Finally tested compression on my 300D - Page 4 - PeachParts Mercedes-Benz Forum

cmac2012 · #46 01-26-2020, 01:17 PM

Quote:

Originally Posted by Maxbumpo

The ALDA uses the pressure from the turbo to increase the fuel flow from the injection pump, so using a miti-vac to put pressure into the ALDA is correct, but limit the pressure to 15 PSI. If the ALDA leaks down quickly or won't hold pressure at all, you may be able to take it apart and replace the o-rings to fix that.

I gave it 15 psi (would that be correctly referred to as negative PSI?) and it held well. I had to look pretty close to see the needle moving downward. The heat gun method worked pretty well. Warmed the end of the old tube to get it slightly soft and jammed it over. Tight as hell now. The line not really in bad shape after I cut of 1/2 inch.

cmac2012 · #47 01-26-2020, 01:31 PM

Quote:

Originally Posted by cleeves

You're saying the injectors nozzles should be like new if they've run 135K miles? I don't agree with that. Mine were in deplorable condition at 135K on a 1-owner well maintained example. 3 out of 5 were shooting a straight line of fuel and the remaining two weren't far behind. All had cupped, concave nozzles.

Henry

It's tough call. I called my mechanic, he said he has a machine that tests them, which he did, as I still have them out he invited me to bring them in so he could show me. The nozzles look flat, they all look pretty damned good.

Oh man, I would give a lot to know the maintenance history. The title trouble was almost a blessing in disguise as w/o that I likely wouldn't have interacted with the PO. As I mentioned, she said her father was a VW mechanic, "from the factory in Germany," I can only guess that means either factory trained or previous engineer of some sort at the factory. Their name is indeed German, and much about the car is in pretty good shape. The father owned the car for the first 20 years or so, and only passed away a few years ago. That's one reason she was so helpful with the title renewal issues, and they wanted her to jump through hoops. Wanted her mother's death certificate (they had proof of her father's death), inheritance distribution (she had not titled the car in her name after her mother's death), a letter from her 'personal representative' (poor man's notary, best I can tell) verifying that she releases interest. I sent her photos of my first trip (below). She said she was so happy to see her car having adventures in the world and that her father would be smiling that someone was restoring it.

So who knows, would a guy with the means and knowledge replace injectors at say, 80K? My car sounds a bit like you describe yours. The body has a few tiny marks but the doors all close with that lovely, solid thunk sound. Even the cruise control works.

OTOH, the tach does't work (it's on the list) or the clock, and the climate control is always hot. Vacuum is not good (definitely on the list).

But hey, working cruise control is like a miracle. Works very well, really useful on the long trips.

barry12345 · #48 01-26-2020, 02:09 PM

Quote:

Originally Posted by cmac2012

I blew on it, could just barely get air through. Does the union thing on the firewall have any dirctional flow or is all just connected there? I see the one line that goes over to the manifold.

Perhaps I should remove that and see if cleaning is needed.

Air normally just gets compressed and decompressed in that line. So there is no signifigant air flow as such. It should be okay. You will know as soon as you drive the car.

It appears that over time some of the soot etc from the egr introduction to the intake manifold lodges in the manifold fitting specifically. Plus sometimes reaches the boost limiter. Since the time the line broke off there would have been air flow in that line with some of the egr gasses and soot etc. Was why I though to blow on it was a good ideal. The boost limiter could be directional. Is a possibility. When there is an obstruction it usually will be in the manifold fitting.

Maxbumpo · #49 01-26-2020, 04:22 PM

Quote:

Originally Posted by barry12345

Obviously if the car was sluggish from the first time you drove it. You did not create the problem..

Just before you hook up the new hose to the alda. Blow on the end to make sure there is no obstruction in the over boost valve or the manifold connection. That line when functional does not really have constant air flow as such. It relays the air pressure from the manifold to the alda. By just compressing the air.

With that line open there would have been air flow. This might have included some of the egr garbage fed into the manifold going through that line. That increased the chances of soot buildup in the manifold fitting and the over boost protection valve.

So you just make sure that the system is still open by reducing the air pressure applied. Or just take the car for a short drive to make sure the sluggishness is gone. The engine was just simply fuel starved.

This is a great point, the pressure line fitting at the intake manifold and the over-boost control valve can get plugged up with soot, and then you get a sluggish engine. You said you can barely blow through it, to me that means a fail. I'd recommend you remove the fitting from the manifold and spray it out with brake cleaner and maybe push a bit of wire in / out.

Maxbumpo · #50 01-26-2020, 04:24 PM

Quote:

Originally Posted by cmac2012

I gave it 15 psi (would that be correctly referred to as negative PSI?) and it held well. I had to look pretty close to see the needle moving downward.

