Shudder at idle due to injection pump problems

Hi Paul,

Did you get your injectors balanced out? I don't recall your full history of the works since you had it rebuilt.

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 injection pump.

Would you mind divulging the cost of your diesel injection pump rebuild?

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 method) 110 Checking injection timing (begin of delivery) (flow pressure method) 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 nozzles 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. Doug

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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