1982 300D engine troubles

[GARY L.]

Let me start by saying that I am new to this forum and while reading other post's I found such a welth of knoledge here that I just had to join to ask for help.

I am in the U.S and just purchased a new to me 82 300D 4 door sedan with 205k on the clock.
Fine car but has a very strange problem that I am seeking help with.

On cool days less than 26c the engine starts right up and runs just great, even better than expected. It runs along on the freeway at 80-85c on the temp gauge and does not have any problems.

On warm days 28/29c+ it is a completly different animal. The engine does not overheat but the temp reads 100-105c and I notice a bit of a surge from the engine and yes the A/C is off and it is not the compressor causing it.When exiting the freeway the engine runs very rough and sometimes dies. Today after getting off and stopping for a coffee when I got back on the freeway the car was running so poorly that it took over 6km to get up to speed.
There is no smoke or strange noises hot or cold and the problem is temp related.
Here is what I have done so far to try to solve this.
adjust valves
service EGR
replace rack dampner
change fulel filters
check timing chain and engine mounts.
verified temp gauge
clean fuel injectors
I have ordered a new radiator to help solve the higher than normal freeway temps but why is this doing this?
The car shows that it has been well serviced and spent it's entire life here in this town.
I look forward to your ideas.
Thanks
Gary

 

[Bolide]

What on the car is temperature-sensitive or temperature-controlled?

If it's like a W124 then there's a cold-start enrichment device built onto the back of the IP. Is this defective or has it been wrongly adjusted?

Is the ignition-controlled fuel shutoff valve opening completely?

If you've adjusted the valve clearances then I assume it doesn't have hydraulic tappets

I'd be inclined to rig up an alternate fuel supply straight to the lift pump & IP to rule out fuel as a problem. Then I'd pull the injectors, test the opening pressure and pattern and test the output of the lift pump & IP

If all that tests OK I'd do a leakdown test and a compression test on the engine. That should finally pin it down

Nick Froome
www.w124.co.uk

 

[GARY L.]

What on the car is temperature-sensitive or temperature-controlled?

If it's like a W124 then there's a cold-start enrichment device built onto the back of the IP. Is this defective or has it been wrongly adjusted?

Is the ignition-controlled fuel shutoff valve opening completely?

If you've adjusted the valve clearances then I assume it doesn't have hydraulic tappets

I'd be inclined to rig up an alternate fuel supply straight to the lift pump & IP to rule out fuel as a problem. Then I'd pull the injectors, test the opening pressure and pattern and test the output of the lift pump & IP

If all that tests OK I'd do a leakdown test and a compression test on the engine. That should finally pin it down

Nick Froome
www.w124.co.uk

I am not aware of a cold start enrichment device but will check.
This car is a 123
I did check the shutdown and no problem there.
I have also checked all linkages and lubed just in case.
I drove the car this morning 114 miles with no problem but each afternoon the problem comes back when outside temps are higher. Maybe I am wrong but I would think that a compression problem would be cold and not hot. How would I keep the engine hot enough to do a hot compression check with water temp at or near 100c?
What in the fuel supply changes with amb temp thatI should be looking for?
Your ideas are great and I will start with the easy first.
Thanks