I have a 1994 S350 TD. A problem has manifested itself with the arrival of cold weather. I pull out of my 60 degree garage into 40 degree ambient temperatures. At first the accelerator pedal feels fine and operates normally. After about a 0.5 miles at 25 MPH, the throttle response becomes "sticky". When I back off the pedal, the engine throttles down very slowly. When I step on the pedal, it feels like it has more resistance and the car suddenly feels very under powered. Shortly after the engine gets up to normal operating temp, the problem becomes much less noticeable or goes away entirely. When the car has been park outside in cold weather, the problem is very pronounced.

After looking through this forum, I think the problem is in the IP (specifically the fuel rack is gummed up). I've checked the linkage and it seems fine. Another symptom is the complete lack of smoke under hard acceleration, which to me suggests fuel starvation (the turbo is boosting).

My question is, what options do I have. Obviously I can go to the one and only local dealership; however, their usual recommendation is first buy a new car, followed by telling me I need a new IP for $2,500.

What about a pump rebuild or purchase of a junk pump? I'm pretty sure there's no miracle additive that will magically clean the pump. I'm reasonably sure removing, disassembling, cleaning and reinstalling the IP is beyond my abilities.

Can anyone recommend a competent mechanic in the northern Illinois or southern Wisconsin area, who could work on this car? I'd drive 200 miles for decent reasonably priced service.

If you are confident your filters and tank screen are free flowing, and that the IP linkage isn't binding, then I'd try some Lubro Moly Diesel Purge before spending any serious monies.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Are you only using Diesel Fuel?
What viscosity of Oil are you using and are you using synthetic Oil?
Are you allowing time for your Engine to warm up?
Does your Fuel System have a Fuel Heater?
Is there any part of your system from the Accelerator Pedal to the Fuel Injection Pump that uses a Cable. If so I would suspect that the Cable is sticking.

Is there a Spring somewhere in your linkages that returns the Throttle?
Below are some pics. The on the left shows where the Cover on the Fuel Injection Pump is if you want to look at the Fuel Rack. The pic on the right shows a pic of the Fuel Rack itself.
Ouce the cover is off you should be able to move the rack by hand. However, it is under spring tension but you should be able to move it back and forth (when the Engine is not running).
If you notice it is lubricated by Oil from the Engine.
If your Crankcase Breather system is restricted the crankcase pressure can push your Fuel Shutoff Solenoid (Vacuum Shutoff Valve) towards the shutoff position (the Engine might create more crankcase pressure when cold and less when hot due to blow-by).
You might try removing the Vacuum Shutoff Valve Vacuum line and plugging that and using a rubber or plastic cap over the nipple on the Vacuum Shutoff Valve. The cap should prevent the Vacuum Shutoff Valve from being pushed into the shutoff position by Crankcase Pressure. (Just for testing.)
Another comment on the Fuel Rack in the Fuel Injection Pump. To cause it to stick something gummy would have to get into the Fuel to cause the IP Elements to stick or something in the Engine Oil would have to cause the Rack to stick.
If your Engine has a Turbo I do not know if it is possible for the ALDA to cause the Rack stick. But, it could not hurt to clean out the tubing’s that connect it to the ALSD.
After that there would have to be an issue with the Governor inside of the IP. It has several springs and a bunch of levers.

Maybe you could put your Car up on Jack Stands or Ramps and let it sit out over night. In the morning start the Car and have some one maipulate the Pedal while you investigate to see if you can locate where the sticking is.

Attached Thumbnails

   

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84 300D, 82 Volvo 244Gl Diesel

Before offering a suggestion are you burning diesel fuel or waste vegatable oil?

Many of the suggestions already posted are good to check as there could be some kind of mafunction between the pedal and the injection pumps control arm. For example with car engine very cold have someone press the fuel pedal to the floor. Does the arm on the injection pump move to the stop?

Or for some reason you have poor fuel supply issues at cold temperatures. It is kind of early to assume the injection pump itself is the culprit. Certainly it may turn out to be so. But some other things have to be eliminated first.

I could suggest a few tests as well. Yet if others are performing your car service I hope they know enough about old diesels. You could be just ingressing a lot of air for example when the fuel system is cold .

