Time to start discussion on an issue that's plagued our 82 300TD since we acquired her 4 years ago.

The engine does not throttle up until the linkage is around 80 percent+ of the way open. If, with the car idling in neutral, I throttle her up, I can watch the plate on the IP - she barely comes off idle through most of the linkage travel, then finally throttles up once the IP plate is around 3/16" from the full throttle stop.

Driving her is with my foot to the floor - much of the time. When I questioned our mechanic about it (before he retired), he said "hole in the ALDA diaphragm".

Now, I'm wondering if that was a 'shot in the dark' guess on his part, or pure experience. Can I test this with my mighty-vac? Anybody else have the same problem? And what solved it?

Needless to say, the transmission doesn't shift well on it's own either - it's a delicate "with your foot" thing...

Pop the ALDA off and find out, takes only a minute.

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Cheers!
Scott McPhee

1987 300D

Off to work shortly, but I'll do that tomorrow morning.
So, if it has a hole, and I get a replacement? New?

you would need to apply pressure to the ALDA to test it.

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...and if it does have a hole in it, am I likely to pull fuel up into my vac tester?

no. If you use vacuum the chances of pulling up a liquid are pretty slim.... the only thing you might see is crank case oil.... but it is highly improbable.


the way you describe it, this does not sound like the only issue.

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Fuel does not go into the ALDA; it just makes contact with the linkage inside of the Governor that regulates the Fuel.

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84 300D, 82 Volvo 244Gl Diesel

Well, I'll start with a check of the ALDA. Our mechanic had at first told us we'd be best off with another IP - then a year later came up with the "hole in the ALDA diaphragm" thing, leaving me rather confused. It's our daily driver, and it's time to fix whatever the problem is.

Brandon had mentioned, after checking our Ava out, that he had finally given up tinkering with his, and purchased a used, bench re-adjusted and re-sealed IP - loves the results. I'm at a total loss of where to even start searching for such a thing - also want to rule out a bad diaphragm first.

In fact, a bit of history: when we purchased Ava, acceleration was so poor, she couldn't even keep up with leisure traffic flow in town - light to light. Lovins along the way helped - valve adjustments, filters, etc. Then one day, Janet headed off to town, and couldn't climb out the drive onto the highway - she just wouldn't throttle up. A trip to the mechanics for a couple cans of Diesel Purge, and she was back on the road, but she has always continued to struggle. I do the yearly valve adjust and purge...

A year ago, I did a comp check - it was all over the place, so valve adj + main fuel filter full of trans fluid - 4 up - 1 down - so soaked #1 with brake fluid - all comp good and within 10 percent.

I still need to send the injectors in for pop and pattern test.
We also just shocked the tank with biobor...
wow, just how tight does that main fuel filter have to be to not leak???

The ALDA works like an accelerator pump on a carburetor. You only really feel it coming in above idle/'off the line' acceleration. If you have to put the pedal down to maintain speed, the ALDA is not likely.

The ALDA does have a hole in it but it's very small and precisely made. I know there are diagrams of them somewhere. It works just like a VVI (climb/dive indicator) in a plane.

If it turns out you do need an IP, send me a PM or email.

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1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!

You will only be able to check this with a working Tachometer.
Checking the Maximum Speed at No Load

You are only going to maintain the Max Speed momentarily; just long enough to get a reading.

Also it could be helpful to have someone stand by the Manual Shutoff Lever on the odd chance of a runaway.

With the Transmission in park and the Engine completely up to operating temp. Floor the accelerator Pedal and read the highest RPMs you were able to obtain.

The speed should max out at between 4200-5200 RPMs.

If the RPM goes up within that range it is OK.

If it does not go high enough pop the Linkage off of the Throttle Lever and have someone you trust do the Tachometer Reading and push the Throttle lever by hand to Max Fuel momentarily and have that person take the reading.
If the RPM is OK this way you have a problem with your Linkage Adjustment.
If the RPM still does not go up high enough see below.

If it does not go up to high enough RPMs take a look at the Throttle Stop Screw on the Engine side of the Fuel Injection Pump and see if it is backed out too far.
It is the Bolt/Screw in the Red outlined Box in the Thumbnail pic.
Turning the Screw in as if to tighten it increases the RPMs because it allows the Throttle Arm to move forward more and put more pressure on the Governor spring.

If adjusting the Throttle Stop Screw does not help you have something internal to the Fuel Injection Pump Governor that is causing the Problem.

Some causes are a Broken Governor Spring or if the part on the Throttle lever inside of the IP has come loose it will not put pressure on the Governor spring properly.

Also check and see if the Throttle Lever itself is not slipping on the Throttle shaft.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

ALDA
In the thumbnail pushing lever D downward decreases the fuel. So it looks like if your removed your ALDA that would increase the Fuel.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

backing out the screw would be much faster, less invasive and just as effective

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Backing out the screw on the top of the ALDA?

I've played with it some - makes a difference immediately on how/where she shifts...

?

The throttle linkage from the firewall to the injection pump has a couple of devices that change linear motion (the accelerator pedal motion) to rotational motion and then back to linear motion (what you look for at the injection pump linkage). It all requires the bushings and fittings have nice, tight clearances or some of the pedal movement gets lost in slop between the pedal and the injection pump. On a 240D (1982 and 1983 models, at least) there is a male pronged connector at the bracket that hangs off the valve cover that requires a rubber block be bonded to the sheet metal at the female receptors. Between heat and Diesel fuel and other dirt and grime in the area, after 25 years one can expect the rubber to disappear. At which point the slop between the female slots and male prongs takes up about 80% of the travel at the injection pump and you can't make it up a hill.

Not sure about the 300TD you have, but it would not surprise me if the same chunk is used. The ALDA is a method of pneumatically adjusting the stroke of the injection pump based on intake manifold pressure - when the turbo compresses the air you need more fuel, and the amount more is dependent on throttle position and manifold pressure. The throttle position control is up to you, the adjustment for manifold pressure happens outside your direct control. If the linkage to the injection pump is losing 80% of its travel it is, in my opinion, unrelated to the ALDA - that device works inside injection pump housing. My guess is you have the same or similar problem I described for the same vintage 240D. Or, on older 240D's the problem would happen at the bearing support on the firewall - a plastic device that would split and let the rod the accelerator pedal was supposed to twist, just move up and down.

So, have someone step on the throttle pedal, and watch every one of the bearings, couplings and especially the places where the linear travel turns to rotational motion or rotational motion turns to linear motion. If it is the device I noted earlier, I "fix" mine with popsicle sticks stuffed and then wired in the slots of the female part that snug up the male prongs against the edges of their slots. There is also a travel adjustment at that joint on the bracket for the male parts - I adjust it to get the most travel.

Good luck, but don't mess with the ALDA. I don't believe it can address the fact that the accelerator pedal is not actually connected to the injection pump.

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)