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Discussion Starter #1
My 617 motor has decided to run rough at times... I think it is a fuel issue, so... I replaced both the primary and secondary fuel filters....no change...next I replaced the injectors... runs better when it runs good, but still runs the same rough at times, which is getting more frequent. Starts easy, but idles like crap at times. Pulls up hill sometimes and others I have to kick it down to 3rd, and today it still didn’t pull good in 3rd for the first time. I’ve tried adding some additives, sea foam and another. No changes yet with over 300 miles. The car will still go over 85 mph, as of today when it’s running on all cylinders. Feels like it convulses and is only firing on 3-4 cylinders unless I increase the rpm at idle and by running a gear lower so it stays at a higher rpm.......what should I replace next??? The fuel pump, or clean out the tank and the strainer in the tank? Or something else??.. I’m open for suggestions. Thank you for your input and opinions.... air filter is good by the way.
 

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Maybe your engine needs a valve adjustment to restore compression to all cylinders? Maybe you need to adjust the injection timing?
 

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Discussion Starter #4
I don’t think it is the valves. It would run rough all the time it that we’re the problem. A valve adjustment is in the plan for the next 2-3 months though. If it were the injection timing, I would think that it again would always be off. I initially thought I had some water in the fuel, going through the system, but it persists, and the additives and mileage that I’ve driven should have cleared that up....Tell me if I’m wrong about the valves or the injection timing... the strainer is on the short list as well as the fuel pump. Should I take the whole tank out and clean the tank out also. I haven’t looked up the “how” to take anything apart yet. How much time and whiskey should I plan on if that’s what needs done?
 

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At this point, I suggest this:

Drain the tank, clean the strainer, make sure the feed and return lines between the tank and engine compartment are clear, replace the rubber fuel return line and vent line and the hose clamps.

After removing the strainer, get a finger inside the tank and try to “scrape” the area around the strainer to pull some sediments. If you find rust or algae, you will have to clean or replace the tank, especially if your clear filter plugs frequently or you see many particles floating in it.

Check the tank vent, valve and fuel cap. You don’t want vacuum holding the fuel.

Make sure the breather tube is clear. When is running bad, disconnect the hose or remove the oil filler cap and see if that makes any difference.

Diesel purge.

Replace the plastic fuel lines if they look old and make sure you don’t have fuel leaks at the filter housing, injector lines, fuel lines, primer pump, delivery valves.

Depending on the type of IP check valve, you can take apart, clean it and stretch the spring to 27mm.

Adjust the valves and check the timing chain to see if it is loose. You can also check the internal timing to have an idea how worn the chain might be. Also, check the condition of the camshaft.

Compression test. You can do this after adjusting the valves. Normally this a good time to pay attention to the injectors, but already did that.

Check the IP timing

When is running like crap, loosen each of the injector line nuts to see which cylinder isn’t firing. You will have to pay attention to see which cylinder isn’t firing at all or at least weaker that the rest. It could mean compression is uneven or that there is a problem with the injectors, IP or delivery valves.

Clean and inspect the delivery valves. If they look pitted, you will have to replace them. When replacing those valves, you have to replace the seal
washers or you can get leaks that can make the car run rough. Be very careful with this, do not allow dirt inside and do not loose the nuts next to the delivery valves.

Pay special attention to delivery valve #1 because that is one that gets disturbed more often since it is used to adjust timing. A few days ago I read in one of this forums about someone who had one of this cars run rough during years and one day decided to pull the delivery valves out and found that #1 was clogged with sealant. Someone probably removed the valve to adjust timing, and used sealant to make seal. After some time, the sealant came loose and jammed the valve. After cleaning the mess and installing new washers, the car idled normal.

Adjust or replace the rack damper if your car has one. This can be done whenever you want but it works better when you know that all of the rest is correct.

If nothing of that works, you will have to replace the IP or having yours tested and rebuilt because it can be out of adjustment or worn. Some say that a way to tell if the IP is the trouble is to spray the pump with water while is running rough and if the idle improves after that, the pump is overheating or worn. Never have tried that but it makes sense.
 

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Discussion Starter #6
Thanks for the recommendations. I’m going to try and get through the tank, strainer and hoses/ lines to/ from the tank. Does anyone have the part # for the in-line electric fuel pump, and where it’s located? I think I will replace that along with the strainer this weekend, And then cross my fingers....
 

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Diesel models don't have electric fuel pumps.
 

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No electric pump there. Diesel is draw by the lift pump attached to the IP and is all-mechanical. I rebuilt mine hoping that it had something to do with the idle shake, but I didn’t do any difference.

When the lift pump goes wrong, engine oil starts to get diluted with diesel or the engine just quits because the pump is unable to feed the IP.
 

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Discussion Starter #9
Thank you both. Very good information. Ill order a new strainer, and try and get it done this weekend. I’ll try and put up a picture of the old strainer when I get it out. Thanks again.
 

