Cleaned Engine- Low Power- Boost leak?

[MongooseGA]

I spent some time getting the engine in my '85 300D cleaned up yesterday. Just some degreaser and a low-power pressure washer at the local DIY car wash.

The car had been running pretty damn well lately, but I'm now noticing it's low on power. Where I used to feel like I was riding a wave of torque above 2,000 RPM, now I'm lucky to get the engine to spin much faster than that. Above 3,000 isn't bad if I manually hold lower gear, but still not what it should be. I'm not a mechanic by any means, but I have done most of my own diagnostic work and labor since I've owned cars. It seems to me that the engine is running on zero boost, as the 'exponential' engine speed increase that occurs when the turbo is spooling just isn't happening right now. I can barely 'feel' the turbo spooling when traveling at 80MPH/3,000RPM.

Unfortunately I'm not currently in a position to do a whole lot of my own diagnosis. I have no place to tinker and none of my tools available to me. The indy I've visited before is backed up for months and I use this car daily to save on gas in my AMG. I have money to send it to a shop, but I'm way too cheap to bite that bullet at this point. I'm hoping someone might be local to the ATL area and be willing to trade some time for pizza/beer to figure it out, or have a relatively easy way to diagnose potential issues. I'm happy to drive most places around the Metro area if anyone was generous enough to let me make use of their driveway or shop.

I realize my description is rather vague, but I'm not too sure how to describe the car's behavior in less than 10,000 words. If anyone is willing to spend some time on the phone, I'd be very appreciative. FWIW, the engine starts up immediately and holds idle like a champ. I do not believe this to be a fuel related issue.

[mach4]

Your preliminary assessment sounds plausible and it's easy to test. Run down to your local HF and pick up a boost/vacuum gauge. It'll cost you all of $18, or less if you've got a coupon or it's on sale. Tee into the ALDA line, snake the hose out of the engine compartment to the cabin through the window and go for a spin. You'll know immediately whether you've got turbo boost. I did this plenty before including boost on my bluetooth engine monitoring system.

[UriahT]

Check that you didn't disconnect the line from turbo to alda. Or blew open an air leak before turbo.

[MongooseGA]

Originally Posted by mach4

Your preliminary assessment sounds plausible and it's easy to test. Run down to your local HF and pick up a boost/vacuum gauge. It'll cost you all of $18, or less if you've got a coupon or it's on sale. Tee into the ALDA line, snake the hose out of the engine compartment to the cabin through the window and go for a spin. You'll know immediately whether you've got turbo boost. I did this plenty before including boost on my bluetooth engine monitoring system.

This is why I love forums like this. Such a quick and easy response for something that is likely an easy solution. I just haven't had to deal too much with this car besides fuel filters, and I've never owned a turbo diesel before. Thank you!

Originally Posted by UriahT

Check that you didn't disconnect the line from turbo to alda. Or blew open an air leak before turbo.

This is exactly what my thought was. Some line could have been blown off or torn, etc. This is going to sound extremely ignorant, but what is the ALDA, and where is it? If I'm not mistaken, it's located on the IP side of the engine, correct?

[mach4]

This is the ALDA -



Trace back the line to the intake manifold. You can tee in anywhere along there.

[mach4]

I should have been a bit more clear as far as the ALDA line is concerned. Here's a color coded diagram of your '85 with green being the ALDA pressure circuit.



If you've got the "blue flying saucer" for the transmission, you can tap into the line to it temporarily to get a boost signal. Your shifting will be affected to a degree, but will do no harm. Here's the banjo bolt on that style ALDA

[MongooseGA]

Thanks, Mach4. This is what I have:



Would this be a suitable gauge to measure the pressure? http://www.harborfreight.com/catalogsearch/result?q=boost+gauge

I assume I would have to remove the banjo bolt that holds the clear line on, and the boost gauge just fits on the nipple?