Thanks for the replies.

I've only run petroleum based diesel in the car for the past 10+ years I've owned it. Of course anymore, up to 5% to 20% of the fuel is bio-diesel at the BP I buy my diesel at.

The engine oil is 10w30 motor oil (not synthetic) and is changed every 3,000 miles.

I inspected the throttle linkage. There is a cable exiting the firewall. The cable seems clean. There are several ball joint, push rod, bell crank type connections. They appear to be clean and moving freely but without disconnecting the fuel pump and letting things chill down, its hard to say.

I thought about the filters, but as I mentioned, when it's cold, the pedal becomes noticeably harder to depress when accelerating and when decelerating, the throttle comes off very slowly (to the point where you quickly realize its a bad idea to get too close behind another car).

I would think that points back to the linkage or the pump.

I'll look into the Lubro Moly Diesel Purge. And with some time off for turkey day, I'll try a few of the other suggestions.

Any suggestions for a good diesel mechanic within a couple hundred miles of Rockford, Illinois (just south of the Wisconsin border half way between Chicago and the Mississippi River)?

Thanks again for everyones comments (and the photos).

I would get a can of penetrating oil like WD-40 or PB blaster and soak all your linkages. if any are plastic, inspect them and see if they are worn out and causing binding.

__________________
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!

Disconnect the IP from the other linkages and move it by had to see if the resistance is in the IP, or in the cruise linkage / throttle linkage / bowden-cable.

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Gone to the dark side

- Jeff

This.



My SDL had a problem like this where I could rev it to the limiter in park but would be a slug driving... I had a linkage that was sliding internally and severely limiting rack travel.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

I just tried the Lubro Diesel Purge treatment (including fuel filter replacements). I'd like to report that is made a big difference, but that would be a lie. It may have helped smooth things out somewhat, but that's a subjective observation from the guy that just spent $50+ for the pro kit. However, I've got to commend Diesel Giant for their excellent web site. It's a treasure trove of DIY information.

I've ruled out the accelerator pedal and cable. If I pull the "pedal cable" while watching the linkage under the hood, I can see the linkage move slowly back into place after I've quickly put the "pedal cable" back to it's proper position.

Now I know the problem is definitely under the hood. Maybe tomorrow I'll get a chance to pull the intake manifold to get to the linkage.

I thought I'd post the final conclusion of this specific repair project. As you'll recall from above, the main problems were a sticky throttle and lack of power when cold.

I disassembled the throttle linkage. After breaking the first plastic socket on one of the push rods, I learned you pop those off their ball by prying the tip or sides of the socket with a flat blade screw driver. If you pry the rear side (that connects to the rod) you run a serious risk of splitting the socket where it connects to the rod. I ordered a new push rod, but JB weld worked fine on the original one. I noticed virtually all of the plastic linkage sockets were cracked (thanks again green party).

There are several pivot points and a couple of springs in the linkage. I cleaned all the ball and socket connection and used brake cleaner on the bell cranks and springs to remove a considerable amount of greasy goo. I also cleaned the throttle cable and the cable that runs to the transmission. I also re-install the rubber boot on the transmission cable. The transmission cable was a significant portion of the resistance until cleaned. I then used a dry lubricant on everything and reassembled. This fixed the sticky throttle.

While researching this problem, I ran across several references to the ALDA unit and specifically the pressure line to it. This line comes off the manifold and effectively informs the ALDA unit of the current boost pressure so it can adjust the fuel output. Because the line comes off the manifold it is subject to the goo introduced by the EGR valve. I disconnected the hose at the manifold. The port and hose looked clean, as did the end at the ALDA unit. Just to be sure, I shot the line with brake cleaner. At first the cleaner sprayed back out the end I was spraying it into. Then a big wad of black goo shot out of the other end of the hose. Then I noticed the in-line restriction port in the line. I love it when you get results.

I reassembled everything and took it for a spin in the now 9 degree weather. It ran like a champ. No sticky throttle and the power was normal. I'd say the moral of the story is check to simple stuff first!

Thanks everyone for the suggestions and help.