OM617 Injection Pump Timing Question
 

So I have a 1980 300GD with a European OM617 naturally aspirated engine.

Living in Colorado, this truck has to pass emissions every year, just a simple opacity test at a couple load points. The first few years I had it, it passed without issue, something like 13% opacity max with 45% being the max allowed.

Then all of the sudden it was very hard to pass, jumped up to over 50% opacity!

So I did the usual, adjusted the valves, replaced the injectors, new air filter... Nothing helped.

I then took it to a shop figuring it would need the fuel injection pump timed. However, the shop I took it to used a pizo sensor on the #1 cyl fuel to measuring the timing. He said it was basically dead on, no issues.

So I am currently trying to use the drip test to verify his results (I am a little skeptical of the pizo results). After hooking everything up and rolling it over a few times I notice some odd behavior. Basically, it appears to drip (flow actually) multiple times per revolution of the engine. There appears to be the expected flow, from ~65 degrees BTDC to 24DBTC. However, it quickly begins flowing again after it stops.

Below is a link to a video where I am rolling the engine over by hand and the video is looking at the drip pipe. I start at 24 degrees before TDC on a compression stroke of the #1 cyl. I rotate it over and you can see it start flowing again, a bit later I say I am about 180 degrees (crank degrees) away from where I started at 24 degrees.

My issue is that I would not expect fuel to start flowing again here. I would expect it to flow once for every 2 revolutions of the crank (~65 to 24 degrees during compression), then be off the reset of the time.

So, is my injection pump trashed? I also noticed the other valves in the IP for the other cylinders slightly leak fuel while I am rolling the engine over, which I would not expect...

https://www.youtube.com/watch?v=IqRXjEZm66M

Thanks for any help,
Jim

I never had any luck at all with the drip method of timing. What worked for me was:

Pull the #1 injection pipe off the IP.
Pull the glow plugs, partly to reduce compression for ease of cranking the engine over by hand, but more importantly so it doesn't start....
Give it one good solid push past firing point for #1 and it'll squirt all the fuel out of the delivery valve passage, leaving a clear passage down into the DV.
Turn the engine over slowly 1.5 more rotations, then with a large breaker bar on the main crankshaft bolt, ever so slowly bump the engine forwards while watching that passage like a hawk. Stop the instant you see any movement in that passage and read the crank position off the timing cover and pointer. This may take multiple attempts to get right, as the engine takes a bit of force to get started rotating and then it rotates quite easily, making it easy to go quite a ways past the firing point. You may have better luck tapping on the end of the breaker bar with your hand, and the longer the breaker bar the better, as it increases leverage. If you miss it, it'll fill the passage with fuel again and make it impossible to see the beginning of injection. Spin the engine over two turns quickly so it'll squirt the fuel out more forcefully, clearing the passage, then try again.

Make sure you're wearing safety glasses, as you will be spraying diesel around. Also make sure you ONLY spin the engine in the correct direction. If you miss your mark, you missed your mark, continue rotating the same direction and try again.

This seems like a kludge method, but it worked well enough for me. I have one of the later IP's on my engine with the timing port, and using the above method got me dead-bang-perfect on correct timing according to the timing port.

Putting a block under the pedal will get you a pass I would think...
It's not failing from oil smoke is it?

Thanks for the rely guys.

I would rather the car pass emissions as it is supposed it. It used to pass just fine, now it doesn't so something has changed. Enough that the opacity is like 5x what it was inside of a single year.

It is definitely black smoke. A block would likely work to get it to pass emissions as I can see the smoke with a mirror while driving and I can control it with the throttle.

I still have everything apart for the drip test, but I will try looking down the delivery valve when I put it back to see if I like it better.

I think my biggest question is really if fuel should be flowing out while the engine is not on the compression stroke. If it were actually injecting fuel at this time, it would be injecting in the exhaust stoke... However, given that the delivery valve and injector are not installed at the moment, I am not sure if that behavior is normal but wouldn't result in any actually injected fuel when everything is assembled.

