Brandon, I want to pull the injectors on that side because I never have, and now that I know that 185-180 lbs. low compression is on that side, I want to look. It is a wimpy way of proceeding, but a cleatus12r graciously said, he has better shop facilities, and as he graciously did not say, but which is undeniably true, he knows way more about this stuff than I do. So I will continue to learn slowly.

Yes, Tugly has a great write up on the cup leakage test.

P.S. Yes it is true, vans are a pain in the butt to work on.

 

These pictures were taken at top dead center on the low compression cylinder (~180-185 lbs compression)






I stuck a thin white coat hanger down the injector hole and my wife watched as I used a ratchet on the crank bolt (glow plugs are all out) to turn the cylinder to Bottom Dead Center. But the three bores scopes that I had would not light up the top of the piston well enough to see.



Piston top observations:

I assume that is a hole in the piston and that I have no choice but to remove and rebuild or to replace the engine.

 

That just looks like a fleck of carbon to me, but I could be wrong. Cody recently added to his collection of 7.3s, maybe you guys can work something out.

 

Thank you Tugly, I plan to see if a piece of thin stiff wire goes through the "hole" or not. I wonder if I could add more light through the glow plug hole in addition to the light on the bore scope in the injector hole...

Or I wonder if I could guide the wire through the glow plug hole while viewing it with the bore scope in the injector hole?

It occurs to me that I don't need a new bore scope. I just need more light. There has got to be an LED light out there which will fit into the glow plug hole. FYI:

Glow plugs are 5mm diameter.

Injector nozzles are 7mm diameter.

 

Hey Guys. WHAT IS THE MINIMUM COMPRESSION PRESSURE FOR A CYLINDER TO FIRE?

My buddy and I were trying to poke a hole through what looks like at least a dimple in the top of the piston on the 185-186 lbs. low compression cylinder number 1 and could feel the dimple with a coat hanger but it was likely too large a diameter to go through if in fact it is a hole. With a .035 mig wire it was impossible to even find the dimple.

Anyway my buddy asked what is the minimum compression required for a cylinder to fire? Because even if it is not a hole, if our diesels require more than 185 lbs. to ignite, then I am going to be spewing unburnt fuel out of cylinder number 1 because of the low compression, regardless of whether or not the low compression is caused by a hole in the top of the piston, or rings or valves.

We looked at the seven little holes in the nozzle for the injector for cylinder number 1 and they are all plugged. I wish I could get photos for you.

@Cartel is there a simple way that I can get the injector nozzle off without having to go through the top of the injector and disassemble the little parts in injector body?

 

If you think an injector is a problem you can swap it out with another cylinder and see if the problem follows the injector.

 

Thanks Mark.

I can't believe that you Guys made me duckduckgo my own question.

Which must be the absolutely first principle of diesel thermo-mechanics.

It is expressed two different ways:

1) a minimum of 225 psi is required to cause diesel to ignite.

2) or a minimum of a 15:1 compression ratio is required to cause diesel to ignite.

Which means that we need to compress 15 atmospheres into a space where one atmosphere would normally fit (e.g. a diesel cylinder) to cause the diesel in that cylinder to ignite.

One atmosphere is commonly expressed in the U.S. as 14.69595 psi.

14.695595 psi x 15 = 220.433925 psi which in other words equals ~ 225 psi, referred to in 1) above.

 

So, Guys, I ask you what does this mean to me?

And to anyone else with a cylinder below 225 psi?

Well my guess is that a low compression cylinder in a gasoline engine will still fire because of "ignition assist" which are commonly called spark plugs.

But since a diesel has no spark plugs and nothing else to assist ignition other than cylinder compression, a cylinder which is less than 225 psi will never fire. It will never contribute anything.

But it will still accept diesel from the injector and let is slide down the cylinder walls, washing down the oil off the rings, scoring the cylinder walls, and filling up the crank case.

Did I mention that I had more "oil" in the crank case than normal when I started investigating this engine problem with the van?

 

You can see little reflections of light in that spot you are looking at, suggesting it is not a hole. If the oil level is rising that would suggest fuel contamination I guess. Send a sample off to Blackstone (fill it all the way to the top of the bottle) and see if they confirm it. Looks like you might be replacing a piston in the #1 cylinder at the bare minimum, and the injector.

 

Well men, time for a two year update.

