no start
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no start
i've got a 92 7.3 and it was about 5 degrees here today and i went out to start my pickup and it wouldn't start. 
i just put a new set of gp's in it and now i am wondering if it is the gp controller.... is there anything else besides those 2 things it could be??? also if it is the controller is there a way i can test the one on there?
i just put a new set of gp's in it and now i am wondering if it is the gp controller.... is there anything else besides those 2 things it could be??? also if it is the controller is there a way i can test the one on there?
Senior User
Joined: Dec 2004
Posts: 317
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From: Mackinaw, IL
This is from PLC7.3
This is from dieselmanns Page
Glow plug circuit
Check each of the glow plug resistance from its terminal to ground with an ohmmeter--the glow plugs should be less than 2 ohms when cold. Another way to test the glow plugs is with a test light (not a LED/circuit tester). Connect the alligator clip to the positive battery terminal and touch the probe to each (unplugged) glow plug terminal. The test lamp will light brightly if the glow plug is good.
Even one open glow plug can shorten the controller on time sufficiently to affect starting.
Next connect the glow plug harness and check for voltage at the relay "hot" terminal with the key off, then check for a voltage drop at the glow plug terminals (86 and earlier) or at the controller/relay "hot" terminal (87 and up) with the relay energized.
If the voltage is low or drops below 10 volts with the relay energized, check for loose connections at the glow plug relay, starter relay or engine harness connector, or bad fuse link(s). Also check for voltage at each glow plug terminal with the relay energized.
87 6.9 and/or 7.3 loss of voltage to glow plug controller:
Usually as these trucks get older, the wires from the starter relay to the glow plug controller build up resisitance--usually at the engine harness connector--and melt the terminal at the controller, the harness connector or one or both fuse links at the starter relay. The best repair I have found is to overlay a new circuit, by-passing the trouble area of the engine harness connector. You need a 6 foot long 6 gauge starter or ground cable (ring terminals at both ends) and 12 inches of 14 gauge fuse link wire and some 1/2" diameter heat shrink tubing. Cut the end off the two yellow wires at the glow plug controller and remove the double wire or single cable at the starter relay and tape back the ends. About 4 inches from one end of the 6 gauge cable, cut the cable and stip back the insulation approximatly 3/4". Cut the fuse link wire in half, strip all 4 ends. Double up the two fuse links side by side and solder them between the two pieces of cable. Insulate the solder splices with the heat shrink. Install the cable at the starter relay and glow plug controller, routing it along the original harness and secure with plastic wire ties or electricians tape.
Originally Posted by PLC7.3
93/94 year info.......other than some fuses mentioned the 7.3 system 87-94 is basically the same.
GLOW PLUG CONTROL
HOW THE CIRCUIT WORKS
The Glow Plug Control circuit applies power to the Glow Plugs, which heat the combustion chambers so that the diesel engine can be started.
Glow Plug Controller
The solid-state Glow Plug Controller, attached to the top of the engine block, controls the Glow Plug pre-glow and after-glow time. It also controls the circuit’s operation by sensing engine temperature, Glow Plug voltage and after-glow voltage
from the start/run circuit.
When the Ignition Switch is turned to START or RUN, voltage from Maxi-fuse K is applied through the Glow Plug Controller to the Wait-To-Start Indicator Lamp.
The Glow Plugs heat up in zero to fifteen seconds, depending on engine coolant temperature. After the Glow Plugs heat up, the controller cycling switch opens and turns the Wait-To-Start Indicator Lamp off. The Glow Plugs are now warm enough for the engine to be started.
At the same time the Ignition Switch is turned to RUN, voltage from Maxi-fuse K is applied to the after-glow timer (located inside the Glow Plug Controller). The after-glow timer cycles the Glow Plugs for up to two minutes, depending on engine temperature. The after-glow timer then opens. The Wait-To-Start Indicator Lamp will not light during the after-glow period.
If the Ignition Switch is turned OFF, it can be turned to ON immediately, and the Glow Plug heating cycle will start again.
