I have two 190D 2.5 non-turbo sedans both with OM602 motors. One accelerates (relatively) well and is (relatively) torquey, but the other is embarrassingly (& potentially dangerously) slow taking off and has significantly less torque. It is also somewhat noisier. Once up to perhaps 2500rpm it goes as well as the first car and although it is more easily slowed by hills other than that it drives perfectly. When I bought the slower car it was leaking a lot of diesel from the delivery valves on the top of the IP. I replaced the o-rings on these valves and the pump is now dry. The instructions I followed suggested replacement of the copper crush washers was unnecessary so I left the old ones undisturbed. I now wonder if that may have been a mistake, but the local diesel tech says he does not think the delivery valves are my problem - the car was certainly just as slow before I changed the o-rings. The car starts excellently from cold and uses no oil. There is no smoke apart from maybe a little at idle - the same as the 'faster' car. The tech thinks my issue is with pump timing - he says the extra noise is detonation, which he attributes to timing being off, and he also pointed to red sealant at the front of the pump suggesting it had been off the motor. Apart from the detonation he said the motor sounds pretty good. However, he doesn't have much experience with these cars and isn't keen to gain any. He also pointed out that having the pump timing checked by a specialist would likely cost a large amount relative to what the car is worth. I would be very grateful for any insight/suggestions that list members could provide as to how likely this is to be a pump issue - and what else would be worth checking. I notice the EGR is blocked off, though I can't see that making much difference. The tech said accurately checking pump timing is very involved. One thing I've wondered though is would it be feasible/physically possible for me advance or retard the pump timing just a little from where it is now to see if it makes any difference? Many thanks for any help.

Important Info would be how many miles are on both the fast and the slow car.

The general cause for "Loss Of Power" on most Diesel Engines is restricted air or fuel delivery;and by restrected fuel delivery I mean not getting enough fuel into the Fuel Injection Pump (most often a air/fuel filter being plugged or the Fuel Tank Outlet screen or the Fuel Tank Vent being restricted).
After that it could be the Fuel Injection Pump Timing (maybe due to Timing Chain stretch).

You also might want to check outside of your Differential Housing and see if you can locate the Gear Ratio of your Differential to see if both cars have the same Gear Ratio.

I suppose you could mark the Fuel Injection Pump Mounting Flange so that you could return it to where you started from and experiment moving the pump to change the timing to see if it helps. But, it is better to do it one of the approved ways.
I believe your Fuel Injection Pump is supposed to have an O-ring for a front seal instead of the paper gasket as mine does. I there is Silicone Sealant on it it could mean the O-ring is hard and not sealing or the prior owner was being over cautious when the IP was put back on.

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84 300D, 82 Volvo 244Gl Diesel

Thanks for the very quick response. The 'fast' car odometer shows 155,000 km and the 'slow' car reads 167,000 km - so both around the 100,000 mile mark. However, I doubt either is true. Both came here secondhand from Japan and it is very common for imported vehicles to have been odometer tampered. In addition, diesel cars in New Zealand pay a 'road user charge' per kilometre which many motorists seek to evade by running for much of the time with speedometers disconnected. So not very sure on the miles unfortunately. I changed the fuel filter and pre-filter - both appeared just to contain clean diesel. Haven't checked the tank screen or venting, but before I did the pump seals a large pool of diesel would soon appear under the car when parked, so there seemed to be a reasonably clear path from the tank. I have tried running with the air cleaner removed and the only difference was increased intake noise. I've not looked at the differentials, but both cars seem to be doing the same rpm for a given road speed.

A couple of further points I've thought of: When I changed the delivery valve o-rings, I discovered the technician before me had used three different sizes of o-rings, so I guess it's possible he didn't use the correct crush washers either, though it's equally likely he left them alone. The other thing, the car seems to accelerate better for a short time - perhaps a minute - after the motor is started, though this is somewhat subjective....

I have no other suggestions as to what to check.
I forgot to ask if there was any unusual smoke and if both cars have the same diameter of tires?
Is any part of the Fuel Injection Pump delivery controled by a computer?
Does the Slower Car get better fuel economey?

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84 300D, 82 Volvo 244Gl Diesel

Another thought is that when I first bought my car it was very slow also. As it turned out my throttle linkages were extremely sloppy and out of adjustment.
What was happening was when I stepped on the Pedal the Throttle Arm on the Fuel Injection Pump was not being moved far enough to give it the Fuel it was supposed to be getting.

