Very weak acceleration and weird idling - PeachParts Mercedes-Benz Forum

kahlil88 · #1 02-17-2011, 03:26 AM

A few weeks ago, I made the mistake of letting my '78 300D run out of fuel. Had to replace fuel filters and primer pump before it would start again, but now it doesn't feel the same to drive. The acceleration is noticeably weaker than before and I can't push it over 40mph even when FLOORED. The pedal was sticking as well, but a friend fixed it by adding a spring to the throttle linkage. Didn't help the acceleration though.
It's also idling weird -- starts off kind of slow and a little shaky like the engine is about to shut off (as it has before on a few occasions when stopping or driving really slow) then picks up as if the pedal is being pressed slightly. Starting it has never been smooth, but now it's worse. I generally had to accelerate while starting it but now it turns over a few more times than usual before it starts.

t walgamuth · #2 02-17-2011, 05:55 AM

Sounds like you have bacteria covering your screen in yoiur tank or in the fuel filter. I suggest dosing your tank with a biocide and killing off the bacteria. they will then go through your filters and burn off.

layback40 · #3 02-17-2011, 06:31 AM

Quote:

Originally Posted by t walgamuth

Sounds like you have bacteria covering your screen in your tank or in the fuel filter. I suggest dosing your tank with a biocide and killing off the bacteria. they will then go through your filters and burn off.

X2
It does sound like fuel starvation.
Has the car been run on non diesel fuel in the past? Has the car had fuel related problems previously?
You may have air leaking into the fuel system around where the hoses connect to the primary filter.
Could you put some details about the car (mileage) in your signature please.

vstech · #4 02-17-2011, 09:04 AM

did you loosen all injector line nuts at the injectors when cranking after the filter change? often these cars get an air lock in the lines... try loosening the nuts on all the injectors, and cranking over the car. make sure you get fuel on ALL nuts. and no bubbles are present.
fill your fuel tank to the brim. then swap the supply and return fuel hoses and see if the drive improves.
is your primary fuel filter clear or fogged? if clear. look at it after you've driven a while, and see if you have any gunk in it.

kerry · #5 02-17-2011, 09:51 AM

X2 on switching supply and return. You could also run the engine on an alternate fuel supply in a jug in the engine compartment and see if it runs ok then. If it does, problem is in the fuel delivery system somewhere.

kahlil88 · #6 02-18-2011, 05:48 AM

Quote:

Originally Posted by t walgamuth

Sounds like you have bacteria covering your screen in yoiur tank or in the fuel filter. I suggest dosing your tank with a biocide and killing off the bacteria. they will then go through your filters and burn off.

I've been meaning to do that since I got the car -- it sat for a year or two before I got it and my mechanic friend has been suggesting algaecide.

Quote:

Originally Posted by layback40

X2
It does sound like fuel starvation.
Has the car been run on non diesel fuel in the past? Has the car had fuel related problems previously?
You may have air leaking into the fuel system around where the hoses connect to the primary filter.
Could you put some details about the car (mileage) in your signature please.

In the year I've owned it, I've only used standard petrol diesel #2, aside from filling a new secondary fuel filter with B20 one time. As I mentioned in the first post, the car has suddenly shut off on a few occasions when stopping at a light/sign/turn or pulling slowly into a parking space. The first time this happened was about 8 months ago, and it took some effort and a friend's help to start it back up again -- replaced both fuel filters, connected a hand pump to get fuel back into the lines as the old primer pump was busted. Practically floored it for about 10 seconds so it would stay running.

Quote:

Originally Posted by vstech

did you loosen all injector line nuts at the injectors when cranking after the filter change? often these cars get an air lock in the lines... try loosening the nuts on all the injectors, and cranking over the car. make sure you get fuel on ALL nuts. and no bubbles are present.
fill your fuel tank to the brim. then swap the supply and return fuel hoses and see if the drive improves.
is your primary fuel filter clear or fogged? if clear. look at it after you've driven a while, and see if you have any gunk in it.

Cracked open the first injector just to see if fuel was getting through, perhaps I'll give it a shot with the rest of them open. The primary filter is looking pretty clean, but maybe I just need to drive it a little more (I've gone maybe 4 miles since getting it running again).

layback40 · #7 02-18-2011, 06:14 AM

Quote:

Originally Posted by kahlil88

I've been meaning to do that since I got the car -- it sat for a year or two before I got it and my mechanic friend has been suggesting algaecide.

In the year I've owned it, I've only used standard petrol diesel #2, aside from filling a new secondary fuel filter with B20 one time. As I mentioned in the first post, the car has suddenly shut off on a few occasions when stopping at a light/sign/turn or pulling slowly into a parking space. The first time this happened was about 8 months ago, and it took some effort and a friend's help to start it back up again -- replaced both fuel filters, connected a hand pump to get fuel back into the lines as the old primer pump was busted. Practically floored it for about 10 seconds so it would stay running.

Cracked open the first injector just to see if fuel was getting through, perhaps I'll give it a shot with the rest of them open. The primary filter is looking pretty clean, but maybe I just need to drive it a little more (I've gone maybe 4 miles since getting it running again).

There is stuff called startron (maybe wrong spelling) that will fix it. This sounds like classic bug in fuel problems the more you tell us about it !!
Good luck!! Please let us know how you go.

kahlil88 · #8 02-21-2011, 11:31 PM

Acceleration is normal after removing the spring my friend put in the throttle linkage...but the pedal is still kinda sticky at times and I've been noticing a low creaking that I suspect is my brake caliper seizing (happened to my last car, right rear wheel, absolutely destroyed the rotor). Definitely gonna see if O'Reilly has StarTron or something similar when I cash my paycheck tomorrow.

t walgamuth · #9 02-22-2011, 05:58 AM

You often have to go to a farm, truck or marine supply to find it.

toomany MBZ · #10 02-22-2011, 06:44 AM

I agree with t wal, try a marina, farm supply store or truck stop.

Lube all the ball and sockets in the linkage train, also follow the cable at the firewall down to the plastic bushing, lubricate it too.

kahlil88 · #11 02-23-2011, 02:38 AM

Quote:

Originally Posted by t walgamuth

You often have to go to a farm, truck or marine supply to find it.

Yeah, they didn't have it at O'Reilly but I placed an order for Killem. Hope it's as good as StarTron.

kahlil88 · #12 03-04-2011, 10:13 PM

I try not to immediately see correlation as causation, but it seems like ever since putting Killem in my tank, it's been increasingly more difficult to start the car. I just spent $40 filling my tank this evening and after shutting the car off and letting it sit for 5 minutes while I grabbed something real quick from the house, it won't even start! I seem to have a very minor leak in the fuel hose that goes to my primary filter from the tank but I really doubt that's the problem. When I say very minor, I mean there's a very small puddle under the car after several hours but nothing noticeable like fuel spraying out.

kerry · #13 03-04-2011, 10:23 PM

Fuel seeping out means air can get in, especially if the screen is plugged. Try running it on a jug in the engine compartment.

Ether · #14 03-04-2011, 10:27 PM

If the biocide just kills the stuff then it could certainly still be clogging your tank screen and fuel filters. That's why I'm a proponent of Startron, the enzymes gobble up the goop and break it down to particles small enough to pass through filters and into the combustion chamber. West Marine sells it.

Fix the fuel leak first though.

kahlil88 · #15 03-04-2011, 10:32 PM

I'm hoping I didn't put too much Killem in...started with approximately 5mL on Monday at 3/4 tank and 5 more after putting in 10 gallons today. Maybe in the future I'll clean my system with biodiesel.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode