1985 300SD 617.951 Injection pump
 

I know I'm new to this site, and I have done multiple searches but I can not find the info I need. So my questions are:

#1. What's the difference between a 6170704101 IP and a 6170705001 IP?

#2. I'm having a problem starting after the OM 617 engine is hot. Yes it cranks over just won't ignite. The Valves are adjusted properly, the compression is good at a average of 350 with no cylinder more than 10% difference. All injectors test fine at a average of 135.6 bar and spray properly. Glow plugs glow at tip and have a resistance of 0.00 to 0.01 ohm, same with electrical leads. Relay fuse 0.01ohm at 12.9 Volts. Not as much power as I was expecting from this legendary motor plus fuel range is 14 Litres per 100km. I've been given 3 possible trouble area's. Lift pump, fuel check valve or a RSD valve, or the big one, a shot injector pump. Engine was maintained by PO, I have a 3" binder full of passed services. Motor has 425,000km on it. Any extra help would be great, as I've been pulling my hair out trying to nail this down with out throwing money at it.

A big one not covered is air getting in the system somewhere. Check your rubber hoses and clamps for signs of cracking, hardness, or rot. Air in the system (especially when sat) will cause a really hard start.

14L/Km is ~16-17mpg, which seems fairly low. Transmission shifting ok? Dragging brakes? Poor alignment?

It would be worth checking injection timing as well.

Does the engine smoke or run rough? How is the idle? Does it rev readily?

5 speed manual, new breaks will free roll, recent alignment, but small leak from check valve between IP and block. Tightened but no improvement. My mechanic said that I could try the check valve but with the fuel economy he suspects that the pump is done. I'm not going to spend $2500 cnd to fix or $4000 to buy new.

New crush washers will fix the leak and they're cheap to buy. Should be for a 12mm bolt. You'd be surprised how much fuel can leak out of there when you're driving the car. Additionally, if fuel can leak out, air can leak in. The check valve is right on the fuel rack, so if it's leaking, your fuel rack is full of air when you go to restart. Replace the crush washers and move on from there.

You haven't discussed how the engine is running or if there's any smoke.

Slight haze idling, but doesn't roll coal as they say when I floor it. Runs good but not the power I was expecting for a om617 and fuel economy sucks. Starts good cold. In 5th gear with a drive ratio of 0.892 and final drive of 4.56 and 33x12.50r15 should out perform my old v6. And it doesn't.

A diesel isn't going to win any races. A gas V6 of just about any size or manufacture will outperform an OM617 in the seat-of-pants test. The turbo 617 300D's have a 0-60 time around 12-13 seconds. Not exactly a rocketship.

On the engine side of the Fuel Injection Pump is the Fuel Pressure Relief/Overflow valve. If you have the type that can be taken apart you can remove the Spring (careful not to loose the Ball Bearing which is uses as a valve) and stretch it till you get a spring free length odf 27mm.

Remove the valve Cover and line exactly the camshaft timing mark that is on the back of the camshaft timing gear with the mark on the front camshaft bearing tower and then look down at the pointer down by the cranshaft damper and see what degrees are pointed to. That will give a rough estimate of your timing chain stretch and or gear wear.

I don't know the Canadian/US $$ exchange rate but I have no more than $1500 US or so in my Dieselmeken SuperPump and that includes shipping from Sweden. What I am saying is the prices you listed are WAY high. I don't know who in NA does these pumps but if worse comes to worse you can have Goran Lindgren (real name of Dieselmeken) do one for you for a lot less - and he's EXCELLENT!

I'll agree that these engines are NOT all that powerful stock but they ARE tough. Mine is now making 220ish rear wheel HP (stock is about 125 flywheel) as measured on a dyno and the bottom end is basically stock (factory block, head has never been off, etc.) and it has at least 220K miles or so. If you want more HP have Goran build you a pump set up for about 165 HP and it'll make nice power with decent economy and absolute reliability.

I also agree that you need to resolve any fuel/air leaks. Diesels just don't tolerate that well at all. Be aware that your compression readings are on the low side (an excellent engine will be around 400PSI or so) and yours may be low enough to effect starting. Mine are maybe 15-25 PSI higher than yours and I have to glow the darn thing every time I fire it up.

Dan

You do get the odd diesel for whatever reason. Seems to want a little glow plug cycle even warm to fire off. I had a 1.6 volkswagon engine once that displayed that charactaristic. Otherwise seemed fine so I never investigated it.


As for your current problems. I think you have a series of minor tests to do before deciding anything.