Sounds like a passed test to me. Positive pressure, negative would mean a vacuum.

Maxbumpo · #51 01-26-2020, 04:25 PM

Another possibility for causing lower power: EGR is failed in the open position, feeding exhaust gasses back into the intake, so there is not enough oxygen to burn the fuel. Engine will produce smoke and have low power.

cleeves · #52 01-26-2020, 08:02 PM

Quote:

Originally Posted by cmac2012

It's tough call. I called my mechanic, he said he has a machine that tests them, which he did, as I still have them out he invited me to bring them in so he could show me. The nozzles look flat, they all look pretty damned good.

Quote:

Originally Posted by cmac2012

So who knows, would a guy with the means and knowledge replace injectors at say, 80K? My car sounds a bit like you describe yours. The body has a few tiny marks but the doors all close with that lovely, solid thunk sound. Even the cruise control works.

OTOH, the tach does't work (it's on the list) or the clock, and the climate control is always hot. Vacuum is not good (definitely on the list).

But hey, working cruise control is like a miracle. Works very well, really useful on the long trips.

Perhaps the nozzles were already replaced at some point. Or there's some other confounding factor. Interesting.

I guess I'd inspect them at 80K and see how they tested out. But I might wait until 100K? Hard to say.

I'm looking forward to getting my cruise control working again. I guess your cruise control isn't vacuum-powered, which mine is. Also interesting.

Henry

vwnate1 · #53 01-26-2020, 08:07 PM

Yes, the tube and valve *must* have zero resistance when you blow through them, remove both and clean with purple de greaser cut 50/50 with tap water, be careful to not drop the two small & thin copper crush washers on the banjo bolt at the rear end of the intake manifold nor the hard to reach sheet metal screws holding the valve to the firewall .

Once this is all done, the plastic pipes to the ALDA from the valve go: top one to the ALDA, bottom one to the intake manifold, yes it makes a difference .

All done ? good ~ now with the engine fully warmed up and hot, apply vacuum to the EGR valve's nipple, the engine *must* stumble as the vacuum is applied and smooth out as the vacuum is released .

It's very common for these EGR valves to stick part way open, they're easy to clean using a tooth brush and the same purple degreaser and water mix....

Unless you have a sink in the garage be VERY CAREFUL about making sure SWMBO is gone long enough for you to do serious cleaning of the kitchen / washroom sink after you're all done, YOU HAVE BEEN WARNED.

cmac2012 · #54 01-27-2020, 09:48 AM

Quote:

Originally Posted by cleeves

Perhaps the nozzles were already replaced at some point. Or there's some other confounding factor. Interesting.

I guess I'd inspect them at 80K and see how they tested out. But I might wait until 100K? Hard to say.

I'm looking forward to getting my cruise control working again. I guess your cruise control isn't vacuum-powered, which mine is. Also interesting.

Henry

It might be. The vaccum issues are hard to figure. Sometimes the door locking works, other times not. Sometimes the engine will turn off right away, other times not. The cruise control mostly works well, I should amend that. About once a half hour it will suddenly cut out completely. As if you just took your foot off the pedal. I've gotten in the habit of being ready to use the foot immediately, is quicker than resetting the CC, but it will reset and work again just fine until the next drop off. I can only guess it suddenly loses vacuum in those episodes.

I haven't yet mentioned that another issue is my ignition key/st. wheel lock going south. One day I had a bit of trouble with the key, didn't think to immediatly pull the cylinder, that night I suffered the dreaded paperweight/key won't turn sydrome. I was in WA state, in a parking lot, with my mother. I called her an UBER, and started looking hard at what to do. Decided to tow, AAA asked what's up, and then said their policy is to first send a locksmith. Dude did his best, no dummy, had one of those vibrator thingies. Could not get it to turn. None of it sounded good, me 750 miles from my shop. It occured to me that Home Depot was still open, I figured that to buy a batt powered Makita angle grinder to destroy the st. wheel lock would be cheaper than paying a locksmith $500 (WAG) to pull it out. And I'd still have the tool.

Saints be praised, I pulled it off. Will install new stuff soon. The punchline is, for the brief spell I've driven it since, I hooked my mighty vac up to the igntion shut down line. Oh man, that engine shuts off right now when I squeeze the handle. I've GOT to improve vacuum.

barry12345 · #55 01-27-2020, 10:31 AM

Car sounds like it needs just a detailed mainteance run. An assortment of the usual suspects. Time more than money.

Estimate a day or twos time to lubricate everything after the essential issues are dealt with. It is well worth the effort in my opinion. It also can bond the car to you. So may things return to what they were like when new.

