HARD STARTING ABNORMAL COMPRESSION

[ike51]

HI GUYS: IM NEW TO THE FORUM IVE HAD A FORDSON DEXTA FOR ABOUT THE LAST SIX YEARS OR SO WHEN I FIRST BOUGHT IT WOULD HARDLY RUN AND HAD A BROKEN CRANKSHAFT ON THE NUMBER 2 PISTON. WELL I HAD NEVER BUILT A TRACTOR ENGINE BEFORE SO I BOUGHT THE ITT FORD MANUAL AND TORE THE ENGINE DOWN SENT THE BLOCK AND THE HEAD TO THE MACHINE SHOP AND PURCHASED A CRANKSHAFT ALL NEW BEARING AND GASKETS AFTER THE MACHINE WORK ON THE BLOCK AND HEAD WAS COMPLETE I TOOK THE MANUAL AND REBUILT THE ENGINE AND GOT IT BACK TO RUNNING BUT EVER SINCE THE REBUILD ITS HARD TO COLD START AND I LIVE IN GEORGIA USA WHERE THE CLIMATE IS HOT AND HUMID IVE CHECKED THE FUEL SYSTEM FROM LIFT PUMP TO THE INJECTORS ITS ADEQUATE ,ADJUSTED THE VALVES HOT AND COLD MANY TIMES CHECKED TIMING AT INJECTOR PUMP AND ADJUSTED TO THE PROCEDURE ACCORDING TO THE ONLINE MANUAL NONE OF THIS HELPED BUT I DID FIND THAT I HAD THE INJECTOR PUMP SPRAYING THE FUEL IN AT TOP DEAD CENTER OR A NOTCH OR SO AFTER BUT CORRECTED IT AFTER READING MANY OF YOUR POSTS THE LAST THREE NIGHTS I REALIZED THAT I SHOULD HAVE REPLACED THE PISTONS AND LINERS WHEN I REBUILT WELL YOU LIVE AND LEARN I GUESS I DID A COMPRESSION TEST ON ALL THREE CYLINDERS THIS EVENING WITH THE FACTORY FORD COMPRESSION TESTER THAT I USED SAID THAT ON THE DEXTA AT 180 REVOLUTIONS PER MINUTE WITH THE STARTER ENGAGED THE COMPRESSION SHOULD BE 320 PSI ON EACH CYLINDER WELL I HAD 280 PSI ON #1,260 PSI ON #2 AND 240 PSI ON #3 MY STARTER DOES DRAG A BIT BUT THAT WAS AS HIGH AS EACH CYLINDER EVER GOT. SO IT SEEMS I HAVE A COMPRESSION PROBLEM BUT I HAVE NEVER PUT THE TRACTOR UNDER A LOAD SINCE THE REBUILD I PLAN ON HOOKING TO A FORD 101 14 INCH TURNING PLOWING THIS WEEKEND AND SEE IF I CAN SET THE RINGS IN THE EXISTING SLEEVES TO POSSIBLY IMPROVE THE COMPRESSION AT LEAST ENOUGH TO GET IT THROUGH THIS YEARS GARDENING SEASON AND THIS FALL TEAR IT BACK DOWN AND INSTALL NEW PISTONS AND LINERS THIS OLD TRACTOR WAS WORKED VERY HARD OVER THE YEARS AND IT SEEMS VERY LITTLE PREVENTIVE MAINTENANCE WAS EVER DONE. I AM DOING A LITTLE AT A TIME AS I CAN AFFORD IT BUT FOR ME IT IS A WORKING TRACTOR IT MIGHT TAKE A FEW MORE YEARS TO GET IT IN SHAPE WHERE I CAN DEPEND ON IT WHEN I NEED IT BUT I THINK IT WILL BE WELL WORTH IT IF ANY OF YOU GENTLEMEN HAVE ANY SOLUTIONS TO THE MY PROBLEMS ON MY POST PLEASE FEEL FREE TO REPLY AND MANY THANKS FOR YOUR ARCHIVE POSTS. IKE51

[pjjms]

I always found I needed to use the glow plug for 40 seconds for cold starts, even in weather as warm as 20 deg C.

