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220SEb Coupé dies after 30 mins driving

Trouble is, I'm not sure if you can buy the o-ring seal for the impeller cover.
O-ring will be a standard size off-the-shelf easily available item - just get the dimensions (diameter will be easier measured from the component it attaches to). Don't let that put you off opening up your existing pump.
 
Mixture very rich. Black plugs and soot on driveway. leaned mixture. No sooty exhaust, but still stalls.
Doesn't really imply fuel starvation.
Then I decided to deliberated drive it until it completely stalls and listen for the fuel pump (yes, I know. Why didn't I do that in the first place? Sorry...) and no whine from the pump. switch ignition off and wait a minute and fuel pump whines and car drives.
Won't the pump stop when the engine ceases turning? (safety feature). Then re-prime when ignition switched back on?
I'm still a little concerned that the engine seems fine at tickover and will rev in neutral after I'm forced to pull over to the side of the road. As soon as I try to pull away though, it fluffs, but will be ok on tickover..... That's was was directing me towards the coil or condenser being the issue.
Is the mixture weakening during warm up as it should or maintaining cold-start mixture?
 
Sounds like you're getting ready to throw parts without diagnosing the problem. How about getting a fuel pressure gauge or checking the CO. You could be running super rich which would also give you the same symptoms.

The cold start system uses wax and is notorious for getting stuck open.
 
O-ring will be a standard size off-the-shelf easily available item - just get the dimensions (diameter will be easier measured from the component it attaches to). Don't let that put you off opening up your existing pump.
It's about 3 inches diameter, but yes, I will have a go at rebuilding the original, especially as there's a rebuilt item currently for sale for €3,250.
 
Doesn't really imply fuel starvation.

Won't the pump stop when the engine ceases turning? (safety feature). Then re-prime when ignition switched back on?

Is the mixture weakening during warm up as it should or maintaining cold-start mixture?
No, pump is continuous, as there is a return to the tank.
 
Sounds like you're getting ready to throw parts without diagnosing the problem. How about getting a fuel pressure gauge or checking the CO. You could be running super rich which would also give you the same symptoms.

The cold start system uses wax and is notorious for getting stuck open.
Am not throwing anything away, although I always change the distributor for electronic on any classic car I own.

There only seem to be two adjustments on the FI, although do remember I have only owned the car for 6 days and have not yet found a workshop manual!

As for the fuel pump, am happy to pay €100 for a replacement to get me running while I find a kit to repair the original.
 
It's about 3 inches diameter, but yes, I will have a go at rebuilding the original, especially as there's a rebuilt item currently for sale for €3,250.
An exact OD or ID and the cross-sectional diameter (thickness) identifies it by dimensions. Only material unknown. Research typical for petrol. If in doubt buy different types (eg nitrile, viton) and compare pliability with original. Viton works with petrol.

No, pump is continuous, as there is a return to the tank.
Struggling to believe that Mercedes sold a car that in the event of a collision that stopped the engine turning but with the ignition still on would continue to pump fuel to the engine bay (into possible ruptured pipes/components). To get clarity on this I suggest tracing the switching wire for the fuel pump relay back to source and establish that it is a straightforward 'hot when ign on' connection. It coming from anything that is in communication with engine turning/not turning, oil pressure, or fuel pressure suggests the required safety pump-disable is in place.

Only this (extremely suspect) aspect is pushing you to believing it is fuel starved when the clear evidence of sooted plugs suggests otherwise. The evidence suggests cold start enrichment is not being turned down as the engine gains temperature and Alabbasi has already said the the mechanism for this is noted for doing exactly that.
 
I WOULD GO FOR A MORE MODERN ROLLER PUMP - PROVIDED THE OUTPUT PRESSURE AND FLOW RATE ARE SUITABLE! Electric Fuel Pumps (EFP CAM)
intermittant FAULTS like yours are often experienced in components that overheat after a period of time due to mechanical or electrical overloading.
 
Thank you, Bellow and Grober.

Bellow, my car does not have a fuel pump relay. It connects directly to the fuse box. But your point about it continuing to pump fuel in the case of an accident is well-made. I am now entering my second week of ownership and will go through the pipework tomorrow.