What struck me as perhaps not normal was your low indicated fuel milage. Now it is important to know if this car is or was on waste vegetable oil for fuel.


If not first close off the return line at the injection pump. It will not hurt anything and you could mention what you observe. One of our esteemed members suggests that a small length of clear hose be installed there. This perhaps next if the first test shows nothing useful.


That allows you to establish if air is the problem. If the results of the first two tests do not indicate anything to some of the members. I would next run the engine on a can of vegetable oil. The thicker viscosity helps seal the injection pump elements if they are worn. This just to see if the engine will start when hot. Over time many members have developed somewhat of a systematic approach in attempting to narrow down certain issues.


As a general statement but of course there are exceptions the injection pumps are usually not the suspect early in the troubleshooting game.


It also sounds like your mechanic friend may not be up to speed on these particular engines and that is not uncommon either. .


Run on diesel fuel these pumps usually last a very long time. Since these cars perhaps are new to you. The odometer may not be correct. Perhaps going back through the file of service invoices can verify the overall milage.


At your milage in our climate I usually expect to still find the drivers seat still in pretty good condition with no bolster wear etc. Not so much with the true leather interiors. Common issues are the odometers fail and also are so easy to manipulate that when these cars where newer I think a lot where rolled back. Now if some simple testing indicates you need another injection pump.


Used ones acquired certain ways are a fairly safe risk and reasonable in cost. As a general rule these cars were not scrapped because of injection pump issues. You have the injection pump with the visable tang that is useful for checking the pump timing.

In the archives the location will be described. Basically you put the engine damper on the right degrees. Take a small mirror and look for the tang in the port of the injection pump. If not in the center turn the crank exactly one revolution to the same degree setting. Look for the tang in the centre of the port. If not there with either crank position your injection pump timing is off.

Driven on the highway at the speed limit I would expect 30 mpg on 3.78 liters of fuel that is an American gallon. With a five speed manual and the original rear end. The car should be peppier than the automatic version as well.

Actually your description of the problem made me have thoughts about your egr valve. Cold starts would work because there would be no burnt gasses and the engine would get oxygen. Hot engine not so much. Performance would aqlso be bad. Since the engine could not burn the fuel properly. Fuel milage would probably be low as well.

Poor injection pump elements if the idle sounded reasonable would to me indicate. Perhaps not enough fuel injected giving low performance but I suspect you would still retain decent fuel milage. If certain simple tests indicated nothing also a semi obstructed exhaust might be present and there is a plug to remove as a test.

What I am trying to do is make you keep an open mind. Simply because I do not like how your symptoms add up or do not. To me you have a way to go and it is all cheap except for a little time. Yes it still may be the injection pump but you have no solid indicator it is yet. Excuse my long post as I am not a working mechanic. There are a lot of smarter guys on this site to help you as well. If you own one of these cars you are in the right group as the support is massive.

Actually your post took me way back to the first years when I was a member here. We knew far less especially about these injection pumps. Frequently people were changing them out but they were not the problem. We just did not know enough of how many things impacted others on these cars.


Over time simple tests members developed or adopted got pretty much past this issue. Today members seldom change an injection pump out unless it is proven the issue. In fact I do not remember this being done for quite some time now. Shotgun troubleshooting has almost gotten to be a thing of the past almost as a result. By at least members here. I think it is this or I think it is that is no longer needed.

As for working mechanics that are really up to speed on these engines. Not that many are still out there.

As an add-on to my post - I agree with the guys that the likelihood of a really bad injection pump is pretty low. Of course, anything is possible. So yes, I'd go thru all the troubleshooting steps first. I was just making a suggestion if you decided to swap pumps at a later date.

Dan

I have no ideal of how much you studied the archives. Anyways one thing that should be checked when sluggish performance is present.


That the fittings and line are not blocked that come off the intake manifold. That is part of the system that controls turbo boost. Soot buildup is not that uncommon.


This is not your hard hot start problem. Just something fairly common to have an issue with. When low power is reported as a problem. Multiple minor issues are not unknown.

I forgot you are a new member and some things are just so common we forget to mention them. Anyways it only takes a few minutes to verify that it is open. Call it part of a general tune up. It is probably open but you want to make sure.

I know this, the reason I chose this engine was for the torque. But expected more.

HP is how fast you hit the wall, torque is how far you go through.

Have the new type. The timing marks line up and the chain is tight.

According to my mechanic and Mercedes source I know the the compression is good. Cold starting at -20 C no problem I do glow it a little longer.