85 300TD IP throttle arm slop

[DieselWillys]

Hi all,
I've searched previous posts and haven't found the same problem - maybe someone can help?

When I'm under the hood controlling engine RPM using the arm that attaches directly to the IP, I get virtually no response to movement until the throttle arm is about halfway through its full motion. I've checked and rechecked and I've even reached down between the IP and block and controlled right from the arm that enters the IP - no response for 1/2 its travel. I suspect this is why acceleration is lacking and top speed is only about 40 MPH (if I'm lucky).

Does anybody know if this means IP replacement is necessary or is there another option?

I got frustrated trying to fix this a couple months ago, and temporarily gave up, but now I need this car to work or else it's gotta go.

Thanks,
Lars

[Biodiesel300TD]

Maybe you linkages are way out of spec. The Shop manauls have all the specs on the lengths you might check those, to make sure you linkages are all the right length.

When did you change your fuel filters last? They might be horribly clogged. and you really have to give it fuel to get enough to go by to raise the RPM.

[DieselWillys]

Thanks, I've replaced the filters, maybe it's the filter in the tank - perhaps I'll try to run the car from a gas can to test that theory.

I've checked and eliminated the linkages as the problem. At least up to the actual arm on the IP. I wonder if that arm can slip on the shaft that enters the IP?

Lars

[klataklatacoupe]

is your turbo spinning, be sure it didn't lock up. take the air cleaner off & the plastic tube going to the turbo, start the engine & watch 2 see if its turning. also check vac and turbo limiter.

[winmutt]

Originally Posted by DieselWillys

Thanks, I've replaced the filters, maybe it's the filter in the tank - perhaps I'll try to run the car from a gas can to test that theory.

I've checked and eliminated the linkages as the problem. At least up to the actual arm on the IP. I wonder if that arm can slip on the shaft that enters the IP?

Lars

Did you read the FSM on linkage adjustment? When the pedal is pressed down you should be reaching the max stop adjuster.

[DieselWillys]

I've checked and tried the above - linkages all OK, filters new, turbo's moving fine, vacuum's good.

I ran across an IP from an 84 300D - anybody know if it will work on the '85?

[Brian Carlton]

Originally Posted by DieselWillys

I've checked and rechecked and I've even reached down between the IP and block and controlled right from the arm that enters the IP - no response for 1/2 its travel

You've done a good job at troubleshooting.

It's not your fuel filters.

It's not your turbo.

It's not your linkages

When the arm that is right on the IP doesn't affect the engine rpm, the problem must be in the IP. The slightest movement of this arm should move the rack and increase fuel to the engine. I don't see any other option.

The '84 should fit the '85 just fine. However, check for any additional throttle switches on the '85 that might be in the neighborhood. The '84 won't have them.

[DieselWillys]

Thanks Brian.

Well now I've got the old IP out, and I'm ready to install the new one. Now as to that pesky bolt between the IP and the block, and below the small metal housing with the electrical fitting. The older (pre-'84) IP's didn't have that extra housing (so I'm told). Can it be removed and blocked with a plate without adversely affecting the vehicle?

[Brian Carlton]

Originally Posted by DieselWillys

Thanks Brian.

Well now I've got the old IP out, and I'm ready to install the new one. Now as to that pesky bolt between the IP and the block, and below the small metal housing with the electrical fitting. The older (pre-'84) IP's didn't have that extra housing (so I'm told). Can it be removed and blocked with a plate without adversely affecting the vehicle?

If you're talking about the lower bolt, I don't see any way of getting it started with the oil filter housing in place. In reality, I think the IP would survive without it.

[DieselWillys]

Now it works great!

I replaced the IP with the one out of an '84, and now I have a car that runs like a scared cat up to 60 MPH and beyond - much better than the 40 MPH top speed it had a couple days ago!

Thanks for the suggestions and advice on troubleshooting. Replacing the IP was a scary thought before I started, but once I got into it it was just a matter of paying attention to the details.

[Brian Carlton]

Originally Posted by DieselWillys

Now it works great!

I replaced the IP with the one out of an '84, and now I have a car that runs like a scared cat up to 60 MPH and beyond - much better than the 40 MPH top speed it had a couple days ago!

Thanks for the suggestions and advice on troubleshooting. Replacing the IP was a scary thought before I started, but once I got into it it was just a matter of paying attention to the details.

Good job.

That's not an easy task.........especially for a person without M/B experience.

Glad it worked out for you!

[toomany MBZ]

I love a happy ending!