I have a neglected 300TD that seems to have some power issues. I replaced fuel filters, fuel injector tips, did a valve adjustment (it was pretty awful), and also adjusted the spring below the body that adds resistance to the accelerator pedal (not sure if that makes a difference).

It seems that maybe it's just not getting full throttle. I have a 300SD to compare it to, and the pedals work very differently - I have to press my 300TD's pedal down half way before ANY acceleration happens. I'm not sure if there's something with the throttle that can make my accelerator pedal more 'sensitive'? That's probably my first thing to adjust - it just really seems to never reach max power (like the turbo never engages) except some very rare cases. Maybe something is wrong with engaging the turbo? I'm not sure how that works, how/when that's engaged, if it's a throttle lever issue, or something else. I've been told that when you put the pedal to the floor, the turbo should always engage (it rarely does).


I'm thinking of getting a compression testing kit, to see if maybe it's something internal to the engine. There's one online for $60, with a manual - does that seem like a good idea to have in general? Or maybe just renting one from a local auto parts shop if they lend it out. I'm just not sure if it's worth bothering with if I can't do much in terms of fixing internal issues without an expensive/time-consuming overhaul. Maybe at least it'll give me peace of mind that it's NOT (or IS) a compression issue.

I'm also wondering if maybe I didn't install the fuel injectors back correctly. Is there a trick to ensure they are tight enough? I only have standard ratchets, should I get a ratchet that also measures torque and have the injectors fit to a certain torque? I don't think it's on as tight as it was before (probably was at factory setting), but I didn't want to force it too much and end up breaking/cracking something. I've read that doing it too hard can damage the injector casing.

Finally, is there a trick with the fuel return lines (the rubber ones with the fabric exterior) to make then not leak fuel? I got brand new lines and for some reason, one piece keeps on leaking - it doesn't look cracked, maybe there's some trick to how to cut/fit it. I'm just wondering if there's maybe some sort of air leak that's causing air to get into the intake that might be decreasing overall pressure.

Thanks!

The pedal travel issue, before the car wants to go, sounds like a throttle linkage issue.

The lack of turbo response could be related or could be a blockage or tear in the sensing line from the manifold over to the overboost switch and the ALDA on top of the injection pump.

Linkage: with the car not running, move the linkage at the injection pump up and down to see how much travel you have and make sure it isn't binding. Then have someone else start the car and press down on the pedal while you observe how much movement you are actually getting when the pedal is depressed.

Common problem on w123s: There is a fitting/flange at the firewall, with a big rubber bushing/isolator, where the throttle actuator comes through the firewall. If the nylon fitting inside comes apart with age you will only have partial movement in response to throttle input, which results in symptoms as you describe.

A very dry set of linkages, as in sitting for an extended period, can actually also restrict movement as well.

Assuming the likages are ok, trace the plastic line that runs from the overboost switch across to the manifold, where it joins to a banjo bolt. Make sure the line isn't cracked/broken/disconnected, if it's ok then carefully pull the banjo bolt off and clean it. These often become clogged with soot over time and restrict the signal to the ALDA on the IP for fuel enrichment under boost. Be very, very careful retightening the banjo bolt as they apparently strip easily.

There was recently another thread on a similar issue with a w116 300sd, which may have some helpful info:

1980 300SD - pedal/linkage at full throttle, only idles

If you are going to be pulling the injectors a torque wrench is a MUST. It's also helpful to have the specialized injector socket.

You did install new heat shields (crush washers) when you reinstalled the injectors, right?

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Thanks....

The injector tips came with heat shields.

Is there an adjustment to the linkage I can perform (shortening or lengthening a piece, perhaps)? Looking under the hood, I actually don't see the linkage move as I press on the pedal until it's about 1/4 of the way. It then doesn't get any acceleration until maybe half way. Is there an adjustment on the pedal itself?

I cleaned the line/banjo bolts from the ALDA to the turbo, I'm not sure if it's cracked or what. Is that part of the vacuum system (or separate)? I have a serious vacuum issue otherwise (may be elsewhere).

The rubber bushing that holds the rotating throttle lever into the firewall is broken into two pieces. But it's still in solid pieces, ie there is no lose horizontal/vertical play in the rod.

Should I spray some WD40 on the linkages?

That is what I was talking about. You need to get a new assembly. That will fix the acceleration problem.

As a temporary fix you can use JB Weld to glue it back together but it will only last a week or two, based on my experience.

WD40 isn't a lubricant except for temporary use. The original spec is ATF but many people now apparently use the new types of white grease instead. Whatever you use has to be heat resistant.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Does the ALDA have anything to do with the vacuum system? My vacuum system is all wonky and so I'm wondering if the ALDA isn't operating at all, whether that might weaken the engine from not getting enough turbo.

Under what conditions does the turbo normally engage? Is it gradual depending on the speed/RPM's?

No connection between the vacuum system and the turbo. Turbo comes on noticeably around 2400rpms. Sounds to me as if you have a linkage problem.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

85's alda is connected to vacuum, but it's not affected by it.
the engine should pull to about 2000rpm before the turbo makes power.
you need to have someone push on the throttle slowly, while you watch what moves and what does not. fix what doesn't move.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Where is the 85 Alda connected to vacuum? I haven't noticed it on mine.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Flying saucer

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Why is the ALDA connected to the vacuum if it's not affected by it? What does the connection do?

I have noticed that the pedal seems to stick at times, probably some linkage inside that needs lube.

I looked at a diagram and there seems to be a pneumatic cylinder/pump connected to the pedal inside under the dash (possibly to move the pedal back into place once depressed), and was wondering if these are known to malfunction, etc?

I am getting a new throttle bushing (that mounts to the firewall and connects to the pivoting linkage), and noticed that there seem to be two identical spots (one slightly to the left of the other) where it could go... (ie 2 sets of holes)

Does it matter? It's currently on the right one, and this seems to line up with the pedal linkage, but it makes the pivoting linkage seem crooked (and almost touches the injector rods with some burn marks that I've noticed).

If I moved the bushing to the left position then the pivoting linkage seems straighter, but then I'm not sure if the pedal linkage is then in the right position to reach it properly (or maybe it can be adjusted/rotated, I'm not sure).

Any ideas?

There is no cylinder/pump to push the go pedal back into black. There is a spring on the firewall that pulls the pedal back out.

The linkage bushing should go in the right hole (closest to the brake booster).

__________________
'85 300TD "Puff The Magic Wagon" - Rolling Resto
'19 Mazda CX-9 Signature - Wife's sled
'21 Morgan 3-Wheeler P101 Edition
'95 E300d - SOLD
'84 300TD "Brown Betty" - Miss this one
'81 240D "China Baby" - Farm grocery getter

It may feel that way, but 90 percent of the time the problem is under the hood.

If the pedal itself actually starts to bind, it may be a sign that the plastic/nylon grommet at the back of the pedal, which connects it to the actuating rod, is disintegrating from age. They can eventually break.

Yes they aren't elegant but as far as I know that is how they came from the factory.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

This is not exactly accurate.

The "flying saucer" utilizes a pressure signal from the manifold to regulate vacuum to the transmission.

The same pressure signal is utilized by the ALDA to regulate fuel.

To conclude that the ALDA is connected to vacuum is not correct.

That sounds like it might be the transmission kickdown switch.


The steering wheel is on the left; the glove box is on the right. With that in mind, on which side is the throttle bushing located?

The right "hole" happens to be the left one, which also happens to be the one closer to the brake booster.

That makes sense. I had been scratching my head trying to figure out how vacuum could be connected to the ALDA.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13