Author Topic: 280SL 1968 won't start. (Read 14343 times)

Thierry du Laos · « **Reply #25 on:** January 22, 2019, 08:15:19 »

I meant this part

mrfatboy · « **Reply #26 on:** January 22, 2019, 12:21:42 »

That is the BC (barometric compensateor) or altitude compensator. See the wiki here for description.

https://www.sl113.org/wiki/Engine/AltitudeCompensator

Edit.

I just noticed that you posted twice. The description in the wiki will ultimately answer your question. But the short answer that you are probably looking for is the BC (working or non working) should not cause the rack to get stuck.

Here is the wiki on the entire FIP.

https://www.sl113.org/wiki/Fuel/Injection

Also, don't try to open up the BC. You will ruin it. 😖

Thierry du Laos · « **Reply #27 on:** January 23, 2019, 03:40:13 »

An other question:
- How do the gears turn the pistons, in the cylinder to regulate?
- What kind of mechanical device connects them?

Shvegel · « **Reply #28 on:** January 23, 2019, 09:56:55 »

Thinking back on your past posts involving machine tools and remebering how much you did yourself on your car I assumed that where you were things might be marginal in terms of getting things done. I applaud your efforts.

The only thing that keeps the rack from moving is friction between the cylinders (Barrels) and the pistons (Plungers). The rack turns the pistons and the cylinder are retained in the pump. Unfortunately, I think you may be in trouble. When you removed the cylinders the little gears that turn the pistons may have skipped out of place. Added to that the pistons have springs in the bases (not the fat return springs) that are preloaded by twisting the piston as it is installed which preloades the rack so it closes. I don't remember where those springs are indexed in the whole scheme but if they index to the cylinder the tension is lost.

Lets worry about the first thing first. If you remove the side cover all the little bare steel slit collars with screws in them must be in the same orientation and should not be pointing in different directions. If they are messed up you might be done already.

The top can device is acrually a barometric compensator. push on the shaft a bit and as long as the shaft is free it is probably OK. Don't see how far it moves just make sure it is free or you risk altering it's properties.

BBB will do you no good. There is nothing on the internals of the pump. there is a Bosch rebuild manual online. Let me see if I can find it.

Shvegel · « **Reply #29 on:** January 23, 2019, 10:09:03 »

The factory Bosch manual is listed under "MFI Repair" in this link. I had to keep clicking on the downloaded zip file to get to the manual.

https://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm

Benz Dr. · « **Reply #30 on:** January 23, 2019, 16:18:22 »

There are certain external adjustments that you can make to an IP and even then you need to have some idea about what you are doing. Going inside the pump to mess with things is NOT a good idea even if you have manuals that describe how to do it and I think that no one here should ever advocate going in that direction. This is specialist work ONLY and not for the novice DIY kind of owner.

ja17 · « **Reply #31 on:** January 23, 2019, 16:51:21 »

Illustrations from Early BBB that may help...……….. It shows the early 2cyl IP for sedans but the concept is the same.

Thierry du Laos · « **Reply #32 on:** January 25, 2019, 05:02:20 »

Thank you for your understanding and informations, ALL.
The gears turn the pistons, but the cylinder is a different part that come on top to, guide and avoid the fuel to go down

I don't know if the cylinder is only moving verticaly or also rotates with the gear?
Moving verticaly, sure because it is the way to regulate the fuel quantity.
I don't think it rotates, and hope too, otherwise as you wrote: I am done.

Look at the pictures I have collected and put together to my understanding.

Thierry du Laos · « **Reply #33 on:** January 25, 2019, 05:07:28 »

I remember when I first open the FIP and the rack was locked. The rack got freed only when I took out the last cylinder, which was hard, the No3.
I check again now that you gave me all these informations.

Pawel66 · « **Reply #34 on:** January 25, 2019, 09:48:29 »

Thierry, when you remove the side cover of the pump, you will see (among many other things) 6 small pins in the upper part of the opening. These are the pins that are supposed to hold the cylinder in place and prevent it from turning. If the cylinder is turning with the piston, there is no pumping action of the piston (the hole in the cylinder and the slant in piston are not taking, lifting and giving fuel).

So cylinder must not be turning. Make sure you have all the pins there.

Shvegel · « **Reply #35 on:** January 25, 2019, 22:57:43 »

The top of the pistons have a slant machined on the side of them. This lines up with a hole in the cylinder. By turning the piston you are exposing more or less of this slant which in effect alters the point where the piston seals and pressure begins to build. Think of it like holding the intake valve of an engine open. The piston travels the same up and down but compression is less because the valve is delayed.

Thierry du Laos · « **Reply #36 on:** January 28, 2019, 04:30:02 »

Thank you for these explanations.
So this Saturday I remove all again but found out that the rack was kept free for and aftward, if during inserting the cylinder aligned, I was pulling the rack forward!!!
A thing I didn't do before, and left it in central position.
I dont' know if it is real, but it worked. After installing all of the 6 cylinders, check valves and pipe connections torqued, the rack was moving nice.
I tried to start, but the engine was running on 3 cylinders !!!
So I disconnected the lines at the injector side. Put some plastic bags and crancked.
There was fuel on all 6 lines.
So I removed the injectors, and will take them to a shop who fixes the diesel engines! And ask them to clean and chek the spray.
Lets see for next?

Thierry du Laos · « **Reply #37 on:** January 28, 2019, 07:36:05 »

Here are some pictures....

Pawel66 · « **Reply #38 on:** January 28, 2019, 07:40:53 »

Looks very familiar...

And the spark plugs in those cylinders that were not woking - after engine running/cranking - were they dry or wet?