Since the van started spewing white smoke driving uphill pulling a boat over the Sierra's near Truckee in ~2012 and lost power and died on the side of the road, I have kept the 1995 Ford Bronco, my wife's Dodge Dakota and her Mom's Corolla working. I am pretty good with a wrench now, although the only engine I have torn down and rebuilt is a 1988 two cylinder 2-stroke stand up jet ski engine which seized due to a lean condition because a rear crank seal wore out. More on that later.

So because of jet skiing I met a somewhat recent immigrant Russian OTR truck driver former Chevy diesel mechanic with a meticulously clean diesel Savana van. He came over and focused on cylinder # 1 which was the lowest compression at 185. He explained that I had likely not put enough oil into the cylinder when I tried to seal the rings with oil for a second compression test because the top of the diesel piston is a cup which must be over-filled with oil which must drip down the sides of the piston to the rings to seal them to differentiate between a burned valve and poor ring to cylinder sealing. So, he put what he considered to be the appropriate amount of oil in the injector hole, put the injector back in, hooked up the Snap-On diesel compression gauge to the glow plug hole and in eight revolutions the gauge went up from 185 psi to 500 psi.

Which indicates that it is not a valve problem but a problem of poor compression ring to cylinder wall sealing?

We cleaned the cylinder by squirting carb cleaner in and then used the below Depstech 5.5mm Android Endoscope to look at the cylinder walls. (At 5.5mm diam. it fits down the injector hole no problem.) They were scratched, but not deep at all. He said all cylinder walls have some scratches and mine were not bad at all. There was no hole in the top of the piston, there was no broken ring part or other debris on the top of the piston, the top of the piston did not appear to have melted, there were no aluminum deposits on the cylinder wall.




He asked me how I over heated it. I explained that I knew that my van was fuel starved because the paint that Ford had applied to the inside of the oem galvanized steel fuel tank (which was painted on to prevent the sulfur in the diesel from reacting with the zinc in the galvanized tank) had flaked off and almost totally plugged the between the valve covers oem fuel filter. And then he said something that rang a big bell with me:

"You had a lean fuel condition which increased the ratio of air to fuel which caused the engine to overheat."

He said that if I am very lucky the compression ring is just stuck in the piston lands and, possibly but unlikely they could be freed up with the use of a chemical. He suggested a Risalone product which I cannot find locally. He said his dad in Russia freed the rings on a Volga by using Kerosene. I didn't have Kerosene either, so I put a quart of AFT in and let it soak. Then after 24 hours I used the remote starter to puke that out and poured a solution of 50% AFT and 50% Acetone and it has been soaking. Then I will cycle the engine with the remote starter with the hope that the rings stick to the cylinder walls enough to break free and spring out and seal better.

He asked me does the 7.3L have cylinder sleeves? And I looked up my Ford Service Manual and it looks like no sleeves. Rather, it looks to me like the cylinders are bored into the block. Am I correct?

After he refused to charge me and left, I did some research about low compression in overheated engines and it doesn't look promising. Even though the cylinder wall is not deeply scratched the cylinder can oval as a result of overheating. And even if stuck rings are freed, the piston rings won't seal properly against an oval shaped cylinder and compression will remain low. Attached is a pdf of a great article I came across from "It Still Runs" about stuck rings:

https://itstillruns.com/symptoms-mot...s-8608495.html

So, I have three low compression cylinders (see previous post in this thread). I will try to free up the compression ring in the worst cylinder (cyl. # 1) and dry out the cylinder and then test for compression again. If the compression comes up I will move on with the same technique to the other low cylinders. But I am realistic and understand that freeing up rings to fix low compression in this manner would be very lucky.

So I ask you experienced guys, do I only get three bores in a 7.3?

Is an overbore of 0.030 the largest I can go?

If a cylinder becomes ovalled, is it possible to bore it to round?

Can our 7.3 engines be sleeved?

My guess is that I will be pulling the engine in two months when I have some time and then taking it to a machine shop to have them check the cylinders to see if they can be bored to round again.

My jet skiing Russian diesel mechanic truck driver friend agrees that low compression is likely the only problem with this engine, because it only had 120K miles when I stupidly drove it to over heating trying to limp home from Idaho.

Anyway, I miss you guys and will eventually get this running although it is the last of the major projects I have to deal with and it is still behind a couple which I need to complete first.

 

Just read this whole thread.

First, you’ve revealed THE problem with compression testing a diesel. My experience is this test is often misleading - exactly the case with your test. I’ve seen engines that run perfect ‘fail’ a compression test and I’ve condemned engines with ‘low compression’ and found nothing wrong at tear down. IMHO, compression test is not a good test. A leak down test to identify poor valve seal, etc is a better test - but only if you suspect low compression and DO NOT have blow by/pressurized crankcase while running. If there’s blow by (pressure! All these engines have oil vapor coming out of the open oil filler), there’s nothing short of a rebuild that can fix it.

