1980 300d non turbo - runs rough/smoke at startup - turn back key when running fix - PeachParts Mercedes-Benz Forum

tdoublenastywitit · #1 08-25-2017, 09:07 PM

It runs good for like the first 3 seconds but after that it does the following:

i start my car from cold it runs pretty rough, sounds like it's missing or has air bubbles running thru the fuel. And it smokes pretty bad, the smoke seems to correlate with the misses btw

Although here is the kicker, which I'm hoping will lead someone here to quickly knowing what the problem is.

If I turn back the key and then turn it back to on really fast, so quickly the car doesn't shut off, then the smoke stops and it starts running good again without missing.

This works for a few mins and then If I'm just idling, I will have to do it again. Basically until it's halfway warm. But if I just start driving after I do it once I don't seem to notice.

Now it only works if I turn the key back far enough as to where the glow plug light comes back on.

So is this doing this because the glow plugs are coming back on and heating up the fuel or is me turning the key back reset the lift or injector pump pressure??

I've also heard this could be leaky delivery valves, because when I first start it the fuel system is pressurized but then the delivery valves leak and unpressurizes it.

Any help is greatly appreciated.

Diesel911 · #2 08-25-2017, 09:35 PM

If it was delivery valves why would manipulating the Key change anything?

Check you glow plugs with a Volt/Ohm meter.

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The other think that the key manipulates is the Vacuum Shutoff valve on the Steering Wheel Lock. Once the Engine is started disconnect the Vacuum Line from the Fuel Injection Pump Vacuum Shutoff and see of the rough idle and smoke goes away.

tdoublenastywitit · #3 08-25-2017, 09:48 PM

Ok and ya I didn't know if the key had anything to do with the delivery valves in some sort of way.

edit: the reason the guy told me delivery valves is because he thought possibly the guy manipulating re pressurized the fuel system, thus making the delivery valves totally operable but when tbe pressure falls back to idle fuel pressure that the valves leak again because they not under pressure. He seems to believe there is a starting fuel pressure and an idle fuel pressure and a fully warmed up engine fuel pressure. I'm not so sure about that tho

And ok I'll do thay trouble shooting and get back with results

tdoublenastywitit · #4 08-25-2017, 09:56 PM

Btw for any other further input the car has absolutely no trouble starting up at all even in cold weather. And just starts running rough after the few seconds.

It seems.to point.to.glow plugs for me.too, or at least it's definitely the first thing to checke trouble shooting list

NZScott · #5 08-25-2017, 10:14 PM

Sounds to me like your engine is running rough when cold and the glow plugs are making it run better. So could be a number of things. What colour smoke, white?

marco5 · #6 08-25-2017, 10:42 PM

Try a valve adjustment

Diesel911 · #7 08-25-2017, 10:58 PM

Quote:

Originally Posted by tdoublenastywitit

Ok and ya I didn't know if the key had anything to do with the delivery valves in some sort of way.

edit: the reason the guy told me delivery valves is because he thought possibly the guy manipulating re pressurized the fuel system, thus making the delivery valves totally operable but when tbe pressure falls back to idle fuel pressure that the valves leak again because they not under pressure. He seems to believe there is a starting fuel pressure and an idle fuel pressure and a fully warmed up engine fuel pressure. I'm not so sure about that tho

And ok I'll do thay trouble shooting and get back with results

The Deliver Valves deal with the fuel leavening the Elements on the way to the Injectors and are sort of one way valves with the exception they provide something called retraction.

The retraction feature is designed so that when the fuel flow to the Injectors is cut off the Valves close in a manner that reduces the shockwave/s inside of the Fuel Injection Hard Lines.

Once the Fuel enters the Elements it is sort of a seperate system. I call that the fuel injection Part of the system.

The other part of the system I call your fuel supply system. That is all the stuff including your Fuel Tank forward to the Fuel Supply/Lift Pump, and the Fuel Pressure/Overflow valve.

After that it is a fuel return system.

