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Discussion Starter #1
New to diesel trucks so bear with me as I'm still learning...
Before posting, I read a lot of information on this and other forums to get educated on diesel trucks and issues but I have a long way to go before I truly understand what's going on.

Details: 1996 F350 7.3L, dually, stock (no mods), 173,000 miles.

Problem: Truck hard to start, runs rough when it does start and shuts off in a couple of minutes, then it won't start again till it's cold again. Fuel pressure while cranking is very low at 10 psi so suspect the pump or FPR.

This is what has been done so far:
New starter, new Ford HPOP, rebuilt IPR, new ICP (generic brand), new CPS (Motorcraft), dropped both tanks and replaced broken tank pickup tubes and cleaned tanks (re-used the diesel fuel), cleaned FPR screen, openend up IDM and no visible signs of damage like burn marks, buzz test shows injector 5 weak at first but passes all injectors the second time around, did the BB mod to FPR.

Removed the passenger valve cover and inspected connectors. They looked ok, no obvious burn marks or burned insulation but the pins did appear to have some oil (not sure if this is normal). When the truck did manage to start, I noticed that only two injectors had oil coming from the oil spouts.

I did record live data using Forscan but have no idea what I'm looking at, perhaps someone here can help me interpret it - it would not let me upload the fsl files so I just uploaded a couple of screenshots.

The thing I can tell is that the CPS is working since the engine shows nearly 200 rpm when cranking. The IPR also seems to be working but I'm not sure what the waveform should look like. Also, the IPW does not look right. I'm not sure what normal ICP, IPR and IPW signals are supposed to look like on buildup, idle and WOT.

Do these waveforms look normal or is there a red flag that goes up when you look at the data?

Any help would be greatly appreciated.
 

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Never used Forscan for the PC, but ICP should not be spiking at 3800+ PSI at idle, repeatedly. When I look at ICP with Torque or Forscan for Android, ICP stays nice and steady at idle. I would try replacing ICP sensor with the old one or a new Ford part and see if it changes.
 

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The display is reading in Milliseconds, so the pulsations may be somewhat "normal"
however , the ICP spiking high after the IPR is fully closed leads me to think the ICP sensor may be bad and the IPR valve is "sticking"
overtightening of the IPR valve can cause this or metal particles in an old valve on the magnetic core

The injectors should be outputting oil on all that are firing -- I would think that only firing on 2 cylinders would be a noticeable miss

I don't have a 7.3 to compare readings with, so no way to give comparison readings
 

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Discussion Starter #5
Never used Forscan for the PC, but ICP should not be spiking at 3800+ PSI at idle, repeatedly. When I look at ICP with Torque or Forscan for Android, ICP stays nice and steady at idle. I would try replacing ICP sensor with the old one or a new Ford part and see if it changes.
It's worth a try, the old sensor should be floating around somewhere in the glove box or a toolbox. I may also rebuild the IPR as I have the o-ring kit already.

Thanks
 

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The display is reading in Milliseconds, so the pulsations may be somewhat "normal"
however , the ICP spiking high after the IPR is fully closed leads me to think the ICP sensor may be bad and the IPR valve is "sticking"
overtightening of the IPR valve can cause this or metal particles in an old valve on the magnetic core

The injectors should be outputting oil on all that are firing -- I would think that only firing on 2 cylinders would be a noticeable miss

I don't have a 7.3 to compare readings with, so no way to give comparison readings
I have not touched the IPR valve. I've assumed that the mechanic who changed out the HPOP would have also rebuilt/replaced the IPR but that is probably a bad assumption. This is why I wanted another pair of eyes to look at the IPC signals to see if they were normal. I agree that they are spiking much too high. I do have an IPR o-ring kit so I'll have a go at it this weekend and see if that helps.

Thanks
 

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It's worth a try, the old sensor should be floating around somewhere in the glove box or a toolbox. I may also rebuild the IPR as I have the o-ring kit already.

Thanks
I have not touched the IPR valve. I've assumed that the mechanic who changed out the HPOP would have also rebuilt/replaced the IPR but that is probably a bad assumption. This is why I wanted another pair of eyes to look at the IPC signals to see if they were normal. I agree that they are spiking much too high. I do have an IPR o-ring kit so I'll have a go at it this weekend and see if that helps.

Thanks
Try one or the other first so you can determine what failed :)
 

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Caution on overtightening the valve -- 17-20 foot pounds

Just because it takes a large socket to fit, some think it needs to be he-man tight
this can cause the valve to bind up
 

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Discussion Starter #9
Caution on overtightening the valve -- 17-20 foot pounds

Just because it takes a large socket to fit, some think it needs to be he-man tight
this can cause the valve to bind up

Just because it takes a large socket to fit, some think it needs to be he-man tight
this can cause the valve to bind up[/quote]

UPDATE:

Decided to check the compression before mucking with the IPR.

This numbers are on a cold engine since I have not been able to start it to warm it. Had trouble threading the hose into cylinder 7 so I saved that one for last. Here are the numbers:
1 - 380 psi, 3 - 300 psi, 5 - 320 psi, 7 - ?
2 - 350 psi, 4 - 340 psi, 6 - 260 psi, 8 - 310 psi

After finally getting the hose to thread into number 7, I got a reading of Zero.
It would appear that the piston rings are worn or cracked, or the valves are stuck open, or something else but a reading of zero can's be good.

I double and tripled checked the pressure and still got zero on #7. I checked that the rocker arms and springs were moving on #7 while cranking and they were. Is there something else I can try while I have the covers off?

Can a badly leaking injector lead to zero compression?

Thoughts?
 

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Soo, compression gets out of a cylinder in only a few ways besides normal
- hole in the piston / broken rings / scored cylinder -- there will be puffing from the crankcase vent / filler cap
- bad intake valve -- should hear a sucking/blowing sound in the intake when cranking
- bad exhaust valve -- should hear a sucking/blowing sound in the exhaust

380-410 psi is what your looking for -- a few of your readings are off quite a bit -- I don't like to see more than 50psi total spread on the readings
- the compression gauge has to seal to get a good reading -- and should be read at the third and sixth compression -- most of the pressure should be obtained by the third compression
 

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Discussion Starter #11
Soo, compression gets out of a cylinder in only a few ways besides normal
- hole in the piston / broken rings / scored cylinder -- there will be puffing from the crankcase vent / filler cap
- bad intake valve -- should hear a sucking/blowing sound in the intake when cranking
- bad exhaust valve -- should hear a sucking/blowing sound in the exhaust

380-410 psi is what your looking for -- a few of your readings are off quite a bit -- I don't like to see more than 50psi total spread on the readings
- the compression gauge has to seal to get a good reading -- and should be read at the third and sixth compression -- most of the pressure should be obtained by the third compression
Didn't keep track of the number of compression strokes, but instead watched the needle on the gauge and stopped cranking after the needle stopped rising with additional compression strokes. When #7 registered zero my first thought was that the gauge had stopped working so I hooked it up to #5 and again measured around 300 psi - so it wasn't the gauge.

The rocker arms and springs on #7 look "normal," as in not bent or cracked. Is it possible to confirm valve damage just from looking under the valve covers? Probably not - as in a burnt valve. If I get the truck running again, I'll try to listen for the various sounds as you suggested. I seem to recall that when the truck was running previously, I did notice that the exhaust pulsed and that the truck blew white smoke until it warmed up.

Just had a thought... is it possible to look inside the cylinder using a scope by removing an injector?

Given the large spread in the cylinder readings I take it the engine is worn and would need to be rebuilt or replaced.
 

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are you gaining oil? if the compression is that bad on #7, there will probs be fuel leak by..

if you have a small enough camera you can stick it in through the glow plug or injector hole.
 