Im also going to say your Russian friend is wrong. There is no such thing as a ‘lean condition’ in a diesel and specifically that 100%, no exceptions, can not ever cause an overheating situation.

Moving forward, or backward - let’s focus on the original complaint and establish a goal. It sounds like ‘the engine lost power and started smoking’ while under load. The goal is for you to keep this van ‘forever’. (I assssumed the latter).

Loss of power and smoking could easily be low fuel pressure and or a bad injector. Often, people focus on stuff the dirty air directly affects. The term ‘dusting’ an engine makes me twitch as it gets tossed around a lot and is as misused as ‘wet stacking’ - but I digress.... My point is dirty air = dirty oil. Specifically silica content in oil. ALL high compression/Diesel engines have some blow by. Partly past the rings and some through the valve train as Cody explained above. This contaminated oil is really hard on our 7.3’s HEUI system. The point here is excess wear on the oil side of injectors and HPOP is to be expected from an engine that has ingested dirty air. Especially if there is scoring present on the cylinder walls.

With all of that under consideration, my instinct would be replace this engine. Either find a good running engine from a wreck or rebuild what you have or buy a rebuilt 7.3 from a reputable source like Asheville Engines.

If the budget does not allow this investment, I’d go back to square one and fix the initial complaint - smoke and loss of power. Put the injectors, etc back in the engine, pull fuel from a clean source and verify fuel pressure is adequate. Get the engine to run and let’s do a proper diagnostic. It will be sad if this thing has been mothballed all these years because it needed injectors.

FWIW, the factory fuel filter does an EXCELLENT job of protecting the injectors. It is highly unlikely contaminated fuel from the delaminated tank made it to the injectors. I am experiencing delamination AGAIN in my cab chassis truck and will be replacing my tank with the now available plastic replacement as soon as I have time/money....

 

Sorry, I did not go back and read the whole thread just the last few posts.

Wanted to drop a thought in though. I have read low fuel pressure will kill injectors. If you know low pressure was an issue then what’s the thought on damaged injectors?

I did pop up to the first few posts but didn’t see what the true symptoms are so not sure my comment has any relevance.

 

Jason, thank you for reading the entire thread. It is truly appreciated (and RacinJason its ok that you didn't).

What is my best path forward?

I can do a leak down test on cylinder # 1. I have the OTC leak down tester (bought for another reason). But I really don't know how to use it. But I can follow the instructions.

But what about the fact that adding oil to cylinder # 1 brought the compression from 185 psi up to 500 psi? Does this not rule out valves? Does this not rule out a leaky head gasket?

Dude, cylinder # 1 looked great to me on camera (I ordered the same endoscope so I will be able to post up some photos next week).

There was blow-by out the oil fill tube as I remember, but it was not a freight train engine smoke stack type of blow-by.

Should I take the head off the passenger side and check for a blown head gasket? Could adding oil to cylinder # 1 tighten up a leaky head gasket or valves and bring the compression up to 500 psi?

I don't believe I have fully diagnosed the cause of the white smoke or the low compression. The engine could still be good.

If I have to replace the engine I will. And although other people have recommended Jasper engines for a rebuild, I will go with Asheville Engine. But remember my engine is different somehow, because it is in a van.

https://ashevilleengine.com/product/...iesel-engines/

 

Good to see you again Tim. I am with SSJ in saying that there is no such thing as lean overheat in a diesel engine. In reading through your thread, I am wondering if your Russian friend added so much oil that you were almost in a hydrolock condition during that compression test. My freshly rebuilt engine only managed 420psi for the compression test. 500psi is a lot. If that is the case, then you could conceivably be sealing leaking head gaskets or valves with that much oil in there.

 

Never remove a head in the truck. Head gasket failure is almost unheard of in stock 7.3’s.

Compression testing is a waste of time. Disregard ‘results’ from this test and move forward. ‘Blow by’ is PRESSURE, not smoke or vapor. No pressure, likely no problem.

My recommendation is put the engine back together and let’s make it run. If you are committed to keeping the van, consider putting a fresh set of injectors in now. Bitterroot Diesel stock remans are $1250 and only $1300 for stock with 30% over nozzles. Best source for injectors IMHO.

The only thing I have to say about Jasper is I’ve replaced a few of their engines after they broke.