Thierry du Laos · « **Reply #39 on:** January 29, 2019, 04:08:34 »

Sorry, I cranked so many times with and without the spark plugs to save my battery, that it was not evident.
I tried that at the begining, indeed, and it was dry, that is why I went to check the FIP.
And found the rack was locked.
Now that I freed the rack and starts again, I look for the 3 cylinders I've lost...!
Yesterday I went to the Diesel shop! But they have a tool to test the Diesel injectors, with a gauge out of order.
After that, I think 2 or 3 injectors are not correct.
I talked to my Mercedes garage friend, he said that they used to soak them in brake fluid, and blow them to clean.
And there might be, at the Vientiane Lao-German technical school, a bench test for these old injectors?
So I am working on that... Step by step.

Shvegel · « **Reply #40 on:** January 30, 2019, 02:09:05 »

If you think your injectors are flowing the same amount I wouldn't put the blame on them for the cylinders not firing. The later CIS system ran the injectors all the time and the fuel would just pool up behind the intake valve until it opened and dumped it into the cylinder. If the proper amount of fuel is reaching each cylinder it should fire. Maybe not perfectly but it should fire. Is there any chance you have missplaced the firing order of the spark plug wires at either the spark plug end or at the cap? I believe the rotation of the ignition rotor is clockwise but you should check by removing the cap and cranking the engine (watch the distributor cap clips as they tend to snag the rotor) After you verify rotation then find plug number one at the cap and make sure the rest follow the order cast into the valve cover.

ja17 · « **Reply #41 on:** January 31, 2019, 23:50:49 »

Move the suspected bad injector to another cylinder and see if the problem follows.

Thierry du Laos · « **Reply #42 on:** February 04, 2019, 02:40:13 »

I swapped two injectors and both spark plugs came black.
Then I bought new spark plugs as after cranking so many times they were getting not so reliable any more.
And all the cylinders are running now, but far too rich.
I tried to adjust the linkage to lean, but couldn't make it as I get out of adjusting range.
I blanked air succion hoses for cold start and brake power.
FPI disconnected, and resting in idle position, I open air admission and it runs properly a 2 000 rpm.
Also, when I push backward on the rack, it runs fine.
So I plan to reset all the linkages back to origin and plan adjusting the screw at the back of the FPI toward lean!!!
Maybe my injectors are better than previous, maybe I pulled too strong on the rack when it was locked, ...??
That's my understanding today...

Pawel66 · « **Reply #43 on:** February 04, 2019, 20:06:55 »

But it sounds like a progress!

As advised by the Members before, rich condition may be the result of many factors
- just adjustment (full load, idle)
- WRD sticking
- WRD shims
- barometric compensator stuck
- barometric compensator shims

and some others, I am sure, too.

My experience was that it took the car some drive for the new settings to come fully through. I know it is odd, but that is what I observed.

Thierry du Laos · « **Reply #44 on:** February 05, 2019, 03:44:50 »

Sorry what is WRD?

mrfatboy · « **Reply #45 on:** February 05, 2019, 03:47:56 »

Warm Running Device

Thierry du Laos · « **Reply #46 on:** February 05, 2019, 07:52:49 »

Do you think the WRD can interfere with the rack movement?
I have isolated the WRD hose and blanked it!

ja17 · « **Reply #47 on:** February 05, 2019, 22:43:46 »

The WRD will influence the position of the rack, but will not prevent it from moving.

Thierry du Laos · « **Reply #48 on:** February 06, 2019, 08:23:00 »

I tried to ajust the screw at the rear of the FIP, but can't reduce the fuel.
So as in the past I added a little shim to close 100% the air S-O valve when hot, I am going to remove it. To check if it is not what increase the fuel?
And after that, if it doesn't work I will have to send the FIP and injector to a specialized shop.

Pawel66 · « **Reply #49 on:** February 06, 2019, 13:27:40 »

Thierry, maybe I am repeating what you already know very well, if so - sorry.

WRD - as Joe said, it cannot lock the rack, but it influences it to increase fuel when engine is cold. The simple first thing here to test if WRD is responsible for rich condition is to check if it "switches itslef off" when engine is warmed up. You do it either by listening to the air loud noise as it is sucked through the little filter on the WRD (the noise must stop when engine is warm) or you unscrew the filter and feel with your finger if you get suction through the opening. If the device sucks air with warm engine - the WRD may not work ok and cause rich condition. Then there is the whole procedure with shims.

Barometric compensator - if it is broken it usually causes lean condition, bu for instance mine was stuck in the "up" position making mixture rich. Some reading here: https://www.sl113.org/forums/index.php?topic=12175.msg82217#msg82217

I think you may also have cold start solenoid on FIP - but I have not studied how to test it, so I do not know, sorry, my FIP has no solenoids.

Adjustment idle: just to make sure we have it correct - the knob outside (do not turn it while engine is running!) is just for idle, i.e. up to 1500-1700rpm more or less. Clockwise - richer, counterclockwise - leaner.

Adjustment full range: this is another adjustment we may decide to touch while carefully noting down the number of clicks towards each side. It is the screw in the back in the top right corner of the back plate of the pump. It adjusts fuel in the entire range of rpm. Clockwise - leaner (!!), counterclockwise - richer (!!). you can try this one if you are not afraid. You will need small flat screwdriver.

What we cannot touch, I think, are the partial load screws, light and dark, located next to the idle screw. What we also cannot touch is the linkage lever on the pivot at FIP.

Good reading as well:
https://www.sl113.org/forums/index.php?topic=28224.msg203581#msg203581

Hope I am not adding confusion....

News:

Author Topic: 280SL 1968 won't start. (Read 14343 times)

Thierry du Laos

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