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Post Number:#1  PostPosted: Fri Mar 18, 2016 10:36 am 
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I am trying to figure it out, what is causing a difficult engine start when the engine is at operating temperature.
This is the scenario what I am experiencing: pulling up to a fueling station (engine hot), turning engine off.
If I restart the engine within 2-3 minutes, it starts right away. If it sits longer than 3 minutes, I have to crank for 5-10 seconds to get it started. At that moment a black cloud of smoke is expelled from the exhaust pipe.
That indicates unburnt fuel, but why? Faulty injectors?
However, the cold start is excellent without any smoke, blue or white. Faulty injectors would also cause a hard cold start. Am I missing something?
Anyway, I will remove all injectors and test them for spray pattern/leaking and injection pressure.

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Post Number:#2  PostPosted: Sat Mar 19, 2016 7:34 am 
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I would try a few seconds of glow-plug. Mine requires it after sitting more than five or ten minutes and always has... I would make sure the fuel is up to par with respect to cetane rating.

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Post Number:#3  PostPosted: Sat Mar 19, 2016 10:00 am 
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In the past I owned Mercedes and VW Diesel cars and none of them required activating the glow plugs when starting a hot engine.
I have the first indication that it may be a injector problem. Yesterday, I removed two injectors from a used spare cylinder head. The first injector I tested had an acceptable injection pressure but bad spray pattern. It was spraying sideways. The second injector was a disaster. It had very low injection pressure, no spray pattern, just leaking. Today, I will remove the injectors from my working car (Diesel Astro). I'll keep you posted.

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Post Number:#4  PostPosted: Sat Mar 19, 2016 8:23 pm 
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Mine is an SD-22 with indirect injection. In spite of the high comp ratio, it and my previous SD-22 were cold blooded. They and other ones I have worked on always needed some glow after sitting for more than five or ten minutes even in the summer. Not much; only about 5 seconds worth. I don't have the timer in mine; just a push button controlled power relay. Your Mercedes and VWs are direct injection which is with warm starts without aid.

At any rate, bum injectors sure don't help...

NR

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Post Number:#5  PostPosted: Mon Mar 21, 2016 4:25 pm 
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Nissan_Ranger wrote:
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Your Mercedes and VWs are direct injection which is with warm starts without aid.

The cars I owned were older '80s, pre 1996-97, where VW and Mercedes introduced direct injection diesels engines. Before that time the engines were indirect injection engines, like the LD28.
Anyway, I tested all injectors and all of them displayed out of spec. (low) injection pressure, about 1100 PSI, as opposed to 1800-1900 PSI. One injector was as low as 1000 PSI. In addition, the spray pattern was not a nice cone, it was more centered. Obviously the injectors are tired. Rebuilding the injectors cost $37.00 ea. I decided to rebuild myself (for now) with a method I learned on a BOSCH Injection Service course 35 years ago. Rebuilding is a bit exaggerated. What I did is just cleaned the injector nozzle and adjusted the injection pressure to spec.
Now I am waiting for the copper seals (crush washers) to arrive that go between the injector assembly and the cylinder head. Stay tuned..

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Post Number:#6  PostPosted: Wed Mar 23, 2016 10:41 pm 
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dieseldorf wrote:
Now I am waiting for the copper seals (crush washers) to arrive that go between the injector assembly and the cylinder head.

You can anneal those copper washers by stringing them on a thin wire and hitting them with a simple propane torch until they glow red. Let them cool naturally, and they will be soft as new.
It's the heat shield washers that you want new each time you reinstall the injectors.


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Post Number:#7  PostPosted: Thu Mar 24, 2016 6:16 am 
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I anneal new copper gaskets too.
I use a bit of different process though.
I've always quenched them in water when they are cherry red.
The SS heat shield ones have an UP and and DOWN too.
You gonna change the return rail washers as well ?

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Post Number:#8  PostPosted: Sat Mar 26, 2016 4:15 pm 
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It would be really nice to have an tutorial on rebuilding the injectors!

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Post Number:#9  PostPosted: Fri Apr 01, 2016 11:36 pm 
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Not exactly LD28 injectors but the internals are very similar:

HOW-TO: Rebuild Diesel IDI Injectors
http://vincewaldon.com/index.php?option ... &Itemid=28


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Post Number:#10  PostPosted: Sat Apr 02, 2016 8:11 pm 
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Quote:
HOW-TO: Rebuild Diesel IDI Injectors
http://vincewaldon.com/index.php?option ... &Itemid=28

This is an April Fools joke, right? :roll:
If you follow his instructions, you will render your injectors useless. That guy doesn't understand how an injector works. Adjusting the injection pressure by grinding the inner parts? :shock:
You suppose not to interchange any injector parts with the parts from other injectors because of very tight tolerances involved, much less grinding these parts with sandpaper on a glass pane. Horrible!
I will post my instructions shortly. Need to make some pictures.

Update: I found a second web site http://www.peachparts.com/shopforum/diesel-discussion/299321-diesel-injector-cleaning-diy.html where they recommend to lap the intermediate disk. I am very suspicious of that step since it was not mentioned in the BOSCH Injection Service course. I need to research this further.

Update2: I searched the internet for several hours, mainly German Mercedes, VW/Audi forums. I could not find one instance where someone was lapping the intermediate disk for any purpose. Anyway, that is up to you if you want to follow these instructions.
I found interesting web site (german only) with info on http://www.kerzendorf.net/martin/mercedes/einsprit.htm legacy Bosch injectors.

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'86 Ford Escort Wagon Diesel MT Sold 07-17-08


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Post Number:#11  PostPosted: Tue Apr 05, 2016 11:12 pm 
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dieseldorf wrote:
If you follow his instructions, you will render your injectors useless.

Nope. I've had great success, at least 50-60,000 miles with smooth performance.

dieseldorf wrote:
That guy doesn't understand how an injector works. Adjusting the injection pressure by grinding the inner parts? :shock:

He's not adjusting the injection pressure by grinding the inner parts. He's removing the wear grooves by carefully sanding with very fine sandpaper, on a smooth hard flat surface. Those wear grooves can cause leaks, inconsistent POP, and dripping between injection events.

dieseldorf wrote:
You suppose not to interchange any injector parts with the parts from other injectors because of very tight tolerances involved...

Yes, agree. Where did you get that he was mixing up parts? Here is a quote: "Lay out all the parts for reassembly. I tend to keep the parts from each injector together as I work thru the process… seems to result in less leaking and also keeps the breaking pressure as close to original as possible."

dieseldorf wrote:
Update: I found a second web site http://www.peachparts.com/shopforum/diesel-discussion/299321-diesel-injector-cleaning-diy.html where they recommend to lap the intermediate disk. I am very suspicious of that step since it was not mentioned in the BOSCH Injection Service course.

Maybe because at that point (worn) they would replace with new? Not really available to us at this late stage of the game.


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