Diesel engine : Kromhout Gardner 4LW 1940

[ajoeiam]

Regarding thermal expansion, I think it is not a problem because With 4 pumps and 4 injectors only 1 injector does not seal when the temperature is increased.
I think there's a problem with the way I make the injectors

Hmmmmmm - - - - before you go down the road to "the way I make the injectors" - - - I would suggest that you very very carefully measure your injection pump. You might find (have to measure to at least 0.0001" (0.002 mm)) that that one problem port that your body is either a tiny bit larger or the internals are a similar bit smaller. Commercially this equipment is measured using air gauging - - - - and that's working to 0.000010" (0.0002 mm). This level of metrology is not simple nor easy - - - - temperature control is crucial (IIRC assembly area is controlled to +/- 0.5 C) - - - - one can't hold the parts in a bare hand and expect them to be able to be assembled - - - steel moves at 6 millionths of an inch per inch per degree F (sorry - - - memorized that way don't know the SI equivalent off hand), carbide is some 3 millionths . . . , aluminum moves far more - - - thinking something like 12 to 14 millionths if not more but check that one if you're using aluminum (Machinery's Handbook has tables for coefficients of expansion (pgs 369-370 25th ed) .

Building one's own injection pump means that one must work to the tightest tolerances - - - yes there are tighter but not for somewhat common items. So I wouldn't consider what you have done a failure - - - - rather the opposite. So please just check that particular section very very carefully before you pitch a very great (good) effort.

 

[minh-thanh]

Hi All !
An update:
After injector repair
Test run,., adjust,..Test run....and the engine runs for about 10 seconds then stops and doesn't have any feeling it wants to ignite.
After finding out the cause....I found out I missed 2 bolts for the cylinder head - 2 cylinder heads is a total of 4 missing bolts, I don't understand why I could be wrong ... - 4 bolts!!!????????

 

[Mechanicboy]

Bolts with low tensile strength 8.8 were used? Use bolts with high tensile strength 12.9. Tighten with a torque wrench as indicated in the table. The tensile strength indicates the breaking point in the material of the bolt, while the yield point indicates how much the material in the bolt can withstand load before permanent deformation and damage occurs. This is the distinction between elastic and plastic zone. Increased strength class gives increased tensile strength and yield strength, which is good, but also increased hardness.

 

[minh-thanh]

Missing - that means I forgot to install bolts in those places
Bolt is not broken
I use socket head cap bolts 3mm

 

[Mechanicboy]

Missing - that means I forgot to install bolts in those places
Bolt is not broken
I use socket head cap bolts 3mm

Quickly made to forget..

Hope all will be in order..

 

[grahamgollar]

Hi Minh
A couple of minor observations which may (or may not!) be relevant :-
There appears to be quite a difference in the lengths of the injector pipes which might create false timing and
I cannot see if you have spill pipes from the injectors to release excess fuel after injection?
It's still a marvellous model!

Graham

 

[minh-thanh]

Hi Graham !

Hi Minh
A couple of minor observations which may (or may not!) be relevant :-
There appears to be quite a difference in the lengths of the injector pipes which might create false timing

Graham

A piece of information worth noting . Thanks !

My injector it doesn't have spill pipes

 

[Mechanicboy]

As rule the diesel engine has same length to all injectors in a multiple cylinders engine due the pressure in the pipeline must be same. If the length of the pipeline is difference, it will affect the timing and the pressure in the short pipe is higher than the longer pipe due expansion of pipe wall affected by the pressure.

 

[minh-thanh]

Hi All !
An update:
After reassembly of the engine
Test run, n
n..+1
n..+2 : Engine runs for about 10 seconds
....
....The motor runs about 15 seconds
....
....Engine runs for about 20 seconds and then it doesn't want to run anymore
Again : 3 out of 4 injectors are not sealed, I removed the injectors to check...as shown in the picture
- Needle : stainless steel
- Nozzle : C45 steel
- Fuel for test run is diesel oil
My plan has two options: use the same materials as in the 1-cylinder engine or do all of them with stainless steel.

