Running engine with intake removed...
 

'97 E300 is developing fuel leaks somewhere in the IP/delivery valve area....pretty minor, so far, but would like to nail it down and fix it. It's been suggested I can run the engine with intake removed in order to see all the fuel system components working under pressure.
My concerns are many....... Is this a normal procedure and often used technique? Seems a little "unorthodox" to me, but, I'm definitely a "newbie" when it comes to MB diesels (or any other diesels, for that matter).
What should I be aware of (besides sucking foreign objects into the intake ports) when doing this? Will the engine "start", and more importantly, "shut off" normally? I'd imagine there'll be OBD codes after?
Also assuming this is the only way to pressurize the fuel system in order to check for leaks on everything that's quite well hidden by the intake manifold? I "think" my delivery valves are leaking, but I can't be sure of that due to not having access to clean them off and observe during operation. Could be a loose line/nut or one of the clear lines/o-rings or the shut-off valve, etc. Even the IP, itself, I'd imagine.
I was hoping, maybe, with just the crossover pipe removed (for observation purposes), I may have more access, and avoid the brittle plastic CCV tubing that's gonna crumble in my fingers during removal. Or, am I just gonna hafta "bite the bullet" on this one and remove the entire intake? I assume any part replacement in that area is gonna require the entire intake be removed, anyway. Any thoughts? Thanks

I'll sometime's have engine running with intake off my 98 E300 when removing glow plugs. Just don't drop anything down intake port and you should be fine.

Ok, thanks Jim. I don't know why, exactly, but the idea of doing this seems a little intimidating.
Guess I'll give it a shot. Gonna be interesting, to say the least! There's a first time for everything.....

Make a rugged screen to cover the intake ports, one that won't get sucked in???

Just a thought...

The ideal situation is to have some sort of screen. Which would be something you would have to make. Likely aluminum window screen would be the best choice. However, above idle speed I am not sure on that.

Thanks for the suggestion. Seriously, I was thinking the exact same thing (like minds think alike). It also occurred to me it would need to be fairly stout screen. More like a "grate", maybe. But as you go "up" in gauge, the holes/openings in the screen will increase, too. Which, of course, defeats the purpose. I guess just be super careful, make sure there's ABSOLUTELY NOTHING loose lying nearby and don't get carried away with the RPM's.

Two layers of screen would work, the inner layer could be metal and strong with larger openings. The outer could be finer and unlikely to get sucked in past the inner strong screen.

Good luck and please post your results!!!

Great idea! Good thinking. Why limit it to just 1 screen/1 size? Probably wont get to this phase of the project til the weekend (life, job, etc). I'll be sure and post the results. Thanks!

A screen is more likely to get sucked into the intake and you'll do damage. just use a blow gun to remove any dust before removing the intake manifold. Get rid of any loose debris. It's perfectly safe to run it without an intake manifold temporarily.

Definitely would NOT want that to happen! After looking around, through my accumulated piles, couldn't find anything suitable. Guess I'm gonna go "bareback". As you mentioned, clean 'er up really good, remove any and all debris. Should be ok as the actual run time will be fairly limited as will the RPM's. Just need to get fuel pressure everywhere and find the leak(s).

How you do something is as important as what you do. No issue at idle speed.

Explain the physics on how it would get sucked in. The most restricted area is at the intake valve itself meaning the piston side is where the low pressure is going to be generated. The intake port being larger will not have the fast flow.

If someone is skeptical they can use 1/4th inch mesh screen.

This.


There's a ton of overpreparing happening here - keep your workspace clean and you'll be fine.

I don't know where you got that idea but it's dead wrong. Do not have your fingers, tools or anything anywhere near those ports while it's at idle. OM606 ports are smaller than om603 or om617. Do not fuk around with these by trying to put a screen in the way. You've been warned.

I've run several with the intake off, and never had a problem, Futzing with a screen sounds like a waste of time and more trouble than its worth.

I'm going to agree with previous two post. I've done this many times and never had issues but I clean everything up real good before starting engine with intake off.