New To Me Engine, Won't Start

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Matt5

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I am always impressed here (sadly) maybe I'll be wrong

The test is suspect because the cylinders are all equal???????????????

"Pressures are: 1-240 3-240 5-220 2-200 4-190 6-210"

Um, pressure should be 10% variation highest to lowest... (I will admit this is for gas but I would assume diesel would be the same 10%)... 240 to 190 is OUT OF SPEC...

10% of 240... 24... that gives us 216 as the lowest cylinder... EVEN if we do 20% its 192... not 190... so compression is already out of spec because they are too far apart yet it is suspect because they are all the same?

I mean... really? If we bring those numbers up 2x (as they should be...) we get 480 vs 380.... lolwut? This is the same? That's a bad motor LOL...

OP already ohmed out the plugs.. doubt all 8 are bad...

Like, compression is too low... I mean I don't have alldata at the moment... but I would bet spec is 350psi or more....

So like, until compression is over 350... kinda pointless (imo) to look at anything else...
Know what is REALLY funny?


https://www.steelsoldiers.com/showthread.php?158579-6-2-Diesel-Compression-Check&p=1920452&viewfull=1#post1920452

Should not have more than 10%


240 - 190

"The compression test is also suspect because all of the cylinders are equal to each other. This never happens. "

really funny part is, the compression numbers here have the same variation as the thread I linked LOLLL

Best of luck...
 

richingalveston

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my apologies that I miss read the post, I did not see the post of the test, I thought I saw a comment that they were all at 200. I have been traveling the past few days and did not go back and re-read everything.

just because they were ohm tested does not mean they are glowing at the ends and that they are getting the amperage they need.

I am just trying to help, not get in a pissing match with anyone.
 

helobravo

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OK. I finally had time to get back on this project, and not to be a hit and run poster, here's some pics and info:
Batteries charged. Brass, screw in compression tester. A pic of an even bank (all 290-300 pounds) cylinder and an odd bank cylinder (all 220-230 pounds)
The next post will be heads off, cylinders and heads.
25v.jpgbrass tester.jpg#2.jpg#5.jpg
 

cucvrus

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What is the dental pick scratching the chambers supposed to indicate? And the heads look fine but should still be looked at by a competent automotive machinist. I am asking because everything looks normal to me. Good Luck.
 

cucvrus

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Never heard or seen it. Most cumbustion chamber cracks are invisible when cold and require much more than that to be found. I sure wouldn't trust that as a reliable test.
 

richingalveston

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what did the gaskets look like. the motor has not had coolant for quite some time, they could have dry rotted. I can't see any problems, maybe throw some gaskets in it and retry the test. IF you have a place to check the heads then that might not be a bad idea.
 

Tinstar

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If no one is close to check the heads, you can order a Magnaflux Kit.
It’s a NDT dye penetrate that will show any cracks.

It’s used in Aviation everyday and works extremely well.
 

cucvmule

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Most of the heads that I have looked at are cracked between the valves. True that a micro crack when cold will be harder to see, remove the valves and check for visible cracks, discoloration. Water leaking into the cylinder from a cracked head will have the carbon removed from area of the crack, or the cylinder head in that bore will have most carbon removed.

Cylinder bore cracks that I have seen will have a more noticeable crack that is vertical in length.

More probable that the ring land is broke between the rings from hydrolocking the cylinder. You can get some ring condition indicators also by looking at the cylinder walls. Are the wear marks consistent, circular pattern, sealing? Use some light oil on the top of the piston, rotate crank and look at how the ring wiped the oil away.

Are there clear scratches circular around bore? Rings butting end to end from overheating or not enough clearance will also break the ring or break ring lands. Low compression that cylinder, wet looking.

The heads in the picture look like they are consistent with carbon except one chamber top left picture looks either wiped down or cleaned? That chamber if not having been cleaned looks like water may have been leaking into, cleaning off carbon. A clear indicator of a cracked bore or head crack between valves.

These are my observations from working on gas or diesel engines. Unfortunately the 6.2, 379 has two achilles heels. Cracks between valves that from my point of view can be found rather easily, by looking closely or by Tinstars method of magnaflux . Or by looking at the bore for no carbon, and looking at the head gasket for failure.

The other is main web cracks. Harder to see but on a major rebuild looking for web cracks is a must. As for cranks I have 10 10 them for minor work or easy polish.

Most guys have their own ways to diagnose and may disagree with my thoughts but again these are some of my own experiences with the 6.2 Detroit, a steady performer that like all machines have some special design features.[thumbzup]
 

cucvmule

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Also remember to use NEW head bolts as after being yielded once, stretched bolts will have a different torque to get an as before result. And may fail in doing so.
 

helobravo

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what did the gaskets look like. the motor has not had coolant for quite some time, they could have dry rotted. I can't see any problems, maybe throw some gaskets in it and retry the test. IF you have a place to check the heads then that might not be a bad idea.
I have pics of all sides of both head gaskets. They looked fine. No signs of anything crossing the gasket anywhere.
I dumped another 150 bucks into it and put Fel Pro gaskets and a set of new FelPro head bolts. The pressures are still low.
The cylinder walls all looked great. No scratches or anything abnormal.
 

cucvrus

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Did you have the heads checked over? Leaking valve seats can cause issues with compression. Do it right the first time. Quote:
"
The definition of insanity is repeating the same actions over and over again and expecting different results. If the heads and valves and not sealing you can change the head gaskets daily with the same results. Good Luck.
 

cucvmule

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Did you check rings with oil to see if they are sealing while heads were off? Did you tear heads down and at least lap the valves? Were the pistons at top of bore at top dead center?

Advice or help can only be givin, then reason has to be a self decision.
 

richingalveston

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might be worth a try to pull a head from your existing motor, the one with bad starter bolts and put it on this motor to test compresion. This should let you know if it is a ring problem or a valve seat problem. you can use the same head bolts just dont do the last bit of torquing. They will be tight enough to check compresion.
 

helobravo

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So, I pulled the pistons and I had a machinist friend come down and check the cylinders. They are 3.978" and square.
The used top ring gaps were .024-.025. TM says should be .016-.022, so I picked up some new rings.
The new rings are Mahle rings and the gaps are .023-.024. I called the tech support at Mahle and he said it's no issue.
I believe I will put the engine back together and, as suggested, put my other set of heads on it.
 

cucvrus

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Putting on another set of heads is all well and good. But before you do all this work take that set of heads and have them checked.
Use a competent automotive machine shop. Just switching parts around and adding this and that will make an engine.
But will it run? And will it last?
Do as you wish. But getting into rings and pistons???? I would get the entire engine checked at a machine shop and know I have good parts. Line bore, cam bearings, cam shaft and crankshaft. All sorts of things before just replacing rings. At this point buying a $1500. running 6.2 may be your best bet. Have a Great Day. Good Luck. Be Safe.
 

helobravo

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Hone, new rings and replaced heads. 400 psi on both banks.
The motor is on a pallet and starts up as it should.
The glow plugs and pink wire are hooked up to manual switches.
I will connect the cooling system later and run it for a while.
Since I am on a pallet, what do I need to do for the other two connections on the IP to get it to idle while cold?
I'm probably going to sell this motor, on the pallet running. What's a fair asking price?
 
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