Ah, roger that. I’ve already preordered one, looking forward to installing it.
Have you done the stretch?

You want to make sure that you still have overflow from the relief valve after any modification of the spring. Wise to verify it even before. For example the lift pump might be weaker with age and need refreshing as well. Also filter obstruction can lower base fuel pressure in the injection pump.

For example if the lift pump has weakened in age to the point it is unable to open the current relief valve. Changing the spring will do nothing. Neither will restoring the original to the intended length before sagging.

At the same time I feel that having proper fuel pressure in that supply system is important on the 616 engines especially. Fortunately things that can impact this are easy and cheap to rectify if found lacking.

So for those that restore a sagged spring or replace it. If they feel no difference In the seat of their pants especially. Further investigation is warranted.

A weak fuel pump or lift pump if you wish. Is pretty easy and cheap to rebuild. If in a weak condition the chances of failure on the road increases as well. Now that can be expensive. If for example it tests weak you have to eliminate things like a fairly obstructed tank filter is not the issue.

In other words the relief valve regulates the pressure of the fuel in the injection pump. It cannot regulate really low pressure.

There also is considerable localized heat created by the compression of the fuel in the injection pump elements. The overflow from the relief valve removes some of that heat. Yet another reason to keep the system in good shape.

Proper pressure out of the lift pump means a better and more constant flow out of the relief valve. Removing more heat in the process. Over and over again I read posts of difficulty in starting in cold weather. A good lift pumps check valves if sealing well stop back draining. So when they are tired. You start cranking but fuel is not present in enough quantity from the elements to light off intitially.

It instead gets blamed on many things like the engine is old. Where this is true in a lot of cases. The situation if it exists still makes the situation harder than needed. There is a simple test to check this. Say it is thirty degrees out in the morning. Have someone pump the primer pump before you try to start. If there is a massive improvement in start up time. You have a back draining problem to examine that occurred during the night.

To me it is not a case of the valves in the lift pump have failed. As much as crud over the years has accumulated on the valve seats allowing leakage. The kit is cheap to renew them so it is also not a big issue.

In fact after rebuilding the pump if needed it may be good as a test to check it for back leakage. When off the car. When it is not working both valves in it act like two closed check valves in series. .

Why do you check things out before plunging in? In my case I never usually got enough service records to determine what was repaired before I got the car. Maybe that lift pump was rebuilt or replaced five years before and is still like new. I see some people randomly changing things without thinking about this factor. It instead is better to spend the money where the proven need is.

If you want reliability close to a new car. Or as close as you can get in practical reality with cars this age. Over time there are a lot of things to check. I have two 240ds, a 300d NA and a 300d turbo. These are all very old cars. The best thing of all is the needs are cheap in general to address if and when found. If you do them yourself usually fairly inexpensive compared to paid for service as well.


Many are for your own safety as well. In the 240ds you want all the power that is available out of those engines. It may even save your posterior getting into a traffic stream someday. This means checking valve clearances, Chain stretch and some other things that can kill your engine with time as well if ignored.

I stretched the factory spring back out to the 27mm spec. Next time I opened the overflow valve, the spring was broken.

I put Greazzer's spring in, completely happy since. I don't notice any extra power in normal driving, but after Greazzer's spring I was able to pull hills in 5th gear that I'd previously had to drop to 4th gear for.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

That wasn’t making a rattling noise by any chance was it?

Maybe, but nothing that could be heard over the rest of the racket the engine makes. The new spring did make an improvement in engine noise when running, though. Pure supposition, but my guess is that without sufficient pressure in the fuel gallery, the fuel elements don't fill completely, causing nailing.

If you're tracking down a rattling noise, there's about a million things it can be, including stuff that isn't rattling at all. Head to YT and listen to videos about injector nailing, important to be able to distinguish the difference. SOME rattle is normal, nailing is not.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

I’ve been tracking down, trying to track down, some very intermittent arythmic rattling that occurs only on load around 20-40mph -infrequently enough to pin down to anything obvious. Not nailing but rattling. Almost like a bearing ball... maybe.

.

I've put 2 mm shim to compensate 4 mm stretch missing...no problems since

cheers

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w126 500SEC gen II euro, powered by OM617 turbo stolen from 84 300SD 2.88 diff,EGR blinded
next wish/project: w114 coupe OM603 powered

what did you use for shims?