No wait to start light when hot

Scotchneat

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Hi all
This truck 92 f250 4x4 zf5 for a almost year has always started almost immediately, light goes out turn key it starts
new harness and plugs 6 months ago
3 times now after a short trip with the trailer and the engine definitely up to temp, on trying to restart the wait to start light will not come on. Engine cranks and cranks and eventually starts. I get home, the next day I go to dig into what's going on jump in, turn key, wait light comes on and truck starts
Anybody run into this? Best guess on where to look
The ignition switch is worn but I couldn't manipulate it into getting the light to come on
 

Minuteman96

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That sounds like a something to do with the glow plug controller. I know on automatic systems (I have a manual press button system which I would recommend to avoid issues like these) the controller is connected to a sensor and the controller dictates how long to kick on the glow plugs based off of engine temp. Because your wait to start light isn’t coming on, and it takes forever to start, that sounds like the controller isn’t receiving a signal from the sensor or isn’t taking that signal and applying it to the glow plugs the way it should thus it taking longer to start. You might have a short in a wire or something too effecting the whole process and also I’m pretty sure that sensor I referenced is in the back of the block now that I think of it.
 

Ferdy Mint

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We run manual glow plug control. No sense heating up the GPs here in Texas, 95% of the days it's not cold enough. Just pull the ground wire off the GPR and run it to a momentary switch on the dash somewhere.
 

Nero

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I had a similar problem with my truck, the Mai power feed wires from the start solenoid on the fender, where they go through either the rectangular black connector or the newer gray connector, the wires had melted the housing and caused a bad connection. Butt spliced the black/orange wires straight to the yellow wires bypassing that connector cured it. No need to swap the whole system to a push button.
 

Slicknik

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Sounds like the controller is starting to go, CDD sells a nice manual glow plug switch kit for this type of headache

Also once your truck is up to operating temperature it shouldn’t need glow plugs to start up again,
 

Jesus Freak

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I had a similar problem with my truck, the Mai power feed wires from the start solenoid on the fender, where they go through either the rectangular black connector or the newer gray connector, the wires had melted the housing and caused a bad connection. Butt spliced the black/orange wires straight to the yellow wires bypassing that connector cured it. No need to swap the whole system to a push button.
I'm with Nero, it's nice when our old stuff more or less works like it's supposed to.
 

Prospect62

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Not sure if it's relevant but my glow plug light doesn't come on when the truck is warm either, and I was pretty sure they were designed that way. Granted mine is older than yours but it's the same principal. When the engine is above a certain temp, glow plugs aren't needed or called for by the system. At least that's the way I understood it, so I never questioned why my light doesn't come on when warm. Truck starts fine. When cold, the system operates as it should as well.

I've read that warm/hot start issues can be an indicator of a failing injection pump. Not sure if that's your issue but I can say that my truck starts fine when warm with zero glow pluggage. I think most diesels do the same.
 

Black dawg

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Anything over about 120 degrees coolant temp, and these engines start easily without glow plugs.
 

HKT Firearms

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My 94 idi does that when a glow plug is not working or when the glow plug went bad. Mine always lights for about 7-8 seconds when everything is working right.
My 95 powerstroke is controlled by temperature.
Word of advice is to get 2 sets of autolite plugs. Guaranteed for life. When it becomes hard to start change the plugs out. You'll get it down to about 15 to 30 minutes bring the old set back and get a new set. Always keep a new set on hand especially in cold weather. I'm in a very warm climate here in Florida and I do mine once every year to two years.
The power stroke will go a whole lot longer time without having to do them which is good because they're a pain in the ass.
Manual momentary button is the way to go to make them last longer and make them more reliable.
 

Scotchneat

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Hey all an update and more mystery
I changed out the glow plug controller and short trips around town worked great
A 2 hour trip to state college to pick up radial arm saw and no light and no start
Suspecting the ignition switch I checked voltage at the fuel solenoid 12 vdc
Son 1 cranked off and on maybe 2 minutes nothing we. Would just hear the batteries fall off a little bit he said switch the tanks? I said why not three seconds later it's running
Stopping for refreshments same thing in reverse
I don't know much about how the tank line switch happens
If the pump is the problem (200,000 miles) why does switching tanks prime it?
Could the problem be at the tanks?
Next time will try the wet rag on the pump trick
I do understand the glow plug controller a little better and how it works
It knows the temp and adjusts the time on pre heat and after run
On a hot motor no pre heat no wait to start
It knows how many good glow plugs you have and let's you know if your short
Sorry for the long post
A little jazzed I just bought a 1990 7.3 motor and radiator
truck had 53,000 miles on it $1250
 

