300TD suddenly very sluggish - PeachParts Mercedes-Benz Forum

GreenMedallion · #1 05-05-2007, 07:47 PM

OK, I've put a good 600 miles into my "new" 300TD. Has been running very well. An MB-only Mechanic checked it out as well, and agreed it was a strong running engine. Had the valves adjusted, filters replaced, fluid changes, etc.

Today, though, it suddenly is just dead in the water on any hill, and completely lacks acceleration from a dead stop. Once you get up to 40 or so, nothing can stop you! But seriously, I had to put it in "L" to make it up a steep but short hill in my nieghborhood. I've done this hill before in this car, with no such problem. Let me give you all I know-

-Today was the first I've driven since last Sunday. So it was sitting for 6 days, but started right up!

-Have been running B100. This afternoon replaced the spin-on filter, with no difference in performance. In-line filter looks clean (a few specs of black gunk) so I'll change that.

-Very little smoke - even less smoke then when i bought it. Have purged as well, just once. Smoke will be white/light gray and only at acceleration.

-Whirring sound when I am coming to a stop. Is this normal? Are my brakes dragging? Regardless it made this sound BEFORE today's sluggishness, so likely not the cause.

-Replaced the old style glow plugs, which has helped the slow starts i was having before.

-Oil pressure. Reads between 15-30 lbs/sq in at idle, jumps to the top (45) as soon as I hit the gas.

-Idles so smooth. I dont know if it was the B100 or what, but is idling nicely, better than before.

So, all seemingly normal? Why the sluggishness? It seems to run just fine, but suddenly no power.

TMAllison · #2 05-05-2007, 08:00 PM

Fuel tank filter screen assuming the two filters up front are as clean as you say they are.

Bio cleans more than 25 years of gunk out of the fuel system very effectively.

Biodiesel300TD · #3 05-05-2007, 08:17 PM

I second the tank screen if you other filters where just changed, escpecially since you've been running biodiesel. Make sure you replace the o-ring on the screen when you put it back in. It may leak if you don't, and it's a pain to pull out. You have to run the tank nearly as empty as possible, then be ready to catch several gallons of fuel when you pull the lines off the bottom of the tank.

tobybul · #4 05-05-2007, 08:50 PM

B4 doing anything, check this valve. Its the one in between the 2 banjo bolts (one at the intake manifold and one at the ALDA). The valve is located at the firewall right behind the brake booster.

This baby gets plugged up with soot and so do the banjos and possibly the lines connecting them. When they do, kiss your turbo boost goodbye.

Its a simple, no cost fix in case its the problem. With mine, thats all it took. I used brake cleaber spray to get the junk out.

The valves may need adjustment regardless since its suppose to be done every 15k miles. The changeover valve should also be checked every 5k miles or sooner once it gets sluggish.

GreenMedallion · #5 05-05-2007, 08:51 PM

Thanks! I hadn't even thought of that after my mechanic said there was no need to change it. But that was before all the B100!

Do I dare try this on my own? I don't have jacks. Maybe I just take it to the mechanic, it cant be a hard swap once they Benz is up in the air.

GreenMedallion · #6 05-05-2007, 08:54 PM

Oh, it's a non-turbo though. So I shouldn't have an ALDA?

(Yes I am a noob)

tobybul · #7 05-05-2007, 08:59 PM

Quote:

Originally Posted by GreenMedallion

Thanks! I hadn't even thought of that after my mechanic said there was no need to change it. But that was before all the B100!

Do I dare try this on my own? I don't have jacks. Maybe I just take it to the mechanic, it cant be a hard swap once they Benz is up in the air.

I wouldn't worry too much about the screen/strainer. I doubt this is the problem. I went thru the same thing before and can now say that none of what I did helped (changed fuel filters, purge, almost did the strainer) until I cleaned the changeover valve.

I was told by a loooong time diesel(s) owner in my area that if the strainer is plugged up, the engine won't be idling and revving right due to the constriction. It does not sound like this is your issue (nor was mine). Just low power.

tobybul · #8 05-05-2007, 09:02 PM

Quote:

Originally Posted by GreenMedallion

Oh, it's a non-turbo though. So I shouldn't have an ALDA?

(Yes I am a noob)

Ok, my bad... I guess I should read closer

I still don't think its a strainer problem since you are idling ok.

Brian Carlton · #9 05-05-2007, 09:11 PM

Quote:

Originally Posted by tobybul

Ok, my bad... I guess I should read closer

I still don't think its a strainer problem since you are idling ok.

Here's a bit of a story on the SD with power/idle issues:

The SD runs excellent.........until you cross the 450 mile point on the trip meter.

Then, at about the 16 gallon consumption point, the idle gets noticeably slower and it doesn't quite have the power that it normally does.

Take it to 500 miles..........17.5 gallons........and the idle is so poor that you think it will stall........a much rougher idle with reduced speed. On takeoff, it's very sluggish.........like it's missing a cylinder or so. The concern is so great that you seek the nearest station. Leave it running while filling. Get back in after the fill and it's immediately back to its normal self.

So, if that's not a tank screen................

tobybul · #10 05-05-2007, 09:28 PM

Well, I guess since you put your 2 cents in there, Brian, I'll have to trust it a good one.... you've been at it a lot longer than I've been.

Medallion, let us know after you do the strainer what it looks like. Pics would be great.

JimmyL · #11 05-05-2007, 09:30 PM

Quote:

Originally Posted by tobybul

B4 doing anything, check this valve. Its the one in between the 2 banjo bolts (one at the intake manifold and one at the ALDA). The valve is located at the firewall right behind the brake booster.

This baby gets plugged up with soot and so do the banjos and possibly the lines connecting them. When they do, kiss your turbo boost goodbye.

As stated in his signature AND posts, this car is a non-turbo, so it doesn't have the items to clean that you keep bringing up.

Quote:

Originally Posted by tobybul

The valves may need adjustment regardless since its suppose to be done every 15k miles.

Also in his post he states that the valves were adjusted...

Quote:

Originally Posted by tobybul

The changeover valve should also be checked every 5k miles or sooner once it gets sluggish.

See paragraph 1.....

It is always nice to help, but pay attention to the details.

We don't usually get info as good as his first post. Very thorough!

Palangi · #12 05-05-2007, 09:32 PM

Bad Fuel

Get a gallon of known good fuel (real fuel from dead dinosaurs). Figure out a way to southern-engineer a gallon jug of fuel under the hood on the drivers side. (A Delo or Delvac oil jug will rest in there nicely). Put both the fuel feed and return lines in it. Go for a 5 mile drive. After a mile or so, if it starts to run right, you will know what the problem is.

tobybul · #13 05-05-2007, 09:39 PM

Quote:

Originally Posted by JimmyL

As stated in his signature AND posts, this car is a non-turbo, so it doesn't have the items to clean that you keep bringing up.

Also in his post he states that the valves were adjusted...

See paragraph 1.....

It is always nice to help, but pay attention to the details.

We don't usually get info as good as his first post. Very thorough!

Ok, Ok, already......my bad

JimmyL · #14 05-05-2007, 09:41 PM

Quote:

Originally Posted by tobybul

Ok, Ok, already......my bad

Now you know we can't pass up a dog pile!!

All in fun.....

Whiskeydan · #15 05-05-2007, 10:48 PM

My guess would be fuel starvation. Tank strainer or filter(s).
Be prepared to experience this problem several times until the third or fourth tank of B100.
Had this same problem with every old diesel on a new diet of Bio.