engine fails to accelerate after 3500 rpm when temperture gauge is 80 celsius

[Gazoo]

Hello I have a 1969 280sl ,the engine starts well and runs well when cold ,after driving for about 10 minutes and the temperature gauge is barely higher than 80celsius (about 60%of the max temp)
The engine runs well below 3,500 rpm ,runs well in the traffic but when I push the gas and the engine goes over 4,000 rpm the engine cant go fast ,I am not an expert but it seems that it chokes ( I dont know if is too much gas or few gas)
In Mexico we dont have mechanics for this cars so the one that is helping me  change ,wires,sparkplugs,distribuitor cap,condenser,and the electric pump that is near the gasoline Does anyone has an idea of what could be wrong?
Thank You

[Cees Klumper]

From your symptoms and what you've done so far, I would suspect the fuel delivery system (clogged up fuel filters, main and in the tank, sediment in the tank etc). Have you checked fuel pressure and flow?
There are ten members of this site in Mexico, many in Mexico City, perhaps worth a try to email them directly and ask for tips on competent mechanics. Good luck,

[Gazoo]

Thank you ,i have also change the fuel tank one year ago ,and replace fuel filters ,also put one between the tank and electric pump,the thing is failure comes when car is warm .
Very good advise i will try to contact Mexicans members
Thank you again

[Cees Klumper]

Since the car runs well when cold, the issue can also be in the fuel injection settings when warm (too lean). Someone should really go through the linkage tour etc, probably it's something fairly basic.

[Gazoo]

Thank you

[ctaylor738]

Also, classic symptoms of a failing ignition coil.

[A Dalton]

A common Pert problem on these chassis is the module switching is a " Switched Ground"...meaning the black wire from the coil seeks a good ground thru the Pert module to  dist. ground in order  to  complete the coil circuit.

The problem can be a poor ground between the dist casing/housing and the block.
A poor connection here  will mimic a weak coil.

 A simple Test would be to simply run a jumper wire from the dist casing back to the battery Neg/- terminal and go try the car ...

 If Yes, then you have found your spark fault.

Can also be ohmed or V -drop tested, but the jumper is the easiest test  to assure a good ground.

One can also check that the ground flex wire in the dist is intact and tight.