Engine trouble. Please help

Danny

T1N,NCV3
Hey everyone, I have a low compression reading in cylinder 1. The engine has a rough idle but rides smooth when on the gas. Did a compression test and found the low compression. I swapped the injectors around to see if maybe it was the injector causing the misfire but this is not the case. That is what lead me to the compression test. Think I may have a hole in the piston? Rings? Valves? I'm not sure if there is anything else I can do before I have to tear this engine apart. Can anyone help?
 

sailquik

Well-known member
Danny,
What are your compression readings?
What devices did you use to take the compression readings.
Are the compression values for other 4 cylinders all pretty close and #1 is drastically lower?
Did you find any "black death" residue around the #1 injector?
Have you pulled the #1 glow plug to ensure it's sealed?
Read up on the process of removing the glow plugs as if you break them off you face removal
of the entire cylinder head to get the broken pieces out.
Take your time, use plenty of penetrating fluid, work the threads back and forth very patiently.
Roger
 
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abittenbinder

Doktor A (864-623-9110)
Hey everyone, I have a low compression reading in cylinder 1. The engine has a rough idle but rides smooth when on the gas. Did a compression test and found the low compression. I swapped the injectors around to see if maybe it was the injector causing the misfire but this is not the case. That is what lead me to the compression test. Think I may have a hole in the piston? Rings? Valves? I'm not sure if there is anything else I can do before I have to tear this engine apart. Can anyone help?
There is an easy, crude but effective cyl leak down test you can do yourself.

Cyl #1 is the easiest to test because the crankshaft pulley has an etched and labeled line across the width of the outside of the perimeter mass ring, labeled 'OT'.

This mark locates TDC of the #1 piston travel but it's up to you to determine if the valves are closed or if you need to rotate a further 360 degrees to have the cyl on 'firing' TDC.

Use shop air and a simple air gun and rubber stopper that seals the open injector bore.

Apply air pressure and a healthy cyl at 'firing' TDC will pop the gun/cork combo out of the top of the injector bore even with moderate effort to hold it in place.

IF it's easy to hold in place you can listen for the escaping air path to determine leak path. Oil cap opening hiss = piston or cyl damage, loud hiss at intake manifold opening = intake valve issue, loud hiss at exhaust pipe = exh valve issue.

Doktor A
 

Danny

T1N,NCV3
I didn't check the glow plug. I will check that. Thank u.
Doktor A. I would apply air through the center of the rubber plug?
 

abittenbinder

Doktor A (864-623-9110)
I didn't check the glow plug. I will check that. Thank u.
Doktor A. I would apply air through the center of the rubber plug?
Yes. You're modifying your air gun to seal into the injector bore.

Once you located the pulley mark and lined it up with the indicator cast into the timing cover, try applying air pressure.

If the air gun does not pop out of the bore, turn pulley 360 degrees and try again.

IF neither position will contain the pressurized air, you likely have a mechanical issue.

To then find firing TDC, to aid in identifying the leak path, remove the vacuum pump to reveal the camshaft drive sprocket.

The drive slot for the vacuum pump is vertical when cyl 1 is at firing TDC. Then you can proceed with air gun for audible clues to identify the leak path.

Doktor A
 

Boater

New member
I got a leakdown tester to help me diagnose mine, it is unbranded and almost certainly of Chinese origin but looks identical to the ones used in many youtube videos of leakdown testing. Chances are they are not too expensive in US/Canada. The only place I could screw it into was the glow plug hole, I believe the injector hole is preferred but not really feasible with unthreaded injectors.

As Doktor A says a leakdown test is useful because you can listen to where the air is escaping - you will lose a little through the valves if you are not on TDC on the compression stroke, I found it took me a while to set most cylinders up right, but No.1 is much easier because you can use the timing marks.

You will be able to work out if you are hearing air escaping from inlet or exhaust, if you are pressurizing the coolant, or if it is coming out through the crankcase (may need to refit the rocker cover before you can convince yourself of this). It can't tell you whether air escaping through the crankcase is from piston rings or a piston hole so you won't be able to order parts before you take the head off, but at least you will have a much better idea of whether you should be looking at valve seats/seals, gasket or pistons/liners.

Definitely look up diesel leakdown test on youtube - it takes a bit of practise so watching a few people who know how to do it and interpret it can be pretty useful, it was for me anyway. One of the guys has videoed himself using a new to him tester on a customers broken engine with no practice run so you even get to see a couple of possible pitfalls as he gets the hang of it.

Good luck!
 

Danny

T1N,NCV3
Leakdown is done. I have air escaping into the crankcase. Looks like a rebuild or new motor here. Damn!!
 

Boater

New member
Pistons* and/or rings are cheaper than a head so it's not worst case scenario!

Good luck sorting it out.

*for one cylinder anyway.
 

Danny

T1N,NCV3
This is true. I'm gonna have to tear into it. Thanks for all the info. Sure helped a lot.
( do you think this could have happened because to much oil was put in ?)
 

Turbo John

New member
Leakdown is done. I have air escaping into the crankcase. Looks like a rebuild or new motor here. Damn!!
Danny I have done literally hundreds and hundreds of cyl leak downs on race engines and many street engines..
Cyk leakage % are all different for different engines.

Most race engines leak 2 -12 % The smaller the number the better. I have had some of my fastest engines leak 12-14 percent on 2 ring pistons. They ran fine.

All engines will leak some air past the rings and into the crankcase.....just depends on what the number is?

The leakage will go by the valves and rings. So just because you have air leaking into the crankcase does not mean its all bad.

Was the engine warm or cold?...big difference in those two readings as things expand with heat.

