no compression

[ncbrew]

I did a minor overhaul and now the engine turns over but has no compression

ncbrew

[MicHughV]

does the engine have compression release ???

[ncbrew]

Originally Posted by MicHughV

does the engine have compression release ???

yes it has 3 levers but I took the valve cover off so those levers are not releasing the compression

[Viking Sailor]

It sounds like you have a volvo MD17C/D. Their is a compression release on the shaft end of the engine. It is located near the top of the engine and activated by pushing in a small rod (~5/8" dia). This rod can get stuck in the decompression position (pushed in).

[ncbrew]

Originally Posted by Viking Sailor

It sounds like you have a volvo MD17C/D. Their is a compression release on the shaft end of the engine. It is located near the top of the engine and activated by pushing in a small rod (~5/8" dia). This rod can get stuck in the decompression position (pushed in).

I have a Yanmar 3gm30f. I took the cover off so those release levers are not in the picture.
I replaced all the parts below the injectors

[skipperpete]

Originally Posted by ncbrew

I did a minor overhaul and now the engine turns over but has no compression

ncbrew

Define “minor overhaul”

[SailingHarmonie]

If you are sure about the decompression levers, it sounds like your valve timing is WAY off, and a valve is open during some or—all—of the compression stroke.

I can’t think of any thing else that would give you zero compression on all cylinders.

[SailingHarmonie]

Originally Posted by ncbrew

I have a Yanmar 3gm30f. I took the cover off so those release levers are not in the picture.
I replaced all the parts below the injectors

ALL the parts below the injectors? What does that mean? Valves? Pistons? Crankshaft? All are “below the injectors.”

Don’t make us pull details out of you. Write a paragraph about what you did, and another about why you did it, and a third about what exactly you see as symptoms.

[skipperpete]

Originally Posted by ncbrew

I did a minor overhaul and now the engine turns over but has no compression

ncbrew

Turn off the raw water intake if you’re doing a lot of dead cranking !! ….How do you know there’s no compression? What lead you to this conclusion?

[Cheechako]

Maybe you got the rings in upside down?
Did you buy new rods and pistons? Usually recommended on the 3GM.
If the rings are right, it pretty much has to make compression unless your valves aren't closing.... Can you see that the valves are closing, loose rocker arm when closed?

[MicHughV]

You took what cover off ??...and what are these 3 levers you are talking about??

are they levers or rocker arms.....the arms that push the valves down..???

Just wanna make sure we are all on the same page here.....

Lotsa smart people on this forum, but you gotta ask the right question to get the right answer..

[Wotname]

On a 3GM30F the decompression levers are mounted through the valve cover. When ncbrew tells us he has removed the cover, he is telling us the decompress levers can not be the source of his low compression.

But yeah, more detail would be very helpful at this stage.

[MicHughV]

There are several online threads about this particular engine's decompression levers..
Also several threads on this CF regarding same.
I just glanced thru' them, but it looks like an answer could be found there..

[ncbrew]

Let me start over.
The engine was smoking very bad when starting but cleared up after about 2 minutes.
I wanted to try to stop the smoking which a few people said was due to fuel leaking in to the cylinders.
I removed the head and rocker arms and took them to a local diesel shop.
He said he cleaned and reset the injectors to factory specs.
He also said he cleaned the head.
I purchased the parts that go into the injector holes below the injectors. They are:
O ring, heat insulator, Chamber gasket, rear chamber. And 2 washers.
I do not think the problem are the decompression levers.
When I try to start the engine it spins very easy and does not fire.
I could try to reset the valves but I don't know how to tell when the #1 cylinder is at Top dead center.

[MicHughV]

Well, simple enuff....if you can rotate the engine, just watch the valves, with the cover off....when the inlet valve is all the way down on a particular cylinder, that means the exhaust valve is likely to be fully closed, easy to see by watching the cam lobe on the camshaft controlling those valves. Check the gap of the closed valve and adjust to recommended clearance. Repeat for the exhaust valve and move to the next cylinder.
rinse and repeat.
After installing new head gaskets, etc, these gaps are likely to be off.