Fuel Injection Pump

[sens]

Hello Pagode friends,

I hope you can help me with an issue I have quite some time now...

My European 280 engine starts and idles fine, however when driving the car I have 3 issues (especially at full operating temperature):
- some popping after throttle release
- some grey smoke in combination with the popping
- at higher speed (> 80km/h) some minor hesitating (sputtering) of the engine; not much, but noticable.

Some facts:
Engine overhauled about 1000 km ago.
New injectors, tested.
123 ignition is set correctly.
valve clearance is set correctly.
spark plugs are slightly braun.

Another important fact:

I bought the 250SL with a 280 block which is combined with the original FIP for an 250SL: PES 6KL 70A120 R18Z
The official model for a 280 SL block however is an: PES 6 KL 70B 120 R21

So my question is: could this "mismatch" between block and FIP be the reason of the issues I have.

What would be your advise?

Thanks a lot!!!

Halvor

[MikeSimon]

What head to you have on your 280 block? The R21 is not the only FIP for a M130-983.

[sens]

Thanks for your reply!

On the head it says:
130.016 000 1

See picture

And indeed, the block is M130-983

Halvor Sens

[sens]

I think for EU cars the possible FIP’s are R 21, R23, R25, right??

[Cees Klumper]

Hi Halvor - I am not an expert on the FI system by any means, but my guess would be that a 'mismatch' of this nature should not be causing the symptoms you are experiencing. I would look more into something like a vacuum leak, too rich adjustment of the FI pump, stuck pistons inside the pump or the rack not moving freely, that sort of issue.

[sens]

Thanks for your reply Cees!

In the mean time I called a FIP expert and he told me it could cause the symptoms, but not sure…
He said that the slight hesitating at higher throttle could be caused by the fact that the 250 pump does not deliver enough fuel for the 280 engine.

I checked the vacuum with a smoke test; looks ok.
I also tried to make the mixture leaner but that makes thing worse: more hesitating at higher speeds.
I think the rack moves freely, because there is a perfect respons on the throttle. Idle is good.

Could I check the things you mentioned by opening the side cover of the pump?
Should I take the pump out to investigate?

[Jack the Knife]

Not to start a goose chase, but when I was disassembling everything, the inside of my throttle body was so encrusted with crap that it looked like a decades-old uncleaned charcoal grill in a public park. Yet, surprisingly, it still moved freely. But was all this cleaned when the engine was rebuilt? Maybe some encrustation in there delaying throttle response?

Is the popping in the engine or the exhaust?

Is there any way you can upload a top-down view of the engine bay?

[Cees Klumper]

"I also tried to make the mixture leaner but that makes thing worse: more hesitating at higher speeds."

Have you tried making the mixture richer?
Although that could cause more grey smoke, unburnt fuel?

Have you tried checking the CO level? Not sure whether simple testers like the Gunson can do that at higher revs, I've only used mine to set CO level at idle.
There are adjustment screws for the various rpm ranges on the pump but experts always say not to touch those.
Perhaps having the pump bench tested by a shop with the proper Bosch setup/calibration machine would be a good idea. At one point, I remember Van Dijk in Lisserbroek had such a machine.

[sens]

Thanks Cees!

I will follow your suggestions (make the mixture slightly richer) and see an expert to see what happens.

I'll report back!

Halvor

[sens]

Hi Jack!

Thanks for your reply!

Yes, I looked into the throttle body and it is clean.

Popping is comming from the exhaust, together with a small grey smoke puff when I release the throttle.

Attached some pictures of the engine bay.

Cheers!

Halvor

[Pawel66]

I am not a mechanic, but:

Is your vacuum line connected?

If this thick rubber hose is the vacuum line - I am not sure if it is the right type of hose for a vacuum line... Maybe try a correct one?

There is clearly tension applied to ignition leads - they are too short. This tension is pulling connectors and distributor cap. I would sort it out...

There are several wires coming to coil connector - is it not too many?

[sens]

All very fair comments Pawel! Thanks!
It shows the power of a picture...

The vacuum line goes on my 123-distributor and reduces its diameter just before the throttle body. Probably not original, but no leaks...

The tension on the spark leads is too high, I agree. I will change that. Easy fix!

My 123-ignition has long wires and I decided not to cut them yet, so that confuses when you look at the picture. Well spotted. I attached another picture.

Thanks again for your comments!

[Jack the Knife]

All very fair comments Pawel! Thanks!
It shows the power of a picture...

The vacuum line goes on my 123-distributor and reduces its diameter just before the throttle body. Probably not original, but no leaks...

The tension on the spark leads is too high, I agree. I will change that. Easy fix!

My 123-ignition has long wires and I decided not to cut them yet, so that confuses when you look at the picture. Well spotted. I attached another picture.

Thanks again for your comments!

