[bappleman21]

I have a 1992 f 350 with the 7.3 idi. The old glow plugs on my truck burnt out so I took out the 6 volt glow plugs with 12 volt glow plugs so they will not burn out. I also took out the relay and timer and put a continuous duty sylonoid in to replace them and a switch in the dash to run the glow plugs. Once I installed all of this I tried to start it to test the glow plugs I cycled them for 45 seconds and tried to start it and it turned over but never tried to start it just kept turning over. I tried it a few more times and the same thing happened so I let it sit over night and the next day my dad tried it. He cycled them for about 30 seconds and it didnt start so he tried it one more time after cycling them again and it started. He said it started really rough like one cylinder started at a time. That is the only time it has started since. It acts like it is not getting fuel to ignite to start and I dont know why it would act like it is now. Any ideas on what to try or test to see how to start it?

 

[Snotzalot]

Low batteries.

 

[cdnsarguy]

If the old GPs were Autolite burn out is a given, if you use the Beru/motorcraft ZD9 there should be no problems. The Solid state system is the best there is..... manual operation is not advised. You probably already burned up the new GPs.

7.3 Liter Diesel Motorcraft Glow Plugs - Ford 7.3 Liter Diesel Motorcraft Glow Plug $9.99

 

[BuilderBob]

Oh Diesel Lord,
Forgive those who know NOT what they do.

2nd the idea to go back to the way it was, stock is best, don't forget the piece of stainless steel, (on top of the relay) it is very important.

 

[bappleman21]

Why would the new GP's be burnt out, this fast. My understanding is that the 12 volt are next to impossible to burn up.

 

[hotrod220257]

bob ask me why that piece is important
lets say under my dash is not color coded anymore
they may be burnt cause this is a 12v system
the relay keeps them from burning out
a 45 sec continuous burn will kill any gp it will over heat and crack or break the tip

on here there is a gp relay wireing thing to hook it up for manual burn
ah here on ziggsters page Ziggster's pagebookmark it that is like a bible that is for a 6.9 so wire colors are wrong but it still works

run hot to a relay 2 10 gauge wires and then one to each bank then 10 gauge to each gp
then you wont burn up your wires
then run a switch to the relay
thats the best way
and check the gp removal article if you want a horror story

 

[bappleman21]

what is a quick way to see if I did burn them out?

 

[6.0f250]

Either test for ohms between the glow plug terminal and an engine ground, Or use a test light between the positive battery terminal and the glow plug terminal, if it lights up more than likely it is good.

 

[BuilderBob]

bob ask me why that piece is important

The stainless steel part is what I have called the zig-zag resistor. Stainless steel has higher electrical resistance as compared to other metals.
This resistor is in series with the GP's. One side of the resistor is bolted to the relay (solenoid), the other isde goes to the GP's.
It does 2 things, it limits the total current draw, and it drops the voltage that goes to the GP's.
On paper, we can say that the batterys supplies +12 VDC, minus the voltage drop across the resistor, which is about 3VDC, that leaves about 9 VDC to the GP's. The GP's are ground or the negative side of the battery.

In real life, the batteries are pulled down due to the current draw of the GP's. When the GP relay (solenoid) is close, battery voltage is likely pulled down to about 10VDC, every truck is different due to age and condition of batteries.