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BMC 1.5 oddities, advice appreciated.


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I have been reading posts in this forum since I obtained the boat back in 2011 and I greatly appreciate the information members here are willing to share. I've made it through most all of the BMC posts and still don't see anything that quite parallels what I'm experiencing so I would love to get some feedback and opinions.

 

I was told by the previous owner that the boat runs 'perfect' so long as you leave the glowplugs on for 90 seconds before cranking. Even in the beginning it would eventually start up after holding the plugs several times for well over 90 seconds (ill advised I know, but I got away with it without any burst or broken plugs). Of course warm weather or restarting after the engine is warm is and always has been easy. Cold starts are now worse than when I first got the boat. Here is what I have done so far:

 

  • replaced the injector nozzles (pop tested at 2000psi)
  • cleaned the DPA pump and replaced all of the consumables available in the 'rebuild' kits
    • injectors seemed to pop off fine with good spray patterns when run out of the motor but that's just my observation
  • new thermostat (72c)
  • cleaned out the tube stack in the bowman heat exchanger
  • removed the head (had overtightened an injector and broke off the head of a heat shield)
    • had it boiled out and checked for warping
    • modified the head (GP ports) to accept ACDelco 60G glow plugs (someone had already done this previously the two rearmost cylinders so I wanted them to match ps. I am a machinist)
    • lapped the valves by hand
  • Had the starter motor rebuilt (rewound at the local starter/alternator shop)
  • replaced the batteries and have two 12v in parallel for starting
  • replaced the water pump
  • replaced the fuel lift pump with a 12v electric pump

 

Recently I have just been using starting fluid, the smallest amount possible, and it gets the motor going on the first crank and works great the rest of the day.

 

Suspecting compression I had a mechanic come over and we found the compression (cold) to be 220,240,220,240 when I was hoping for 280 psi. He told me to try performing a valve adjustment and retesting. I did so (0.015"), bought my own compression tester and read, get ready for this, 480,480,490,480 🤯. I thought I had a faulty gage so I borrowed another and retested at 490,500,485,500psi. Still starts hard, still runs fine after it gets going, by the way the starter sounds very strong.

 

It's possible that both of my the latter gages were faulty and the readings were bogus but I'm not certain where to go from here. I am considering just ordering another head gasket so I can get in there, inspect for cylinder wear, check the carbon buildup, glow plug depth etc.

 

Would also consider buying one of those injector sets off eBay for $135 (cheaper then sending them out) as perhaps they are calibrated better than I was able to do on my own.

 

Trying figure this out, most of all I want to be able to start easier and rest easier knowing that I'm not just ignoring some deeper issue that's going to result in damage down the road. If necessary I'm willing to replace rings, bearings, bore, hone, whatever. But I'd like to only do what is necessary and I'm having difficulty figuring it out on this one.

 

Here are some photos for reference:

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Edited by Julian Xavier
typo
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I've been doing some more digging around and found this topic of spill timing the injector pump. I have never felt confident with the injection pump timing so it sounds like another good place to start in conjunction with another compression test to confirm what I was finding before.

 

If I understand right the procedure is to find 22 degrees before TDC and that should be the point at which the spill cuts off on that injector provided you remove some hardware (looks like some sort of check valve) from the injection pump coupling.

 

There was also some mention of always rotating the pump and the crank pulley in the direction of normal operation to account for any backlash.

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Sounds like you done loads  of work, but BMC 1.5s coke up regularly between the glow plugs and combustion chamber. So the heat generated by the glow plugs doesn't actually reach the combustion chamber.

Almost certainly you need to remove the glow plugs and use a long 4mm drill bit to push into the glow plug hole and break up the carbon crusted build up behind them.

I have done this on 2 of my boats now, both were BMC 1.5s. You can search on my threads under " boat not started properly for many years" previous owner always used easy start to get it going. It will take a couple of hours to do but it's fairly simple and become routine now 

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2 hours ago, Julian Xavier said:

I've been doing some more digging around and found this topic of spill timing the injector pump. I have never felt confident with the injection pump timing so it sounds like another good place to start in conjunction with another compression test to confirm what I was finding before.