Quick video I just took of the car's start up. Because it starts so easily and idles so smoothly, I don't believe it to be a fuel issue. It also revs smoothly with no sputtering. Rules out ignition to me as well. To my tiny mind, that leaves air. I also noticed how loose my throttle linkage is. Any process on replacing bushings on it maybe to tighten it up?

https://www.youtube.com/watch?v=OK5BCCYHVo4&feature=youtu.be

[mach4]

Yes that's the boost gauge you want.

The clear line is permanent so just remove the line to the vacuum transducer for the transmission temporarily.

[gatorblue92]

Originally Posted by mach4

Yes that's the boost gauge you want.

The clear line is permanent so just remove the line to the vacuum transducer for the transmission temporarily.

The line he needs to remove looks pretty rotten. Could that be the source of his trouble?

[MongooseGA]

Originally Posted by mach4

Yes that's the boost gauge you want.

The clear line is permanent so just remove the line to the vacuum transducer for the transmission temporarily.

Thanks! For an intelligent guy, I sure need a ton of pictures and arrows to pick something like this up.

Originally Posted by gatorblue92

The line he needs to remove looks pretty rotten. Could that be the source of his trouble?

Funny you say that. I noticed the stress cracking in the line there and trimmed it back passed that point. I also adjusted the bowden cable on the trans a little (different issue). The car runs like a raped ape now! (Which is a relative term when talking about these turbo diesels... It's hell getting back into this after a week of driving my E55)

I did notice there was a little bit of turbo surge when I first pulled out of the driveway. Meaning, I could feel the boost coming in and out. Actually not unlike the symptoms I've had with a clogged primary fuel filter. I ran the crap out of it and everything cleared up. Thoughts?

[mach4]

Originally Posted by MongooseGA

Thoughts?

I think you've got it. Sometimes a good inspection is all that's needed.

So because you had the leak, the ALDA did not call for additional fuel under boost, so the engine was running essentially as a normally aspirated one would.

[MongooseGA]

Originally Posted by mach4

I think you've got it. Sometimes a good inspection is all that's needed.

So because you had the leak, the ALDA did not call for additional fuel under boost, so the engine was running essentially as a normally aspirated one would.

"as a normally aspirated one would." That's exactly what I was thinking. I feel sorry for the N/A 240 guys!

I had a little more of the on/off boost on a test drive just now. I'm wondering if there's still a little leak at the ALDA. Would you happen to know the specs of that rubber hose? I'll likely buy a few yards and just replace every piece in the engine bay. If that one was on its last legs, I imagine the rest are, too.

[BillGrissom]

I think it is just regular "vacuum hose" you can buy at any auto parts. Even better, buy silicone vacuum hose on ebay. It will last forever and comes in cool colors.

When I measure boost, I tap off the tube coming off the intake manifold (rear). In many 300D's, I think that runs straight to the ALDA valve, but I recall that in my 1985 CA, it goes thru a solenoid valve first (check yours), so you might not be measuring manifold pressure. Just secure the gage under the windshield wiper to view while driving. For more permanent, push a vacuum tube thru one of the rubber grommet holes into the cabin. Some guys mounted a gage in the cig lighter space.

A funny related story. After putting the replacement engine in my 1985, it wouldn't go faster than 5 mph in a test drive. Strange since the engine ran fine on the ground. I quickly hooked up a vac/boost gage and saw a large vacuum as I pressed the pedal. Since diesels are supposed always be "wide open throttle", I knew there was a restriction. I removed the turbo air inlet and found the paper towels I had stuffed to keep things out of the turbo (missed them working in the dark). BTW, I recently learned that new CDI engines do have a throttle plate.

[toomany MBZ]

Seems like too much play in the linkage to me too.

Are you able to determine if the linkages are set correctly?

If possible have a helper push on the pedal while you observe for any other problems.

[Vilnis]

I had the same problem after washing the engine. Turned out that rubber line that goes from intake to ALDA is just cut off with water jet at ALDA side. Shortened same rubber line and put it back on ALDA and it worked as before.