Left turn power loss! 78 300 cd - PeachParts Mercedes-Benz Forum

Phillytwotank · #1 02-26-2013, 12:47 PM

Ok here's the deal. Calling on the brain bank to help with any fresh ideas on this nagging problem. Probably one of the most perplexing problems that I've had to deal with.

I had posted a thread asking for help a while back but didn't generate many ideas. So, I'm gonna try again to explain what's happening and what I've done so far in attempt to correct the problem.

The Problem: the title says it. Cold starts fine, idles fine, accelerates fine, top speed is fine, no smoke, nothing but a hesitation after taking a left turn at speed then some "chugging" for about 20 seconds afterwards.

Left turn and only a left not a right turn.

I've done about everything that I know how to do to diagnose and/or correct any possible fuel restriction and/or air leaks.

Tank strainer clean, new hoses and clamps, two new filters, newer bolt with fresher o rngs on spin on filter, newer good lift pump, Cleared tank vent, visualy checked everywhere for leaks.

Bonus diagnostic tip: been runnin straight D in the 2 tank. When I switch over to the 2 tank all symptoms are GONE. In fact, feels like it rips harder with the new lift pump. So, have to assume that any part of the system that is common flow is good. Would include: the lift pump,IP, fuel pressure relief valve.

Any ideas anybody? Feel free to chime in. Any other diagnostic techniques?

I'm thinking about maybe pressurizing the fuel system with air to look fo leaks. Don't really have any ideas on how to find a flow restriction.

vstech · #2 02-26-2013, 01:28 PM

motor mount?

PNO TECH · #3 02-26-2013, 01:41 PM

Vstech, could you clarify that, please? I have experienced the loss of power/chugging in the new-to-me 300TD on left turns on several occasions. Felt like the time I had an air leak in my SD's fuel line.

gatorblue92 · #4 02-26-2013, 01:59 PM

Quote:

Originally Posted by vstech

motor mount?

You think it could be pinching a fuel line?

You could always stop turning left

whunter · #5 02-26-2013, 02:15 PM

Quote:

Originally Posted by vstech

motor mount?

Possible.

But I would reverse the fuel hoses on the fender, and test.

I suspect your sucking off the vent line at the moment.

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vstech · #6 02-26-2013, 02:16 PM

yeah, I thought of this, but it would do it only when the tank is below 1/2, not all the time...
got a pic of your orientation of the fuel lines?

whunter · #7 02-26-2013, 02:18 PM

Please identify which car this is..

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vstech · #8 02-26-2013, 02:18 PM

bear in mind, if the motor mounts are bad, the mounts themselves are not causing the engine to stall, they are allowing the engine torque to stretch weak/damaged fuel lines.

also, we are guessing what vehicle you are asking about...

Phillytwotank · #9 02-26-2013, 02:30 PM

i'd never make it as a nascar driver.

'78 300 cd...sorry about that.

the motor mounts are fairly new, probably three years, but the left side mount has had a splash of fuel a couple of times so i suppose it could be a bit soft. i do have a spare so i could swap it out and see.

i'm going out right now to triple check that the supply is indeed hooked up to the supply and the return to the return.

Phillytwotank · #10 02-26-2013, 03:58 PM

confirmed. supply is coming in on the "lower"(inboard) of the two hard lines.

whunter · #11 02-26-2013, 05:08 PM

Quote:

Originally Posted by Phillytwotank

confirmed. supply is coming in on the "lower"(inboard) of the two hard lines.

Call me to discuss this.

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barry12345 · #12 02-26-2013, 05:54 PM

It seems stranger than it is. Depending how your fuel line filters etc are set up. Turning left may release a large retained air bubble where it tends to develop and does not break loose when going to the right or straight ahead.

My first example was a volkswagon jetta that the engine totally quit on just co incidentally left hand turns as well . Only on turns of a shorter radius than on the highway though.

There was air leakasge into the large rear water separator though a crack. I imagine it accumulated. Then when I swung left the engine just died out but quickly restarted. I was suprised it was that as the effect was pretty fast and the rear water separater was way back around the rear axel.

The important thing was changing that part out cured the issue. What baffeled me was that it could be so quick acting. Plus i have to assume my thoughts about how it was doing this may not be accurate.

In your case I would investigate the additions to the fuel system that have not been installed by the manufacturer carefully. Your problem is almost unknown as far as I am aware on the factory fuel set up. Some switch over valves are known to create problems on cars set up for alternative fuels as well remember. Somewhere there may be a refferance to the bad brands of them.

Phillytwotank · #13 02-27-2013, 12:06 PM

Quote:

Originally Posted by barry12345

Turning left may release a large retained air bubble where it tends to develop and does not break loose when going to the right or straight ahead.

this is what i imagine is happening

whunter · #14 02-27-2013, 01:59 PM

Quote:

Originally Posted by Phillytwotank

this is what i imagine is happening

Good talking to you today.

As discussed, the WVO valve, fitting or hose seem the most likely cause.
Hope you have time to return the fuel routing to MB factory soon.

If this eliminates the issue, you can continue diagnosis on the WVO system plumbing at your leisure.

Have a great day.
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