Slow crank after possible overheat

greenskeeper

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Even with that low compression (if accurate) you would still be seeing white smoke out the tailpipe while cranking if everything else is working correctly.

head gasket failure is very rare on the 7.3PSD
 

Luke_IDI

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After an improved compression test, numbers are up around 300 psi. Not great, but should be able to fire I imagine. The search continues. Going to start evaluating the fuel system for air.
 

greenskeeper

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After an improved compression test, numbers are up around 300 psi. Not great, but should be able to fire I imagine. The search continues. Going to start evaluating the fuel system for air.

Did you ever confirm oil coming from the injector spouts while cranking? Without oil there is no point in looking any further until that is corrected
 

Luke_IDI

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Did you ever confirm oil coming from the injector spouts while cranking? Without oil there is no point in looking any further until that is corrected
I have not but that is first on my list of things to look at before looking at fuel supply further. The video you posted of where the oil comes out was very helpful. If I do not have oil at the injectors, given that I have good ICP and a good pulse from the IDM, would that indicate failed injectors? If so, what would cause injectors to be suddenly wiped out enough to cause a no start? I am thinking back to the driver’s initial observation of sludge in the oil when drained and white smoke (probably fuel-related) everywhere when the initial loss of power and stall happened.
 
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Rdnck84_03

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I still feel that this is electrical. I kinda quickly scanned the previous page and didn't see anything except for where you got 20v. Did you ever get a high voltage pulse from the idm? Voltage should be 100v minimum.

Also where were you checking the pulse voltage at?

James
 

Luke_IDI

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I still feel that this is electrical. I kinda quickly scanned the previous page and didn't see anything except for where you got 20v. Did you ever get a high voltage pulse from the idm? Voltage should be 100v minimum.

Also where were you checking the pulse voltage at?

James
I am checking the voltage at the injector connector, with the connector disconnected from the injector, positive probe on the white wire, negative probe on the black wire.

The result I got was generally reminiscent of a +50v spike followed by -50v. The results were similar with both IDMs. Looking at my screenshots, I am noticing that the scope sample rate was at 1 MHz. This would not be enough to capture the whole pulse, which is less that a millisecond, as I understand. So the picture I have is probably not complete. The problem I am running into trying to look at this with a scope (which I am somewhat new to) is that it is a short pulse spaced widely apart. Tough to get the scope to see this as a pattern. Especially when you have to crank the engine every time you want to produce the wave, and are wary of over-stressing the starter. I’ll put this on the list of things to try to get a better picture of. Regardless, we do see that both IDMs are providing a similar pulse to the injectors, and it is definitely more than 12v. What kind of failure I might be looking for there, those things being the case?
 

Luke_IDI

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I took a video of the injector buzz test today. This is with the valve covers off. It’s about 90 degrees today.

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Luke_IDI

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The injectors all sound very much alike, however I think they may be very quiet compared to a strong engine. I intended to do this test on my friend’s Powerstroke today as well, but his truck would not connect to the scan tool.
 

Luke_IDI

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The guy in this example says that with a buzz this quiet, the truck will not start cold at all—the block heater must be plugged in to get it to fire. I am thinking the injectors in my buzz test sounded more like the bad test in that video.

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I think a next easy test to do would be to pop the known-good IDM back in and repeat the buzz test. If it sounds louder, that would seem to be a good indication of a failing IDM.
 

greenskeeper

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I took a video of the injector buzz test today. This is with the valve covers off. It’s about 90 degrees today.

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sounds like all 8 are buzzing and at the same intensity, with the valve covers off they should sound louder in my opinion, but that could also be the audio quality of the camera. Also you should be able to count after the initial all at once buzz to each injector number.

can you post a video of the engine cranking and zoom in on some if not all of the injector spouts

again, if there is no oil then it's pointless to look at the fuel side right now

Did you confirm oil at the HPOP inspection port to be no more than 1" from the top?
 

Black dawg

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Your buzz test is extremely quiet. Do you have a know good injector to plug in to hear the difference?
 

Black dawg

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Had a bad idm cause a weak buzz test like that here recently. Truck started slightly slow, but it was every warm out at the time. How many miles on those injectors, oil changes?
 

Luke_IDI

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Your buzz test is extremely quiet. Do you have a know good injector to plug in to hear the difference?
I do not have a good injector, could possibly get one but that would require pulling one out of a friend’s van. I’d prefer not to have to do this but I will keep the suggestion in mind.
Had a bad idm cause a weak buzz test like that here recently. Truck started slightly slow, but it was every warm out at the time. How many miles on those injectors, oil changes?
It has been very warm here too. Some days when we tried to start it it was close to 100 degrees. Also tried a known-good IDM with no change, though I did not do a buzz test with the good IDM, which I plan to do.

I have zero idea of the maintenance history this truck. Probably not much was done given that the driver described draining sludgy oil out of the truck after the breakdown. My current theory is that sludge settled to the bottom of the crankcase while the truck sat for a year or more, then was sucked up into the oil system after a 1/2 hr of driving, “clogging” the injectors. I am not sure if such a thing has been heard of before. Swapping IDMs and repeating the buzz test may shed some light on this theory.
 

Luke_IDI

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Had a bad idm cause a weak buzz test like that here recently. Truck started slightly slow, but it was every warm out at the time. How many miles on those injectors, oil changes?
Truck has about 200,000 miles on it. I have zero clue about what maintenance was performed on the truck. Possibly not much, if the oil sludge that came out of it is any indication.

I will try the other IDM I have and redo the buzz test.
 

Luke_IDI

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I repeated the buzz test today. I wanted to make doubly sure that the injectors have enough voltage to fire.

I unplugged the number 8 injector connector and inserted pins into the plug. It’s pretty tight to try to backprobe a high voltage wire there without touching the pins together.

While doing the buzz test and while cranking, I see approximately 50v pulses at the injector using a scope.

With the IDM from the running truck, I see the same thing.

It seems like it would make sense for the injectors to buzz quietly if they are only getting half the voltage they should. And this will need to be resolved before the injectors can fire.

Here is a video taken during the injector buzz test.

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I am wondering, why are the injectors getting 50v?
 
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