 

[Mechanicboy]

Stainless steel is not ideal as an injection nozzle needle. Use steel because it is harder than stainless steel and easier to grind until the nozzle needle is tight to the nozzle needle seat. Use the same material for both parts due to thermal expansion, which means that it does not leak in the cone at the end of the nozzle needle/valve seat.

 

[minh-thanh]

Stainless steel is not ideal as an injection nozzle needle. Use steel because it is harder than stainless steel and easier to grind until the nozzle needle is tight to the nozzle needle seat. Use the same material for both parts due to thermal expansion, which means that it does not leak in the cone at the end of the nozzle needle/valve seat.

I know thermal expansion....but how can one measure or determine it with a diameter of 1 or 1.4 or 1.6 or 2 mm with the tools everyone has on hand???

 

[Mechanicboy]

I know thermal expansion....but how can one measure or determine it with a diameter of 1 or 1.4 or 1.6 or 2 mm with the tools everyone has on hand???

Use shaft of drill (where the chuck is holding the shaft on the drill) or steel pin made from lathe to measure diameter in the hole. Micrometer to measure outer diameter. We can use steel ball with known size to measure hole diameter.

 

[xander janssen]

Mr Find Hansen made his injector "free floating" to avoid this problem.

In one of his youtube videos he explains what this means. Basically only the tip is in contact and the stem is free over its entire length. Only the spring touches the other end. He clearly states that you need springs with square and parallel ends.

I will try to find the video again.

 

[Lloyd-ss]

Much of this work is custom fit to a "feel", that experience tells us is right. Material is often what we have on hand and will not be ideal, but will be good enough. There is a big difference between building a model engine that might never see 50 hours, and a manufactured engine that needs to go half a million miles. And above all, it must be fun, not a burden.
Just my 2 cents, nothing else.

 

[minh-thanh]

Mr Find Hansen made his injector "free floating" to avoid this problem.

In one of his youtube videos he explains what this means. Basically only the tip is in contact and the stem is free over its entire length. Only the spring touches the other end. He clearly states that you need springs with square and parallel ends.

With 4 injectors, I made 4 different styles, one like you said

 

[minh-thanh]

Much of this work is custom fit to a "feel", that experience tells us is right. Material is often what we have on hand and will not be ideal, but will be good enough. There is a big difference between building a model engine that might never see 50 hours, and a manufactured engine that needs to go half a million miles. And above all, it must be fun, not a burden.
Just my 2 cents, nothing else.

 

[ajoeiam]

I know thermal expansion....but how can one measure or determine it with a diameter of 1 or 1.4 or 1.6 or 2 mm with the tools everyone has on hand???

Correct - - - -with the tools on hand I wonder if there is even 1 person on here that can measure to millionths of an inch or hundred thousandths of a mm - - - I doubt it - - - this is very high precision country.

I was taught to use the coefficients listed in something like machinery's handbook (pgs 369 and 370 25th ed) znc calculate what they would be given your temperatures (that also needs to be measured accurately. IIRC it is also possible to find the coefficient of expansion for particular metals for a specific alloy
on a quality provider's website (not always true but sometimes!).

 

[Lloyd-ss]

Correct - - - -with the tools on hand I wonder if there is even 1 person on here that can measure to millionths of an inch or hundred thousandths of a mm - - - I doubt it - - - this is very high precision country.
...........

Quote snipped for emphasis.....

But Joe, I can tell the difference between zero gear train backlash and a few millionths, ha ha! That's a joke from a few years ago, remember? Gotta have fun!
Lloyd

 

[minh-thanh]

With this engine: I've done more than 2 fuel pumps - which means 8 cylinders, 20 sets of ball valves and other parts, I already know a little more about the pump and it's fine now.
I did 8 injectors, each is a little different and only 2 works fine, maybe I'll go back to the injector design I did in a 1 cylinder engine.

 

[minh-thanh]

Hi All !


View attachment 148969

A more interesting information
I just discussed my injector problem with a friend in my country, he is a pretty good injector, fuel pump and diesel repairman.
He said: "the cause may be due to too much lubricating oil or fuel and then it does not burn completely and create soot and prevents the injectors from self-sealing."
An issue worth noting