Hi, First I'd like to thank many on here for the time they dedicate toward helping others with their vehicle issues. I bought my first Ford f250 6.9 last fall. My last Chevy went and in a bind purchased a Ford... it was built tough! Thanks to all the help and advice I received on this site I made the 850 mile trip to North Carolina Where I turned around and resold the 85 6.9 for double what I purchased it for. The 85 was not worth getting too deep into it out of the fact it had serious rust issues. I used that money and Purchased a 1987 f250 with 6.9 and 113,000 miles. No Rust at all!!!


I am working no my present set of problems... Most times I find the answers to the problems by searching thru old posts. On this one I've had no luck after several days of reading.


The prior owner replaced glow plugs with Autolite I will change them out soon to Motorcraft. I turn my key on and the glow plugs heat up, after several seconds they go out.. I hear the clicking, I turn the key and it starts right up and drives fine. I Stop after 15 min and enter store 15 min later I turn key and glow plugs on and starts. I drive 30 min turn off Key and when back on the Glow plugs cycle? Restart with no issues. After 45+-minute drive the glow plugs will finally not cycle on. It seems I am driving for quite some time before the glow plugs decide to not cycle on? Is this a temp sensor going or a thermostat not operating correctly?? Also there is no consistency to this occurrence? Sometimes longer or shorter amount of time. This happened all during warm weather with some variation to the amount of time to took to seem as if warmed up enough to not cycle.


Also: and possibly related to the same... After I have finally warmed it all up and glow plugs no longer cycle on. I can start up instantly just moments after turning off engine. If I return after 10 min and glow plugs do not cycle on Its very difficult to start. ... cranking and cranking and pressing/ pumping for fuel. Finally starts rough and lots of smoke... clears up after a few and then drives/runs fine. ??


Together: I start when cold/ glow plugs cycled, it starts and runs fine, a small amount of blue/grey smoke... clears in seconds. After Warm: (longer than seems normal to warm) Glow plugs don't cycle, I have a hard rough start .. lots of smoke but clears and runs smooth after a few longer than norm. I'm consistently a good smooth fast start provided glow plugs cycle on ??

 

Congrats on the purchase!

When the engine is up to temp the glow plugs won't cycle. They're not needed on a warmed up engine.

Hard start on a warm engine usually indicates a dying injection pump. Next time it does it pour some water on the IP to cool it off. If the truck then starts right up then a tired IP is confirmed.

 

****Lukewarm water NOT COLD WATER!!!

 

Thanks! Let me add this; My engine power seemed sluggish. I did a purge by filling new fuel filter with 3/4 seafoam 1/4 fuel. Ran 40 seconds. I let sit over night. Started next morning and ran it hard. My engine seems much better. Except since then it seems to have the symptom of hard start when warm. I have read of the water on the IP. My issue does not seem the same as those others posted. It will start while still hot... it just takes a more cranking and working it. I'm just used to it always starting instantly with just turning my key with no pump or press of my pedal. The Purge Seemed a Good idea??


Getting back to my other Question. My 85 after 5-10 min was plenty warm and the glow plugs never came on again, unless it sat for seems 45 - 60+ min before starting again. Why is it taking so long for my 87 to warm up? What is normal when its 70 - 80 deg. outside? Or is it warmed up and not sensing it?? Could that be a Thermostat stuck open? Could that be some sensor not telling the glow plugs to cycle? I'm fairly certain my inside temp reading shows it as hot! I believe the glow plugs Should stop cycling after something like 180 deg.

 

My understanding is that on the 87+ 7.3s, the controller decides when to cycle; it does not use the temperature sensor. It exclusively uses the resistance of the glow plugs to determine the temperature. It also uses this resistance on each cycle. This is why it is important to keep all connections in good condition(more resistance = controller thinks the GPs are hotter = less GP time), and have all working glow plugs(resistors in parallel = lower resistance, so when one becomes "open", you have a higher resistance and the controller cycles for a shorter time).

 

Hi Macrobb, So what tells the Glow plugs not to come on at all? I thought, as with the 85 that the heat of motor or coolant told it not to cycle the glow plugs. So, is it the warmth surrounding the glow plug itself? From what I posted, does what is happening with my 87 seem normal to you; or is there something faulty? I understand its a different system from my 85 so I'm not sure on what should be correct. If it is in fact not correct and the glow plug itself signals when to go on via the Controller, what causes the problems I seem to have? ( Start engine on, turn Off, Start again off again driving around making stops... vehicle plenty warm and it still cycles on the glow plugs long after it seems it should. Finally, after some time Glow plugs will not go on and will not come on again until after a very long period of time.) My vehicle starts up great from the normal cycle of the glow plugs. The inside of engine compartments looks like a 5 year old vehicle... very clean, all stock, wires all wrapped, all connections tight... etc. ( As with the other issue; it is during this period of time that engine is warmed/hot that I'm having a fairly hard time starting. It was easier... but now suddenly gotten more difficult. but, it will start up without having to cool down.)

 

I suspect your controller is working correctly.

Try this:
Make sure to pour the water on the steel "head" at the back of the IP, where all the lines come out, not the aluminum front of it.

Let us know what happens.