NO POWER then LOTS OF POWER then NO POWER in my 300TD
 

hey there. just bought my 3rd 300TD today, (though this is my first turbo) and am having some TROUBLE! I'm planning on doing a cross-country road trip, moving to Oregon in a couple days, so it'll come as no surprise that i'm freaking out about this!

Picked the car up today from a used car lot in south Houston, TX, and drove it home around 15 miles on the highway. she did GREAT on the interstate, but HORRIBLY after exiting and driving city streets.

she began really lacking power, and would hardly MOVE! tried to drive up into a friend's parking garage, and the short incline was too much for her. she stopped moving forward, and even after pushing the pedal to the floor, she wouldn't rev or have any apparent change in effort.

she has 198k on her, idles decently, starts easily, and fluid levels all seem fine (though the oils a little high). all vacuum hoses and connections appear normal, and both fuel filters appear newish. the car dealer replaced all the injectors (i can see they're new), but she smokes quite a bit when started.

don't imagine it's related, but all the dash gauges seem totally berzerk...the fuel level will read low one minute and full the next...the oil pressure goes straight to the top with any accelleration, and the coolant temp is pegged out to the top at all times.

after reading the manual, sounds like i'm supposed to be suspicious of the turbo, and in general, the fuel injection system / fuel injection pump....

the ductwork / "turbocharger intake pipe" seemed loose, and had a bit of oil in it...as well as on the turbo's "compressor wheel" and i can't tell that the turbo is functional (when i was cruising on the interstate, she didn't really "bolt" when i pushed down on the pedal. i tightened the intake pipe clamps, but she'll still barely move, though with some goosing will rev while in park.

what y'all's diagnosis and best guess? what should i do/check? pls lemme know, i'm freaking out about this impending trip!

Clogged fuel filter is the most likely cause.

Ditto.

Tank strainer may also be plugged/nasty. It will require draining the tank when you check it out.
The turbo will not cause it not to move up the incline you spoke of, although you may still have boost issues. Not a concern at this point.
Filters then strainer most likely. You certainly can't tell anything by looking at the primary filter. And look at that air filter too.
A constantly pegged temp guage would certainly mess with me.....

There is a push on connector on the middle of the cylinder head by the injection pump. Disconnect it and see if it changes your gauge reading.

Where abouts in Oregon are you headed?

You power problem really sounds like fuel filters. Change the primary and the secondary fuel filters, and see if that fixes it. If not then try cleaning the tank screen.

Your oil pressure is supposed to top out when you are accelerating or maintaining speed. It should drop when take your foot of the pedal and when the car is idling. It should be around 2 when the engine is warm and idling.

You jumpy gauge could be a dirty sending unit, which is easy to remove and clean, lots of info here on doing that.

The temp gauge could be a big concern. It could be the gauge itself or you may be really running that hot which is NOT good. You might want to take it to a shop and see if it is really running that hot. A pegged temp gauge can be a sign of a bad gauge. Does it go straight to pegged out when you turn the key to runthe glow plugs, so the engine isn't running? If so then it's the gauge.

Most gauges if disconnected or the power wire is cut will go to max. Look at that connector mentioned on the prior post. The one at the driver side of the engine between the 2nd and 3rd glow plugs. If loose or disconnected would cause the temp gauge to max out. But my first thought is the power plug at the back of the gauge cluster is loose, partially unplugged etc. that would affect both the temp gauge and the fuel gauge. I agree about the fuel filter lack of power issue but with the engine off and someone pushing on the throttle, can you see any slack, wasted motion before the throttle pivot goes to full throttle? on the engine linkage. Follow the linkage from the engine side of the firewall to the injec pump and verify it goes to full throttle mechanically.

Why don't they do that when the switch is turned off?

Don't know about the other issues, but the low power is Tank screen, gotta be. Switch fuel line coming in with the one going out. Then go for a drive. This will do two things--will tell you if it's the screen, since the return line has no screen at then end of it in the tank, but it may also "blow out" your tank screen and buy you some time until you can get it changed or cleaned. Good luck!