 

If I understand right the procedure is to find 22 degrees before TDC and that should be the point at which the spill cuts off on that injector provided you remove some hardware (looks like some sort of check valve) from the injection pump coupling.

 

There was also some mention of always rotating the pump and the crank pulley in the direction of normal operation to account for any backlash.

 

Injection pump couplings normally refers to the device that joins an inline injector pump drive shaft to the mating part that sticks out of the engine. Although spill timing often is adjusted on those coupling on inline pumps yours does not have one.

 

Likewise on inline pumps you remove the number 1 delivery valve from the injector pipe union to do spill timing but again your engine does not have delivery valves.

 

If you have a pump coupling and delivery valves it's not a BMC 1.5.

 

If the compressions are 400 psi plus then it's OK and should start, if they are just over 200 psi it's far from OK.

 

I don't like the sound of the broken injector heat shield, are you 100% sure you were sold the nozzles for a 1.5? When top hats get broken its usually because the wrong nozzle was fitted.

 

When you pop tested them did you use the  spacial adaptor or a procedure that allows you to test the auxiliary spray hole? 1.5s use pintaux nozzles with a small hole in one side of the "nipple" formed around the pintle. If you did not test the auxiliary spray hole you may have been sold pintle nozzles.

 

Did the injector bodies have the locating pins in them to ensure the auxiliary spray holes  point in the correct place. If not and even if you did get the correct pintaux nozzles you will get poor cold starting. A working auxiliary spray hole in the correct orientation is vital for good cold starting.

 

Are you sure 2000 psi is the correct pop test pressure? Please check in the manual.

 

I assume the AC plugs are the large pin 1.8 type. If you bored the hole for the pin oversize it will reduce the compression and might cause poor cold starting but at 400 psi + I very much doubt this is the case.

 

I would never buy parts from Ebay, especially diesel fuel system parts. Go to your local injection equipment specialist and get your injectors overhauled. Ask them to ensure the nozzles you fitted are the correct ones. Hopefully even US diesel shops should know about UK injectors.

 

 

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I reckon your knowledge is way more than mine but I think I would try advancing the injection timing a wee bit and see if that helped.  Rotate the pump backwards against the direction of rotation.

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9 minutes ago, Bee said:

I reckon your knowledge is way more than mine but I think I would try advancing the injection timing a wee bit and see if that helped.  Rotate the pump backwards against the direction of rotation.

 

 

I agree, if he does not have the timing gauge to reset the pointer  trial and error will be the easiest way.

 

 

 

Just checked the manual, the injector break pressure is 135 Atms and that is close enough to 2000psi to not affect cold starting.

Edited by Tony Brooks
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Just twigged, the injectors seal on a copper washer sitting on the  "brim" of the inverted top hat heat shield, not the bottom of it. So if the OP broke the crown out of the heat shield he has at least one wrong nozzle fitted.

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47 minutes ago, Tony Brooks said:

Just twigged, the injectors seal on a copper washer sitting on the  "brim" of the inverted top hat heat shield, not the bottom of it. So if the OP broke the crown out of the heat shield he has at least one wrong nozzle fitted.

Correct. the seal is on the rim of the heat shield with a copper washer. The fire washer is steel inside the heat shield and seals around the nozzle tip. Are they the correct fire  washers so that the auxiliary spray hole is clear? 

 

If someone has put Perkins injectors in, they are longer and break out the heat shields. Also they are not Pintaux nozzles, they won't have the vital side spray hole.

No way will overtightening an injector cause heat shield damage unless its the wrong injector or there is more than one fire washer in the heat shield.

 

I see no mention of cleaning the skew gears and filter driving the injection pump. If the gears are badly worn due to neglect the injection timing will be all over the place when cranking.

 

You have lots of batteries to run the starter but are the leads, connections and earth straps in good order? Is it cranking over fast enough?

Using acetone starter is cheating. There are stories of engines becoming dependant on it but I never see why this would be so.

 

If the timing is retarded you will get white smoke on start and idle.

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32 minutes ago, Tracy D'arth said:

Correct. the seal is on the rim of the heat shield with a copper washer. The fire washer is steel inside the heat shield and seals around the nozzle tip. Are they the correct fire  washers so that the auxiliary spray hole is clear? 

