‘91 F53 No Spark

[Joe Rambler]

First time posting, I hope this gets to someone who knows old Fords.
I’m working on a ‘92 Southwind built on a Ford F53 7.3L (460). It ran fine last year, used mainly during football season. It’s been in storage through spring & summer. Son-in-law says he started it every month but getting ready to travel a couple months ago, it wouldn’t start. He replaced the old weak/dead batteries. Still won’t start. It’s getting fuel, no spark. Replaced original coil, cap & rotor, plugs & wires. Still cranks fine, insufficient spark from the magneto. Found a stray red wire in one of the black corrugated protective sleeves in the battery compartment with a female connector but haven’t been able to find a stray male tab that it goes to.

So, I have a few questions.
Why is it not getting enough spark from the magneto?
Any idea what this stray wire is or where it goes?
If I can get a mobile mechanic out to the RV storage farm, does anyone know for sure where to plug into the EEC?

Any helpful feedback will be vey much appreciated.

 

[House Husband]

I believe your OBD1 port is close to the drivers side of the radiator, under hood.
You do not have a magneto, it's a distributor.
The red wire is probably the wire that should help the computer maintain it's memory. Fleetwood was famous for leaving that wire unconnected from the engine battery. Will not cause a no start problem.
Do you have fuel pressure? If not, there is a 30 amp fuse under the hood that supplies voltage to the ignition and fuel pump.
You could have a bad coil wire, distributor, TFI, EEC, etc.
At the age of you MH, you could have a electrolytic capacitor bad in the EEC. I just went through that.
You'll probably need a professional to trouble shoot the problem.

Richard
95 Bounder F53

 

[Joe Rambler]

Thanks Richard!

 

[ashtonexplores]

It’s not actually a magneto on your ’92 F53 460, it uses Ford’s EEC-IV with TFI ignition. A few things to check:

• Common no-spark causes are the TFI ignition module on the distributor, the PIP sensor inside the distributor, or the EEC power relay/fusible links. Weak or no spark almost always traces back to one of those.
• With key ON you should see ~12V at the coil’s positive side. While cranking, the negative side should pulse. If it doesn’t, the TFI or PIP isn’t triggering.
• The stray red wire in the battery compartment could be important. On these chassis a fused red wire feeds the PCM/EEC relay or ignition system. If it’s disconnected, the PCM won’t power up = no spark. Check it with a test light to see if it’s hot with key ON.
• The diagnostic connector (EEC-IV/OBD1) is under the hood, usually on the driver’s side near the firewall or brake booster. It’s a gray trapezoid plug with a single-wire pigtail. You can pull codes with a cheap reader or just a jumper wire and count the CEL flashes.

I’d start with:

1. Verify 12V at the coil with key ON.
2. Test for pulsing ground on coil negative while cranking.
3. Inspect/replace the TFI module (very common failure).
4. Trace that red wire—if it’s the PCM feed, reconnecting it could solve the whole issue.

 

[House Husband]

TFI ignition module on the distributor,
Just so you know.
The TFI on 460 F53s is on the fire wall, drivers side. Mounted on a heat sink.

Richard.00000