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  #46  
Old 11-16-2005, 12:11 PM
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I just had a thought when I was writing the last post and I thought I'd run it by you. Let's assume for a minute that my problems are entirely due to an air leak in the fuel line before the IP.

Facts:
1) the problem was more pronounced when running on diesel on a hot engine.
2) the engine would cold start on diesel long after warm the idle on diesel was bad.

What these two operating conditions have in common is that the fuel is at the same temperature as the coolant (or at least somewhat close).There are no thermal gradients accross seals and the thermal stress on metal sealing rings is reduced compared to hot engine, cold fuel. Fuel hoses should be less affected by thermal expansion than metal seals. Following this theory the culprit would be a metal seal (copper or aluminum) at a banjo bolt or the lift pump.

The only seal where I can't see the fuel afterwards is the seal on the banjo bolt that connects the fuel line to the IP (two seal rings that look like aluminum - non-magnetic). I also used to open this bolt to bleed air out of the system when changing VO filters as it was the only point in the system that both systems had in common. Do the seal rings in a bonjo bolt fail if you open and retighten them too many times?

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  #47  
Old 11-16-2005, 05:30 PM
burnin veggie
 
Join Date: Jul 2005
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seals on banjo bolt

i would replace the seals, i think they are just aluminum crush washers, you can get them at http://www.aircraftspruce.com/.. i actually just used copper crush washers when i changed my banjo to a solid bolt i only put one on top. It looks like there should maybe be one in the middle but it didnt seem like there was one to pull off so i left it that way and it doesnt seem to leak, so i just put one at the top where there was the aluminum one.
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  #48  
Old 11-21-2005, 10:21 AM
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Update

OK, finally the combination of owning a compression tester, a warm day and some free time came together and I checked the compression.

Cylinder #1 and #2 are great at around 330 and 340 PSI, respectively.

The compression tester then started to leak (the quality!) so the needle would fall slowly. The pressure still went well above 300 PSI, I'd estimate around 320 PSI.

Cylinder #5 measured around 280 PSI, which isn't as good as the others but should still be ok. It's also probably higher since the leak of the compression tester seemed to get worse.

The verdict is that it's not the compression that is keeping the engine from starting.

I also noticed quite some layer of carbon on the injectors. I imagine some is normal (we all know these engines produce smoke) but since I have never pulled injectors before I don't know how much is normal.

The next thing I will try it to put everything back together and change the seal washers on the banjo nut at the inlet of the injection pump (see previouse post).

To be continued...
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  #49  
Old 11-21-2005, 01:20 PM
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I think that it is important to note that the stock VO filter in the greasecar kit does not have a water seperator. So hopefully that has cause no damage, I would reccomend that you either replace that filter or put a second filter with a water seperator in the line. Racor filters are nice, but very expensive... [Over $100.]

Otherwise, I wish you the best, and the knowledge of the forum users keeps impressing me... I learn a bit every time I come here .
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  #50  
Old 11-21-2005, 04:45 PM
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thanks for giving us the update on your progress...

compression sounds good in some of those cylinders but i don't think there should be a difference of @ 60psi between any cylinders... this seems like a big gap to me, although others on the forum could probably tell you more...

crush washers should def be replaced every time you remove them...

so you are still having trouble starting on diesel??
revert your system back to as stock as possible and start working out your problems from there...

maybe you've tried these things already but they can't hurt:
eliminate any & all air leaks as a possible contributor to hard starts...
make sure your battery is fully charged and starter is in good shape...
make sure the preglow system is fully operational...
recheck the valves to make sure they are in spec, and adjust as necessary...
probably a good idea to check injection timing at this point too...

double check to make sure you aren't eliminating something obvious by assumption... for example: make sure your fuel valve(s) are working and hooked up correctly, or eliminate them entirely for the moment and just concentrate on getting the diesel system operational.. (maybe you've been trying to start on vegetable oil the whole time accidentaly?)
in fact, maybe you should pull the fuel feed and try to start with fresh diesel in a small auxiliary tank (bottle) under the hood...

if you do get it started, try diesel purge to clean the gunk out of the injectors & fuel system and keep an eye on everything...
if you still can't get it started but you know you are getting fuel to all the cylinders and have good compression... then it's a mystery to me..
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  #51  
Old 11-21-2005, 04:58 PM
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coelcanth,
thanks for the ideas. You're right, 60 PSI is a big drop for the one cylinder although I suspect this is due to the compression tester failing. I'd have to look up the spec but I think it's something like 3 bars max difference. I will re-test one of the cylinders that were good to see if it's the tester. However, shouldn't the car start with only one cylinder off-spec like that?

The car is currently on diesel only with clear hoses to see air bubbles. The VO system is bypassed at the moment. The fuel comes from the tank but is fresh diesel, nice and clean after draining the tank.
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  #52  
Old 11-30-2005, 01:00 PM
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Update

I rechecked cylinder #1 with the dying compression tester and it came out to be the same cylinder #5, around 280 psi. That means that cylinder #5 is similar to #1, which measured around 340 psi or around 23.5 bars when the tester still worked.

All cylinders are nicely above the minimum spec of 18 bars and are also within the spec of 3 bars (45 psi) difference between cylinders.

Still, no start. With starting fluid (no glow plugs) it would now fire just a little giving a few "clacks" but not start. Smell of ether and burned smell came from the tailpipe.

What else can keep the engine from firing? Excessive carbon buildup? What should I look at next? Injection Timing?
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  #53  
Old 11-30-2005, 03:30 PM
Brandon314159
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Have you tried loosening up the injetor lines and seeing if you are getting fuel out the lines?

I would check this...(unless you already have)
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  #54  
Old 11-30-2005, 04:06 PM
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Yes, fuel comes out of all injector lines when cranking the engine.
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  #55  
Old 12-21-2005, 10:41 PM
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The next thing to do, if you can set it up, is to connect an injector, one at a time, to each of the 5 IP output ports. Crank and observe if you are getting a good spray pattern.
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  #56  
Old 12-23-2005, 09:20 AM
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MB Diesel starting tips:
A diesel engine will start and run on WD40 sprayed into the inlet manifold (air cleaner housing with cover off).
Have someone spray the WD40 into the inlet while you crank. Ask them to spray the WD40 until you signal them to stop, or until the engine stops. I have done this on a few different diesels, including the OM617.

Even without a working IP, the engine should start and run.
If the IP is working correctly (no air in the IP) the engine, running on WD40 should start to inject fuel and improve the running, progressively, until the engine can run on the IP and tank fuel.

A small amount of RUG (about a teaspoonful) in the inlet manifold will assist the starting of a diesel engine, if the GP are not working. Use as little as possible, consistent with desired results. CAUTION: this may cause preignition if GP are hot.

The MB automatic transmission will allow you to tow start the engine. Have a friend tow you at 40 MPH and turn ignition on and drop the trannny into "S". The engine should turn over and (hoopefully) start to fire as the heat of compression is much greater when the RPM< are high.

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