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All, my 1997 7.3L slowly became difficult to start. replaced glowplugs about 5yrs ago. very few miles since replaced. I noticed slot number 22 30A maxi fuse continues to blow after replacement. this controls the fuel line heater and glow plug controller. and power control system relay coil. any ideas what is going on, and how to test for culprit?
 

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Possibly a shorted fuel bowl heater , that will trip the fuse . It’s actually pretty common . Most guys simply unplug the bowl heat in the hopes of eliminating that blown fuse .
There is limited need for the fuel heater unless you’re in Canada or the northern Midwest I reckon .
Try unplugging it and see what happens .


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For checking the injector/glowplug wiring: From each valvecover gasket connection's outermost pins (2 per connector) to ground you should get 0.1 to 2 ohms (indicates good plug and wiring). From each valvecover gasket connection's center pin to each immediately adjacent pin, you should get around 3 ohms (indicates good injector solenoid and wiring). You should not get any continuity from any of the outer pins to the 3 inner pins (indicates no shorts between injector and glowplug wiring). You should also get 0 to 1 ohms from each of the external harness connectors outer pins back to the Glowplug Relay's large terminal on the GP side (indicates good wiring from external connections back to the relay).

To check the glowplug relay (GPR), measure the voltage drop across the GPR's large terminals. While the GPR is active (up to 1.5 to 2 minutes after the key is turned to Wait-to-Start) put your meter leads on the large terminals (one lead on one large terminal and the other lead on the other large terminal). The measures how much voltage is being "lost" across the relay. A reading of 0.3V or more indicates a bad relay. Also, check the relay’s control wires (smaller wires) disconnected from the relay for battery voltage at the Red/Light Green striped wire and ground at the Purple/Orange striped wire (check both when the key is turned to Wait-to-Start).

Cheers!
 

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For checking the injector/glowplug wiring: From each valvecover gasket connection's outermost pins (2 per connector) to ground you should get 0.1 to 2 ohms (indicates good plug and wiring). From each valvecover gasket connection's center pin to each immediately adjacent pin, you should get around 3 ohms (indicates good injector solenoid and wiring). You should not get any continuity from any of the outer pins to the 3 inner pins (indicates no shorts between injector and glowplug wiring). You should also get 0 to 1 ohms from each of the external harness connectors outer pins back to the Glowplug Relay's large terminal on the GP side (indicates good wiring from external connections back to the relay).

To check the glowplug relay (GPR), measure the voltage drop across the GPR's large terminals. While the GPR is active (up to 1.5 to 2 minutes after the key is turned to Wait-to-Start) put your meter leads on the large terminals (one lead on one large terminal and the other lead on the other large terminal). The measures how much voltage is being "lost" across the relay. A reading of 0.3V or more indicates a bad relay. Also, check the relay’s control wires (smaller wires) disconnected from the relay for battery voltage at the Red/Light Green striped wire and ground at the Purple/Orange striped wire (check both when the key is turned to Wait-to-Start).

Cheers!
Lots of good info there, saved.
 

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If you need to replace glow plugs use only Ford stock ones, other brands can be problematic as the ends can swell break or burn off. If glow plug relay needs replacing the White Rogers (Stancor) Relay PN 586-902 are much more robust then stock. I’ve not replaced one, once installed on our trucks and the stock ones typically I’d get 1.5 year out of them.

If you look in bottom of fuel filter canister, once filter and fuel is drained there should be a flat plate with a metal wire running around the plate (fuel heater). Typically the wire become loose off the plate and shorts the fuse. Lots of guys just unplug the harness on the outside and tape up the end to prevent shorting on the wire end of harness. If you remove heater plate remember the stand pipe inside filter housing is reverse thread. From what you’ve explained I’d say three things as noted above, shorted fuel heater, GP Relay and/or glow plugs.

Typically where I reside in Western Canada winter can be cold at times, I usually unplug and/or remove as preventative maintanence, the fuel heaters are a poor design. With winter fuel diesel I’ve never had a gel problem since 1990, check with your fuel supplier in your jurisdiction as winter fuel additives may be different.
Cheers,
j
 
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