Grober, yes, I have ordered a Pierburg item (from Gremany...just noticed it on Ebay, lol). This was kindly recommended on this forum. I'm still concerned that the car doesn't actually stall when it fails. Let's see.....

I always say that owning a classic car is a journey. Unfortunately, without a workshop manual, I am undertaking that journey without a map!

You may also find it amusing that the odometer doesn't work and neither the fuel tank sender; a particularly awkward combination !
 
My 6,3 used the same mfi system and fuel pump. 100% sure that the pump is not continuiusly running with ignition live.
 
Hi All and thanks so much for all the great replies. Much appreciated! Well, one thing I noticed this morning was that it is missing the main engine-to-body earth strap. Goodness knows how it was even running. But that wasn't the problem. Tried switching coil-to-distributor HT lead. Nope. All pipes for venting are brand new and I tried running the car with one of those emergency petrol caps, which was a loose fit. Still conked out. Mixture very rich. Black plugs and soot on driveway. leaned mixture. No sooty exhaust, but still stalls. Fuel tank was professionally cleaned and the whole system checked right through to spray pattern from the injectors (when the car was rebuilt in 2019, prior to two years in the museum). Then I decided to deliberated drive it until it completely stalls and listen for the fuel pump (yes, I know. Why didn't I do that in the first place? Sorry...) and no whine from the pump. switch ignition off and wait a minute and fuel pump whines and car drives.

I'm still a little concerned that the engine seems fine at tickover and will rev in neutral after I'm forced to pull over to the side of the road. As soon as I try to pull away though, it fluffs, but will be ok on tickover..... That's was was directing me towards the coil or condenser being the issue.

So.....assuming it is the electric fuel feed pump and this does seem a distinct possibility after two years of inactivity, what are my options ? Haven't checked for a replacement yet, but does anyone have any recommendations?

Thanks again and here's a link to some pics of "Hugo".

My post is of absolutely zero help unfortunately, but "Hugo" is a really lovely looking car.
Sadly I guess it will inevitably come with a few 60 year old problems.

I genuinely hope you get them all resolved, because I will stay subscribed to this thread for more updates
 
Won't be the first time I've misdiagnosed a problem and certainly not the last!
 
My post is of absolutely zero help unfortunately, but "Hugo" is a really lovely looking car.
Sadly I guess it will inevitably come with a few 60 year old problems.

I genuinely hope you get them all resolved, because I will stay subscribed to this thread for more updates
Thanks Shaun, your message of support is greatly appreciated!
 
New coil arrives tomorrow, but am not too hopeful that is the issue.....that was about 4 diagnoses ago!
 
Fuel pumps don't typically fail by causing the car to run worse over 30 minutes. The electric pump on this car is simply a delivery pump, the mechanical injection pump that's bolted to the side of the engine is where the action happens.
 
The 220seb coupe has the fuel injection pump mounted to the engine at the rear on the side. It is a delicate piece of kit and not a lot of people know how to work on it nowadays and personally I wouldn't go plumbing in electric fuel pumps in case you wreck the injecton pump. They are near impossible to source if you wreck it and cost an arm and a leg to have reconditioned. These fuel systems are now a dying art and only a few people know how to work on them.

I would comtact Roger Edwards Motors who are specialists in these older injection systems and cars so run it past them and see what they think. With a car like this, I would definately join the Official Owners Club as you get a lot of good accurate technical advice and help on the older Mercs from that club.

If the car is not starting when it cuts off , carry a can of carb cleaner with you and the next time it happens, squirt the carb cleaner down the air cleaner intake directly in to the engine and see if it fires. If it does, its the fuel system, if it doesnt't its ignition related.
 
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Here is the news. There is no news. Coil fine. Original fuel pump fine. All I'm left with is muck in the fuel (although previous owner assures me that the tank was thoroughly cleaned). Now you're going to say that I should have checked the fuel filters already, but the thing is, I can't find them ! I'm used to a glass bowl affair from my P1800. My manual says to change the paper element, but I can't find where it is !

Help? :wallbash: Thanks as always!
 

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