[Aussie Frank]

Hi Ike,

Low compression can be caused by rings or valves. Squirt some oil in each cylinder and repeat the test. If the compression goes up rings are the problem. If it doesn't make much difference, then maybe all you need to do is a valve regrind. It doesn't take much rust on a valve to knock compression right down.

You are probably right to suspect rings not bedded in though because you said that the head and block were sent to the machine shop. If it has not had much hard work since reassembly a good hard days work should fix your compression problem even if the bores and pistons are worn a little. Most machine shops would tell you if the bores are worn beyond service limits.

Also as pjjms says make sure your glow plug and primer are working. I found that it makes a huge difference with cold starts as well.

Regards, Frank.

[Bensdexta]

Are your injector pump and injectors in good condition?

BTW please don't post in CAPS - it's heavy on the eye

[dexta roadless]

If your starter is a bit slow I would check that first. On a diesel it is essential to get maximum speed to get high enough heat to ignite the fuel. That also lowers the compression pressure. if the rings are the problem it should breath a bit trough the ventpipe when running

[russelm]

A few comments from me

1) Did you do the compression test with the throttle wide open (as there is a throttle butterfly on certainly the standard Dexta which if closed will give lower readings)

2) The most important thing is not the absolute pressures but, how close the pressures are to each other, yours are fairly close (although by no means perfect)

3) Beware the oil trick as adding anything to the cylinders will naturaly reduce the squish area which will increase the compression ratio even if the rings are fine (and hence you need to interpret the results very carefuly and only use a very small amount of oil)

[ike51]

I :hi fellows: I appreciate the information that you shared in your recent posts but i must say that i have never tried the glow plug because i really didnt know its function until i started reading the posts it is currently unwired but i will wire it up and give it a try and see if it helps hopefully it will. i have never had the injector pump or the injectors checked but i did some reasearch today and found a shop locally that can test and or rebuild them so i am going to remove them this weekend and drop them off next week i think they probally need reworking since i really dont have a history on the tractor.As far as the compression test im going to put a small amount of oil in each cylinder and retest if it improves im still going to work it hard and see if possibly breaking in will improve the performance if it does maybe i wont have to tear it down. but at least i have some clues to follow now, thanks very much i will post any progress. ike

[Superdextaaja]

Hello Ike and everybody else!

I am looking for information about the right compression pressure for Fordson Super Dexta -63 engine. What does your measuring instrument say about this maschine? Are there any values set in some diagramm? Or does anybody else know? There seems to be no information through internet on this at all so would be great to find out for other Super Dexta owners as well. I am living in Finland and we have a lot of these maschines here but this knowledge seems to be gone for some reason.

Thanks and good luck with your startingproblems! You should press the preheating knob at least for 30 sec. and then the starting squirt once or twice. Then heater knob again for 10 seconds. If no start, repeat this. Some good fuel, or fuel in general at all, in tank helps also a lot. Check and clean oil bath air filter and fuel filter and your starter too. Helped me to get rid of all startingproblems after I brought the starting maschine to a shop to be overhauled. Gives good and enough rotation now.

[warwick]

Hi all
I was having the same problem with starting and was advised to have the injectors checked . Took them in to be tested and was told they were knackered £98 later and 3 serviced injectors starts ever time but make sure you use the glow plug

[Gavin]

I was always told that there was no correct compression reading for a diesel and that it was more a matter of ensuring that all were close together. I'm sue there must be a minimum at which the engine would run but have never heard it.

[russelm]

Indeed it is more a case of checking they are all pretty close together.

A rule of thumb is:

Pressure = (Compression ratio - 1) ^ 1.1 x Atmospehric pressure.

so given the diesel Dexta has a compression ratio of 16.5:1 and atmospheric is nominaly 14.7psi (at sea level) we get:

Pressure = (16.5 - 1)^1.1 x 14.7 = 300 psi.