Could you measure the internal diameter of this vacuum line before the diameter is reduced?

[sens]

Certainly!

I just measured 4.5 mm internal diameter; the connection tube on the 123 ignition  5 mm.
I think that is OK; no leaks.

[Jack the Knife]

https://www.authenticclassics.com/Distributor-Vacuum-Line-Mercedes-230SL-250SL-280SL-p/auth-005108.htm

The internal diameter of this line I have here (white vacuum line) is 1.5mm. External is 3.75mm. I am not a mechanic, so I don't really know the interaction this line has, but it might be wise to have the right line. You don't have to buy this one from Authentic Classics -- I didn't -- look at the part number in the kit and order everything separately from autohausaz to save quite a bit of money.

[Pawel66]

At Mercedes:

vacuum line A 000 158 14 35
rubber sleeve connectors A 117 997 09 82

I do not think this alone is a culprit, it is more about general clean up...

[Peter h]

I'd check the basic settings. It doesn't look right to me, but I could be wrong.
 Peter

[sens]

Yes, I agree.
There is no flow through that line, just vacuum, so diameter is not so important.

Thanks and again, well spotted!

Halvor

[sens]

Wow!
You guys are detectives!!!

It looks like the two arms are parallel, but that is vaused by the angle of the camera.

Attached another picture where the throttle is partly open to have a better view.

I think it is OK.

Thanks!

Halvor

[Peter h]

I would also first route the ignition cables and wires correctly. What engine is installed? It could be that certain components don't belong together. I think you should check everything first. The surprises on these cars never end, but that's the fun. Peter

[sens]

Yes Peter, you are right.
Engine and FIP don’t belong together.
But is that a real problem?

[rosch]

Generally  a good running engine needs air and fuel in a right mixture and a correct timed ignition.
Here are just some thoughts :

 -The 123 ignition may cause some light popping at throtthle release , this seems to be normal behavior and is reported by many users.
-Popping in the exhaust accompanied with grey smoke  however may indicate unburnt fuel in the exhaustsystem. This , together with your slight hesitating ,may be pointing to :

1.a fuel/mixture problem in general or - I had the same experience - a leaking injector causing uncontrolled /erratic fuel supply to a specific cylinder , resulting in the same syptoms you have.
A simple check with a "Colortune" ( just google it) helped me find the culprit and also made fuel adjustments easy ,even at higher rpm's

2. an ignition problem  think of wiring ,caps ,wrong or damaged sparkplugs ( check for thin cracks/black traces at the insulator)

If you like to enrich your mixture as a first  try-out,then just add a thin washer underneat the baro compensator.
You may also read my mini serie of postings about "230SL bad starting and running problems".A lot applies to your car as well.

Good luck !

[sens]

Hello Rosch!

So nice to get a good comment from somebody living next door! Almost...

I fully agree with your remarks:

-The 123 ignition might cause some light popping. Could be. I do have a Crane transistor ignition which I used for my MGA. I read some positive comments about that. I could mount it on my Pagode and see what the effect will be.

1a. A year ago I bought 6 new injectors. Last week I tested all of them with an injector tester and indeed one of them looked more like my wife watering the plants in the garden. I replaced it by a new one and that was a lot better.
I looked at the color of the spark plugs and the color of the injectors (No4 from left) to find the problem. (see picture) The spark plug is fully fouled and the injector has no discoloration like all the others, indicating a very bad combustion, I would say.
After your experience about the Colortune I was going to buy one, but I remembered I had one for my previous car. And surprise... it has the same size and is brand new, I never used it. I will definitely use it in the near future!!!

2. Spark plugs are relatively new; so is the wiring. I think ignition timing is set correctly. I checked yesterday.

I always thought that popping in the exhaust meant the mixture was little rich. But I just read on this forum it is just the opposite!!! Mixture is too lean.
Also the little hesitating at full throttle indicates a lean mixture.
So I just did what you suggested and added a 0,1 mm washer underneath the barometric compensator.

I will have a test drive tomorrow and come back with my findings.
In the mean time I will study your postings!
 
Thanks for all your suggestions!!

Halvor, Drunen

[sens]

I took the car for a ride this morning.
It runs more or less OK, but still some popping at throttle release; maybe a bit less.

I did the Colortune test like I show in the first video.
I would say adding 0.1 mm washer (total 2.2 mm)  under the BC makes the engine run richer; I would say too rich.

I removed the 0.1 washer and took a video at idle.
Still rich I think, however CO looks OK. (not calibrated)

As a next test, I could put the Crane ignition on the car just to see if there is any difference.
What do you think?

[Cees Klumper]

I don't expect changing the ignition will make a difference - unless the 123 ignition is somehow faulty and needs to be replaced.
Still would be good to test the CO level, maybe at your local APK station you can ask them to check it?