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  #1  
Old 04-25-2005, 02:46 PM
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"not enough (diesel) fuel injection pressure"

1987 300SDL with 230,000 miles of which 25,000 miles I put on myself.
I am having a "fuel injection problem".

My problem is that I can not get the injection pressure to pop the injector and get the fuel into the cylinder.
I have the injection pump timed at 15 degrees after top dead center with the "vee" right in the middle of the governor's hole.
I even went further and did the drip test, using an injector line and at 24 degrees before top dead center, the fuel sat there and dripped about 1 drop per second for at least 35 minutes and would have continued if I had not turned the engine using the crankshaft bolt.
I've tried loosing the injector seal and measured the amount of fuel pumped using vinyl tubes attached to each injection pump fuel outlet.
The fuel would flow as much as I wanted it to.
To gushing out to fill the vinyl tubes quickly, (a few tries of turning the switch), to hardly any fuel being pumped, based on how tight the injection pump fuel outlets are tightened.
The fuel would pump through the injection pump, but would not build up enough fuel pressure to activate the fuel injector to inject the fuel.
To test to see if fuel was being ejected into the cylinder, I used a fuel line and attached an injector and turned over the starter and look for fuel injection.
And though fuel would pump, I've had no success getting the fuel to build up enough pressure to inject the fuel.
Can anyone help me solve this problem?

Thanks in Advance

BenzDiesel

Last edited by whunter; 07-19-2006 at 11:52 PM.
  #2  
Old 04-25-2005, 03:11 PM
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Quote:
Originally Posted by BenzDiesel
I...Anyway, I've learned alot about Mercedes Diesels to include having experienced the "run away" engine, which in my case was caused by the oil case being over filled with diesel fuel, which I don't know exactly what caused the fuel to flow into the oil crankcase....
Sorry I don't have a lot to offer on your pressure issues, but one thing that jumps out at me is do you think it is related to your fuel-in-oil problem? Have you checked to see if your lift pump is working properly? Seems like either lift pump or internally in the IP would be the only places for fuel to get into the oil in large quantities. May be wrong though.
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  #3  
Old 04-25-2005, 03:38 PM
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You say you've done everything, but I didn't see mention of having your injectors tested. Could it be as simple as a defective injector?
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  #4  
Old 04-25-2005, 03:38 PM
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Replaced the injection pump with a known good one.

Habanero,

I replaced the injection pump. And the answer to your question is yes, the cause of the over fueling problem HAD TO BE the injection pump, which I replaced.
Anyway, thanks

BenzDiesel

Last edited by whunter; 07-19-2006 at 11:56 PM.
  #5  
Old 04-25-2005, 04:09 PM
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The cause of your fuel getting into the oil didn't "HAD TO BE" the IP, it could have been the lift pump, which may or may not have been replaced along with the IP.

It sounds like you are more interested in griping than finding an answer, so I will end my troubleshooting at this point.
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  #6  
Old 04-25-2005, 04:09 PM
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No, I didn't test the injectors

Old300D,

No, I didn't test the injectors. I used "test" injectors that were known to be good.

BenzDiesel

Last edited by whunter; 07-19-2006 at 11:58 PM.
  #7  
Old 04-25-2005, 05:23 PM
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I didn't mean to bring up the obvious, but I read you attached injectors to the new IP and cranked it. You had fuel flow from the pump, but none out the injector -- that's the only reason I mentioned bad injectors. It sucks that you are "guessed out", but given Mercedes parts are already expensive, I'm again stating the obvious that shot-gunning the diagnosis can end badly.
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Last edited by whunter; 07-19-2006 at 11:59 PM.
  #8  
Old 04-25-2005, 05:56 PM
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Quote:
Originally Posted by BenzDiesel
I've tried loosing the injector seal and measured the amount of fuel pumped using vinyl tubes attached to each injection pump fuel outlet. The fuel would flow as much as I wanted it to. To gushing out to fill the vinyl tubes quickly, (a few tries of turning the switch). To hardly any fuel being pumped, based on how tight the injection pump fuel outlets are tightened. The fuel would pump through the injection pump, but would not build up enough fuel pressure to activate the fuel injector to inject the fuel.

To test to see if fuel was being ejected into the cylinder, I used a fuel line and attached an injector and turned over the strarter and look for fuel injection. And though fuel would pump, I've had no success getting the fuel to build up enough pressure to inject the fuel. Can anyone help me solve this problem?
Since you have utilized multiple injectors and two different injection pumps, I am going to conclude that neither of these components are the problem.

