Glow Plugs 101 Tutorial
Senior User
Joined: May 2011
Posts: 497
Likes: 0
From: Morgantown, WV
yes thats normal.you want to start the engine as soon as the light goes off.this way those extra clicks are done while the engine is running.this is called afterglow and helps reduce white smoke,and keeps it running smoother when cold.
there is no need to install a manual push button for the newer style unless the truck isn't worth replacing the controller due to condition,cost or if funds don't allow.
if the truck is still in decent shape and will be around for a while and you can afford to replace a failed controller,that's best.the early style wasn't worth fixing.too failure prone and would fail often in the ON position which burnt out your gp's.not a common issue with the newer system.
there is no need to install a manual push button for the newer style unless the truck isn't worth replacing the controller due to condition,cost or if funds don't allow.
if the truck is still in decent shape and will be around for a while and you can afford to replace a failed controller,that's best.the early style wasn't worth fixing.too failure prone and would fail often in the ON position which burnt out your gp's.not a common issue with the newer system.
New User
Joined: Dec 2014
Posts: 6
Likes: 0
Tried Everything...
1991 e350 7.3 idi
I started off with some bad plugs and a fast blinking relay, which resolved for less than a week after changing the plugs to autolites. And now the wts light will not come on at all.
I have replaced the glowplugs (motorcraft), controller and relay, cleaned battery terminals, and cleaned the ground for the white wire, still no wts light.
I HAVE NOTICED THAT THE IGNITION POST ON THE RELAY GETS NO VOLTAGE AT ANY POINT DURING MY DIAGNOSIS. So fed up considering selling my rig. Its been parked for over a month and I am worried about being towed away.
Read the directions for hooking up a button from the post for the white wire to the ground. Is it also possible to wire a button between the battery post and the glow plug post? I've tried hooking up glow plugs between these two and have only had results sometimes.
I started off with some bad plugs and a fast blinking relay, which resolved for less than a week after changing the plugs to autolites. And now the wts light will not come on at all.
I have replaced the glowplugs (motorcraft), controller and relay, cleaned battery terminals, and cleaned the ground for the white wire, still no wts light.
I HAVE NOTICED THAT THE IGNITION POST ON THE RELAY GETS NO VOLTAGE AT ANY POINT DURING MY DIAGNOSIS. So fed up considering selling my rig. Its been parked for over a month and I am worried about being towed away.
Read the directions for hooking up a button from the post for the white wire to the ground. Is it also possible to wire a button between the battery post and the glow plug post? I've tried hooking up glow plugs between these two and have only had results sometimes.
Fleet Owner
Joined: Jul 2006
Posts: 20,322
Likes: 789
From: Mi'kma'ki
over on the fender mounted starter solenoid are connections.at these ring terminals are little block looking things.these are fuseable links.one of these lines feed that ignition terminal.if the fuseable link burns up,of course no power to the terminal.
do you have power to the FSS? if you hear no click/test and have nopower there either,be sure to check the fuse. "K" (for 92-94 idi trucks anyway.seek your manual for fuse locations for your '91)
New User
Joined: Dec 2014
Posts: 6
Likes: 0
I do not think my 91 has a fuse for the fss, or at least it doesn't in the block by the brake pedal. If there is another fuse block hidden in the engine compartment (tight fit in this old van) it is a mystery to me.
I put my probe from the flat metal in the fss connector to ground and back to the other side of the connector and read no voltage, what does that mean assuming that I probed correctly? I hear no click.
I had replaced a fusable link, I will go back and check the connections, when it stops raining.
I put my probe from the flat metal in the fss connector to ground and back to the other side of the connector and read no voltage, what does that mean assuming that I probed correctly? I hear no click.
I had replaced a fusable link, I will go back and check the connections, when it stops raining.
Fleet Owner
Joined: Jul 2006
Posts: 20,322
Likes: 789
From: Mi'kma'ki
you'll have to search for the fuse and fuseable link locations for your '91 van (on the van itself/in the forums/google/buy a book.) whatever it takes to find this vital info,to help you restore power to the ignition terminal and the FSS.
for the 92-94 trucks,that fuse box is the power distribution box under the hood.
if you have no power at the FSS with the key in the run position,the engine will never start.not even with starting fluid.
for the 92-94 trucks,that fuse box is the power distribution box under the hood.
if you have no power at the FSS with the key in the run position,the engine will never start.not even with starting fluid.
New User
Joined: Dec 2014
Posts: 6
Likes: 0
Is it possible to run a jumper wire to it? What does this FSS do?
It would make sense for the fss to be shot, as this electrical problem began with a leaky oring at the water separator and for a couple hundred miles my motor was being bathed in diesel. Maybe I fried a bunch of electronics, urg.
It would make sense for the fss to be shot, as this electrical problem began with a leaky oring at the water separator and for a couple hundred miles my motor was being bathed in diesel. Maybe I fried a bunch of electronics, urg.
Posting Guru
Joined: Dec 2012
Posts: 1,065
Likes: 2
From: western washington
bacon if your relay is not the correct relay it will not work . a relay that is for a starter, looks very similar however the I post is connected to one of the high current lugs when the relay is tripped. the energizing circuit is to from one post, to ground. you need the proper floating ground relay. there is no connection between the two systems. you must have the correct one or it WILL NOT WORK. the controller grounds the relay to trip it. so when the key is on one large post and one small post will have voltage. the power sources for this are coming from two different places. the high current side (for gp's from Batt) and low current side, (from key).
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New User
Joined: Dec 2014
Posts: 6
Likes: 0
Definitely the right rely, it came installed atop a brand new solid state. There is no voltage coming from the ignition side (low voltage side) and I will have to check back into there being no power to the fss either. Do you know the location of a power distribution box inside the engine compartment for the e350 van? It is a retired ambulance so I will check under the seat where the dual battery switch is and some old inverter that isn't working.