Diesel Start/Run
The diesel engine uses two batteries to provide extra power for starting and Glow Plug heating. Power is applied from the batteries, through heavy gauge wires, to the Starter Solenoid (located in the Starter Motor assembly). When the Wait-To-Start Indicator goes out, the Ignition Switch can be turned to START.
With the Ignition Switch in START or RUN, voltage is supplied to the Fuel Heater, Fuel Shutoff Solenoid, and the Engine Temperature Switch through Maxi-fuses K and U.
The Fuel Heater is in the Fuel Filter/Separator. It heats the diesel fuel, melting any wax that might clog the filter. The heater has an internal thermostat to turn it on as needed at 32*F.
The Fuel Shutoff Solenoid controls the flow of fuel into the injection pump. With the Ignition Switch in START or RUN, the Solenoid is energized, and fuel is allowed to flow into the injection pump. When the Ignition Switch is turned off, the solenoid is deenergized, fuel flow stops, and the engine stops running.
The Engine Temperature Switch provides voltage to the Cold Timing Advance Solenoid and the Cold Idle Solenoid. When the engine temperature is below 112°F (44°C), the Engine Temperature Switch is closed. When the Ignition Switch is turned to START or RUN, the solenoids are energized, advancing injection pump timing and engine idle, allowing the engine to run more smoothly when cold. When the engine temperature reaches 112°F (44°C), the Engine Temperature Switch opens. This deenergizes the solenoids, returning the timing and idle to normal.
GLOW PLUG CONTROL
HOW THE CIRCUIT WORKS
The Glow Plug Control circuit applies power to the Glow Plugs, which heat the combustion chambers so that the diesel engine can be started.
Glow Plug Controller
The solid-state Glow Plug Controller, attached to the top of the engine block, controls the Glow Plug pre-glow and after-glow time. It also controls the circuit’s operation by sensing engine temperature, Glow Plug voltage and after-glow voltage
from the start/run circuit.
When the Ignition Switch is turned to START or RUN, voltage from Maxi-fuse K is applied through the Glow Plug Controller to the Wait-To-Start Indicator Lamp.
The Glow Plugs heat up in zero to fifteen seconds, depending on engine coolant temperature. After the Glow Plugs heat up, the controller cycling switch opens and turns the Wait-To-Start Indicator Lamp off. The Glow Plugs are now warm enough for the engine to be started.
At the same time the Ignition Switch is turned to RUN, voltage from Maxi-fuse K is applied to the after-glow timer (located inside the Glow Plug Controller). The after-glow timer cycles the Glow Plugs for up to two minutes, depending on engine temperature. The after-glow timer then opens. The Wait-To-Start Indicator Lamp will not light during the after-glow period.
If the Ignition Switch is turned OFF, it can be turned to ON immediately, and the Glow Plug heating cycle will start again.
Diesel Start/Run
The diesel engine uses two batteries to provide extra power for starting and Glow Plug heating. Power is applied from the batteries, through heavy gauge wires, to the Starter Solenoid (located in the Starter Motor assembly). When the Wait-To-Start Indicator goes out, the Ignition Switch can be turned to START.
With the Ignition Switch in START or RUN, voltage is supplied to the Fuel Heater, Fuel Shutoff Solenoid, and the Engine Temperature Switch through Maxi-fuses K and U.
The Fuel Heater is in the Fuel Filter/Separator. It heats the diesel fuel, melting any wax that might clog the filter. The heater has an internal thermostat to turn it on as needed at 32*F.
The Fuel Shutoff Solenoid controls the flow of fuel into the injection pump. With the Ignition Switch in START or RUN, the Solenoid is energized, and fuel is allowed to flow into the injection pump. When the Ignition Switch is turned off, the solenoid is deenergized, fuel flow stops, and the engine stops running.
The Engine Temperature Switch provides voltage to the Cold Timing Advance Solenoid and the Cold Idle Solenoid. When the engine temperature is below 112°F (44°C), the Engine Temperature Switch is closed. When the Ignition Switch is turned to START or RUN, the solenoids are energized, advancing injection pump timing and engine idle, allowing the engine to run more smoothly when cold. When the engine temperature reaches 112°F (44°C), the Engine Temperature Switch opens. This deenergizes the solenoids, returning the timing and idle to normal.
