seems to be loosing prime....but.....? - PeachParts Mercedes-Benz Forum

tadco · #1 11-24-2012, 08:15 PM

So my 82 300 TDT with 280,000 was starting to really need cranking to get it to start when cold (below 60F). Once it started it runs and starts all day. The longer I neglected it the worse it got. I then started to prime it with the pump. That seemed to work a few times. I replaced all the small injector return lines. I replaced the prime pump with a new one. I even put a electric pump before the one on the injector pump to help prime it. All glow plugs are good and getting power. It will start and run good if it is about 70F (but sometimes idles a little rough). I do not have a block heater and never needed one before. Where should I look for my trouble?

Tony

layback40 · #2 11-24-2012, 08:23 PM

Quote:

Originally Posted by tadco

So my 82 300 TDT with 280,000 was starting to really need cranking to get it to start when cold (below 60F). Once it started it runs and starts all day. The longer I neglected it the worse it got. I then started to prime it with the pump. That seemed to work a few times. I replaced all the small injector return lines. I replaced the prime pump with a new one. I even put a electric pump before the one on the injector to help prime it. All glow plugs are good and getting power. It will start and run good if it is about 70F (but sometimes idles a little rough). I do not have a block heater and never needed one before. Where should I look for my trouble?

Tony

Try parking your car facing down hill with a full tank of diesel & see if there is an improvement. I realize its a wagon, but I have found it works if the hill is steep enough. If it makes no difference then its probably not an air leak.
Have you set your valves recently? Tight valves will make for hard starting when cold. Rough idle is likely to be caused by tight valves.
Have you removed your GP's & checked that they do glow?

tadco · #3 11-24-2012, 08:29 PM

I did not remove the GP's I checked continuity and power.

I did put on an injector pump from my wrecked 80 300D and it still will not start and I think it is on correctly (as I have done this before), however it has been on a shelf for 2 years.

It is currently on battery charge and the front is up on stands. It is full of fuel also. I think I will move the stands to the rear. However when I crack the banjo fitting from the fuel pump to the filter I get plenty of fuel.

Tony

tadco · #4 11-24-2012, 08:30 PM

I have not set the valves in far too long and I will do it cold while the battery charges.

Tony

layback40 · #5 11-24-2012, 08:45 PM

Quote:

Originally Posted by tadco

I did not remove the GP's I checked continuity and power.

However when I crack the banjo fitting from the fuel pump to the filter I get plenty of fuel.

Tony

One thing at a time is best.
If you remove the return line from where it joins the steel line going back to the tank, do you get a stream of fuel when you pump the primer?
Is the banjo bolt on the injector pump that controls the fuel pressure in the IP good? You should be able to hear it when you pump the primer.
Please post back what you find with the valves. They need to be done cold. If you have valves with little or no clearance, you have probably found your problem.

tadco · #6 11-24-2012, 09:10 PM

The first intake I checked has 0 clearance. This is gonna take a while as I have lost my spoon wrenches and have to make new.

Brian Carlton · #7 11-24-2012, 09:16 PM

Quote:

Originally Posted by tadco

The first intake I checked has 0 clearance.

Problem found.

Nothing whatsoever to do with fuel. No issues when running warm also confirms this.

Silber Adler · #8 11-24-2012, 09:56 PM

Before I adjusted the valves on my car all of the intakes were zero. The exhausts had between .oo2 and .008" It still started normally and ran. Not as smooth as now.

tadco · #9 11-24-2012, 10:03 PM

At least one valve on each cylinder was too tight. It did crank a little long but it runs fine. I think it will start in the AM also. I really wish I hadn't changed the injector pump.

Thanks for the help,
Greatly appreciated,
Tony

whunter · #10 11-24-2012, 11:17 PM

Quote:

Originally Posted by tadco

So my 82 300 TDT with 280,000 was starting to really need cranking to get it to start when cold (below 60F). Once it started it runs and starts all day. The longer I neglected it the worse it got. I then started to prime it with the pump. That seemed to work a few times. I replaced all the small injector return lines. I replaced the prime pump with a new one. I even put a electric pump before the one on the injector pump to help prime it. All glow plugs are good and getting power. It will start and run good if it is about 70F (but sometimes idles a little rough). I do not have a block heater and never needed one before. Where should I look for my trouble?

Tony

#1. So my 82 300 TDT with 280,000 was starting to really need cranking to get it to start when cold (below 60F).
Note: Your car is a 300TD Turbo W123.193 model produced 1980-1985, the TDT is a W124.193 model made in 1986 - 1987.

Answer: This is a cold start issue, typically valves out of adjustment and/or bad glow plugs.

GLOW PLUGS:

FYI: Trying to OHM a heating element designed for high temperature operation at ambient temperature gives a deceptive reading.

A new glow plug reads 0.7 OHM.

Heating the air to a minimum starting temperature of 850°C is critical for diesel engine start-up.

FYI:
The most common (good quality) "NEW" glow plug failure is over torquing the 8 MM wire nut = damaging the electrode internally.
This is an ELECTRICAL connection = watch the wire, and STOP tightening when it begins to move.

All of this being said, I junk any glow plug reading 0.9 or higher.
For best reading:
* Disconnect the glow plug harness from the relay.
* Red OHM meter wire goes on the 8 MM wire nut threaded pole/terminal.
* Black OHM meter wire goes on the steel body of the glow plug.

