I got my newly rebuilt pump back from Pacific Injection a couple of
weeks ago and finally have had time to install it and the oil filter
housing. The car still has a rough shudder at idle speeds below about
1000 rpm, but changing the pump has made it a lot better.
Does the timing of a diesel engine change with rpm like a gas engine?
Maybe the timing is slightly out? The engine does not run
suspiciously smooth like a gas engine, which would indicate retarded
timing, and it does not overheat, which would indicate advanced
The vibration at idle now is not extreme like it was. It's not going
to vibrate the car apart or shake a trim piece off the fender. At
highway or even surface street speeds the car runs smooth, has good
power and gets excellent fuel economy. I consider the car usable now,
but I still have a little bit more of a roughness at low idle speeds
than I would choose.
I don't believe the timing changes with RPM. It's pretty easy to
check or set the injection timing. There is a fancy little widget
that goes on the injection pump where the #1 line is normally
connected. Essentially it's a drip tube. You watch the where the
drips stop relative to TDC on #1 while rotating the engine by hand.
If necessary you loosen the pump and move it slightly. Having had
the pump rebuilt, you would have to do that to get it set correctly.
Not sure exactly which engine you have. If you need the procedure, I
can look it up for the 617 engine.
I need the procedure for the 617 engine. I have the Benz shop
manual. I am not sure if that method is in there, but I am going to
try timing it by ear with the motor running one of these days.
I sent my injectors to Gus at Pacific injection to get them balanced,
but the Post Office lost them. Instead of just delivering them when
the found them, they returned them to me. By that time Gus had sent
me a newly rebuilt pump and we both decided I should put the engine
together and see what happened and then go from there. I will be
talking to him this week and see what he thinks I should do.
Gus told me to have my engine at 24 degrees BTC when I took the pump
out and to leave it there and he put a locking device on the pump when
he sent it so it was timed properly for 24 degrees BTC. I installed
the pump and then removed the locking thing and replaced it with a
plug so the timing is pretty close. It starts right up and runs good
except for the sometimes wild thump at idle.
The procedure is in the service manual for the engine. If for some
reason your manual doesn't have it, let me know and I can find it in
mine and post the exact procedure.
The timing has to be set whenever you remove the injection pump,
because to set it you loosen the pump and then slightly swivel it one
way or the other It's supposed to be set so that at 24deg BTDC the
fuel that drips from #1 line has slowed to barely a drip.
I also took a quick look at the service manual and there is indeed a
timing advance mechanism. I'm not sure exactly how it's
interconnected to the fuel delivery system or how it works, but from
the service information, it's located in the front of the engine,
connected to the timing chain. I would guess that the timing chain
drives the advance mechanism and then the advance mechanism drives the
I have this procedure in a manual of mine and it is called "start of
delivery timing" or something to that effect. I have it in both PDF
and a paper version (Haynes Mercedes Diesel Manual) that I can send if
you like. The PDF I have is the w123 service manual and its section
07.1, Diesel Injection System that has the procedure.
This is the topics for each category in the PDF manual:
07.1 - Diesel injection system
001 Survey model -- engine -- inejection pump
010 Operation injection pump with governor
015 Operation engine-transmission overload protection
100 Adjustment of idle speed and idle speed adjuster
105 Checking maximum speed at no-load
108 Checking injection timing (begin of delivery) with digital
tester (RIV method)
109 Checking injection timing (begin of delivery) (high pressure
110 Checking injection timing (begin of delivery) (flow pressure
111 Checking injection timing (begin of delivery) (position
indicator RIV method)
114 Adjusting injection timing (begin of delivery) with digital
tester (RIV method) -- following checkup
115 Adjusting injection timing (begin of delivery) (high pressure
method) -- following checkup
116 Adjusting injection timing (begin of delivery) (position
indicator RIV method) -- following checkup
135 Checking injection nozzles
137 Disassembly, cleaning, assembly and adjustment of injection
140 Venting injection system
145 Checking fuel pump and bypass valve
150 Checking vacuum shutoff for leaks
200 Removal and installation of injection pump
201 Installation of injection pump (with locking screw)
210 Replacement of pipe connection, delivery valve or copper sealing
ring on injection pump
220 Replacement of vacuum control unit at injection pump
230 Removal and installation of injection nozzles
235 Removal and installation of fuel pump
240 Removal and installation of injection timing device
#110 is the one that uses the drip tube, but I think the Haynes manual
is easier to follow. Let me know if you want it.
I don't know the cost of the rebuild because the injection pump was
part of the overall "remanufacture" of my engine by Metric Motors in
Canoga Park, CA. The place that did the rebuild considered the pump
still under warranty and sent me a replacement newly rebuilt pump at
no cost to me.
Thank you to those who offered to send me the procedure for timing the
pump. I have both the pdf version and the shop version. I have the
Haynes manual too, I think, if I look for it.
It does have the timing advance device at the front of the injection
pump. The device is inside the timing chain case, behind the vacuum
pump. Like Trader4 says, the timing chain drives the device. The
device then drives the IP axle (and the vacuum pump too). I don't
recall if the IP has axle bolt or not. If not, IP can be removed
without even removing the vacuum pump.
To keep IP and chain at 24 BTC helps the installation but it does not
mean the timing is precise. The IP can be rotated in place to further
adjust the timing. Use the drip tube method, keep the three mounting
bolts loose so IP cab be rotated.
BTW, the drip tube method works on OM617 but not the later OM60x (190D,
300D, 300SDL, 350SDL, etc.) which requires electronic instrument.
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