You got caught by the magic ignition tumbler. Any sensation of it becoming an issue at all. Members should replace it right away. They are too well known to cause real grief otherwise.

Usaguy · #56 01-27-2020, 10:31 AM

Quote:

Originally Posted by cmac2012

It might be. The vaccum issues are hard to figure. Sometimes the door locking works, other times not. Sometimes the engine will turn off right away, other times not. The cruise control mostly works well, I should amend that. About once a half hour it will suddenly cut out completely. As if you just took your foot off the pedal. I've gotten in the habit of being ready to use the foot immediately, is quicker than resetting the CC, but it will reset and work again just fine until the next drop off. I can only guess it suddenly loses vacuum in those episodes.

On you car it's done by a servo motor that's right next to the power steering pump. And cutting out is a sign of cruise ecu going bad (bad caps and cold solder joints I have a diy link if you want)

Quote:

Originally Posted by cmac2012

Saints be praised, I pulled it off. Will install new stuff soon. The punchline is, for the brief spell I've driven it since, I hooked my mighty vac up to the igntion shut down line. Oh man, that engine shuts off right now when I squeeze the handle. I've GOT to improve vacuum.

On a W123 with OM617a an engine driven vacuum pump does:
1. engine shutoff
2. brakes
3. central locking (no separate electric pump like in a w126)
4. automatic transmission shifting (VCV simulates vacuum so it's like in a gas engine)
5. egr
6. climate control pods

so as you see there is a huge potential for leaks

If you test your vacuum pump by itself it should be making minimum 15 inches of vacuum

I would start by testing other systems with a mityvac

cmac2012 · #57 01-27-2020, 01:11 PM

Quote:

Originally Posted by barry12345

Car sounds like it needs just a detailed mainteance run. An assortment of the usual suspects. Time more than money.

Estimate a day or twos time to lubricate everything after the essential issues are dealt with. It is well worth the effort in my opinion. It also can bond the car to you. So may things return to what they were like when new.

You got caught by the magic ignition tumbler. Any sensation of it becoming an issue at all. Members should replace it right away. They are too well known to cause real grief otherwise.

Holy crap I was kicking myself hard. I knew that a dead tumbers were a big problem. I just didn't think it would happen that fast. I had my Makita 18 volt screwgun with me - two batts. So buying the grinder w/o batts wasn't too steep. I've been around tools long enough to know that grind/cutting (those .048 thick carborundum wheels) works a lot better on hardened steel that drill bits, hacksaw, etc. Trying to drill out the tumblers struck me as way tough. Would need a good corded drill and parhaps diamond bits. One bad move and you scar up your dash. Grinding from underneath wasn't easy, a couple of times I thought I was at a dead end but it worked.

cmac2012 · #58 01-27-2020, 01:16 PM

Quote:

Originally Posted by christuna

On you car it's done by a servo motor that's right next to the power steering pump. And cutting out is a sign of cruise ecu going bad (bad caps and cold solder joints I have a diy link if you want)

On a W123 with OM617a an engine driven vacuum pump does:
1. engine shutoff
2. brakes
3. central locking (no separate electric pump like in a w126)
4. automatic transmission shifting (VCV simulates vacuum so it's like in a gas engine)
5. egr
6. climate control pods

so as you see there is a huge potential for leaks

If you test your vacuum pump by itself it should be making minimum 15 inches of vacuum

I would start by testing other systems with a mityvac

Great info, thanks. I really want to get on top of the vacuum issues, I just needed to get to greater priorities.

What you say about the CC makes sense. The vacuum is too inconsistent to operate the CC as well as it works. I would like that DIY link. Won't get to it for a while. If it went completely south I'd proably get to it quicker.

Usaguy · #59 01-27-2020, 01:49 PM

diagnostics:

https://sites.google.com/site/mbcruisecontrolrepair/home/diagnostics/1982-1995-electric-servo-cruise-control-diagnostics

repair of a cruise amp (half way through the first post is your model):

HOW-TO: Cruise Control Amp Repair 14-pin

same guy can also do it for you. his new website:

Cruise Control Repair

vwnate1 · #60 01-27-2020, 10:42 PM

(it's never fun)

However, it's do - able, I spent some time to - day diagnosing the leaky HVAC in my '82 240D, before I started I bought some 3.5MM silicone vacuum hose from Pelican Parts and replaced most of the short straight bits I touched .

It turned out to be the trunk lock actuator so I disconnected it and plugged the yellow plastic pipes and the door locks all work fine gain, I'll place an order for the actuator, supposedly it's in stock now .

Do the little basics first and you're car will run and work better making you happier as you go along peaking and tweaking it......