Timing a 8/1

[somian]

I am trying to actually persaude my 8/1 start-o-matic set into life, as yet only with the handle, but I have two questions. The manual I have seems to suggest that the timing marks on the flywheel line up with the centre line of the cylinder, yet that seem svery vague. Is this correct? If it is, how do folk determine where the middle of the cylinder really is?

The other question relate to compression; or in other words I am not sure my engine has enough of it. My early indirect injection Petter AV1 is very difficult to pull over compression on the handle without using the decompressor, yet the 8/1 can be pulled up through compression. So far as I can tell the start-o-matic machine when motoring has to pull it over with the decompressor disengaged, so it seems it is possible. Any guidance you can give me, folks?

Ian

[AdeV73]

I can swing my 6/1 through compression, if I take a run up at it (about 1.5 turns backwards, then haul it round as fast as possible). If it doesn't start on the 1st compression, it ususally goes on the 2nd.

As I understand it, the S-o-M will motor with the decompression lever engaged, for a number of seconds (determined by a bi-metallic strip) before pulling both the decompression off & opening the fuel rack at the same time. The engine keeps motoring, but it's using the inertia in the flywheels to help pull it along.

[somian]

Presumably your 6/1 has a compression changeover valve, and what you write about just being able to pull it through compression is with it screwed in. Mine, being an 8/1 effectively runs on low compression all the time. It certainly seems like mine has less compression than yours, but if yours has the COV screwed in mine will have less.

Ian

[AdeV73]

Presumably your 6/1 has a compression changeover valve, and what you write about just being able to pull it through compression is with it screwed in. Mine, being an 8/1 effectively runs on low compression all the time. It certainly seems like mine has less compression than yours, but if yours has the COV screwed in mine will have less.

Ian

Yes, that's with the COV screwed in on mine (it won't start with the COV out, unless it's already warm).

Are you getting white smoke when you turn yours over?

[compig]

At 17.5 : 1 the 8/1 is in between the 6/1 high and low compression positions. Has your 8/1 been standing for a while ? If so , the rings may not be seating and also the valves may be leaking a little. It should be ok once it's had a few hours running. Try directing a hot air gun down the intake to persuade it to start initially.

[somian]

It has indeed been standing for at least 5 years, possibly more. It was installed in premises in Leicestershire, move to near Cambridge, where it stood outside, but sheeted over, and is now installed in a wooden shed by my house. Its previous owner (the one near Cambridge) saw it running before it was moved from Leicestershire, but it has not run since. I have freed off the injection pump, checked its timing (such as one can with such a vague timing mark on the block), and changed the oil etc. One distinctly odd thing was that it had no comression at all when I got it, because neither valve had any clearance and neither sealed as a result. I have adjusted the tappetts, with the result it now has some compression, but I am not convinced it has all it should have. I suspect muck on the valves/seats, but the rings may be stuck as well. I have turned it over with the injector out, but connected, and it injects into a tin, but I can't really judge the spray quality. I don't at the moment know if there is diesel vapour coming out of the exhaust, and in truth the pipe is probably long enough that it would largely have condensed by the outlet any way.

So far I have only tried to start it on the handle, without success. I must now get another battery so that I can motor it over. I am hoping that if I can get it started the first time it will clean valves/seats as it runs and possible loosen stuck rings if they are stuck. It is just that I need to start it that first time.

[compig]

To avoid a partial strip down try the following. With the piston at least an inch down the bore , push the valves down and let them snap shut half a dozen or so times. Squirt penetrating fluid down the intake with the piston around TDC , then rock it over TDC 10 or 15 times , then repeat the process. Then let the engine sit overnight.  This combined with a hot air gun down the intake when cranking will have a good chance of firing it up , then it should sort itself out with a few hours running under load.

[lowspeedlife]

With the injector out, a small squirt of oil into the cylinder may increase the compression enough to get her started.
You mentioned the timing marks lining up with the center of the cylinder, you may be reading that incorrectly, if i remember correctly the marks will line up when the piston is at top dead center on the compression stroke. if i'm wrong about that i'm sure someone will correct me, please.

scott R.

[Stan]

Be careful with injectors.  If you get any skin near the "front" end of an injector it will inject diesel right through your skin and into your blood stream.  This is NOT GOOD!  People die this way.
Stan

[somian]

To Low speed life,
There are two marking on the outside of the flywheel on mine, one states TDC, the other which is somewhat before it when the thing is going in the correct direction is the zigzag symbol. As set up the zigzag lines up with the centreline of the cylinder when the flow through the pump stops, which I take to be correct.

[lowspeedlife]

I believe you are correct. In your original post I thought you were refering to the timing marks on the crank, cam & idler gear.  Stan, does Penelope have a zigzag mark on the flywheel for the fuel injector timing?

  Scott R.

[Stan]

Yes, Penelope has a zig zag mark on her flywheel, but no other mark that I can see.
STan

[somian]

IT STARTED!!.

Please excuse the shouting, but it seems justified to me. I got the 24V electrics finished yesterday, and on the second try it started. It was motoring over much quicker than anyone could hope to crank it, but the fact remains, I now know it will go. So far I have controlled the pump rack manually, because I am not sure the governor works, (though I have no particular reason to think that it won't). I am now rigging up frequency measuring kit so that I can let it gently up to speed and see whether the governor will limit it at that.