I am reminded of the poor chap who posted here some time ago complaining of inadequate power. After much investigation and consternation, he found the problem. The carpet was bunched up under the accelerator pedal.

Problem is most likely fuel filters, but thought I would throw out another possibility...

Crankcase breather hose pinched in some way, possibly by a disintegrating hood pad.

FWIW, easy to check.

okay, i'm ready to get to work on resolving this problem this morning, and will begin along the fuel filter/fuel strainer line. sounds like i should ignore the turbo and discount the injection pump b/c she did fine on the highway?

wondering what everyone thinks of that idea of switching the "send" and "return" lines to start sucking fuel from and "unstrained" fuel tank source? if so, where IS the return line???) will that be risky or ill-advised on some level,
OR for that matter,
can i plug some sort of hand-pump into the fuel sending hose and force air back to reverse back through the hose and strainer, hopefully clearing it out and buying me some time? can you think of any reasons not to? (i'm trying to get this resolved within 24 hours, starting on a sunday morning in a friend's apartment parking lot, with no way to drain the tank myself).

also, should i be worrying about the fact that somebody replaced the little fuel hoses that run from injector to injector with some really wimpy vacuum tubing? or will that serve fine for a while?

also, the last injector's outlet nipple (nearest the firewall) just has a piece of fuel hose on it that's been plugged with a little plug...i can't remember noticing that on my other wagons, so can someone tell me if that's normal?

That's definitely worth worrying about.

What does you primary fuel filter look like, contamination wise? If you can, cut the secondary filter open and inspect.

First off you need to do more diagnosis and give us a little more to go on than just "no power". It could be hundereds of different things. Do you get power every time you start the car and then it goes wimpy after it warms up? Is it getting worse and the power never returned?

Replace your filters.

I don't know how the tank is plumed on the inside. If you reverse the lines you might suck air, but either way it should blow out the screen a little. Sounds like a good way to get out of being stuck on the side of the road. Another diagnostic is the coke bottle trick. Secure a gatorade bottle or something like that in your engine compartment and run the fuel lines into it. You might need some extra 5/16" feul line. Use that as a temporary fuel tank just to see how it runs.

People replace those injector return lines with clear fuel lines to see if there's air in the fuel and to try to track it down. Keep an eye on them to see if fuel leaks out while idling (replace), or if air is leaking in from elsewhere. Sounds like this car was having problems before you bought it.

Your temp guage will peg if the wire is grounded. Check the wire. You need a temp guage if your driving cross country. If you can't get it to work put in an after market temp guage. I got one for $20 at O'rieley's.

The turbo is an expensive part and it almost never fails. Check to see it the ALDA has been jacked with. Pull out the air filter and see how it runs. If you still suspect the turbo pull off the U-shaped intake tube and see how it runs. This is for diagnosis only. With the tube off rev the engine you should see the impeller (compressor wheel) spinning. You may need a mirror and a flashlight and an extra hand. There's almost always oil in there.

If everything still check out. Bypass the lift pump with your coke bottle.

Still no power. Your valves or IP may be out of adjustment. Or you could have clogged exhaust, open the headers. I suspect the IP, but there's no way to tell from here. This is one of the most expensive parts, so check every other possible thing first.

Check the throttle linkage, make sure it working correctly. I had an old 240D (R.I.P) same problem, pedal to metal but no power, linkage was to blame, worn rubber grommet( that holds linkage in firewall engine comp side) was worn out, so linkage was sloppy, prevented throttle full open.

Simple check, cheap fix.

