Hey guys, title says it all. My '02 7.3 PS will turn and turn when its cold out, but never fire. When I plug it in for a few hours it fires right up. I'm guessing its bad glow plugs, but a buddy of mine suggested looking into replacing the fuel heater. What do you guys think, and what else could be my problem?

 

99% of the time fuel heater probs blow fuses. I would check the Glow Plug relay first.

 

I checked all my fuses under the dash, is there a way to test the fuel heater to see if its working? Also, how do I tell if the glow plug relay is good or bad?

 

put a screwdriver across the two big terminals with the key on and then start the truck. if it fires then you need a new relay

 

My first guess is gpr, also.

If you try starting when it's cold, and it just cranks, do you see white smoke coming out?

Do as muktown suggested next time it's a cold start: jumper the glow plug relay, then try cranking.

 

Yeah, white smoke is coming out when its turning over. Sounds like glow plugs?

 

Check that relay first, its alot cheaper and easier than the Plugs

 

Probably gpr. Try jumpering the terminals on the gpr, and then crank, If it starts up then, it's probably the gpr.

Glow plugs are usually when it's tough to start, then runs rough as if it's not firing on a few cylinders, and then clears up after a few minutes. If it's the gpr, it'll be tough to start, but then should run smoothly once started.

 

If you don't want to wait till it is cold to check the gpr, measure the voltage at the relay. With the key in the start position you will battery voltage at both big post for around 90-120 seconds after to turn the ky to the start position. No voltage at the one post, if I remember right it is the one with the yellow wire, the gpr bad.

 

AC9 CHECK GLOW PLUG RELAY CIRCUIT
Check voltage between glow plug relay Circuit 38 (BK/OG) and chassis ground.
Is battery voltage present?
Yes- GO to AC10 .
No- CAUTION: Confirm resistance to ground is above 10,000 ohms before attaching to starter relay. INSTALL new relay feeder wire fusible links 299 (DB).

AC10 CHECK GLOW PLUG RELAY
Connect all glow plug connectors.
Connect glow plug control connector on side of relay.
Disconnect EOT.
Connect voltmeter between relay terminal with two brown wires and chassis ground.
Measure voltage with key off and key on while wiggling wires connected to relay (relay will remain closed for two minutes with key on).
Does voltage change from 0 to battery voltage and stay at battery voltage for approximately 2 minutes?
Yes- GO to AC11 .
No- INSTALL a new glow plug relay.

AC11 CHECK GLOW PLUGS
Note: Run these checks if starting difficulty is in cold temperatures.

Note: GO to Pinpoint Test KC for circuit diagrams.

Disconnect glow plug/injector connectors at both valve cover gaskets.
Check resistance between ground and each glow plug connector using a digital multimeter and Glow Plug Adapter 418-F221, or equivalent.
Is resistance between 0.1 and 2.0 ohms?
Yes- GO to AC12 .
No- REMOVE valve cover and INSPECT harness for opens and shorts. If harness is OK, INSTALL a new glow plug.

AC12 CHECK GLOW PLUG CONNECTORS
Check resistance between each glow plug contact in the engine harness and the two brown wires on the glow plug relay.
Is resistance between 0 and 2.0 ohms?
Yes- INSPECT inside of air filter-to-turbocharger air duct. If dirt or abrasives are present, engine may be worn. GO to the Workshop Manual for engine testing and repair procedures.
No- INSTALL a new engine wiring harness.

 

I tried jumpering the gpr and I pissed off the relay under the drivers seat panel. The relay labeled fuel injector module is continously clicking when the key is turned forward. When you touch either small post on the gpr with a test light the clicking switches to a different relay on the drivers side fender near the firewall. All small terminals on both the gpr and the intake heater relay are only getting 7.8 volts. The wait to start light is also not going off, and the truck will not start at all. I drove it to where I started to work on it this morning and there it sits. Any ideas?

 

Please help, I've only got about 15 hours til the local performance diesel place opens and my wife makes me pay too much to fix this problem.

 

Only getting 7.8 volts point to bad batterys

 

Both the batteries are at 12+ volts.

 

Is that during cranking? and was it with the batts isolated and not still conected 1 bad batt can be hidden by a good one.