Jim

The lift pump can only supply ~15PSI of pressure. The injector requires >1500PSI of pressure to open. Whether or not the pumping element dribbles fuel with an open circuit is irrelevant, the injector is only going to pop when the pumping element closes the spill orifice and compresses the fuel in the hard line.

Rolling black smoke usually indicates an overly rich fuel condition. If you have EGR, have you pulled the intake to see if it's coked up?

If you have an ADA device on the IP, have you tried adjusting it leaner? When's the last time the injectors were cleaned and/or rebuilt and pop/spray tested? If you're dribbling or making a poor spray pattern, you can expect poor combustion as a result.

This truck has no EGR or ALDA. The Injectors were replaced last year with ones that were supposedly calibrated before shipping for the NA 617. There was a pick up in power then (seat of the pants meter), but the smoke remained mostly unchanged.

I guess it makes sense that it would spill fuel out when the valve and injector are removed as it is just filling the chamber with fuel that would be pushed out the injector on the next compression stroke.

Then my measurements would validate the shops, we both have it at about 24 degrees BTDC.

Maybe the PO had a block on the throttle and it fell out!

Bio Diesel does not smoke as much as Diesel Fuel does but it will clean out your tank of crude. So you would need to drive off several tank fulls before going to the emissions test. Also drive the car as fequently as you can at high speeds (witn in the law) before the test.

Check your valve timing. It is sort of less accruate test to see if your timing gears are worn and Timing Chain stretched.



As far as what you did some details are lacking. The Throttle Lever is supposed to be in the full fuel position. I get some wire to wire it in that position and then put note on the Steering Wheel to remind me that the Throttle lever is wired at full fuel.

Your the fuel coming out of the fuel injection pump seems weird because you expectation of what you think is supposed to happen.

And If I had an element in front of you it would take only 1/2 a minute for you to understand but wit mere words it is difficult to explain.

When you use the drip methodl you remove the central valve from the Delivery Valve Assembly and the spring and put the Delivery Valve holder back on.

On eaceh of you elements inside of the Fuel Injection Pump there is one or more fuel feed holes. As long as those holes are uncovered and the Delivery Valve and Spring are gone fuel is going to come out of the top of the Fuel Injection Pump.

So we are going to say the Element Plunger is at the bottom. As it goss up fuel is going to be coming out the top. As it continues up the Plunger starts to close off the fuel feed hole and you the fuel coming out decreases till if you are turning the engine slowly you get those x amount of drips per second. Immedieatly after that as the plunger move up is the begin of Injection and the plunger is going to push fuel out of that drip tube.
As the plunger moves up the plunger still covers the fuel feed hole and is fuel will still come out. However, as the plunger rises it reaches the shutoff section (a special cut in the plunger) uncovering the fuel feed hole and fuel is going to start flowing out.

As the plunger comes back down there is also a short blip where no fuel will come as the fuel feed hole is again covered. As the top of the plunger goes down pas the fuel feed hole it is again openend and fuel flows again.

So there is only 2 tiny blips where no fuel is going to come out and if you are rotating the Engine or the Fuel Injection Pump to fast you go right past it. And as you have noticed there is a lot of time where the fuel feed hole is open.


When you re-install the fuel Injection Hard Lines you are going to need to bleed the air out of them up to the Injectors. Tighten the Fuel Injection Hard Line Nuts at the Fuel Injection Pump and just put the on loose on the Injector end of the hard lines and crank the Engine till fuel is coming out of them and then tighten them and see if you can start.

The N/A engines don't have an ALDA, they have an ADA which is supposed to correct the mixture for altitude differences. If it is stuck for some reason, it would certainly stand to reason that the mixture could be richer than it needs to be.

All other things being equal and all options being exhausted, you could always tweak the max fuel setting of the IP to lean things back out.

This is a grey market truck, which I do not believe had any kind of altitude correction. Looking at the IP the only thing I see hanging off of it is the shut off valve. I figured it would smoke more than it did when I first bought it because of the lack of altitude correction and the fact that I live in Denver.

Jim

Opacity Test Failure
 

It's time to do the basic, you didn't mention them :

Diesel purge and is the primary fuel filter (the clear plastic intake screen) actually ful of clear fuel or is there crud in there ? .