Now this is a rule of thumb and the variation from changes in atmospheric pressure alone are quite large plus, it assumes ideal conditions (and engines dont work like that) so dont expect to get that figure.!

Also remember that when doing the compression check, you may need it on full throttle (certainly for a standard Dexta) as the Dexta is a little unusual in having throttle valves on a diesel engine.

[Superdextaaja]

http://ytforums.ytmag.com/ttforum/viewt ... 1b623bef8b

I found this talk about right pressures in internet.
I also found the following links which might interest any Dexta owner:

http://www.engineservices.co.nz/tips.htm
scroll down to Perkins head gasket where they say more about the following:

"It would appear that these engines will need their heads re-torqued as soon as operating temperature has been reached and then a few hours later.We have been recommending this for some time for Perkins 3-152 & 4-203 engines."

Here are also links to a couple of very handy manuals for Perkins 3.521 and Dexta 3.114 and Super Dexta 3.152 motors

http://www.ferguson-talli.net/Ohjekirja ... MANUAL.pdf
http://www.fordson-dexta.de/downloads/section3.pdf

They say both that when replacing a new head gasket, it should be attached with some jointing compound on both sides of the new gasket. I found as an example such as:

http://www.ldsengineering.co.uk/Stag_We ... 31837.aspx
http://www.4pcorporation.com/Hylomar.asp

Anyone have any experience using such jointing compounds?

The older manual from 1962 says that new liners are to be pressured on place with help of using tallow as lubricant. Perkins manual says you should add some engine oil on the outer surface of the liners. How do you find that? Whale fat by any chance anyone in their tool box?
It is also said that the liners for 3.114 Dexta engine are thicker wall type, and the liners for 3.152 Super Dexta engine are of thinner wall type. So it is definately not necessary to replace the worn liners always in Dexta 3.114 motors, but just to let them be drilled again since they have more thickness than Super Dexta liners, which need to be replaced as soon as they are worn more than 0,18mm. To pull out the liners is really difficult sometimes. And pushing replacement liners in place with violance might cause cracking of the block.

http://www.konedata.net/Traktorit/fordsonDexta.htm
Recognize your Dexta here?

[JC]

Pressure = (Compression ratio - 1) ^ 1.1 x Atmospehric pressure.

That's a good thing to know. What do the numbers -1 and ^1.1 stand for?

[Superdextaaja]

http://web2.0calc.com/

At least the ^ means "raise to higher power" like 2^2=2x2=4 , 3^2=3x3=9 etc.

For Super Dexta, or as it would propably be called Fordson 2000 in the US, and for other Perkins 3.152 engines with compression ratio 17,4:1 the figures would be:

(17,4-1)^1,1x14,7=318,89...psi

What 1,1 in the calculation means, I don´t know and would be interested in that information too.

[Superdextaaja]

Well, I asked professor "search mashine" and found several sources answering some of the questions. The following link was very good f.ex.

http://www.ehow.com/how_6453303_calcula ... ssure.html

But I was still not able to figure out what are -1 in (17,4-1) and 1,1 in (17,4-1)^1,1 exactly in the calculation?

I Heard that higher compression ratio results in improved cold-start ability in Super Dexta 3.152 as in standard Dexta 3.114 engine.

[Bensdexta]

But I was still not able to figure out what are -1 in (17,4-1) and 1,1 in (17,4-1)^1,1 exactly in the calculation?

A total guess but perhaps the -1 is subtracting off 1 atmosphere from the compression ratio and ^ raising to the power of 1.1 is to do with adiabatic compression (ie the gas gets hotter when you compress it)?

Perhaps Russ can elighten us as to the source of his info

[russelm]

Yup....the -1 is subtracting one from the compression ratio (because the base is 1 at the BDC)

and the 1.1 is a power to (some more efficient engine designs use 1.2)

The source is an old set of Lucas calcs that I have used for years to give rough guide readings.

[Superdextaaja]

Thanks guys! And thank G for our daily Dexta providing us never ending problems to chew on!