 

 

and did he make sure the old fire washers were out before putting new ones in, if that is what he did.

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4 hours ago, Tracy D'arth said:

 

 

 There are stories of engines becoming dependant on it but I never see why this would be so.

 

 

I think the theory was that the acetone washed the oil from the cylinder bores and buggered the compression, no idea if correct or true

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18 minutes ago, Phoenix_V said:

I think the theory was that the acetone washed the oil from the cylinder bores and buggered the compression, no idea if correct or true

 

I suspect more theory hen practice, but incorrect use can initiate combustion while the piston is still going up. This causes a pressure spike that can and does break piston rings and piston lands and thus create low compression and even worse starting. Ether injection facilities was fitted as standard on MOD diesel trucks for Arctic operation when I was working for  them so correct use should be OK.

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Thank you very much for the replies, I will attempt to answer the questions raised to the best that my memory serves:

 

  • I reamed out the glow plug ports with the largest drill I could fit in the ports and turn by hand so as to try not to create metal shavings. The new GP has a 5mm thick element so I'm sure its a tight fit, I did not modify anything in the head past the threads. Unfortunately I don't have one of the old glow plugs for comparison.
    • picture of the new GPs bellow
  • As to how I managed to break of part of the top hat. I believe that at the time I had misunderstood and used a copper washer in the bottom rather than one of those stamped stainless steel atomizer washers and the copper turned out to be too thick. I have a picture describing where I've now placed the sealing washer and atomizing washer.
  • The replacement nozzles were sourced from ASAP supplies and they are indeed the Pintaux nozzles clocked correctly with the pin.
  • I have tried the trial and error method of timing in the past, will do again, just wasn't confident in my results. What do you look for other than a subjective "good" running sound when making this adjustment?

Too bad the spill test method won't work for this pump that would have been a nice way to set the timing.

 

I will have to take my gages and triple check them against my shop air to make sure those readings for compression weren't totally off. Difficult to do though as my compressor doesn't reach the same pressures needed, I've heard that pressure gages have a sweet spot for accuracy.

 

 

Atomizer washer:

Atomiser Washer for BMC Injector Nozzles (Replaces 12H220)

Injector prior to cleaning and installing the new nozzle:

aQM-gegkVLsZs6ygIjtvhcqkLfsx_Q4ZeKIG5OAgba-_RzBRpWLW4j4M1ho_FBryKm8KjtEP4jhU_XJ16K4a61xs_h621_tuOVXBYDD-XUJX2Ho7vJpGbIyFCBemAK6ElHZpo0Hdd8UmSMRKR0Vv8oljSqfvMSg6V0hTFCLkFtV0PgUKjv8nijHVrxgmPuGpkp7RfKAjSU4TyIVtwaPEHahFP3p1eQpkZ3ZFlutwEpgc-y-6STj8RhcXjljrBjfNeTbelb68DI8JTRZ7BrJFOIEk0YnvsYCZoW2-eXiX72lZyYn3XJeBV2woLTEFP6ZX9LB-u5Plnfctgd5aEkLzmrGZ5av-iowGOUXUd89489sitA4b_uWq7PbV-3ZHZMutko5X59K0qXzxhmVx4GkIHczVtCp-KTl-ZwL5m3zDEpNYIolqgjs0g2qGQ3RO5fgE6cGqKlCuC3RlKlO8Cgo9Bn_9R9zb_qZaFP3owua2OWgp78dyaH5TK0W2EWXDVVdv4kWGhwp3OVHcorxMHOU-ay1lH7P9gJ89HjEMlTnuprmJOuj9xtWruA5woyRmPLWogHba2zeG3NYQfiwZ0uc0J9g0gTQ_7ZjkGlLCAYLeK5yQpo6-q4UfW8-xx7njRROtLMA7pl19snsvCp_va_5_HF8GVv3gstvKvJknvjuAHZ0dVrE0eKzfIIa5Foyav_s=w816-h780-no?authuser=0