Glow plug circuit
Check each of the glow plug resistance from its terminal to ground with an ohmmeter--the glow plugs should be less than 2 ohms when cold. Another way to test the glow plugs is with a test light (not a LED/circuit tester). Connect the alligator clip to the positive battery terminal and touch the probe to each (unplugged) glow plug terminal. The test lamp will light brightly if the glow plug is good.
Even one open glow plug can shorten the controller on time sufficiently to affect starting.
Next connect the glow plug harness and check for voltage at the relay "hot" terminal with the key off, then check for a voltage drop at the glow plug terminals (86 and earlier) or at the controller/relay "hot" terminal (87 and up) with the relay energized.
If the voltage is low or drops below 10 volts with the relay energized, check for loose connections at the glow plug relay, starter relay or engine harness connector, or bad fuse link(s). Also check for voltage at each glow plug terminal with the relay energized.
87 6.9 and/or 7.3 loss of voltage to glow plug controller:
Usually as these trucks get older, the wires from the starter relay to the glow plug controller build up resisitance--usually at the engine harness connector--and melt the terminal at the controller, the harness connector or one or both fuse links at the starter relay. The best repair I have found is to overlay a new circuit, by-passing the trouble area of the engine harness connector. You need a 6 foot long 6 gauge starter or ground cable (ring terminals at both ends) and 12 inches of 14 gauge fuse link wire and some 1/2" diameter heat shrink tubing. Cut the end off the two yellow wires at the glow plug controller and remove the double wire or single cable at the starter relay and tape back the ends. About 4 inches from one end of the 6 gauge cable, cut the cable and stip back the insulation approximatly 3/4". Cut the fuse link wire in half, strip all 4 ends. Double up the two fuse links side by side and solder them between the two pieces of cable. Insulate the solder splices with the heat shrink. Install the cable at the starter relay and glow plug controller, routing it along the original harness and secure with plastic wire ties or electricians tape.
Last edited by bigblu78; Jan 22, 2008 at 07:42 AM.
Elder User
Joined: Feb 2007
Posts: 549
Likes: 1
From: Mississippi
you didn't mention whether or not there's a block heater. if you've got one, use it! it's the best thing since sliced bread to make a diesel crank easier and run smoother quicker on cold days. if you don't like the idea of leaving it plugged up all night( i think they're 1,500 watts) you can get a heavy duty timer and have it cycle on for a couple hours before starting. even in the heart of the south, it's lot easier to get the beast going when the block is warm.
speedrdr
speedrdr
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From: Virginia
Originally Posted by prestroke diesel
i've got a 92 7.3 and it was about 5 degrees here today and i went out to start my pickup and it wouldn't start. i just put a new set of gp's in it and now i am wondering if it is the gp controller.... is there anything else besides those 2 things it could be??? also if it is the controller is there a way i can test the one on there?
i just put a new set of gp's in it and now i am wondering if it is the gp controller.... is there anything else besides those 2 things it could be??? also if it is the controller is there a way i can test the one on there?
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first off yes it does have a blck heater but i am at college so there aren't many close enough to where i park to plug it in... and ill check and see if it puffs smoke today. it was dark when i was trying to start it last night.
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Junior User
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also i know that the fuel is not gelled in the lines. it did this same thing to me last week and i thought my fuel was frozen so it has plenty anti gel in it now....
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Junior User
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I would also try plugging your truck in .I have an 86 F250 6.9 with 250,000 mi and plugging in makes all the difference.fires right up.battery size and condition makes big difference too.I have 2 napa legend 75 batterys with 850 CCA at 0 degrees.if she dont turn over fast it starts alot harder.jmo
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mine starts way better plugged in to but if i don't have a plug in then that presents a problem..... and at 200 bucks
i wonder if there is a way to test my old controller rather then go buy a new one....
i wonder if there is a way to test my old controller rather then go buy a new one....
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