how come by car would only nail when cold?

[WANT '71 280SEL]

My car nails when it is cold. It always goes away by 60C degrees or so. Even when it is 60F outside, it still nails. Should I just take the injectors apart and soak them independently? If they were dirty, why would it only happen when cold? The valve were adjusted a couple hundred miles before I bought it, but it has slowly gotten worse over my ownership of about 9 months.
If I went that route, can I just use a regular 27mm socket and an open-end wrench for the injectors? What about the heat shields? What size of those would I want? I've heard there are a few diiferent thicknesses available.
Thank You
David

[SW]

I don't know about the nailing, but if you remove your injectors make sure you get a 27mm deep socket.

[WANT '71 280SEL]

Does it have to be the MB one though?
Thanks
David

[79-240d-project]

Just bought one at Sears, about 9 dollars, works perfectly.

[WANT '71 280SEL]

Would soking the injectors cure this problem?
Thanks
David

[psfred]

David:

Maybe, maybe not, depending on why you have injector knock.

I would try the following:

Get some RedLine diesel fuel treatment and try a whole bottle in a tank of fuel. If the knock goes away (it probably will), but comes back on the next tank, it's compression, injection timing, or a bad (not dirty) nozzles. If it goes away and takes quite a while to come back, it's drity nozzles (carboned up) and you can only avoid the problem by driving it harder or longer once in a while. A nice trip to say, St. Louis.

Remember that some noise is normal. Heavy, loud clanking isn't, but if the rest of the engine is in good shape, it's surely carbon from low speed, low load driving. These engines thrive on hard use, but that's difficult driving to and from school in traffic.

I'd also adjust the valves again -- if it had been a while before the last time, you could have had carbon on the valve. When you raised the temp by adjusting, the carbon burned off and you now have an intake too tight.

Peter

The clatter you hear when the engine is cold is USUALLY cause by marginally or incompletely atomized fuel not burning smoothly in the cold prechamber. This can be caused by ANYTHING that distorts the spray pattern (injector nozzle wear or coking) soot deposits in the prechamber, lower than normal injection pressure, low compression, etc.) and is exacerbated in cold weather. Complete diagnosis would include pulling the injectors and testing them for spray pattern and injection pressure. If one or more valves were a little tight that could do it too.

The "cure" you propose MIGHT work if the the problem is just a few deposits in the injector, but is unlikely to cure anything more complicated than that and it sure won't correct for wear.

I have been using a Craftsman 1 1/16" deep socket to remove injectors for more than 30 years and it works JUST great. Pulling injectors apart and cleaning them in hopes of curing cold start clatter is NOT likely to produce the results you expect, but it can occasionally make an improvement.

I wouldn't consider doing it unless I had a "pop" tester to check spray pattern and injection pressure though and even then the percenatge of times that disassemby and cleaning results in a reliable/prolonged improvement seems VERY small - which is why I stopped pulling them apart and manually cleaning them about 20 years ago. Now if a treatment or two of Techron or Diesel Purge is insufficient, I replace the injectors with rebuilds. I seldom need to replace an injector more than every 150-250 kmi. Occasionally one will not last so long but that's only happend to me a few times.

Marshall

[psfred]

A stretched chain will do this too, from late injection timing.

Peter