240D cold start issue
 

Ok I can finally confirm removing the oil cap does make a difference. It got cold last night car did the usual" try to start try to start I'm dead issue" removed the oil cap it fired right up. So barry you win the prize about requiring more research !!

yes I have confirmed even with an open vent tube it will make a difference removing the oil cap. just one more Item for us low compression members to try in cold weather.

Getting off of the soap box now .

Well I really did not want to be a so called winner about your situation.As I see it there are several possibilities and perhaps several arangements possible.

It seems to me now as hindsight is always so great. The piston rings are somewhat more relaxed when not under heavy load. In theory the blowback pressure should further increase otherwise when running rpms and higher occur.

Instead it is actually lowering. I guess this could be verified if desired with a simple gauge. There is a slight chance something is wrong with the shutoff device making it too sensitive as well.

It is almost a certain given that during the intial attempted start up the presure is pushing the shutoff assembley closed with the internal base pressure in the engine.

Or you are not getting a good normal no vaccum present at the cut off somehow or other when attempting to start. So the first cold engine test would be to disconnect the vacuum line prior to attempting to start the engine.

Some of these cars will retain residual vacuum for a day or so. Simple test really just in case as still in my mind the blowby pressure should be increasing as the engine really starts to run.

That would kill the engine for sure with your symptoms. Or perhaps when engine is actually started the splashed oil on the cylinder walls improves the seal is about the only alternative.

If it is the initial blowby proven by the simple test. You could rig a choke cable to hold the shut off on to get started. There is even a convienient handle to attach it to.

Any other solution to keep the old engine working would mean blowing more oil vapors out. This in my opinion means feeding a second breather hose into the system to deal with the initial blowby if that proves conclusivly to be the issue. In your case I would go for the choke cable. How much milage does this engine average on a quart of oil? It would not suprise me if it is not all that bad.

Very interesting. It confirms a couple of anecdotes to this effect on here.

Not a winner on the situation but for suggesting further research be done. Especially since a few members have encountered the same effect. I have taken the vacuum line off the kill but with no difference.

This leads to the choke type set up you suggest I'm guessing if this scenario is happening you will see the linkage moving the same as if you were killing it manually ? If so all I'm trying to do is overcome the blowby from pushing out on the kill diaphragm ? I'm guessing it has a vent hole open to the injection pump and crankcase internal .

Barry enjoy the limelight the prize was seeing my daughters face when it did actually start and we were able to go to the train show as she had wanted to all week. ;)

Thanks for the suggestions I'll try them and reply.

Kerry it went beyond interesting for me bordering on completely baffled :D

Yes you have to verify the action is transfered to that lever for the choke cable setup to function. It probably is as it is a mechanical system to the best of my knowledge. If tnhe engine will cold start easier with someone holding the lever you know it will work.

The base pressure does impact the reverse side of the diaphpram or whatever is impacted in the pump. Thats where the old test that is now not recommended originated.

You start the engine and plug the breather hose with your finger or whatever. Count the seconds the engine continues to run. Ten seconds is a very good indication the blowby is not excessive. Under five is not so hot.

You probably knew of this test already but others may not. Some feel it may blow out a weak engine seal. So the test is no longer recommended. Let us know if the choke cable approach looks sound and indeed works out. It should but there can be issues with everything but not allways.

Ok did the cold start again . It cranked fast then started to slow down . I watched the lever and never did see the linkage move. Removed the oil cap the engine sped up and started to fire. I stopped before it turned on.

I looked at the mechanical linkage and if we put the choke cable to it it would be the same as turning the bowden cable for high idle . This means the vacuum pod is pulling the rack to the stop position independent of the mechanical linkage . Which now makes sense because if not and your throttle was pressed it would prevent you from shutting off the engine.

You would need to modify the vacuum stop in order to prevent the back pressure from pressing the diaphragm , thus creating a manual on off cable. The only other way would be to pressurize the vacuum portion while starting cold. It would need enough pressure to prevent movement and not so much as to rupture the diaphragm.

I guess I could fabricate an electric opening oil cap similar to the exhaust cut outs on the market. :D

Simple. Remove the existing vacuum line from the shut off valve. Replace it with a rubber vacuum hose running into the cabin. Blow in it when you are starting and suck on it to shut if off.:D

LMAO !! I had to check what forum I was on !!! :D:D

Ok I found out today that my valves were all tight. They were just adjusted 5000 miles ago but I did the spring stretch on the pump releif valve so possibly cleaned out some carbon. I posted results on the releif spring thread. She ran good just wouldnt start. Now it starts good but the temperature is in the 40's . So no conclusive evidence on cold starting.

Here in south Texas it might take a while to try it again but I will post when I find out.

1 vacuum stop valve spared for the time being .

Here come the I told you so's !!!! :o

Well even with the valves adjusted at 40* it cranks slow until you remove the oil cap.

Is there any way to remove the vacuum cutoff temporarily and install a plate ? Or will parts be loose in the injection pump after removal ?

I'm also wondering if this could be a starter issue ?

Are you saying that the cranking speed actually increases when the oil fill cap is removed, or that the engine actually fires up while cranking after the cap is removed?

Fascinating either way!!

Would it be possible to connect a hose to the valve cover, or a good place to get crank case pressure, and connect the other end to the vent on the ignition switch? The thought being when the key is in the run position the shutoff diaphragm would see crank case pressure on both sides, but when the key was turned to the off position then vacuum would be sent to one side and the diaphragm would move as it normally does.

Don't know if it could be done, just a thought. I always have a hard time getting my 240D started in the spring. I will try removing the oil cap in a few months.

Yeah it baffles me as well . I seen it posted and tried it. Amazingly the engine speeds up enough to start firing. Before removing the cap its as if the battery is dead.

Good idea on the vacuum cutoff . It would equalize without the worry of blowing the diaphragm.