Want to know.... poorman's method of setting Injector Pump Timing - PeachParts Mercedes-Benz Forum

300SDog · #1 07-10-2004, 10:40 AM

Beaucoup unburnt fuel in blue smoke blowing out the back, especially at startup - valve clearances are fine. Fuel mileage is at/near 24-28mpg on my '79 240D 4-spd at mostly highway driving.

Without using drip tube or centering IP to timing marks, how's the best method of setting the IP timing by ear?? Can it be adjusted while the engine is running?? What is the procedure just using smoke and engine performance as indicator..... without any fancy expensive guages or devices.

My repair manual is lost; it got left on the roof of the car by mistake and I've never set diesel IP timing in my life. Yet am no novice to working on MB engines, mostly carbureted gasoline cars i've owned over period of many yrs.

Does rotating the pump towards the engine advance the flow? Which are the nuts on the IP that must be loosened to make adjustment??

My plan includes paint marking initial position of the pump, so I dont get lost.

franklyspeaking · #2 07-10-2004, 10:58 AM

I hate to sound negative, but trying to adjust the timing while the engine is running is not a good idea. The drip tube is fairly inexpensive and you could even make one out of tubing. Although your idea to check the fuel timing and adjust it to specification is something worthwhile, you need to face up to the fact that it may not solve your problem. Your problem could be bad injectors or just timing chain wear.

IMHO you need to at least get a Haynes manual and then start your troubleshooting tasks. Make or purchase a drip tube to check the timing, and then eliminate the other issues one by one. You can get the injectors tested at a diesel shop for a small amount (mine were done for free).

Good luck.

rwthomas1 · #3 07-10-2004, 11:43 AM

Never done an MB this way but I have done other mechanically injected diesels: Scribe a reference mark at the pump/engine union so that when the pump is turned you can see how far and in the worse case scenario you can return to where you started. Do this with the engine OFF! Rotate the injection pump in the opposite direction of the pump pulley rotation, this will advance it. Rotate 1/16th to 1/8th of an inch referenced at the scribe marks and tighten the pump bolts. Test drive. Adjust again as you feel neccessary. I prefer to run slightly advanced as the throttle response is better and the engine pulls harder off-idle. You can damage the engine by too much advance so be careful. If the injector rattle sounds too "harsh", especially when accelerating you have gone too far, back it off a good bit immediately. I would certainly make sure your timing chain is in good shape, etc. before playing around. Never try to adjust the timing with the engine running. It will ruin your day. Good luck, RT

300SDog · #4 07-10-2004, 12:17 PM

Thanks for the speedy replies, Frank and RT. I'm hoping to tackle this today or tomorrow.

Got the engine-in-motion timing idea from doing ignition timing on gasoline ignition systems with Vintange MB's that are also amazingly equipped with fine tuning adjustment setting of spark advance while engine is operating to accomodate octane discrepancies.

Last time i checked, Chain wear was at/near 2 degrees. Car has only 145k miles and was diesel purged 8 months ago. Adjusted the valves 3 weeks ago and filters are fresh.

Racked up 30k miles in the last 12 months over which unburnt fuel especially at startup became creeping problem - not a sudden occurance as might suggest jambed injector tip or loose carbon debris fouling the pre-comb chambers.

This is all I'm really asking - Which are the nuts and bolts that I must loosen to adjust the IP?? And which direction advances the timing??

In addition to paint marking the original IP position, my plan includes making 1-2 degree (1/8" ?) adjustments in between checking the results, but I've gotta know which direction advances the system (sounds like towards the engine) which bolts to turn and what hazards i might encounter. I appreciate your advice and caution on this, RT.

Last edited by 300SDog; 07-10-2004 at 12:24 PM.

DieselAddict · #5 07-10-2004, 12:43 PM

Injection timing on these diesels rarely needs adjustment as long as the timing chain isn't stretched. Lots of blue smoke indicates either unburned diesel fuel or if it's thick blue smoke it's oil getting into the combustion chamber. Most likely it's the former. Did you check your glow plugs and are you letting them stay on for at least 15 seconds before starting the engine? Have you checked your injectors for spray pattern and pop pressure? If that all checks out, you should run a compression test. Then I'd mess with the injection timing.

I don't believe the IP oil is to be changed on your model.

300SDog · #6 07-11-2004, 06:40 PM

Success!!

Smacked the IP collar and flat surface of engine block with hammer and chisel on one stroke.... permanently marking initial position.

Loosened 3 - 13mm nuts on the collar and one 13mm bolt behind on pump. Then unbolted fuel pipes at injectors, 17mm. Rocked the pump towards the engine 1/8" which is all the pipes would allow before colliding with valve cover and then tightened up the 13mm IP nuts 'n bolt.

Hairiest part was bending the pipes by hand to accomodate new position of the pump, after removing 8mm spacer bits and loosening fuel pipe collars (17mm) at the IP.

Tools required include 12 pt. 13mm socket and spanner, 8mm and 17mm too. Toughest nut is the IP collar nut closest to the block. Jammed the pipes apart with flathead screwdriver on reattaching the 8mm spacer bits, of which I omitted reinstalling 2 as redundant and unnecessary.

Results: NO more cold start blue unburnt fuel smoke, improved acceleration and smoother idle..... engine sounds 'happier' with steadier idle and at idle the oil pressure guage hardly flutters at all, where it used to tremble a bit.

Total time spent was 3 1/2 happy hours working as slowly as possible doing lots of misc cleaning chores in the engine bay.

wildhorsemfg · #7 03-09-2013, 01:25 AM

i know its a old old old thread . .. but anyone else tried this and seen any improvement in power / mpg ?

whunter · #8 03-09-2013, 02:22 AM

Quote:

Originally Posted by wildhorsemfg

i know its a old old old thread . .. but anyone else tried this and seen any improvement in power / mpg ?

I use drip or A-B timing, depending on the engine.
3.5 hours is longer than it takes me to drip time an OM616 or OM617.

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Drip Timing Threads

If the timing has not been messed with, the real issue may be a worn out timing chain.
Rolling in a new timing chain will frequently pull everything back to factory spec.

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Diesel Timing Chain Thread - PeachParts Mercedes ShopForum

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