After re-adjusting the linkages on my car it was like driving a whole different car.

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84 300D, 82 Volvo 244Gl Diesel

Both cars have the same size tyres. There's no unusual smoke. I don't think fuel delivery is computer controlled apart from there is an electrical connection at the rear of the pump that I think stabilizes idle speed. I drove both cars today and was reminded that the difference in the way they drive is very pronounced. I haven't driven the slower one enough to have a very good idea of economy, but it appears they are similar. The accelerator linkage was certainly loose when I checked it a while back, but adjusting it only moved the point at which maximum (minimal) power was achieved nearer the beginning of pedal travel and didn't improve it overall. There is plenty power much of the time - it's the inability to build revs quickly from low rpms that's the problem. I spoke today with a Mercedes wrecker in Auckland who has a lot of experience with these cars and he wondered if the motor is simply worn out - he reckoned they can start well, not smoke, not exhibit blow-by, yet still have low compression and lack power. I may get a compression test done at some stage and see if he's right. I didn't check pump timing today but did mark the pump's position and then move it away from the motor to match more closely the position of the pump on the other car (approx one full turn of the adjuster). The car started fairly well, but idled worse than before and was even noisier. I then moved the pump back to its original position, then approx half a turn further of the adjuster, moving it a fraction nearer to the motor. It started well, and seems to idle a bit smoother and knock a bit less - overall sounds somewhat quieter than before and less clattery at idle though nowhere near as quiet as the other car. Maybe a bit better acceleration - certainly no worse. Definitely seemed to start better from hot. I'll report back if I make any more progress - bit disheartened that the motor may have low compression, but not totally convinced of that. I still don't really understand the function of the copper washers in the delivery valves - I have a set of washers and more o-rings and would be happy to fit these if there was any chance they could be the problem..... Thanks for all the suggestions.

If I got the correct Pic out of my file this should show where the Delivery Valve Crush Washer is and you can get some Idea as to what it is sealing.


Also if as you stand in front of your car facing and facing your car; if your engine turns Clockwise; moving the Fuel Injection Pump towards the Engine Block advances the timing and moving it away from the Engine Block retards the timing (also refered to as late timing).

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84 300D, 82 Volvo 244Gl Diesel

I've had time to read earlier posts about delivery valves and am wondering if I should re-do them. When I got the car it was leaking a lot of diesel from the top of the IP and my understanding at the time was replace the o-rings and "she'll be right". However I now see that if fuel can leak at the copper washers less will get to the injectors, and at lower pressure. The o-rings had been changed previously and when I took out the delivery valves certainly one, and possibly more - I can't remember now - surprised me how loose it was. This makes me wonder if the washers were already losing pressure when I got the car, and still are because I didn't change them. Does anyone think this could be the cause of the detonation noise (I don't know if this is another word for 'nailing' - sounds like a tractor at idle) and lack of acceleration, or am I just clutching at straws?

This is a East European Service Manual site. I could not find a 190D there but it does have list a 300D 2.5 OM602.962. I will try to direct you to the part where you check the Camshaft Timing. If the Camshaft Timing is off due to a stretched Timing Chain the Fuel Injection Pump Timing as well as the Camshaft Timing will be retarded/late.
When the page opens up the manual is on the Right side.
Click on the "More" arrow (triangle) to go to the next page.
Look for 300D 2.5 Turbo at the top of the page; when found go down and click on the "93" bubble.
After the next page opens up click on the rectangle with "Continue"
When the next page opens click on the bubble next to "Engine Manual"
When the next page opens click on the bubble next to "Mechanical Manual"
When the next page opens go down the list to 05 "Engine timing, valves"
When the next page opens go 6010 "Checking basic position of camshaft"
This should take you to a PDF on how to align your Camshaft to compare it to the degree marks on your Crankshaft Damper (from the factory is aligned to top dead center on the compression stroke).
Except that you will align your Camshaft Marks as shown in the pic on the Compression Stroke after which you will look and see what degree is lined up with your pointer on your Crankshaft Damper. (On mine it lines up with 2 degrees past top dead center indicating I have aproximately 2 degrees of timing chain stretch and the my Cmashaft Timing is 2 degrees retarded/late and that my Fuel Injection Timing is also late assuming no one has retimed the Fuel Injection Pump since the car was built.)
Anyway here is the site:
http://mb.auto.pl/component/option,com_wrapper/Itemid,62/

Also, I did not catch before that your idle was not smooth. Besides the timing this could also indicate your injectors need to be checked although I do not think they would cause a big loss of power without visable smoke.

