7.3 idi no start
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6th Gear
Joined: Mar 2025
Posts: 6
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7.3 idi no start
Hello I have a 1989 7.3 idi. Truck ran good for awhile but cannot get it started now. Excessive smoke when cranking. Here is what I have checked so far:
glow plugs are working properly
electronic fuel pump is working
fuel in and out of the injection pump
FSS is working properly
fuel at all injectors
no loss of coolant
any help would be greatly appreciated. Thank you in advance
glow plugs are working properly
electronic fuel pump is working
fuel in and out of the injection pump
FSS is working properly
fuel at all injectors
no loss of coolant
any help would be greatly appreciated. Thank you in advance
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6th Gear
Joined: Mar 2025
Posts: 6
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Yes the batteries are good. Cranks pretty good in my opinion. Seems plenty fast enough.
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6th Gear
Joined: Mar 2025
Posts: 6
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block heater currently doesnt work.
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6th Gear
Joined: Mar 2025
Posts: 6
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It will start with spray but I would like to start it without the spray. Replaced glow plugs last year with OEM Motorcraft plugs.
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Lead Driver
Joined: Apr 2002
Posts: 5,362
Likes: 1,258
If the glow plugs are operating shouldn't need starting fluid. Some caution to only use starting fluid if glow plugs are disabled as damage can occur to the plugs.
Excessive smoke and hard to start could be due to a loss of compression. Head gasket? Are you using any oil?
Could have fried the glow plugs with ether? Check them again.
Excessive smoke and hard to start could be due to a loss of compression. Head gasket? Are you using any oil?
Could have fried the glow plugs with ether? Check them again.
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6th Gear
Joined: Mar 2025
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So I removed all the glow plugs and checked them. Reading between 1.0-1.2 ohms on all 8 plugs. Not sure what resistance reading a good plug should have. These are motorcraft ZD-9 plugs from the auto store.
Tuned
Joined: Jun 2013
Posts: 441
Likes: 61
From: Craigmont, Id
Ohms law for amps is voltage divided by resistance. So lets say you have 10 volts to the glow plug system and you divide that by your 1.0 ohms resistance that gives you ten amps of current draw. A good plug draws around 20-22 amps. All 8 plugs will draw close to 200 amps if the system is working right. So I would say you have bad plugs. Go to an auto parts store and buy a 30-0-30 amp meter and test then using that. Look for that 20 amp draw.
Thread Starter
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6th Gear
Joined: Mar 2025
Posts: 6
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Ohms law for amps is voltage divided by resistance. So lets say you have 10 volts to the glow plug system and you divide that by your 1.0 ohms resistance that gives you ten amps of current draw. A good plug draws around 20-22 amps. All 8 plugs will draw close to 200 amps if the system is working right. So I would say you have bad plugs. Go to an auto parts store and buy a 30-0-30 amp meter and test then using that. Look for that 20 amp draw.
Lead Driver
Joined: Apr 2002
Posts: 5,362
Likes: 1,258
Don't forget to ohm your test leads first. And subtract that from the reading on the plug.
I have a new Motorcraft plug in my shop I'll go out and check it later and post what I measure. I always have tested with the bulb in situ.
I have a new Motorcraft plug in my shop I'll go out and check it later and post what I measure. I always have tested with the bulb in situ.