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  #1  
Old 12-02-2014, 11:38 PM
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W124 Diesel Fuel Bleeding at IP - HELP!

Hello,

I've read a bunch of tips of how to bleed the diesel fuel system on the W124s from this forum but I'm still having trouble. Specifically, my trouble is that no fuel is coming out the the IP when the pressure valve holders are even the slightest tight.

The car is a '87 300TD with a leaking injector pump. The leak can be seen where the pressure valve holders thread into the injector pump. I decided to fix this in an attempt to fix my terrible idle and get the car running better.

To fix the leak, I R&R the copper washers under each pressure valve holder and the rubber o-rings too. In addition, I replaced the main fuel filter and the pre-filter. Naturally, I introduced a bunch of air into the system.


From what I've read, air must be bled from the system by cranking the engine for 20 seconds at a time (allow sufficient time between cranks to charge the battery and let the starter cool).

I've diagnosed the problem up to the injector pump. I've got fuel going into the injector pump (visual check at each joint, i.e. make a mess) but nothing comes out!!

The weird part is, if I crack the pressure valve holders, it shoots fuel out like a fountain. However, if hand tighten the holders just a little bit - no fuel! I'm talking about two fingers tight - no fuel!


I've done a few other tricks to coax the air out:

-Filled both filters with fuel.
-Blocked up the return line. There is no fuel returning to the tank.
-Bypassed fuel thermostat. It was leaking.
-Checked for leaks. No leaks but where is the fuel going!?

Any ideas, y'all? This is very frustrating and I miss driving my tank.

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  #2  
Old 12-02-2014, 11:48 PM
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Join Date: Oct 2014
Location: Chattanooga Tn
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Loosen the injector lines to the injectors. Bleed that way, plus you will know if fuel is going to injectors. It doesn't take much torque to tighten the nuts on the injector line to stop diesel from coming out.
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  #3  
Old 12-03-2014, 01:01 AM
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Location: Long Beach,CA
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Anthing inside of the Fuel Injection Hard Lines between the Fuel Injection Pump and the Injectors has to be able to overcome the Spring tension inside of the Injectors.

When Air gets into the Fuel Injection Hard Lines it compresses and moves only a tiny bit towards the Injectors. Trying to do that can easily kill a Batter and overheat a Starter.

In order to allow the Air an easy way to escape as jsain86 said you loosen the Fuel Injection Hard Lines at the Injectors and allow the Air a place to escape to. When you are geting Fuel out of those lines you can tighten the Nuts and attempt to start.

If you are just doing a Filter change it is best to fill the Filter with as much clean Diesel Fuel as you can so that less Air will get inside the Fuel Injection Pump Housing.
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  #4  
Old 12-03-2014, 05:17 PM
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I have tried bleeding at the injectors by cracking each one open. However, my problem is that no fuel is coming out of each pressure valve holder (the part with the 32 spline -please see picture below) The injector lines are completely off.

http://www.peachparts.com/shopforum/attachments/diesel-discussion/74968d1260239975-bad-news-state-inspection-w124-300d-motor-mounts-delivery-valve-seals-car-maintenance-12-07-09-011e.jpg

The weird part is, if I crack the pressure valve holders, it shoots fuel out like a fountain. However, if hand tighten the holders just a little bit - no fuel! I'm talking about two fingers tight - no fuel!

Am I missing something? Please let me know what you think.

This is getting pretty frustrating... Yes, this is my first diesel.
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  #5  
Old 12-03-2014, 05:58 PM
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I have cracked the fuel lines at each injector to no avail.

Currently, the fuel lines are detached because no fuel is coming out of the pressure valve holder itself (the part that threads into the IP with the 32 spline socket).

When I crack that holder, it squirts like a fountain. If I get it finger tight, no fuel! Ugh, very frustrating!

Let me know if you have any ideas regarding this problem.
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  #6  
Old 12-03-2014, 07:29 PM
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Join Date: Oct 2014
Location: Chattanooga Tn
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Sounds like something went wrong when you replaced the o rings on the IP. I would do the job over, make sure to torque to spec. Re trace your steps. It has to be something simple considering it was running before you worked on it.
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  #7  
Old 12-04-2014, 03:19 AM
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Location: Eastern TN
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Not just torque to spec but do the torque-loosen-torque-loosen-torque routine.

Sixto
MB-less
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  #8  
Old 12-23-2014, 01:19 PM
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Thanks for the help y'all! This forum is a plethora of knowledge.



I was lucky enough to find a used replacement injector pump. After the long swap process, the car fired right up. I definitely messed up something internal to the old pump - I just wish I knew what I did wrong!

When cold, it runs very rough with no power and a lot of smoke (white smoke but not coolant) but runs very smoothly after it gets warmed up. In addition, there is a bit of knocking at idle (at any temperature) but it smooths right out above idle. I've yet to look into these problems, I'm just excited to be driving it again.

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