Mountain Pass
Joined: May 2009
Posts: 147
Likes: 0
Ok I have an issue with the writeup. in my case I have solid back gp connectors I cant stick a tester on it unless i pop the connector off which makes it a pain to try and trouble shoot.
for clarification should I be getting 12V across the gp connector and the red battery cable while the truck is on but the gp relay has long since expired the wts time?. should I be sticking a clip over the green marked glow plug terminal instead?
It has the new style controller in the back. should there be a voltage difference on the white wire and the red battery cable or the chassis?
FORDF250HDXLT instructions for no wts lamp are confusing.
if the WTSL doesn't turn on
unplug the connector at control unit.
connect a jumper wire from the harness side to ground.
turn ignition switch ON.
if the WTSL remains OFF,replace the bulb or trace out and repair the wire.
what connector at control unit? the white wire? or what im confused.
connect a jumper from the harness side to ground... is that the glow plug terminal listed in green?
for clarification should I be getting 12V across the gp connector and the red battery cable while the truck is on but the gp relay has long since expired the wts time?. should I be sticking a clip over the green marked glow plug terminal instead?
It has the new style controller in the back. should there be a voltage difference on the white wire and the red battery cable or the chassis?
FORDF250HDXLT instructions for no wts lamp are confusing.
if the WTSL doesn't turn on
unplug the connector at control unit.
connect a jumper wire from the harness side to ground.
turn ignition switch ON.
if the WTSL remains OFF,replace the bulb or trace out and repair the wire.
what connector at control unit? the white wire? or what im confused.
connect a jumper from the harness side to ground... is that the glow plug terminal listed in green?
Fleet Owner
Joined: Jul 2006
Posts: 20,322
Likes: 789
From: Mi'kma'ki
"should I be sticking a clip over the green marked glow plug terminal instead?"
reword this part please?
It has the new style controller in the back. should there be a voltage difference on the white wire and the red battery cable or the chassis?
FORDF250HDXLT instructions for no wts lamp are confusing.
if the WTSL doesn't turn on
unplug the connector at control unit.
connect a jumper wire from the harness side to ground.
turn ignition switch ON.
if the WTSL remains OFF,replace the bulb or trace out and repair the wire.
what connector at control unit? the white wire? or what im confused.
connect a jumper from the harness side to ground... is that the glow plug terminal listed in green?
FORDF250HDXLT instructions for no wts lamp are confusing.
if the WTSL doesn't turn on
unplug the connector at control unit.
connect a jumper wire from the harness side to ground.
turn ignition switch ON.
if the WTSL remains OFF,replace the bulb or trace out and repair the wire.
what connector at control unit? the white wire? or what im confused.
connect a jumper from the harness side to ground... is that the glow plug terminal listed in green?
what seems to be the problem with your wait to start light? whats it doing exactly? anything at all? quickly flashing or remaining on? or?
Mountain Pass
Joined: May 2009
Posts: 147
Likes: 0
Green marked gp terminal mentioned previously was referring to this pic. which now that i think bout it means that metal piece that is z shaped that you mention to clip to is part of the green terminal.
the first question was referring to below. I dont have a light or extra hands so its a bit tricky to read the volt meter while half way out the cab. I could slide the leads under the hood an connect to the gp terminal and a chassis ground so i could read from inside the cab when it gets turned on.
Thread Starter
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Logistics Pro
Joined: Apr 2005
Posts: 4,221
Likes: 17
Ah, that picture is showing voltage at the glow plugs, you don't have to disconnect for that as long as you can get contact from the probe to the wire or the connector.
The way it sounded originally was you were trying to test the glow plug itself witch is done with the system off and the GP disconnected and using a test light or an ohm meeter.
AFAIK there is no glow plug fuse, but there is a fuseable link in line to that battery terminal. Also the block connecting plug is a known fail point.
Yes, you're correct, there should be voltage there at all times.
The way it sounded originally was you were trying to test the glow plug itself witch is done with the system off and the GP disconnected and using a test light or an ohm meeter.
AFAIK there is no glow plug fuse, but there is a fuseable link in line to that battery terminal. Also the block connecting plug is a known fail point.
Yes, you're correct, there should be voltage there at all times.
Postmaster
Joined: Oct 2005
Posts: 3,724
Likes: 0
From: Clarksburg WV
Just thought I'd chime in with a couple things I learned while working on my truck.
#1- If you have the new-style glow plugs with the "bullet" connectors and something happens to your original connector (I had two GP's short out and torch the connectors to the harness), a 10-12 gauge spade terminal will work in a pinch. The end of the connector that the wire is supposed to go into will fit perfectly onto the GP if you expand it slightly. So, you can crimp a female spade connector onto your lead and use the male connector to attach to the glow plug.
#2- When trying to remove the glow plugs, especially on a turbo engine the back two are really difficult to reach. Once they're loose (turnable by hand), if you push a length of 1/4" rubber hose over the GP you can turn it out like this, then use the same method to get the new one started into the hole.
#1- If you have the new-style glow plugs with the "bullet" connectors and something happens to your original connector (I had two GP's short out and torch the connectors to the harness), a 10-12 gauge spade terminal will work in a pinch. The end of the connector that the wire is supposed to go into will fit perfectly onto the GP if you expand it slightly. So, you can crimp a female spade connector onto your lead and use the male connector to attach to the glow plug.
#2- When trying to remove the glow plugs, especially on a turbo engine the back two are really difficult to reach. Once they're loose (turnable by hand), if you push a length of 1/4" rubber hose over the GP you can turn it out like this, then use the same method to get the new one started into the hole.