If you are in the 10-15 % area and all the cyl are the same then its not that bad.

"Blow By" the rings is common to all engines except some very expensive race engines with perfectly round cyl's and a special hone for a particular piston ring.

Dont throw the baby and bath water out together. Check another cyl and give us the percentages%? If you have big differences then its a problem.

Remember all engines will leak air past the rings and valves to a certain extent.

You can get a piece of carbon under a valve and it will leak like crazy but the valve job is still good....there are so many variables to a cyl leak down.

Make sure both valves are closed at TDC like Doc A says.

We used to leak different depths of the bores as sometimes something at tdc is good and .150 down the bore it was bad......

Dont freak out because you have air going by the rings. You should listen in a valve cover when its leaking 5-10%........sounds like a hurricane passing thru, but the engine is fine.

Engines are not perfectly sealed unless you want to go spend what NASCAR spends.:rad:
 

Boater

New member
Sorry, I had jumped ahead and assumed Danny would have tested all 5 (or 4?) cylinders in order to be able to differentiate more leakage on that one than the others. He has already used a compression test to make him suspect No. 1 though.

When I had head troubles (cracked) I also found a cracked piston (No.1) which I changed at the time. Wasn't running very smoothly after that so did compression and leakdown tests and identified 5 as particularly bad but all of 2 through 4 were down compared to 1 (no surprise there!).

The real surprise I had was after I changed the rings on the remaining 4 pistons and did a cold leakdown test, all cylinders were reading under 20% - on a 16 year old 205k mile engine. Still haven't had it properly warmed up to do it again and see how much better it is warm. They aren't race cars but Merc engines seem to be pretty hard wearing!

Trouble is all these tests rely on experience for interpretation, and I don't have much. What Turbo John says about major sounding air leaks if you are even a tiny fraction of a degree off TDC is true, I spent ages trying to get each cylinder to the best position - of course with a newly built head I could pretty confident that any unusual noise from a valve indicated dumb operator error rather than a real leak!
I'm pretty happy with my findings so far!
 

Danny

T1N,NCV3
Hey there. Thanks for all the great advice. Im gettin 20-25% leak down in cylinders 2 through 5. Cylinder one I'm gettin 80%. And I hear it goin into the crankcase. Nothing through exaust or the Intake. Any thoughts?
 

Boater

New member
Sounds like piston or rings to me, need to take the head off and use Mk1 eyeball from here on in.
Well, some internal calipers and a suitable mic to check the bores, but they are aids for the eyeball :D:

If you did the test cold 20-25% is probably good, if you did it warm it's not necessarily bad as long as they are all similar (within 5%), but you might want to do all the pistons first time so you don't end up with 1 cylinder better than the others (been there, second rebuild to change rings on the other 4!)
 

Danny

T1N,NCV3
It was a cold test. So I have the same thoughts as you do. I guess we'll find out when I open it up. Damn! Hopin its just the rings
 

lindenengineering

Well-known member
Danny
First I recommend doing an oil analysis to determine what is in the oil.
I have just received a bad blowing Tinny & 2.7 litre engine in the shop.

I had a shot at it by scanner diagnosis and "exterior visuals", but held off on a tear down until the results arrived from Blackstone who I use a lot for my fleet customers to predict problem in the making.
www.blackstone-labs.com/

Results:- High silica in the oil--dust and dirt being injected which "crooked" the cylinders.
Evidence high %age of chrome, cast iron, alum (pistons?) copper and lead (engine bearings?)
Surprise for me it was low on carbon and suspended fuel which rules out bore washing!
So first I need to check the intake for rupture or leakage at the air filter clam shell cover. Then look to see if dirt is in the inlet tract etc before proceeding with the big stuff.

Also some notes on re-ringing etc. Do remember to de-glaze the bores for good bed down of the rings etc. I don't recommend it but the "dooberry ball" hone is often used by DIY er's and Pro mechanics a like.
Reason:- The factory cylinder finish is a plateau hone to about 35 to 42 CLA which gives the bores that cross hatch finish. This aids cylinder oil retention and reduces oil loss from pumping action reducing E figures.

CLA:- "Clear light average" Basically like placing a straight edge over the cylinder plateaus (plateaux??? ) Parlez vous Francais :laughing: And measuring the light passing through the valleys on the cylinder wall

What ever you do after first removing the under piston jets and honing is wash the cylinder bores with good old fashioned soap and water and agitate with a stiff nylon brush. This removes all microscopic traces of grit participates adhering to the cylinder hone valleys. After all you don't want these wearing your new rings on start up as they wash out with oil splash.
Once washed, I dry with compressed air and lube immediately with some fresh clean oil to avoid corrosion prior to assembly.
Cheers Dennis
 

lindenengineering

Well-known member
Hmm, I guess my deglazing with a scraper blade was inadequate then!
Boater
Nah mate, won't work!
You are harking back to the Albion Claymore days of the 1960's!
That's when I was snot nosed kid apprentice in Gloucester , and Scotsmen exclusively drove Albions (made in the Glasgie Yoker works) with a wee dog in the cab!:thumbup:

That's even when Bathgate works was a twinkle in BMC's eyes!:laughing:
Cheers Dennis
 

Danny

T1N,NCV3
Thank u for all the info. I will use it all. I have this engine almost out. The only thing holdin it back it the main wiring goin from the cab to the top of te engine. Is there an easy way to disconnect it? Seems like inside te cab is not an easy option. And on top in the motor I have to take out all the fuel lines for the injectors. Are these the only options?
 

lindenengineering

Well-known member
Danny
Simply disconnect the engine harness at the ECM and thread it through the bulkhead (firewall) and you are ready to pull the lump out.
Dennis
 

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