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  #1  
Old 08-12-2009, 08:59 PM
79Mercy's Avatar
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Starter and Idle Probems-76 300D

I drove the car this morning and for some reason it stalled when I came to a idle. It just barely re-started. I got to a gas station and it died as soon as I took my foot of the pedal. Would not re-start, the motor would turn very slow almost as if the battery was dead. The battery was 5 years old so I decided to get a new one due to the age of it.

After it sat for awhile I jumped it and it started, but I had to drive with 2 feet all the way home or it would die at idle. I replaced the fuel filters, air filter, and replaced the injector return lines today. It still will not idle when hot and in gear.

When it stalls the starter turns the motor over very slowly, even on the brand new battery. After the car has sat and cooled down thestarter will start the motor no problem. Does this sound like a bad starter? It is a 13 year old starter from Pepboys

When the motor is cold it idles perfect, but when hot it wants to stall when in gear. Im thinking I just need to turn up the idle a bit. What do ya'll think?

Thanks

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

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  #2  
Old 08-12-2009, 09:20 PM
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Not sure if the Starter is related to your idle issue. Most likely separate issues.

Simple things first:
One of the causes of the Engine running poorly hot can be valve clearances that are too tight; as the valve clearances get tighter with wear. Some members have reported have zero clearance; being unable to get a feeler gauge in.

In the past I had a small air leak that only showed up when the Engine was hot. My fuel inlet hose was hard and no amout of clamp tightening helped. For a few dollars I replaced the hoses with 5/15 fuel hoes and that cured it.

If you have the old style Hand Primer Pump with the hard Plastic Knomb on it they are noted for causing air leaks also.

Since the begining of the year some members have had Fuel Supply Pump issues or problems with the IP Over Flow Valve (big thread by cervan on this; it controls the fuel supply ressure).

Out of curioisity while the Engine is at idle you might clamp the Cigar return hose quickly; long enouth to see if the idle smooths out. This would override the Over Folw Valve and you would be creating more pressure than the Over Flow Valve can do. If the Idle smooths out it could be an indication of a problem with the Over Flow Valve not holding enoug pressure at idle.

To check the Fuel Supply Pump pressure is more complicated as you need some way to dampen the Gauge as the needle jumps around too much.
I bought a liquid dampened Gauge for this purpose and made a fitting to do the check but never have gotten around to doing it. (I am not having a problem; but it is good to test something when it is operating normally so you know what normal is.)


You did not say if while the idle trouble was happening if there was an abnormal smoke?
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Last edited by Diesel911; 08-12-2009 at 09:34 PM.
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  #3  
Old 08-12-2009, 09:26 PM
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yes, I think both are seperate issues, the starter has nothing to do with the engine not wanting to idle hot.

Sorry, I should have put this in the first post.

I did a valve adjustment last week, only 3 valves were out of spec.

The W115 300D has a different style primer pump than the W123. Its more of a big button mounted directly to the fuel filter housing.

Air leaks are a posiblility, though I see no visable fuel leaks.
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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
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  #4  
Old 08-13-2009, 12:41 AM
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Quote:
Originally Posted by 79Mercy View Post
yes, I think both are seperate issues, the starter has nothing to do with the engine not wanting to idle hot.

Sorry, I should have put this in the first post.

I did a valve adjustment last week, only 3 valves were out of spec.

The W115 300D has a different style primer pump than the W123. Its more of a big button mounted directly to the fuel filter housing.

Air leaks are a posiblility, though I see no visable fuel leaks.
The problem with Air Leaks is that tiny clearances let air in but the viscosity of the Fuel and Atmospheric Pressure that is around 14.7 psi can keep the Fuel from leaking out.
When the supply pump starts moving Fuel you now have a negative pressure inside of the Fuel Hose and 14.7 psi trying to push in.
In the Fuel Hose example that happend to me I had no external Fuel leak.

Did the hot rough idle problem show up before or after the Valve Adjustment?
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  #5  
Old 08-13-2009, 12:52 AM
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Does your Fuel Injection pump have a Mechanical or a Pneumatic Governor?

Is it possible to squirt some thick oil or put some grease around the Hand Primer Button to seal it to see if it is leaking air?

Does your Fuel Filter look like item #5 with item #128 as the Hand Primer:
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=115114&M=617%2E910&GA=722%2E109&GM=716%2E003&L=760%2E101++++++++++++++765%2E700&CT=M&cat=143&SID=07&SGR=120&SGN=04

Perhaps the gasket item #7 could be the source of an air leak.
When it is running good what is the idle speed?
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Last edited by Diesel911; 08-13-2009 at 01:06 AM.
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  #6  
Old 08-13-2009, 12:55 AM
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what are the chances your alt. is overloaded and forcing your engine to slow to a halt?

Could this load be from a fault in the starter?

edit: a bit far out, I suppose.
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Last edited by jt20; 08-13-2009 at 01:02 AM. Reason: brain fart...
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  #7  
Old 08-13-2009, 01:15 AM
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actually, can't a dying battery put a high demand on the alt? That might make more sense, especially since the battery is weaker at higher temps and you live in Fl.
this would explain the inability to start as well.

edit: I see you replaced the battery and it still happened. Ignore my ramblings.
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Last edited by jt20; 08-13-2009 at 11:36 AM. Reason: more flatulence
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  #8  
Old 08-13-2009, 08:35 AM
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Quote:
Originally Posted by jt20 View Post
what are the chances your alt. is overloaded and forcing your engine to slow to a halt?

Could this load be from a fault in the starter?

edit: a bit far out, I suppose.
Alternator can not absorb enough energy to kill a normal idle. It can seize though and burn the belt off.
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  #9  
Old 08-13-2009, 10:51 AM
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Did you get traped under the car? How is everything going.
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  #10  
Old 08-13-2009, 10:59 AM
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You should have a manual idle speed control knob on that car I think. Is there a problem with that mechanism.
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  #11  
Old 08-13-2009, 05:32 PM
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Guys I thought he said: "When the motor is cold it idles perfect, but when hot it wants to stall when in gear. Im thinking I just need to turn up the idle a bit."
I don't see anything here or in the origional post to indicate a Battery or Alternator problem as it starts OK when cold.
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  #12  
Old 08-13-2009, 09:43 PM
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So today I pulled tank strainer only to find out that there isn't one installed, just a metal plug...... Thats wierd......

It still turns over very slow when hot, bad stater?

There are no little air bubbles in the clear filter while running, at any engine speed.

The idle adjustment cable is fine.

I did do a diesel purge, wonder if that could have lowered the idle? I seems that I read a post where a guy stated the idle dropped after using diesel purge.

The alt puts out 13.5volts at an idle. The battery voltage is 12.7, but drops to 10.5 when starting, thats normal.

So I think I need to adjust the idle on the IP and install a new Bosch reman starter.
__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
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  #13  
Old 08-13-2009, 10:44 PM
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Might want to check delivery capacity on that lift pump - should be 150 cm after 30 seconds at idle - those little primary filters are .6 mm mesh (600 m) and can put a lot of unnecessary load on the pump if clogged with big particles that your missing tank strainer did not filter. Probaly need to invest the $19 for a tank strainer as well.

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