30 amp fuse blows every time i turn the ignition. 2002 f250 super duty 7.3ll. replaced starter,glow plug relay,starter relay. checked all wires and gounds. truck will start when i jump starter selenoid.

check engine immobiliser and crank position sensor . Run fault codes and replace faulty units.

Relay or control module?

Motorcraft Glow Plug Relay 7 3 PowerStroke DI Turbo Diesel

Motorcraft Glow Plug Control Module

Hello, Follow your Glowplug wires back to a box and that box is your Timer. You should have wires going into the Timer from either the Ignition or from a Relay between the Ignition and the Timer.

When you turn the Key to Run, there should be power going into the Timer box. If there is power going in and nothing is happening, then the Timer is bad. If there is no power going into the Timer, work your way up to the Relay.

On your truck the Relay should be a DY 861 Motorcraft. It will look a little like a starter Relay. Check the power in and out, there is a fuse in the panel for this too! But if the fuse blew it will probably do it again until a bad part is replaced.

Your glow plug relay is located on the top of the engine on the right side toward the front. Some models there are 2 solenoids. A large one toward the front and a smaller one right behind it. The glow plug relay is the smaller one toward the rear. The larger front one is the intkae heater relay. To test the glow plug relay turn engine to on. dont start it. both of the large terminals should have power with key on. then turn engine off. only one large terminal should have power. If when you turn engione to on you only have power on one side then go to this test. Turn engine on and test smaller wire. it should have power. If it does replace the relay. If the smaller wire does not have power you have an ignition problem or power (wiring) problem to the relay.

is it the crank fuse if it is could be starter drawing to many amps try new starter

Is anything plugged into the lighter? If so take it out. If it still blows, check inside the plug, if it looks ok, disconnect the wires to the lighter socket, the socket may be shorted.

It is the fuel heater, All you have to do is unplug it.

Check fuses.Then check the glow plug relay 7.3l has relay mounted on front top of engine looks like a starter solenoid.... Switch truck ignition on to the normal preheat position, u can use insulated screwdriver or the like to touch the 2 larger bolts (of the four total) at the same time in order to make them 'connect'... hold this for about 30 seconds.. to activate glow plugs... if engine starts, sounds like u need GP relay. If truck doesnt start you may have 'under valve cover' wiring problem. DO NOT use ether to start your truck it will cause damage to your engine.

Check your solenoid by jumping it with an insulated screwdriver,(connect the 2 and hold for 30 sec.s), (it will spark atiny bit if u wiggle it around,) make sure the truck ignition is in the ON position FIRST , If this activates the glow plug system then the relay itself is the problem. Usually, it seems to me, the problem is the relay (or solenoid),the glow plug controller or the under valve cover wiring. The under valve cover wiring comes attached to your new valve cover gaskets.

Do you have access to an amp clamp to check amps going to the glow plugs. Remove the oil temp sender which is on the back of the hi psi oil pump reservior 2 wires. This will make the relay run longer. Then hook clamp over the 2 brown wires on glowplug relay should have about 175 amps if its working right. I have also seen the fuel heater inside the fuel filter housing go bad as well. Might check all the fuses as well incase the fuel heater fuse is blown.