Broken heat shield "top hat" :

mG4XBcCJUBlvx2PUDKWLwojuFDEjOKHUuYu9m0JolU4fT1KDZKES46987QZfpRIF9qjgJhX3xN1B6tVAyzcUmtgVohqBAJ1M2GL4YnU-VODvn18ltnZuQgseG_kIZkkS0Dlf-QFITr-NhTniTtix4rSIkUerq1_dbuSJgpzfMoHfepzOkPZFWGtRvXchvkXxexyuNl2AcXE7O8Xldujmuj7na7krCOfnVYBalHlprstG3-UWXkeQ3HiP5TR2AGqyw4EAuwLU7Z2afem9bT-HkJX-uqJfY4BSEIT18Gk6jS4di1KCPpbYejLTvAFG5Hu7EFolhQm2ByBdShX0XuEinoytSv45_tOM4X_XP4TvOs4ZWcCUGuByhzGT7aCvZq-nX0mZJ0dZdBE1Dci4_5g3oCgfeGXzC1QDI9lf1KA5Hlrh8q-yQJ61u6tHEG-8lvas9ChpT6jqeDNf0sjejG2SiG-ikOu1V2G8KJP_HRUplH9OqgZGr8IXdw9SaAkyQBgIU5RxdCdccMqLH4uNcOxsQO0N0e3s32H4yaF4RhrNC3WhcJPlIXw0Om6hFoV6wWIBjYoBwRFBmNiaMscFFksV-V4vuJ-I8ZVoM70BOewe7ZtRa-Ex7y6-XQo3LfL2aXxzMK1E3ih4nOKZ30xbDxKdVQ8W5UsOmo-C-_ZY6fDV4GEqlqUTmGWqQEp_3WXBk4Q=w698-h740-no?authuser=0

Replacement glow plug AC Delco 60G, If I recall the only modification to the head was milling down the face and tapping the M10 threads deeper. The glow plugs seal on the seat so the only depth that should matter is from the seat to the tip of the heating element:

Q8KmRYcWubllpR3dMm5bFu_iJabB_I-jLyVKoFo8RsL00J9A3JakI2N9qVCQGgX-m5BLFSLVoNyG7v4iOlN1zOpXKwkNnMXJfnVZ00_e6liUu0G0ASzbCu8L2QGVMndTq07meHVp757ET6Sl-oYuXfSMhcaO--N2U4_dlC1BzXC2MWB7J8GG6notw02vmC-D5wUb7Ohuamd2ngkCPAxexXQKBSjVq8DYLJTS6rBzAVz1iLZk_uFTUhE3MZJG25ic42_e46mEmHd95ilAU1l6gx-NALKFI7Ns-c-ZkbSqmLqUoVI-8J3-X5CWJBOxw4nVuJJW0-nBO0GJvIMpfcw6VQcN2e1LEWYrtZzcpAV95zd72v4zm1doDwc4FqPJ4KEw-3vR0GeN2MgkNM3BkBGgBeniqdR-r7ulC7JTIqwnTXBcFHKylUUDsEJV_r8IENq44Kdn6xRTZbk6mVKS9ewvV5Ii5Ypg8SOYd53_tj317brvZ47o8mQ2JJjzIlm_44yqMx8mx-7xYKromQJV-9HimOqxjqmrQR-FJtI-1YnLTQ3rpRYv9tPNkLDYOtyIgBc3YX2CKo4bINYHqH0dtj_xw0yrjJsgw7dxRGfEWQCL0gXJgsHFeyNN67AZx8lCrNYFpIndeKgcs7hSbkgxjRkMUjns8mGZimehCSiIMjZAPoHl-k4m-K0MMoj8dB7xyIo=w369-h872-no?authuser=0

FWIW here is a short film including slow motion of the motor running, though this is prior to all the work done on the head:

https://photos.app.goo.gl/c78kVrLPPhdhDduQ6

Edited by Julian Xavier
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ASAP is now part of a major marine suppler so would not expect them to have much technical competence on specific parts - if it has xxx part number  or in xyz bin then it must be the correct part. It won't hurt to pull an injector and post a photo of the nozzle just to be sure.

 

When timing by trial and error its how the engine runs, sounds, cold starts, and the exhaust smoke.

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Heat plug  porting drill is 11/64"

 

Skew gears? If worn will give bad timing especially when starting.