Diesel911 · #8 08-25-2017, 11:17 PM

Quote:

Originally Posted by tdoublenastywitit

Btw for any other further input the car has absolutely no trouble starting up at all even in cold weather. And just starts running rough after the few seconds.

It seems.to point.to.glow plugs for me.too, or at least it's definitely the first thing to checke trouble shooting list

Checking the Glow Plugs would take 2.5-5 minutes if you read up on doing it. You just stand by the Fender and pull off the Connector and then use the Volt/Ohm Meter. Not much chance to get messy and not difficult to do to eliminate them as a source of the problem.

Also check the Glow Plug Relay Fuse (if it has one) to see if it is cracked. When that happen to me I had intermittent glow plugs.

Diseasel300 · #9 08-25-2017, 11:28 PM

Manipulating the key will have no effect whatsoever on the injection pump. What does happen is that you recycle the glow plug relay, but since you don't go to "Start", the glow cycle runs for the full 30 seconds or so that the relay is capable of. The glow plugs running helps mask the mechanical problem you're experiencing.

If the compression is good, it's worth checking valve clearances and injector nozzle spray patterns. Poor fuel spray or questionable compression will certainly cause the problem you're having.

tdoublenastywitit · #10 08-25-2017, 11:44 PM

If I was posting any question on here about my Mercedes engine without having already done the valve adjustment I would understand if u banned me fr the forum... Lol in other words... Yes I've obviously done a valve adjustment.

Thank you for the input. I'm going to check the glow plugs tomorrow. And return with an update

tdoublenastywitit · #11 08-26-2017, 07:58 AM

Quote:

Originally Posted by NZScott

Sounds to me like your engine is running rough when cold and the glow plugs are making it run better. So could be a number of things. What colour smoke, white?

White bluish smoke btw. My book tells me that means that not all my fuel is getting burned

Diesel911 · #12 08-26-2017, 02:11 PM

Quote:

Originally Posted by tdoublenastywitit

White bluish smoke btw. My book tells me that means that not all my fuel is getting burned

Bluish smoke is associated with Oil being burned. Usually the exhaust will smell like burned oil.
Black to gray smoke is associated with poor combustion. Poor combustion can be caused by not enough air, fuel not being burned at the correct time, fuel not being atomized well by the Injectors, poor compression, and stuff like a head gasket leak where compression is lost.
Too much fuel can also be the cause it but nromally Fuel Injection Pumps when they wear don't put out excessive fuel.

Again the fuel burning has to take place within a sicific engine timing.

If you pull one Injector and the heat sheild and look inside a normal combustion chamber is going to have a light coating of dry carbon. If the carbon is shiny/wet looking that indicates oil burning. If there is a thick layer of dry carbon that indicates fuel not burning completely.

White smoke that smells like fuel is actually atomized fuel that is not burned. I had this happen on my Volvo Diesel when I timed the Fuel Injection Pump too late/retarded. The exhaust put out white billowing clouds of smoke.

I have not read anything on a combination of white and blueblack smoke. But, if black is poorly burned fuel and white smoke is entirely unburned fuel that could give some ideas.

tdoublenastywitit · #13 08-26-2017, 08:32 PM

Well it smells like diesel definitely but the engine does burn oil at about a half a qt a month.

The plugs are all good btw.

So it seems to me.like a mix.of burning oil and not burning all the fuel. I have greazzer injectors being made as we speak so we will see if that helps.

It's just odd to me.because the car runs extremely well once warmed up even in cold weather. No shaking at stop lights, no smoke, great power and acceleration for a non turbo.

There is slight nailing and clicking tho, which I'm hoping the greazzer's will fix.

tdoublenastywitit · #14 08-26-2017, 08:34 PM

I guess my question is pretty much answered. I was basically just wondering if the glow plugs turning on was masking a deeper problem.or if the key manipulating was pressurizing the fuel system, which i now know that it is not.

So I'll move onto the next thing a repost results in a separate thread then.

Thanks everyone