OK here is what we have.

93 f350 7.3

Engine cranks and no start.

No wait to start light. No power on ignition post of GPR. Checked fuses and all are ok.

If i jump power to the ignition post on the GPR it will start fine. When I remove the jumper the truck dies.

 

GPR is at the rear of the engine, FSS is towards the front on the injection pump. Your scenario sounds like you may have them confused.

 

I believe that circuit also supplies power to the FSS (fuel shut-off solenoid) on the injection pump, which explains why it dies when you take the jumper off.

When you say you checked all the fuses, did you include the engine compartment fuse box?
Fuse K in that box would do it...

 

I am for sure looking at the GPR.

Yes i did look at all the fuses even the ones in the engine compartment. All good.

There are two red/lt grn wires on the ignition post. one goes to the fuel bowl heater and the other I traced all the way back to the connector near the fuse box. still no voltage there either.

 

I am betting you are going to have a connector that has over heated and lost connection, on the older ones it would be the famous gray one with the big yellow wire, but yours is different and if I remember right, there is a wire connection somewhere in the vicinity of the drivers side battery to look at. It is possible that it is in the ignition switch too.

 

poking around with the tester and found that there is continuity between the negative battery terminal and the small ignition post on the gpr and the large terminal going to the glow plugs. If I am understanding things right there should not be continuity with the ground, correct?

 

Sure, there'd be continuity to ground, through the devices. The glow plugs, when cold, each have .5 to 1 ohm of resistance. They're hooked up in parallel, so there's nearly no resistance to ground through them. The ignition terminal on the GPR connects to ground through the coil in the GPR, through the coil in the FSS, and via the engine temp switch through the coils in the cold idle solenoid and the cold timing advance solenoid.

Pull fuse K out of the power distribution box (engine compartment fuse box) and with the key on, see if there is power to one side. If not, pull fuse 17 in the cab fuse block & see if there is power there... Power comes from the ignition switch, through fuse 17, through fuse K, and to the red/lt.gn wire...

 

if the fuel heater shorts out the truck will not run. try disconnecting the fuel heater and see if it runs.

 

that makes sense about the ground continuity.

my fuses in the distibution box are labeled with numbers not letters. number 1-4 are relays then maxi fuses then regulat fuses. which one would be K?

I tried to unplug fuel heater. still no voltage on ignition post.

thanks for all the help

 

are you checking the fuses with a test light or by eye?

fuses can look good and still be bad.

 

sure sounds like a bad fuseable link to me.
no blown fuses,no ignition power getting to the GPR,yet glows the plugs just fine when getting power via a direct jumping wire.

ground should be 1 ohm or less (but no matter really.your jumping wire to the ignition terminal making it work fine eliminates that being the issue.)


this matches my thinking right here.it's not the switch in this case though right star,because she's turning over ? (and even starting right up once he get's the plugs working via the jumper.)
i think it's pretty clear,the fuseable link is the place to start of course no matter.

still,
why does the truck stall once he removes the jumper wire from the ignition terminal on the GPR though?
hmmmm.

oh! this explains that:
so right back to the fuseable link as the prime suspect anyway.
never mind me.just thinking here......you should see all the smoke coming from my brain working too hard.it doesn't take much.

and................. now im finally up to speed with phy and tjc.i see the light!
well,one things for sure though eldad,is that you have her narrowed down to just a small section.looking forward to see where you do find power.keep us updated.
and does anyone have a diagram for this power distribution box? man,id like to have this.

 

The switch is the last place I would look, but it is possible for it to be getting juice to the starter solenoid and not to the ignition circuit.

 

There is also the possibility of a bad ignition switch, since all of the power to these circuits listed here come from it. Not the tumbler, but the one under the dash on the steering column.

 

Me thinks we done tole him tha same thing. lol

 

If you're standing at the front tire looking at the power distribution box, the bottom left fuse is A, then go up to K...