service, where they determined weak spark, and replaced the coil. Started ran and drove fine. I get down to Renton, and same thing happens.

So I'm wondering did it fry the coil again? Ground wire off battery was pretty warm, and I can hear a whine over the radio.
1988 F350, 460.
Any ideas?

crash2 · Jul 19, 2011

Simple answer---nope... My guess would be something else and not the coil but like a poor connection that was altered when the coil was replaced.

Bodaciouscj7 · Jul 19, 2011

Ford, it's usually a bad ignition module. especially if it has a TFI module on the distributor.

I have had them go away to where they dont work hot and other that you had to warm up to make work.

Little Red Zuk · Jul 19, 2011

Im thinking module on distributor then. That could trigger a weak spark.

crash2 · Jul 19, 2011

I had one that got me some time ago. No spark or injector pulse on a chev TBI--no biggie. Removed the cap and disconnect the pickup coil and check for A/C output. Had output like 800mv which is ok. Hook up my test module and it fires off--bad module and no big deal.

Replaced it and ran it hot/hot soak and let it sit over night to verify it. Again no spark. Went thru the same diagnostics and again it showed a bad module. At this point I got looking deeper and cranked the motor and moved the wires at the pickup coil--found goes open (when checking pickup coil output the connector is in a different position). Just an example of how you can diag something and by testing you have actually removed the problem from your diagnostics.

t1h5ta3 · Jul 19, 2011

that and look at the inside of the horse shoe style conector if it still has that type, ive seen a ton of them with bad contacts. ( including my own truck )

zukkev · Jul 19, 2011

When it cools it starts???
If yes, My money's on the module....The module may or may not be on the dist housing; some were on a heat sync mounted back near the driver's hood hinge on the 460 powered trucks.......

zukkev · Jul 19, 2011

But yeah, check your grounds to make sure they are not loose or corroded. It (neg cable) should not get warm if the ground's good...:;

t1h5ta3 · Jul 19, 2011

zukkev said:
But yeah, check your grounds to make sure they are not loose or corroded. It (neg cable) should not get warm if the ground's good...:;

yha, if the cable its self is getting warm, theres prob corosion inside it.
grab a multi meter, connect pos to the pos side of the bat.
touch neg to neg terminal on bat. note voltage.
touch other end of cable/block. note voltage
touch neg @ coil, note voltage

if any of these are more than 0.01v different than batter voltage, theres an issue.

let me know ifya need me to swing by this weekend.

Totalled · Jul 19, 2011

Replace neg cable and TFI.

JOOP · Jul 19, 2011

Just throwing this out there. Have you checked fuel pressure?

Little Red Zuk · Jul 19, 2011

Update: we did get it started last night. Replaced ground cable and coil (just because that was problem before) plugs were soaked, so disconnected the injector harness and cranked them dry. Plugged back in and went. Still thinking I'll do the module just so I'm comfortable with it.

And towing a dented race Jeep through Skyway at almost midnight gets you funny looks.:redneck:

zukkev · Jul 19, 2011

It's not the jeep that gets the funny looks! :fawkdancesmiley:

Little Red Zuk · Jul 30, 2011

So back on this topic again, as the truck is still acting up:

Started fine this morning, drove to Snohomish.

Went for restart, crank, crank stumble (like a bad ground, which was why I suspected that) then just continuous crank.

Unplugged injector harness, and it fired and burned off what I think is excess fuel.

Re-plug back in, still no start.

Unplug to burn off fuel, so as not to wash cylinders down.

Did this a couple times, then to just try it, we plugged the injector harness back in when it did it's fire to burn off fuel.... It continued running:awesomework:

Quickly drove home, and put in parking spot.... Shut it down... Same thing. Crank and no start. Smelling fuel..

Fuel pressure regulator maybe? or still suspect module? How do you test the FPR?

CHOP SHOP · Jul 30, 2011

does this truck have dual tanks?

If so switch the tanks and see if the problem still exists.

I have a customer with a f250 460 rig and it was having the same kinda symptoms.

Turns out each tank has its own fuel pump and one was acting like poop.

He still hasnt fixed it since I figured out it would run on the front tank just fine.

Little Red Zuk · Jul 30, 2011

It is dual tanks, and I've been running off the rear. When it first happened, I tried switching tanks, and still wouldn't start.

Since then, I haven't switched to the front tank. Once I get it restarted, maybe I'll try that as well.

Little Red Zuk · Jul 30, 2011

And now it starts again... Voodoo Ford:eeek:

zukkev · Jul 30, 2011

If you know you have no spark from te coil when it doesn't start, it's not gonna be a fuel pump issue...Ignition modules are fairly common failure items on these. Try this, have a COLD icewater with you and a rag; when the no start occurs again, douse the rag in cold water with ice wrapped in it and cool the module; if it starts back up faster than it did before without the ice/cold rag, I'd bet it's the module...

Little Red Zuk · Jul 30, 2011

Still had spark from the coil when it wouldn't start today.

t1h5ta3 · Jul 31, 2011

side note. no need to unplug injector harnes....
turn key off, press throttle to the floor, hold it there. this engages the clear cyl function. it will crank/fire plugs, without cycleing injectors...