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84 300D, 82 Volvo 244Gl Diesel

Many thanks for the link - looks like that could be a very useful site. I've saved a copy of the camshaft timing diagram and will take a look at the car in the next day or so. When I mentioned the idle being smoother, it wasn't bad before - definitely no cause for concern. I think it's more that it sounds a bit better now. Sorry for any confusion. Any thoughts on how much (if at all) delivery valve washers could reduce power?

I had a very, very similar problem with my 85 2.2 after a hasty delivery valve o-ring change, absolutely gutless. To this day I am not certain what exactly was wrong but after a very careful do-over (including the crush washers) it purred like a kitten, had plenty of pep and was absolutely as it should be. If I were you I would do it over, very carefully, including the washers, before messing with the timing. It is a bit of a PITA but an inexpensive procedure, and the results may be truly astonishing.

Jim

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2005 C240 4matic wagon (daily driver)
87 190D - 225K (on loan)
85 190D - 312K (on loan)
2011 Subaru Legacy AWD (Wife's)

I decided I had little to lose by redoing the delivery valves and potentially much to gain, plus it was quicker second time as everything was still clean. I was surprised by how pitted two of the copper crush washers were, and I think there's every chance they may have failed to seal properly. As the car had taken ages to start the first time, I left the pipes loose at the injectors and cranked until fuel appeared - first at 2 & 4 then 3 & 5 - I then tightened those lines, cranked again and the car fired straight up. It ran very quietly on four cylinders, then after a little while fuel appeared at #1 so I tightened that line. Once it was running on all five the motor became noisier, and the detonation reappeared, so I wonder if #1 injector or delivery valve may have problems. However, overall it is definitely less noisy than before, and there is significantly better acceleration. There is also more smoke at idle but I can live with that for now. I've not had much chance to drive the car yet but it feels like it's at least part way to being fixed. There is still fuel leaking from the injector bleed-off lines - I changed them for 4mm fuel hose but it appears I need the proper Merc stuff. I also noticed bubbling at the bases of #1 & 2 injectors today that I've not seen previously, so attempting to deal to that is next on the list. Thanks for all the suggestions/assistance - much appreciated.

Kia Ora; I just stumbled across this thread.

The copper washers are the seats for the delivery valve springs. The springs wear into the washers over time, and if disturbed, will not seat properly. This could cause some delivery problems.

Its good to see that you have changed the washers. I did mine about a year ago and the engine nailed intermittently for about 200 km, after which the nailing went away.

For the bubbling issue, I would make sure that the injectors are torqued down correctly. I also had my injectors rebuilt recently; when I re-installed them I found that there were bubbles at the bases; after 600 km the bases of all the injectors are completely dry.

Do not despair, but keep driving the car ( drive to Whangarei and back) and see if the situation improves; give it some time.

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

I've replaced today the leaking leak-off lines from the injectors and now can't see any bubbling at the injector bases because they are no longer wet with fuel. I've used the car back and to to work and I'm sure it's going better than before. However, it's still slow off the mark, and what I notice is it's also slow to respond to the throttle when driving - cruising at say 80-90kph (50mph), if I press the pedal to accelerate there is a noticeable delay where nothing much happens, and then it takes off and pulls like the other car, but the other car would have done so straight away. With the car idling (800 on the revcounter), as soon as I touch the accelerator the revs increase a little - to maybe 900, there's no slack in the cable - but then I can gradually depress the pedal what feels like perhaps an inch and the revs will only increase to 1250. If I hold the pedal at the same spot, it will hold 1250 for perhaps two seconds, then without moving the pedal at all, the revs will soar to 3000+ and would I think continue to increase, but at that point I take my foot off. I suspect this is what is happening when driving - there is a huge 'dead-spot' on the pedal. I fear this may translate to a problem with the injection pump - governor? - though it also strikes me that if the low speed nailing means one or more injectors is/aren't working correctly then maybe the lag is the time it takes to stop nailing and start injecting. Any suggestions/ideas would be very welcome......

At 80-90kph I have the same delay...but watch the tachometer. The engine is not in the power band until about 2300rpm. If I try to accelerate above 100kph, I am at/over 2300rpm already and notice no delay. You may want to compare these numbers with yours.

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec