how to test glow plugs & generator on 75 ford 4500

[ibuildcars4u]

have a 75 ford backhoe that the glow plugs and generator are not working, bought a brand new $250 battery so i know it is not that. not sure if you can test the generator by the following procedure or not : start the tractor, disconnect the pos cable, if it stalls the generator is bad, if it stays running its good, would this method work? and i have no idea how to check the glow plugs, but it will not start when it gets cold. dont know if you can put a metor on the glow plug wire and look for a reading when the ign. is turned on. i have not payed for much in my life to have someone fix something, so i would like to look at it myself to try and fix it, any suggestions? thanks for your time.

 

[SnowRidge]

When you say generator, are you referring to an alternator? You should never disconnect the battery on a running engine equipped with an alternator. The resulting voltage spikes may destroy the alternator diodes.

Glow plugs seldom go bad. If there is a glow plug problem, it is usually dirty, loose, or corroded connections. I would check the wiring first. A cold glow plug's resistance is so low that it generally will read as if it is shorted. The reading must be taken with the wire disconnected. If it reads open, the glow plug is bad.

 

[Paddy]

If you have glow plugs, you have a diesel. Battery disconected would have not have an affect with out ignition.

patrick

 

[ibuildcars4u]

yes instead of a alternator, it is a generator, basicly same as alt, it charges the battery,i know on older cars to test the alternator, you disconnect the pos cable after you start it and if the motor dies, the alt is bad, if it runs, the car is running off of the alt. therefor it is good, but i dont know if it is the same for a generator, thanks for your time

 

[Inspector507]

Alternator/Generator doesn't matter. If it's a diesel it requires no electric to run once it's started. So disconnecting the cable will have no effect, except for maybe on a fuel solenoid.

 

[sightsear]

to see if a generator or alternator is working, they can be initially tested at the battery with a meter. Set the meter at 20volts DC (or higher than 12), red lead to bat. pos, black lead to bat neg. With vehicle off and meter connected to bat posts, you should read 12volts, when you hit the key voltage reading should drop, and when it starts, voltage reading should immediately be higher than before starting, usually around 14volts. If it's still 12 (or lesss), no gen. or alt. output is coming to the battery. Then it's figure out why.

A battery on a charger (with the caps removed) will soon bubble a bit in all good cells, If one doesn't bubble, it's a dead cell and the bat is bad and will not do it's thing.

If all cells bubble it should be able to take and hold a charge just fine. The bubbles are from a reaction to the cell plates inside each cell taking a charge. No bubbles, no reaction, no charge.

the glow plug? I don't know a thing about those guys.

 

[BobReeves]

If you don't have one already, go to Radio Shack and buy a cheap digital VOM meter and a package of clip leads.

Disconect the regulator, temporary clip the two terminals of the generator together, start the tractor and measure the voltage across the battery. If it increases with engine speed the generator is good. DO NOT allow it to get over 20 volts it will fry the battery. If generator checks out replace the regulator.

You should be able to measure some resistance across a good glow plug, my 3000 doesn't have glow plucs so can't tell you what it should be.

 

[RickB]

Disconnecting the regulator on a 4500 will disconnect the generator from the battery making your test invalid. THe test can be performed in the same fashion by reading the voltage at the generator. Test the thermostart by activating it for 20-30 seconds and see if it gets hot. Check for power at the units' electrical terminal when activated.

 

[Soundguy]

<font color="blue"> Disconect the regulator, temporary clip the two terminals of the generator together, start the tractor and measure the voltage across the battery. If it increases with engine speed the generator is good </font>

<font color="black"> Not </font> sure what you are doing Bob.. but that ain't the way to check a B circuit genny... by jumpering the 2 barrel terminals.. or ( later thousand series lucas jobs had 2 rear blade terminals and a stud. )

A B circuit genny was used on the NAA & hundred and thousand series tractors.. say.. 1953-1975 at least. On many thousand series they were 'lucas' ( prince of darkness ) products. On a b-circuit genny, you must power the field connection, as the field coil is internally grounded. Thus applying battery power to the field terminal while the genny is spinning will make charge power at the armature terminal. This test is called full fielding. Incedentally, this is also a method used to polarize this setup. To the original poster.. Jumper battery and field terminals before you start.. unjumper.. then start.. see if your genny now magically works.. if not. jumper while running and see if it starts working. Dash lamp should go out on units so equipped.. or if it has a ammeter inline it will indicate charge... and battery voltage will rise.

On the older A-circuit gennies used on the 8n, you could jumper the 2 barrel terminals the field and the ground, and do a full field charge test.. but first.. you should try to polarze by jumpering battery and armature terminals, with the tractor not running.. then unjumper and start. And then full field by jumpering ground and field, due to the fact that the field terminal is internall y hot by being tied tot he armature, and thus needing field ground from the VR.

As a note... the primary non charging issues are from the need to repolarize. Then from there you see VR problems.. and lastly genny issues, like brushes. NAA and hundred series, and early thousand series VR are about 25-40$ depending on quality and where you get them.. they are generally bullet proof, easy to hook up, and are charge regulated at about 25a. The later lucas jobs are quite a bit more fragile.. have frequent contact problems, and are about 25$, and a bit more involved.. usually due to difficult placement, to replace. They are generally charge regulated to about 20a. I've had good luck retrofitting a NAA/hundred/early thousand series regulator to a later thousand series lucas genny. The only thing you have to watch out about is that in the case of a dead or severly discharged battery, or a high power load from lamps.. etc.. thatt he older VR will try to make the genny deliver 25a.. when the genny should not be asked for more than 20a.. so watch your electrical loads.

Soundguy