 

Timing by ear is not easy, I retard till there is white smoke then progressively advance till the revs rise and fall off again, then retard a bit till revs pick up. Its all guesswork.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Sounds good, I'll post a photo of an injector once I get a chance to pull one. Can the atomizer washer be reused? This is why I have hesitated to pull them out until I have the replacement parts.

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3 minutes ago, Tracy D'arth said:

 

 

Heat plug  porting drill is 11/64"

 

Skew gears? If worn will give bad timing especially when starting.

 

Timing by ear is not easy, I retard till there is white smoke then progressively advance till the revs rise and fall off again, then retard a bit till revs pick up. Its all guesswork.

 

 

Not any more it's not. He has converted it to take modern fat plugs but although suspect his compression does not seem to be badly affected.

 

I agree it could well be worn skew gears, timing chain or chain tensioner. If it is then he will never get it timed by ear.

 

 

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This is the link to the nozzles I purchased from ASAP:

https://www.asap-supplies.com/products/bmc-injector-nozzle-for-bmc1-5-thornycroft-90-engines-12h834-131121

 

As to the 11/64 drill for reaming I expect I used a larger drill as the glow plugs fit easily and the 5mm diameter heating element is larger than 11/64" (4.37mm)

2 minutes ago, Tony Brooks said:

 

I agree it could well be worn skew gears, timing chain or chain tensioner. If it is then he will never get it timed by ear.

 

I can pull the crank pulley and check the timing chain and tensioner.

 

As to the skew gear, is this the component that fits to the injection pump shaft to drive it from the motor? If so can replacements be sourced?

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Ultimately it seems that if the compression is indeed low and I just have faulty values then it would be much more likely an issue with worn piston rings etc.

 

If that's the case I'm I would be interested in honing the cylinders and fitting new rings but I understand that could well mean replacing:

  • rod bearings
  • rings
  • crankshaft bearings (unless it can remain installed while removing the pistons)
  • pistons themselves

In the case that there is significant cylinder wear it could mean boring and purchasing oversized pistons + rings which means all the above with a considerable increase in expense.

 

Anything else I'm missing?

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12 minutes ago, Julian Xavier said:

Ultimately it seems that if the compression is indeed low and I just have faulty values then it would be much more likely an issue with worn piston rings etc.

 

If that's the case I'm I would be interested in honing the cylinders and fitting new rings but I understand that could well mean replacing:

  • rod bearings
  • rings
  • crankshaft bearings (unless it can remain installed while removing the pistons)
  • pistons themselves

In the case that there is significant cylinder wear it could mean boring and purchasing oversized pistons + rings which means all the above with a considerable increase in expense.

 

Anything else I'm missing?

 

It all depends upon degree and how reliable and long-lived you want the engine to be. Personally I would not expect the small end bearings (rod bearings?) to demand changing. The big end bearings can be inspected if you pull the rods and as long as you measure the crank for wear, taper and ovality you could just fit new shells when you rebuild.

 

You can draw the pistons without removing the crankshaft.

 

If its a valve seat problem why would it indicate worn pistons etc? That  would be indicated by low compression with good valves. While considering valve I assume you have set the clearances.

 

You won't really know what is required unless you strip and measure the engine.

 

 

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35 minutes ago, Julian Xavier said:

This is the link to the nozzles I purchased from ASAP:

https://www.asap-supplies.com/products/bmc-injector-nozzle-for-bmc1-5-thornycroft-90-engines-12h834-131121

 

As to the 11/64 drill for reaming I expect I used a larger drill as the glow plugs fit easily and the 5mm diameter heating element is larger than 11/64" (4.37mm)

 

I can pull the crank pulley and check the timing chain and tensioner.

 

As to the skew gear, is this the component that fits to the injection pump shaft to drive it from the motor? If so can replacements be sourced?

 

If you make witness marks between the injector pump flange and the triangular adaptor plate you could take the pump off and use a big screwdriver or some such in the drive splines to test the backlash in the skew gear and timing gear. It should have virtually none. The more backlash the worse the wear.

 

If you take the triangular adaptor plate off having noted the position of the master spline you can pull the drive shaft and thus the skew gear for visual inspection. You will have to ask Calcutt Boats about a new drive shaft but if the skew gear on that s worn then its very likely the one on the camshaft will be also, so that means a new camshaft.