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Camera would need to be pretty small and be able to look back onto itself if used thru the injector hole -- if thru the glow plug then maybe -- problem is that the view is angled wrong

You can blow air into the compression tester adapter, unless it has the check valve -- in that case you would need to use a different adapter or a tip on the blow gun that would seal

Blow in number 7 and see where the air comes out -- removing the tire and inner fender liner, makes getting to the glow plugs much easier

PS: need to turn the engine so the valves are closed
 

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Discussion Starter #14
are you gaining oil? if the compression is that bad on #7, there will probs be fuel leak by..

if you have a small enough camera you can stick it in through the glow plug or injector hole.
The oil does smell of diesel, which means that some fuel is slipping past the ring(s). I'll keep an eye on it, but I'm beginning to think the engine is proably toast especially with such poor compression numbers, not to mention zero on #7.

Thanks
 

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Camera would need to be pretty small and be able to look back onto itself if used thru the injector hole -- if thru the glow plug then maybe -- problem is that the view is angled wrong

You can blow air into the compression tester adapter, unless it has the check valve -- in that case you would need to use a different adapter or a tip on the blow gun that would seal

Blow in number 7 and see where the air comes out -- removing the tire and inner fender liner, makes getting to the glow plugs much easier

PS: need to turn the engine so the valves are closed
Hydro,
I don't have a camera but even if I did have one small enough it sounds like it would be a challenge anyhow. The hose and adapters I'm using do not have a check valve, in fact, the free end has a quick connect fitting that will come in handy to connect to the air source. I'll put the cylinder at TDC and fill it with air and see what happens.

Thanks
 

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Without the check valve in the tip of the adapter, the compression readings will be lower, because the air in the hose will be recompressed each stroke

however the balance between the cylinder readings should be consistent

So, yeah ..sounds like the engine is coming out of the truck, based on your numbers

Question is ...what caused it to go downhill so quickly?
 

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Discussion Starter #17
Without the check valve in the tip of the adapter, the compression readings will be lower, because the air in the hose will be recompressed each stroke

however the balance between the cylinder readings should be consistent

So, yeah ..sounds like the engine is coming out of the truck, based on your numbers

Question is ...what caused it to go downhill so quickly?
Very good question!

There is actually much more to the story than I've let on. In fact, there is a separate thread on the Ford Truck forum that goes into much more detail. I wasn't getting much help there with interpreting the Forscan log data so I started a separate thread here and kept it more focused.

If you have the time and inclination, you may want to read it as it explains the reasons for why the truck ended up in this sad state.

long-saga-truck-starts-runs-rough-then-stops-and-hard-to-re-start-till-cold-10-psi-pressure
 

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After reading thru the thread on FTE, I can see you are chasing after a magic bullet to fix an abused engine

Overheating, running out of oil, and whatever other abuses that have been done

Scrap the truck, or repair/replace the engine -- at this point any further troubleshooting is a waste of time and money

You left a lot of the history information out in this thread -- overheating and no oil should be at the top of the list

Good Luck on your journey
 

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After reading thru the thread on FTE, I can see you are chasing after a magic bullet to fix an abused engine

Overheating, running out of oil, and whatever other abuses that have been done

Scrap the truck, or repair/replace the engine -- at this point any further troubleshooting is a waste of time and money

You left a lot of the history information out in this thread -- overheating and no oil should be at the top of the list

Good Luck on your journey
In my attempt at brevity, I did leave out critical information - lesson learned.

Thanks for your time and insightful comments.

Cheers
 

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  1. Camera would need to be pretty small and be able to look back onto itself if used thru the injector hole -- if thru the glow plug then maybe -- problem is that the view is angled wrong

    You can blow air into the compression tester adapter, unless it has the check valve -- in that case you would need to use a different adapter or a tip on the blow gun that would seal

    Blow in number 7 and see where the air comes out -- removing the tire and inner fender liner, makes getting to the glow plugs much easier

    PS: need to turn the engine so the valves are closed
Not sure what engine you're working on but the glow plugs are under the valve cover on a 7.3 and toward the valley, sounds like you're working on a 6.0 as they are outside the engine by the exhaust manifold.
 
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