IP issues - won't throttle up until 80 percent open -possible hole in ALDA diaphragm?
 

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.

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.

...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.

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

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???

It may have already been said,
 

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.

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.

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.

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

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

I will check on the particular piece of rubber you're talking about.

I have gone through the "proper" linkage adjustment, and have double checked that the pedal to the floor does in fact move the IP to the full throttle position.

When Brandon (superturbo moderator elsewhere) from Portland area looked at this car a couple years ago, he grabbed the linkage with the car running, and 'gunned' the engine.

He laughed, as he moved the linkage to 'full', and the engine "strained" to build speed at all. He laughed, and wondered how we drove it like that!

He showed us how to adjust the rack dampener, and also checked over the linkage...
That's when he shrugged his shoulders with a look of "hmm - not sure what to tell ya" on his face.

He played with the ALDA screw, turning it one direction, saying that would give us more 'under-boost' power - did the opposite - so we played with it on the road to find the best "middle" position.

That's also when he said he replaced his IP with a fresh off the bench unit...

... :/

I meant pop the ALDA (take it right off the car) and try it (go drive the car).

Forget about diagnosing an ALDA... just drive the car and find out if it is the ALDA or not. If it's not, leave it off until you find the problem. Then if you want put the ALDA back on. Then, take the ALDA off again because you won't want it back on...

The screw is covered by a plastic cap and metal cup.
The third pic is of the bottom of the ALDA, the fourth is of the top of the IP ALDAless.
The fixed nut on the bottom is 24mm and the spinning nut on the IP is 27mm.
I adjusted it ccw and now the car starts in first gear, is more responsive and I get worse fuel mileage.

if Brandon looked at it and was at a loss for an explanation, you will probably have to go through the entire fuel supply system piece by piece.

start with small, easy to fix items, work your way through the whole system.... everyone will just be guessing until you find more information.

filters, tank screen, bad hoses, bad clamps, poor ventilation... get busy.

OK, wow, some time spent, annnnd, spent over an hour going through checks and possibilities with our trusted PP tech Roy. We came to 2 basic things, which I tried yesterday.

The first being the fuel over-pressure valve (I'll call it that, anyway) on the block side of the IP. Pulled spring from 22 to 27mm - reinstalled - made no difference, but nice to know that's done.

THEN I removed the ALDA...

OMG - it's instantly like having 2 of the same motors as I've had. And hill climbing?

Well, let me illustrate it this way. The closest 'highway hill' to our house: Ava has been climbing that hill at barely over 40mph for 'ever'. Yesterday's test: She rolled right up, without even shifting down, with 63mph the lowest on the steepest part...

Crap - didn't know she had it in her!!! :)

I then replaced the ALDA, and played once again with the adjusting screw - doesn't seem to do much of anything, and I'm back to having the most gutless car in the world...

So, as a diagnostic test, does this confirm the ALDA is bad?

Or does it simply point to some other possible issue????

You may want to check the cam timing and fuel timing.

I understand if you turn the screw too far counter clock wise, you may damage the ALDA.

Try adjusting it more.

The poor ALDA - I took it apart to check it out - it has been apart before, I believe, by the near stripped head of one of the 4 screws. The seal around the shaft comming out the bottom is definitely shot - I could see daylight around the shaft when it was through the seal...

Hey Joe, glad to hear you've figured out your issue. I'd hit any local junkyards around and see if you can find a couple ALDAs and put one of those on.

Hate to say I told ya so, but... ;) Betcha wished you did this on June 18 as suggested in this thread.

Mine is still off the car. I put a boost gauge in the car instead of trying to find another ALDA... As some people are nervous w/o having an ALDA because it's part of the over-boost protection circuit on this car. Funny thing is, there is not one story out there about a turbo overboost fault on these cars. The rest of the protection circuit is likely plugged with gunk anyway or non-functional (solenoid stuck, etc).

The boost gauge showed I was only getting sub-par boost, I added a manual wastegate controller ($20 EBAY) and set it for 1 bar (14 psi). That showed me new top end power / hiway speed. I have to push the car really hard fully loaded up a hill to see anything near 1 bar on the gauge. There just is not enough fuel coming out of these IP's to push into the danger zone, or worrying about melt down.

Mine had a similar problem, fixed with a replacement ALDA. I could have just removed it, but I didn't want the smoke.

Yes, after 3 years of messing with her, it's nice to finally hit her "sore spot"! So I'm shopping for a good ALDA :)

Reading posts here sure give one an education. I now understand the ALDA for the most part, and how having a compromised chamber can render the car gutless.

As I now understand it, the chambers are sealed in a vacuum, and therefore even at under-boost, they're already 'squished' to some degree; then simply squish more as boost comes on. So, if one (or both) develops a leak, it will relax (thicker than stock) into a state which cuts available fuel to a minimum...

I also see the value in having both the fuel and valve timing checked by a pro - I can imagine things getting a little 'off' after near 30 years, and 340k miles ;)

1982 300TD - Ava

If that was true, the ALDA would not be capable of compensating for anything but transient pressure changes. Unless one aneroid is vented and the other is not. The 617.95 manual doesn't mention that arrangement, however.

Well, happy day:) I kicked myself when a friend suggested I take the ALDA off the 81 300SD in the yard, and put it on Ava... ;)

Well, not so fast. Even though the SD has a nasty-wasty knock, it still gets up and moves pretty good. However, the SD's ALDA placed on Ava gave me the same result as before - little power...:(

What the heck? So, I removed the ALDA, and had the wild but simple idea to blow (with my mouth to the banjo-bolt hole) and see if it was sealed. NOPE - I could blow right through it...

So I dismantled both (man, those screws are tough to get out!), and used the top casting and chambers from the SD, and the O-ring and lower casting w/seal from Ava (couldn't blow through hers, so I knew the bottom seal had started working, thanks to a soaking with 3M wet-type spray silicone), and installed the completed unit on Ava.

Wow - not only is she up and running, but nice smooth power, and the transmission feels a whole new world - shifts on time, and so well.

...and on top of that, the ALDA still even has the cap on it!

What can I say - thanks for all the help!

Kinda funny - I've known the front brakes were due for refreshing, and the steering box is overdue, but now that she really moves down the road, it's real obvious!

:)

ps: after this interesting ALDA education, makes me wonder just how many ALDA's have either a bad chamber or a bad seal, which lead the owners to pop the cap, and start trying to adjust the thing.

My 2 cents? First check to see if you can blow air (mouth, NOT from a compressor) through your ALDA, and go from there.

In retrospect, I wonder just how much these chambers are flattened at atmospheric pressure, and how consistent they are one to the next.

Would be interesting to put a micrometer on known good ones, and bad ones, and see if a tolerance could be established, so we could simply mic them, and determine if they're good or not...

The FSM has a procedure for adjusting the ALDA, which is basically visual/smoke threshold, and mentions that it is a maintenance item so I doubt that many 20-year-old cars are out there with properly adjusted ALDAs, I've never bought one. However, after several 60x cars with mis-adjusted ALDAs, I've not (yet) run into a ruptured one, all seem to respond well to the 1-1/2 CCW adjustment.

Seems like the blow-test is a simple first step though, sure beats spending 20minutes getting to the adjusment just to find it's bad.