Therefore, the only possibility is the procedure utilized to install and remove the hard lines from the injection pump. The statement that the fuel is variable depending on "how tight the injection pump outlets are tightened" does not seem proper to me, however, I don't have the experience with this engine.

I will ask Peter to make a comment about this for you.
  #9  
Old 04-25-2005, 06:19 PM
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Thanks Brian.

I'll be listening. Haynes did an excellent job on the manual for 617 engine. But I guess the information has been kept from them as well or the reward of preparing a manual to cover the 603 is not worth the effort in terms of reward on investment that it would take to produce a good quality book covering the vehicle in such great detail, as they did on the 617. And I believe that the 603 engine operates and was built on the same principles as any diesel engine, especially the 617. The concept of compression, fuel and air and the engine should run is basic in all diesels. Even if the engine didn't start, the fuel should pump. And on the 603 injection pump, the degree in which you tighten or loosen the injector seal holder, you know, the cap in which the fuel line enters the injection pump, will vary how much fuel is pumped out of the injection pump. But this aspect is not the same on the 617 pump, which is rigidly tight. Which brings me to, should the cap or seal holder be as tight on the 603 pump as it is on the 617. Areas like this is where the information is rare. Nobody seems to know the intricate operating functions as to what is "supposed" to happen. I will look forward to hearing what you can find out. Old300D suggested it could be the manuel fuel pump, but as I understand it, that pump is supposed to pull the fuel to the injection pump; and it does that and once the fuel reaches the injection pump, somehow the fuel is pumped with pressure. I've checked to make sure all lines are tight with no leaks, especially the plastic fuel line from the pump to the fuel filter area and the small things like that. Is there some electrical component that activates the injection pump pressure? These are the answers that I'm seeking. Diesels are supposed to be "simple".

BenzDiesel

Last edited by BenzDiesel; 04-27-2005 at 04:30 PM. Reason: Spell check
  #10  
Old 04-26-2005, 02:08 AM
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Hmmm?

Hello BenzDiesel
Suggest:
Unbolt lift pump, leave lines connected, use large channel locks to depress plunger twenty or thirty times, look for plunger leak, listen for squeak of fuel bypass, remount lift pump.
disconnect injector bypass hose from fuel filter housing, cap fuel filter housing fitting, watch for fuel from the bypass hose and crank engine.
Remove or disconnect the TRAP and try starting.
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  #11  
Old 04-26-2005, 10:33 AM
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Believe me, I've looked for the simple things, believe me!

t walgamuth,

Thanks for your positiveness. Believe me, I've looked for the simple, easy to overlook things. I've done the hard things, as well. And am back to looking for a simple thing. I've done my best to cover all of the bases, to include having changed the head, the fuel injection pump, the turbo, the air flow sensor, the over boost protector, EVERYTHING, even the RPM Sensor!. And right now, I'm where I just can't get the fuel to pump THROUGH the injectors. However, whunter has a post, which I am going to respond to next that gives me some additional hope that I am on the right path. As I've said, I've been all the way around the world on this car and diesels are supposed to be simple and straight forward. You get the fuel, the air and compression, and you should hear the car run, even if it runs badly, at least it should start and run. Oh, yeah, and I've checked the timing. No stretch on the chain, at all. The marks on the cam and the cam holder line up, perfect. On the compression stroke (I know it is the compression stroke because I plug the glow plug hole and turn the crank until the plug, a piece of napkin, pops out of the hole when compression forces it out) is at zero TDC and the "vee" in the governor hole on the injection pump lines up at 15 degrees After TDC on the compression stroke, and I get one drop of fuel per second at 24 degrees Before TDC for at least 35 minutes, tested (a steady drip, drip, drip, drip). So, believe me, I've checked. Now, I'm looking to what I need to do to close the deal, UNLESS somebody can show me what I did wrong as to checking the timing or ANYTHING else. And a low compression engine should run, even if it smoked like a train and I've seen that too, during the "run away". But I think whunter has the answer, maybe, and I'm about to ask him a few questions based on his suggestions as to what approach I need to take to solve this problem. And when "confusion" sets in, you just don't know which way to turn. And right now, I'm turning in circles and just need somebody to tell me when I can stop turning and spinning in circles. The 603 is a very "easy" engine to work on.

