IP Giving Low Fuel Seemingly 617 - PeachParts Mercedes-Benz Forum

biopete · #1 11-16-2008, 11:20 AM

.Hi all. I just picked up an 1985 300D off craigslist. I need your help. I've searched and read some IP stuff here and plan to read more.

Here is the deal -- has 298,000 but has been immaculately maintained with all records. What it does is idle rough and not get any power until Wide open throttle. Like if you have foot half way down, nothing, 3/4 -- still nothing floored -- engine starts to rev up. Also, there is no sign the turbo is functioning. I can't hear it at all.

I notice the fuel/stop lever on engine seems to be resting toward the "stop" as it idles low and rough until i pick it up with my hand. I think that is out of adjustment or something. When i pull it to rev engine -- I have to pull all the way till the IP throttle mechanism hits a little pin and the engine will rev high. So the IP seems to not be giving fuel until at WOT.

Any ideas ? Looking at it i see that the idle can be adjusted with the deep socket 14 and a screw driver. However the paint is still in tack so i do not think that is best place to start. Anyone have any ideas what the best approach is? In the meantime, I'm going to do the banjo bolt cleaning and stuff first.

Thanks

coonerboy · #2 11-16-2008, 11:28 AM

I would start with the fuel filters. Cleaning the ALDA line will also help if its plugged. If you still have problems you may want to try running it off an isolated fuel source such as what is done in a diesel purge. The turbocharger on these cars isn't that audible, so unless you are running it with no air cleaner you won't be hearing it.

biopete · #3 11-16-2008, 11:37 AM

Quote:

Originally Posted by coonerboy

I would start with the fuel filters. Cleaning the ALDA line will also help if its plugged. If you still have problems you may want to try running it off an isolated fuel source such as what is done in a diesel purge. The turbocharger on these cars isn't that audible, so unless you are running it with no air cleaner you won't be hearing it.

Thanks for the ideas. Forgot to mention fuel filters, air filter brand new. PO did that before i bought it. Most fuel restriction problems i've seen happen at WOT rather than other way around. Not sure what plumbing in a fresh jerry can would help but it sure would not hurt. I may try it.

I took the Linkage off the IP throttle lever and the Pedal linkage. This should make the IP throttle lever at idle position and car should idle at 650 to 750 rpms with this linkage off right? Well car does not idle well. Should i adjust the idle screw on back of IP? My concern is what would wear or make that come out of adjustment so?

Thanks.

TMAllison · #4 11-16-2008, 11:45 AM

If it runs fine on the temp tank then you've confirmed the constriction is at the tank.

coonerboy · #5 11-16-2008, 11:46 AM

Running it off an isolated source would rule out a plugged tank screen, kinked fuel line, etc. You may want to have someone step on the accelerator pedal inside and watch the linkage for full travel. Make sure the linkage is hitting the stop on the injection pump.

biopete · #6 11-16-2008, 03:13 PM

Well, I adjusted the idle so it idles good with the screw on back of pump. I think ill try switching the fuel supply and return hoses and see if indee it is clogged screen or kinked line.

The throttle lever on IP is hitting stop. The problem is that fuel is not being delivered adequately througout the range of throttle lever. As i move lever, initially it tries to rev then it dies down and is just flat throug out the the whole range of the throttle lever until right before the stop. Then in winds up. At this point I can ease it off and it will continue to wind up down to about mid range in throttle lever. Then it flattens out. Then I move lever for more acceleration and it stays flat again until just right before stop (about 1/8 th inch before).

I'll go try jerry can now to rule that out. Then i guess i'll try cleaning the relief valve on backside of put that the fuel return line comes out of. Maybe that is gunked up or the spring is worn.

thanks

biopete · #7 11-16-2008, 07:44 PM

Ok. I tried the Jerry can. I also cleaned the banjo bolt on back of intake. it was gunked up. Problem still exists. The problem is the engine does not start to rev up until the throttle lever on the IP is almost all the way open -- WOT. It is weird. So i have to floor it all the time and this causes it to always stay in low gears.

