PeachParts Mercedes-Benz Forum - View Single Post

Alastair · #13 01-23-2009, 04:04 PM

Quote:

Originally Posted by franklynb

I don't want to.

BUT, it looks like the p.o. used some hokey-pokey copper washers, which are now seized in the bores of the pump elements. And leaking.

I'm aware that the seals need to be fished out -- normally -- due to expansion from compression stresses. I typically carefully pry them out with a stainless dental pick.

These are much worse than that.

For clarity, here's the style of element/delivery valve arrangement I have on this MW pump. Valves are #50, washers are #47. #53 is pump element. #62 is a shim.

The washers I'm considering R&R are swaged into the pump element counterbore so badly that I need to put them ON A MILL and machine them out for removal.

Obviously, this will require that I remove, and restore the pump elements.
As an aside, one also has a leaky o-ring. I'll replace them all "while I'm in there".

I know, I know. This also means that I should send the pump out for alignment. BUT, this is my "go ahead. make my day" rusty, trusty winter beater. Our four lane city streets are down to 2.5 lanes with ice encroachment. It doesn't pay to park/drive anything you aren't ready to lose to a snow plow.

A pump alignment will cost more than the car is worth, as my local bosch dealer can only tune a repaired pump.

Call it $1200 +-$1K.

So. To the experts. There is no need to repeat the time-honored mantra "you could screw the pump, and the engine, beyond recognition!"

I get that. On to the question of the day:

Can I use the drip method, in sequence on each port, to tune the pump element positions?

In other words: drip test to spec; pull #2; fix it; restore it; crank to 24d + offset where required. set element position to the measured drip rate;
ibid #3, #4, and finally, #1. Repeat as required to get uniform readings.

I'm posting this in the "less travelled" Perf Tuning board in the hopes of having hard-heads weigh in. The thread on glow plug "tuning" got me to thinking. I'm not convinced that a glow plug is linear enough to compete with an EGT sensor, but thats another matter enitrely.

At a glance, the drip method would seem to be a technically sound predictor of "initial fuel rate" -- if carefully performed. I'm talking stopwatch, and perhaps a fuel pressure monitor. I'm not planning to change the shims, as I have no way to re-shim the pump elements correctly.

However, the leaks are progressive, and bad enough that I can't get a drip test to accurately predict fuel rate anymore -- so I'm forced to do something before spring.

Which ain't anywhere near Wisconsin.

Weigh in, please.

--frankb

Personally I don't see why you shouldn't be able to do it this way....

All the same parts (except for washers and seals) so nothing needs to be 'compensated for' or altered because of a change of part.

Do each one in turn, setting the engine position for exactly 1 drip per second on the element to be worked on, and after re-fitting set again to exactly 1 drip per second...No Problem!-
-OK, It aint gonna be as accurate as a Bench Test set up in accordance with the ISO Test-Plan, but better than pissing out valuable expensive fuel everywhere, and Infinitely Cheaper than a S/H Pump!!

Naysayers are often brainwashed by gloom and doom stories/myths told by Fat-Cat Injection-Shops and 'idiot' mechanics....who have their own adjendas-
-Why do you think the owners of such places all drive round in Jags!! (Because its a Rip-Off Trade, Has been for years!)

Unless you Try, You'll Never know!!--If I was in the same position, I would do exactly as you plan. I have often repaired items including FI systems/pumps etc, that I have been told was impossible without 'special-tools/knowledge' but with a bit of planning and lateral thinking has all worked out.....

If you have the time, parts/seals etc,-Go for it!!