Last injector return line with a plug is normal.
I'd replace the filters first. Then try the bottle of fuel in the engine compartment. Put two clear lines in a 16 ox pop bottle, one attached to the return line on the canister fuel filter assembly and the other to the input of the small plastic filter. Fuel should get sucked from the bottle and recirculated back into it. A 16 oz (or so) bottle fits well between the inner fender and a hose on my TD. You could drive it around like that to test it if yours fits the same way.
The return line is the 'fat' cigar hose coming off the canister filter assembly. The incoming line goes directly to the small plastic filter. You'll need some additional hose if you want to switch them, or perhaps you can remove the two hoses where they attach to metal lines.
It might work to blow compressed air through the incoming line back through the tank. It would be even better to extend it, put your mouth on the hose and blow through it to see how much resistance you get. I was having problems in a 72 Chevy wagon dying out and found an additional fuel filter someone had installed in the line by blowing backwards through the fuel line and getting a lot of resistance.

I would start with a fuel filter change. Then go for a drive see if the problem goes away or not. If not then try switching the lines to see if the tank screen is clogged.

The last injector should have a short line with a plug on it. So don't worry about that, but I would change the rest of the lines that are vac lines. Problems probably won't arise instantly but I would find some new fuel line to replace the vac lines with.

The bottle under the hood is another good idea to diagnose the fuel delivery up to the IP. Also, make sure the return hoses between injectors are in good shape and that they are the braided type. I tried to cheap out and use regular fuel line on those and they leaked like crazy. Good luck.

I agree with the fuel filter/tank screen diagnosis. The filters my look fine but could still be plugged. The behavior of the oil gauge is normal, as is the small amount of oil in the turbo. The smoke when starting is likely the valve stem seals. Mine used to smoke when started...now it smokes all the time. Those seals are next up on my repair radar.

Please don't forget to let us know how things are going with getting your Benz back on the road. I've always thought that the ONLY thing wrong with this forum is that the folks asking for advice don't let anyone else know what finally works. That kind of info is priceless. Thanks and good luck with your trip.

well, i'm still tryin'! replaced the primary filter, and upon inspection, the old one did spit out bit of sludge. replacement didn't fix the problem though, and couldn't locate a secondary filter over the weekend, so am going to pick one up as soon as the import shop opens this morning.

did try switching the send and return lines, to no avail. actually, the car didn't even start when i attempted that. tried blowing with my mouth back through the send line and couldn't get any movement or force any air up there....

linkage all seems good, and there's no carpet bunched up under the accelerator :)....
i noticed that two of the fuel tank vent hoses that go to the little auxillary tank near the spare tire are loose and hanging, as that tank's plastic nipples have broken...but i don't imagine that would be a huge problem, would it?

my plan is to try this next fuel filter, and if that doesnt work, take it to a shop here in houston and try to get them to do the in-tank screen this afternoon. I'm hoping and praying that it IS something simple like y'all have suggested so i can get BACK on the ROAD.

my .02 is that you've got a plugged tank screen, vent, or both..
Let us know what finally solves the problem..

If the vent is obstructed, removing the fuel cap should restore normal performance, at least temporarily.

A pop bottle some vinyl hose and a quart of diesel could confirm a problem with the tank quickly. Plumb it in to the system and see how it runs.

Also clean the banjo bolt that contains the line that runs to the turbo switchover valve, and then on to the ALDA. My turbo switch over valve was stuck closed, and the banjo bolt was patially plugged w/soot.

If either or both fuel filters are clogged you can experience no power. So make sure you eventually replace both, especially since one was gooy. Also try the fuel lines in the bottle trick to rule in or out the tank strainer.
Follow the instructions that Diesel Giant gives on his DIY Diesel Purge. Hook the bottle up just like he does in the write-up, but you can just use some clean diesel. This will tell you if the tank strainer is clogged or not.

WELL.
it's been a long couple of weeks, but I'm finally home from my Texas-to-Oregon road trip. i'll be posting another question here in a minute on the comedy of errors and crappy luck plagueing my trip, but, first things first:

sorry i haven't posted an earlier resolution reply, but i've been on the road and internet restricted.

as far as THIS post and its resoulution is concerned:

it baffled me because of the ORDER in which all this bad running/lack of power stuff all happened, but, long story short: both fuel filters were clogged AND the primer pump was bad AND the fuel gauge was faulty.
thanks so much for all your help on this one. got me from Houston to northern New Mexico, before experiencing any other trouble :)