I thought maybe the banjo bolt with spring on back of IP was messed up. So i swapped it with the one on my other 85 300D that runs awesome. Nice have identical cars. No difference on either car. The bolts were different though. One has a ball on end holding spring in and the other has a bolt.

Next I am going to replace the primer pump. I noticed it did not work. It is old style.

Anyone know what could cause this problem of not revving up until WOT?

Thanks

Diesel911 · #8 11-17-2008, 12:15 AM

Pull the hose off of the Vacuum Shutoff and plug the hose. Run the car and see if it helps (I am thinking if the Shutoff gets vacuum when it is not supposed to maybe it is in the partial shutoff).
Connect the hose back up to the Vacuum Shutoff and pop the linkage off of the manual shutoff down by the Shutoff Lever and see if it helps (to see if the manual shutoff is in a partial shutoff position due to linkage not being adjuste correctly).

Pop the linkage off of the throttle levers of both cars and see if both throttle levers have the same range of moation.

Rocketrider · #9 11-17-2008, 09:44 AM

I would definitely go after the primer pump first! It could be leaking air into your fuel system. It's cheap and easy and will have to be replaced anyway.

biopete · #10 11-23-2008, 11:47 PM

Quote:

Originally Posted by Rocketrider

I would definitely go after the primer pump first! It could be leaking air into your fuel system. It's cheap and easy and will have to be replaced anyway.

Alright, changed primer pump. Still same. I can prime a dry filter though now

I wonder if it could be the Rack Damper bolt?

So far this is what i have done:
Cleaned banjo bolt on back of intake.
Checked fuel supply good -- ran straight from a gas can -- and put fresh fuel in it.
Swapped out pressure relief bolt on return from IP with a known good one.
Checked that turbo spins.
Adjusted idle.

Anyone have any ideas? Could the IP have some problems internally? Next i'll try playing with RD bolt i think.

Thanks.

biopete · #11 11-23-2008, 11:53 PM

Quote:

Originally Posted by Diesel911

Pull the hose off of the Vacuum Shutoff and plug the hose. Run the car and see if it helps (I am thinking if the Shutoff gets vacuum when it is not supposed to maybe it is in the partial shutoff).
Connect the hose back up to the Vacuum Shutoff and pop the linkage off of the manual shutoff down by the Shutoff Lever and see if it helps (to see if the manual shutoff is in a partial shutoff position due to linkage not being adjuste correctly).

Pop the linkage off of the throttle levers of both cars and see if both throttle levers have the same range of moation.

Ahh, i forgot to pull vacuum shutoff hose and test. Thanks Diesel911. I'll try it tomorrow. That would be to easy. I did make sure linkage was not pulling it to manual shutoff and that it hits its idle stop screw with it connected and not connected. Also the range of motion on throttle lever looks about the same on both cars.

Thanks

Brian Carlton · #12 11-24-2008, 12:04 AM

Quote:

Originally Posted by biopete

.Hi all. I just picked up an 1985 300D off craigslist.

If you have a good source of fuel and both filters and the tank screen are good, the problem is likely not fuel related.

On a new vehicle, it would be in your interest to check IP timing and cam timing. If they've never been done before (likely), you could be 12 degrees late..........and all performance would be way off due to the late timing.

biopete · #13 11-24-2008, 03:00 PM

Quote:

Originally Posted by Brian Carlton

If you have a good source of fuel and both filters and the tank screen are good, the problem is likely not fuel related.

On a new vehicle, it would be in your interest to check IP timing and cam timing. If they've never been done before (likely), you could be 12 degrees late..........and all performance would be way off due to the late timing.

Thanks. I'll try that next after i rule out vacuum.

rrgrassi · #14 11-24-2008, 03:32 PM

Are you running diesel or WVO in the new car?

Does the car have a trap-ox on it?

biopete · #15 11-26-2008, 10:55 AM

Quote:

Originally Posted by rrgrassi

Are you running diesel or WVO in the new car?

Does the car have a trap-ox on it?

This is straight diesel. Its the emergency car for winter should WVO gel up.
Not sure about trap ox. Where would i find it? Did 85s have those ? The car was sold originally in michigan.

thanks