 

If you are a machinist I would think that you could make a timing gauge from the details in the manual. The problem will be the splines but I would think a decent machine shop would not have a problem, especially as it won't need to be hardened. In fact if you managed it without too much work you could have some customers on this forum.

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58 minutes ago, Tony Brooks said:

 

 

If you make witness marks between the injector pump flange and the triangular adaptor plate you could take the pump off and use a big screwdriver or some such in the drive splines to test the backlash in the skew gear and timing gear. It should have virtually none. The more backlash the worse the wear.

 

If you take the triangular adaptor plate off having noted the position of the master spline you can pull the drive shaft and thus the skew gear for visual inspection. You will have to ask Calcutt Boats about a new drive shaft but if the skew gear on that s worn then its very likely the one on the camshaft will be also, so that means a new camshaft.

 

If you are a machinist I would think that you could make a timing gauge from the details in the manual. The problem will be the splines but I would think a decent machine shop would not have a problem, especially as it won't need to be hardened. In fact if you managed it without too much work you could have some customers on this forum.

I will do all the above, feel and visually inspect for wear. If I can figure out the necessary details to make one of those timing gages I would happily make one for my own use and make them available. I would probably just turn the shaft down and only worry about making the master spline (the large tooth)

 

I believe but do not know that the valves are in good order, last I had them out they looked decent in terms of pitting etc. and I lapped them in by hand. I performed the valve clearance adjustment last week before the compression test (0.015") and triple checked them to be sure.

 

I might ask my mechanic to come down and perform another compression test before I take the head off, but if it still comes back high (480 psi +)

 

If low:

  • I'll remove the head inspect the valves, maybe replace them or have them ground, seats cut, etc.
  • inspect the cylinder wall for wear

if high:

  • I don't really know what to do here, pull the head anyways and check what's going on, clean out carbon if excess buildup is present
  • count my blessings and leave well enough alone, try to address the cold start issues with the injectors and pump timing alone.
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The Scientific method.  You have an air compressor ? if so. If you make up an adaptor to screw into the glowplug hole with a nozzle to connect an air hose to from the compressor, valve seat leakage can be checked.  Screw the adaptor into each cylinders cylinder head glowplug hole in turn.  Each time turn the engine to get each piston on TDC compression'' both valves fully closed'', connect the airline hose to the adaptor on that cylinder and turn on the air. If valve seats are leaking by a hissing will be heard in the inlet orifice if an inlet valve is blowing by, or hissing at the exhaust if an exhaust valve is blowing by, or indeed both might be blowing by, it's best to remove the inlet and exhaust manifolds for this test to listen directly at the heads ports. You will also hear by putting an ear over the valve cover oil filler hole or from the dipstick hole slight piston blow by from the sump, if it's loud or furious then pistons, rings bores in trouble, Don't confuse the slight piston blow by with any valve blow by.  A length of rubber tube with one end held at an ear with the other end held at the inlet and exhaust orifices when the test is conducted you will hear better especially if you plug off the other ear to block out other noises around you.

  Down side. if you happen to be Mutton Geof- stone deaf forget the whole excercise.  :).

Edited by bizzard
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Bizzard I have an adapter that should work. I will bring the compressor & give it a go with the leak down test.

 

However I was able to test the gages at my shop today. The results suggest that if anything I have ~ 500 psi + on each cylinder. If accurate I doubt I have issues with rings or valves. Is 500 psi problematic? Could excess carbon buildup be responsible for that large of a reading?


 

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It could be but I would not worry about that pressure, it should produce plenty of heat to ignite the fuel. In my experience more carbon builds up on the back of the valve heads than in the cylinder. However, you have had the head off so presumably you decarbonised then. You have reduced the volume of the pre-combustion chamber by fitting fatter glow plugs so that would account for some rise in compression.

 

Have you had the skew gear oil jet and strainer out for inspection and cleaning? If not it may be a good next step because if its blocked/collapsed it would suggest the skew gears may very well need further investigation.

 

 

 

 

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The old Motor factors ''Brown Brothers'' with whom I had an account with used to sell the compressed air test kits, but for petrol engines, with adapter to screw into 14mm and 18mm spark plug holes and an air hose. :)

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