Cheesy

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Sounds to me like it could be your injection pump going out potentially. When mine was on the way out after I drove it for a while and shut it off it hated starting back up till eventually it had to sit for a long period of time before it would crank back up. When the motors hot on mine my wait to start light comes on for Meaby a second before shutting back off again

The tank switching thing is a little odd to me. Could be that your selector valve is going bad. I don’t know how you could test that to verify a problem there without just throwing a new one on and hope it solves your problem

I ask this. How many miles does the IP have on it. And to second that. Is it timed properly. Cause your glowplug light or controller shouldn’t have anything to do really when your truck is hot. Seems like it’s definitely a fuel issue. Now it’s just a matter of pin pointing that issue
 
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Special K

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I would check the resistance of your plugs when warm. If they are out of spec, the controller will not operate properly. As I stated in another post, I just dealt with a similar issue and my problem was fake ZD-9 glow plugs I installed. The fakes I had quickly had the resistance change when voltage applied and tricked the controller into thinking they were already warm. I would look for .5 ohms or less. Mine even at .9 made the controller short cycle. If you didn’t buy your plugs from Ford or a known reputable seller, I’d be suspect. These are an example of counterfeit OEM:
You must be registered for see images attach
 

ISPKI

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I would check the resistance of your plugs when warm. If they are out of spec, the controller will not operate properly. As I stated in another post, I just dealt with a similar issue and my problem was fake ZD-9 glow plugs I installed. The fakes I had quickly had the resistance change when voltage applied and tricked the controller into thinking they were already warm. I would look for .5 ohms or less. Mine even at .9 made the controller short cycle. If you didn’t buy your plugs from Ford or a known reputable seller, I’d be suspect. These are an example of counterfeit OEM
Those arent counterfeit OEM, those are just aftermarket plugs from an aftermarket manufacturer. ZD-9 is the part# for the plug. Lots of companies make aftermarket replacement parts and may use the same part#. The OEM is either Motorcraft or Beru. Not exactly sure which one of them actually makes the plugs, probably Beru which then rebrands under Motorcraft.

Also - unless the plugs are extremely hot, they should still light for a couple seconds. The Controller reads the resistance of the plugs in the GP harness to determine how long to light them. The colder the plugs are, the longer they light. Resistance increases with heat in an electrical circuit so, the hotter the plugs, the shorter the heat time. This is why old and/or damaged connections is so detrimental to the GP functionality. When the connection gets dirty or damaged, the controller sees an increase in resistance, thus being confused into heating for less time.

That is a major criticism of the manual push button - many people (not all) encounter short heat times and install the push buttons when they should really just be maintaining the GP system. It works very well when kept in good condition and these issues are usually a sign that something needs to be worked on or replaced.

It does take a lot of driving to get the plugs warm enough to not heat. Driving down the road a few miles with a trailer is not likely to heat soak the plugs enough to cause them to not heat at all. I have driven over 10 miles with 6000lbs on my truck and the plugs still primed for a couple seconds.
 

Special K

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Those arent counterfeit OEM, those are just aftermarket plugs from an aftermarket manufacturer. ZD-9 is the part# for the plug. Lots of companies make aftermarket replacement parts and may use the same part#. The OEM is either Motorcraft or Beru. Not exactly sure which one of them actually makes the plugs, probably Beru which then rebrands under Motorcraft.

Also - unless the plugs are extremely hot, they should still light for a couple seconds. The Controller reads the resistance of the plugs in the GP harness to determine how long to light them. The colder the plugs are, the longer they light. Resistance increases with heat in an electrical circuit so, the hotter the plugs, the shorter the heat time. This is why old and/or damaged connections is so detrimental to the GP functionality. When the connection gets dirty or damaged, the controller sees an increase in resistance, thus being confused into heating for less time.

That is a major criticism of the manual push button - many people (not all) encounter short heat times and install the push buttons when they should really just be maintaining the GP system. It works very well when kept in good condition and these issues are usually a sign that something needs to be worked on or replaced.

It does take a lot of driving to get the plugs warm enough to not heat. Driving down the road a few miles with a trailer is not likely to heat soak the plugs enough to cause them to not heat at all. I have driven over 10 miles with 6000lbs on my truck and the plugs still primed for a couple seconds.
When the plugs are sold under a Ford part number, in Ford packaging but do not come a Ford supplier, they are counterfeit. There are subtle ways to tell, but it is difficult.
 

Black dawg

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Word of advice is to get 2 sets of autolite plugs. Guaranteed for life. When it becomes hard to start change the plugs out. You'll get it down to about 15 to 30 minutes bring the old set back and get a new set.
This is REALLY bad advice........

Autolites for this application are well known to fail in a short time, and very common for them to swell and be stuck in the head.....or the whole tip falls off. Have seen this many times.
 
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