BenzDiesel

Last edited by whunter; 07-20-2006 at 12:47 AM.
  #12  
Old 04-26-2005, 11:08 AM
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"Large channel locks to depress the plunger?"

whunter,

Thanks for replying and for giving me a plan of action based on the step method to diagnosing a car problem. "IF" I need to use channel locks to depress the plunger, then "THAT" could be my problem! I just unbolt the two ten millimeter nuts and just pump away using my thumb to get the fuel to the fuel filter, similar to how the 617 auxillary fuel pump works. Now if on a good auxillary fuel pump, channel locks are needed to depress the plunger, and that pump facilitates "building" pressure in the pump and on through to having enough force to pop the injectors, then I could just have an "auxillary" fuel pump problem, which I really do hope that is the problem. Again, should I be able to depress the pump with my thumb, as I have been doing?

If it not the fuel pump, my next question is: "Listen for squeak at fuel bypass"?, could you elaborate on this? And do you mean (referring to the injector bypass hose) disconnect the "metal banjo" end of the plastic fuel line hose at the fuel filter that leads to the back side of the injection pump, which has the braided, small fuel return lines leading to the #1 injector "side" over flow valve?

"Cap fuel filter housing fitting, watch for fuel from the bypass hose and crank engine." What do you mean by "cap" fuel filter housing? Fuel from bypass hose? Do you mean at the small braided hose end? Or at the banjo? Could you elaborate?

"Remove or disconnect the TRAP" What TRAP?

I really do hope it is as simple as the auxillary fuel pump. This car has almost killed me trying to get it to run right.

And thanks for your reply.

BenzDiesel

Last edited by BenzDiesel; 04-27-2005 at 04:43 PM. Reason: Spelling
  #13  
Old 04-26-2005, 01:39 PM
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question

ok here goes, if i had no output from an injection pump i would loosen the fuel line that supplies fuel from the fuel filter(secondary=big one)to the ip,crank the engine and see if it pumps fuel.if no i got to fix the fuel pump or the fuel lines or put some fuel in the tank. if yes i would retighten the fuel line i loostened,i would then loosten the return fuel line from the ip and again crank,i should see fuel there also but controlled by the relief valve at the ip pump. the ip needs it fuel to be under pressure and if the relief valve dont close at the correct pressure it just wont work right.
assume i have fuel to ip,fuel from the ip then i have to know the ip is being turned,assume its being turned,i have to remove the top most fitting on the ip after the pressure line to injector has been removed,this is the check valve to hold pressure on the injectors while engine is waiting for the next firing,these valves not holding will cause no starting to very slow starting. now i take a straw and place it down to the power plunger of the ip where i removed the check valve assy, again crank the engine, i should see the straw work up and down about 1/4 inch.
assume all test have passed the test,then i probably call my self a few choice words and go back and pull the vac shut off line from ignition key(usually the brown one) off the shut down valve and again crank the engine and listen to the clatter-clatter.
course i would have to know my compression.
hope this helps
larry perkins
71 old cars
  #14  
Old 04-26-2005, 02:58 PM
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I've checked and tested "all" of that.

As I said, I even used clear, vinyl tubing about 6 inches each and placed on each injector outlet on top of the pump. I'm getting fuel pulled up from the tank to the first fuel filter to the fuel pump to the main fuel filter to the injection pump to the injection pump fuel outlets (where I had the vinyl tubing attached to each injector outlet) which let me "SEE" the quantity of fuel being injected into in fuel line and consequently into each cylinder, when the car would actually be running. My problem is the not enough pressure, which I think whunter "precisely" diagnosed. I didn't know BEFORE HAND whether the injection pump produced the pressure or was it the auxiliary fuel pump. And according to whunter, that little auxiliary should be pushing the fuel with a lot of force. He hasn't responded yet, but I will be checking the fuel pump, without doubt.

But my question for you is: What and Where is the pressure "relief valve?" I've heard that the fuel filter regulates the pressure. That is all I need. To know what mechanisms produce fuel pressure in the system.

BenzDiesel

Last edited by whunter; 07-20-2006 at 12:06 AM.
  #15  
Old 04-26-2005, 03:19 PM
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question

benz i am starting to suspect that you are just playing a prank on us,but for sake of me being wrong i will answere your question.
the aux pump produces low pressure to get the fuel to the ip(i think about 10 psi but read if this is important to you), the ip produces high pressure(probalbly about 2500 psi,again read if its important)
the pressure inside the inlet side of the ip is maintained by the fact that the aux pump is working and that the relief valve that is located on the back side of the ip(its screwed directly into the ip pump housing and has a plastic line attached to the fuel filter,it must not be open until it has about 7 psi(again read if its important)take a light and shine in between the ip and the block and you can see.
also would you state your compression values as you have done all that i earlier wrote about?
larry perkins
71 old cars
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