Since you have the delivery valve out, look down in the well with a good flashlight ~ is the fuel crystal clear of cloudy ? . I discovered cloudy fuel in my IP when I took the delivery valves out, the clear plastic screen was perfectly clear and clean, apparently my old IP had fungus growing in it .

Then it's time to test the ALDA and wastegate for ruptured diaphragms, I just discovered both were bad on my Coupe, it runs out fine but never exceeds 24MPG no matter what .

Easy to test both with a cheap vacuum pump .

Do things by the numbers and you'll find the problem sooner than later .

Expect lots of very good help from the folks here but don't skip over the basics as most problems are simple in the end, remember : K.I.S.S. :P .

This is how I use the drip tube to re-adjust the timing on an engine that has been running OK.

I turn the engine in the direction of normal rotation. When I am coming up on the Compression stroke I stop at 24 degrees before top dead center.

I wire the Throttle in full fuel and disconnect the vacuum line at the vacuum shutoff.

I remove the delivery valve central valve and spring and re-install the delivery valve holder.

Then pump on the hand primer to see if you get the number of drips you want. Usually you won't. You are going to get too much fuel coming out because you need to advance the timing of the Fuel Injection Pump.

Before you rotate the fuel injection pump if there is no makes from the block to the fuel injection pump scratch one a crossed both so you can always get the fuel injection pump back where you started from.

If I have to rotate the fuel injection pump I remove all of the Fuel Injection hard lines because it his difficult to rotate the fuel injection pump against their tension.

Loosen the fuel injection pump to block flange nuts and there is also one under the rear of the fuel Injection Pump.

I just nudge the Fuel injection pump rotating (the top towards the Engine)like only 1/32 of an inch of rotation and then pump on the hand primer to build up to an even pressure and count the drips. If I have the right number of drips I snug up the Nuts and pump again to see if it is the same. If OK tighten all the nuts.

If that did happen I keep rotating 1/32 of movement at a time till I get the drips.

If I am having trouble I bring the pump back to the mark I scratched and I start over with even small increments of rotation.

Should have mentioned...

When I first bought the Truck it had a serious fungus problem. Enough to occasionally clog the fuel pick up tube (the W460s used a pick up tube that comes in from the top of the fuel tank and pulls fuel from the bottom, rather than a gravity feed from the bottom of the tank).

To fix this issue I had to remove the tank, have it cleaned, replace the pick up tube, and repeatedly change out the filters, the clean one and the large one. I then ran anti-fungal stuff in it for a couple years, put it in every tank fill. This is all while it was passing emissions.

The plastic filter isn't perfectly clear any more, but I don't see anything floating in it, nor does it appear as though the filter screen is clogged, but maybe it is time to replace it anyway. The fuel coming from the drip test is perfectly clear with nothing in it or any color change, but I am not using fuel from the tank, I am using a separate tank to pressurize everything (4psi), but it is hooked up such that the fuel is still going through that plastic filter. This was all such that I don't have to try to manually maintain a constant pressure with the primer pump.

I can try to pull some out of the tank and make sure everything is clean still.

Jim

Thanks for all the help guys! Sorry my posts my be a bit out of order...

Diesel911 - This is more or less the same thing I am doing. Throttle is zip-tied wide open near the IP, shut off valve is disconnected.

The only difference is that I used an external fuel tank with a hand pump to maintain ~4psi fuel pressure. It just seemed like a more consistent method in my head. This is the way the ************** guy does it. *edit* apparently his name is a curse word here?? Did I make a mistake following his direction?

I have not made any adjustments yet, its dripping as it should at about 24-25degrees BTDC. The only thing I have heard is that an older engine might benefit from some sight advance(26-27 degrees BTDC), but I haven't decided if thats the route I want to take. Id rather make sure everything else is looking good.

Jim

Crud Causing Smoke
 

Unless that clear plastic intake screen is crystal clear, you may well have a tiny bit of crud holding an injector open, this causes smoke......

I'd replace both filters and do a Diesel purge first then f it still smokes and still has crud in the intake screen, address the fungus issue, only when it's gone can you expect new/rebuilt injectors not to drool and smoke excessively .