All of my used glow plugs are tested:
# With the HOT electrode in the jaws of a vice.
# Battery/charger ground attached to the vice.
# Positive applied to the wire nut threaded pole/terminal for 15 seconds.
After you have tested one good glow plug, and personally seen how bright/hot it gets, there is no mistaking weak/bad ones.
Warning: While diagnosing the glow plug system, do NOT touch any part of a hot glow plug.
Glow plugs run 1000° - 1300°C = "2372° Fahrenheit" optimal temperature range.
Touching the glow plug wire nut can cause severe burns, especially if there is a fault causing it to overheat.

http://www.peachparts.com/shopforum/2611938-post13.html

How do Glow Plugs work?
How do Glow Plugs work? | Ask Pete

Please read the following thread for further data.
http://www.peachparts.com/shopforum/diesel-discussion/137732-glow-plugs-link-thread.html#post1019018

VALVE ADJUSTMENT:

If the valve adjustment was neglected long enough, it may require several valve adjustments in the same day.
As the gap between rocker and camshaft reduces, the valve opens sooner + is held open longer.
If ignored long enough this allows uneven carbon deposits to form on the valve mating face and seat = preventing a good seal = compression loss.

The correct procedure is to:
#A. Adjust the valves, reassemble.
#B. Italian Tune-up.
#C. Check the valve adjustment, if needed repeat step #A. and #B until there are no tight valves = you are done..

There is nothing wrong with adjusting valves on a warm engine, a cold adjustment is NOT superior, it is simply another way of doing the same job.
Factory trained mechanics rarely performed a COLD adjustment, they used the hot specification..

.

Silber Adler · #11 11-24-2012, 11:33 PM

I love your brute force method of checking glow plugs. I did the same technique of pulling the plug at the fuse and measuring for continuity got between 1.2-1.7 ohms.

My car sometimes runs rough for a few seconds or needs a double dose of pre heat to get it to run clean initially. Perhaps I need to consider a direct test.
Thanks

Quote:

Originally Posted by whunter

#1. So my 82 300 TDT with 280,000 was starting to really need cranking to get it to start when cold (below 60F).
Note: Your car is a 300TD Turbo W123.193 model produced 1980-1985, the TDT is a W124.193 model made in 1986 - 1987.

Answer: This is a cold start issue, typically valves out of adjustment and/or bad glow plugs.

GLOW PLUGS:

FYI: Trying to OHM a heating element designed for high temperature operation at ambient temperature gives a deceptive reading.

A new glow plug reads 0.7 OHM.

Heating the air to a minimum starting temperature of 850°C is critical for diesel engine start-up.

FYI:
The most common (good quality) "NEW" glow plug failure is over torquing the 8 MM wire nut = damaging the electrode internally.
This is an ELECTRICAL connection = watch the wire, and STOP tightening when it begins to move.

All of this being said, I junk any glow plug reading 0.9 or higher.
For best reading:
* Disconnect the glow plug harness from the relay.
* Red OHM meter wire goes on the 8 MM wire nut threaded pole/terminal.
* Black OHM meter wire goes on the steel body of the glow plug.

All of my used glow plugs are tested:
# With the HOT electrode in the jaws of a vice.
# Battery/charger ground attached to the vice.
# Positive applied to the wire nut threaded pole/terminal for 15 seconds.
After you have tested one good glow plug, and personally seen how bright/hot it gets, there is no mistaking weak/bad ones.
Warning: While diagnosing the glow plug system, do NOT touch any part of a hot glow plug.
Glow plugs run 1000° - 1300°C = "2372° Fahrenheit" optimal temperature range.
Touching the glow plug wire nut can cause severe burns, especially if there is a fault causing it to overheat.

http://www.peachparts.com/shopforum/2611938-post13.html

How do Glow Plugs work?
How do Glow Plugs work? | Ask Pete

Please read the following thread for further data.
http://www.peachparts.com/shopforum/diesel-discussion/137732-glow-plugs-link-thread.html#post1019018

VALVE ADJUSTMENT:

If the valve adjustment was neglected long enough, it may require several valve adjustments in the same day.
As the gap between rocker and camshaft reduces, the valve opens sooner + is held open longer.
If ignored long enough this allows uneven carbon deposits to form on the valve mating face and seat = preventing a good seal = compression loss.

The correct procedure is to:
#A. Adjust the valves, reassemble.
#B. Italian Tune-up.
#C. Check the valve adjustment, if needed repeat step #A. and #B until there are no tight valves = you are done..

There is nothing wrong with adjusting valves on a warm engine, a cold adjustment is NOT superior, it is simply another way of doing the same job.
Factory trained mechanics rarely performed a COLD adjustment, they used the hot specification..

.

Diesel911 · #12 11-25-2012, 11:12 AM

Some people have found bad Glow Plugs testing them on the Batttery that were good when they did the Test with an Ohm Meter.

I looked for My Block Heater and could not find it. One day while I was doing something else I found the Block Heater Cord shoved up under the front Bumper and tied there.
Sure enough I have a Block Heater. It is just real difficult so see as there is a Bracket that comes down below the Turbocharger that blocks the view.

See post #9 is a pic of a Glow Plug that Ohmed out OK but was bad when tested on the Battery.
http://www.peachparts.com/shopforum/diesel-discussion/311514-glow-plugs-bad-how-tell.html

tadco · #13 11-25-2012, 08:00 PM

Well it did not start this morning.

I checked the glow plugs with a meter again as I had only looked to see if they were open before.

I had three well above .9

I put the original injector pump back on.

I went through the valves again and some were a little tight again.

I will blow it out on the x-way and go through the valves daily until they stop changing.

I will do a glow test on the plugs also soon.

Running like a champ now!

Thanks for the help!

TnBob · #14 11-25-2012, 08:36 PM

Just to be clear, the ohm reference point is:
"A new glow plug reads 0.7 OHM"

vstech · #15 11-25-2012, 08:42 PM

I would venture to say .5 to .8 is good. 1.0 will work, but verifying visually is wise.