1995 ford 7.3 litre diesel glow plugs

Are the glow plugs single or dual wire if they are twin or dual wire one wire is positive and one is negative. I will base this on twin wire
I hope it is a negative earth system as I won't bother with positive earth instructions at this stage.
Get a multi-meter that has alligator clips on the cables attach black to a good ground then with the solenoid power wire removed on the starter (so it wont crank) get someone to hold the ignition switch in the on position, then test each pair of wires one will show voltage this is the positive one (mark each positive wire) now release the starter switch and change the multi-meter to ohms test the wires that did not show as active they should show good low resistance (hopefully 0) connection. now you can reinstall the glow plugs making sure positive on the glow plugs is paired with active positive wires that were marked then attach ground wires to the glow plugs.
Reattach the solenoid power wire and try starting it

Hello, Ruslan. The P138B error code usually means that the glow plug relay is faulty. I've also seen this code with faulty wiring harnesses . Hope this helps. Good luck and God bless.

Yes. I'll try to explain this. The glow plugs work by electric resistance. When they are clean and new, they work very well as there is no crud or coating on each part. The material composing each glow plug deteriorates over time something like a sparkplug.

The amount of time it takes to heat up increases as the glow plugs fail. This puts a strain on the wiring feeding the glow plug circuit.

You can test each individual glow plug using auto jumper cables and securing one end to the base and the other is briefly shorted to the top of the glow plug using battery voltage

Be careful-they melt. As you will see, some stay dark(bad) and some glow brightly(good). Or you can just put in all new glow plugs and be done with it.

fuel at fuel filter doesnt mean its getting the correct pressure to operate the injectors. do not spray starting fluid into a diesel motor, you will damage the rings, score cylinder walls, burn valve guides... etc . starting fluid is not designed for diesel engines. the only way to test the fuel system is to test it by hooking up a pressure test gauge to the service port. the next most likely issue would be a faulty glow plug relay or 1 or 2 faulty glow plugs.

first thing to check is voltage to glow plugs on the start cycle, it should be 12 volts or better, if good the do a resistance test on the glow plugs any burnt plugs will not give you a reading, they should all read about the same

test by puting a volt meter to the glow plug top and earh and check for voltage

The first thing to do is locate the owner manual.

Look for the glow plug relay MAIN FUSE location.

The glow plug portion of your van is not working.

This difficulty scale from 1 to 10 is a 9.

You will need a DVM and tool undo the cables to each glow plugs.

It's a 1 to 2 hours troubleshooting job.

I'm going to fire off a quick list

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Check / replace blown glow plug relay main fuse
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Disconnect each center nut of the glow plug wire. PLEASE CHECK ONE AT A TIME.

Read the resistance between the center of the glow plug and the metal base of the plug.

Please take good note on each glow plug resistance reading.

MAKE SURE all cables are put back and tighten properly.

Compare the resistance on all cylinders.

OPEN/high resistance is bad glow plug.

In general 3 ohm or less is OK.

You should buy one and use its value as baseline.

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Glow plug relay can be bad.

You will need the VOM and a friend to turn the key.

Check the voltage to each glow plugs. It should be 12.6-13.6 volt.

Be careful,the plugs will get HOT.

Compare the voltage on each cylinders.

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So the problem can be combination of

glow plug relay

glow plug relay main fuse

glow plugs

ignition switch is unlikely but I'm going to list it anyway.

Once again,this is a difficult and time consuming job. I will ask a friend to help out,

Good luck.

Your Glow plugs are getting weak,try plugging it in to the outlet it should have a cord by the front of the grille. the glow plugs are just to start it.

Suspect the glow plugs or timer not working proper. You could plug your truck in keep the engine warm so it starts easier. Or you could have the glow plugs tested and replaced if faulty. Your engine has 8 glowplugs and even a couple faulty glowplugs will cause problems starting. You could have injector or injection pump problems as well but harder to diagnos yourself.

Hello,
Your 94' F250 must have a 7.3 I'm sure. Is your engine a factory 7.3 powerstoke or a normally asperated diesel? The solenoid pack for the glow plugs has been a real common culprit for these Ford diesels. The following is most likely your problem.
1-bad ground or poor ground at the glow plug solenoid.
2-Defective solenoid for the glow plug circuit.
3-Defective glow plug in the circuit.

Ok to check these problems you can do the following.
Check the ground by taking a DVOM and checking the resistance between the engine or chassis ground and the mounting bolts that secure the solenoid to the engine.
Then check for a min of 11.8 volts to the solenoid input post. Then check the output voltage to I believe the brown ouput wire to the glow plugs. Check the connection furthest from the sloenoid typicly at cyl. 1 and cyl 5. This takes two pepole. Have someone else cycle the key while you check the voltage. If the voltage is good but still the solenoid is cycling off too quickly disconnect the brown output wire to the glow plugs and cycle the key again. If the problem goes away test each glow plug's resistance for a direct short to ground or the wire arness. If the problem persists I suggest replacing the solenoid.