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Discussion Starter #10
The strainer was clean, and there wasn’t any sludge in the tank. I did find that the two lines to the tank on the drivers side were cracked and leaking slowly. They were replaced... and now back to the thread title, “what to do next?”. The car still behaves the same. It will do 90 mph, but not under load/ up hill, and it still idles and runs rough, most of the time. It will run smooth and good at times. The manual pump worked when I primed the system after draining the tank, but threw diesel all over when it was primed. Don’t know if that is supposed to happen, but it locked when I turned it tight. New/ rebuilt injector pump??? Or??? Thank you for your ideas.
 

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The primer pump should not leak diesel under any circumstance. If it does, it has to be replaced because it draws air into the system and that can affect performance and make the engine run rough. When they are shot, you can't even prime the system.

The good news is that the primer pump can be easily replaced for little money.
 

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Discussion Starter #12
The primer pump should not leak diesel under any circumstance. If it does, it has to be replaced because it draws air into the system and that can affect performance and make the engine run rough. When they are shot, you can't even prime the system.

The good news is that the primer pump can be easily replaced for little money.
It leaked\sprayed fuel when it reached prime, and it didn’t take long to prime. Doesn’t leak fuel otherwise when it is twisted to the locked setting. I can’t say yes or no as to if it is letting air into the system. So...

I’m looking on eBay and find Bosch part # 0440017997 Fuel pre-pump for sale from seller partscontainer. His chart says that it doesn’t fit my 84 300d. And only goes up to 81 for the non turbo 300d... Is this the correct part? Or does someone have the correct part #? Or should I just buy the plunger???


Thank you.
 

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0440017997 This is for the lift pump and primer pump.

If the primer pump or plunger is leaking, you need part 2447010038. It’s an updated design that doesn’t require unscrewing, you just push the plunger and you should be able to get a new one for less than $20.

If you want to know whether air is getting inside the system, you can replace the plastic fuel hard lines between the fuel filter housing and injection pump (they get brown with age and don’t allow to see the flow of diesel) to see if there are air bubbles, however they are pricey.

Some suggest that you can replace just the plastic line with another plastic line for temporary use, just to see if there is air inside the system and then replace it with regular rubber fuel hose and clamps. I haven't tried this but if my problems persist, i might give a shot.

I would replace primer pump (or as you call it plunger) because, based on your description, you have the older type that is known for drawing air and leak fuel.
 

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Discussion Starter #14
Yes, I have the old style. And as I think on it for a minute, the cars symptoms have increased each time I use the primer... when I changed the filter the first time, when I removed the injector lines while doing the glow plugs, next when I put in new injectors two weeks ago...so, I will cross my fingers, and replace all of those. I think I will replace both the lift pump and the primer pump. Then I’ll look at replacing all of the hoses if that doesn’t work. The part # that I put up earlier was for a non turbo motor and off one digit. It should be 0440017998 For the 84 300d with a turbo.

Thanks for you help and insight.

I’ll post my results after I work on it next weekend.
 

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Discussion Starter #15
No electric pump there. Diesel is draw by the lift pump attached to the IP and is all-mechanical. I rebuilt mine hoping that it had something to do with the idle shake, but I didn’t do any difference.

When the lift pump goes wrong, engine oil starts to get diluted with diesel or the engine just quits because the pump is unable to feed the IP.
I just finished with the new parts(primer pump, new hose from lift pump to secondary fuel filter, short hose from primary filter to lift pump........

No change...

If the car is emitting some smoke when it runs rough, and not when it is running good...( tested in park or neutral, at different rpm’s). Higher rpms= less smoke. Idle=lots of smoke.

Am I ordering a new lift pump???? If it lets engine oil get into the fuel when it is bad, and as it gets worse, it won’t run at all?

Or...is it a turbo problem? If it idles and runs rough at lower rpm, and runs a little better with some higher rpm... but not under load?

Just thinking out loud again, thanks for your comments/ suggestions.

I don’t know what’s more expensive right now, the parts for the car or the fuel cost of driving one of my wife’s 1ton trucks?
 

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No change...
Well, that sucks.

There are lots of things you can do, you decide what to do, but this is my opinion.

I don’t think the lift pump is the problem, in fact don’t order a new lift pump until you measure fuel pressure (you can find instructions on how to do that on many forums and on the free version of the factory service manual). The lift pump is kind of expensive and shouldn’t be replaced just to see if it makes any difference. You have to be sure is bad.

Smoke could mean a lot of things: unburned fuel due to excessive quantity or poor quality, wrong timing, poor spray pattern, coolant or oil being burned, bad turbo, poorly adjusted ALDA, etc. Just lots of reasons for smoke to show up.

Neither do I think your problem is the turbo. Usually a failing/bad turbo causes other problems like power loss, excessive oil consumption, lots of grey thick smoke and drilling noises. Lumpy idle is not one of the symptoms as far as I know (unless the turbo failed spectacularly and sent pieces to the engine and those pieces destroyed the cylinder walls and piston rings, but your engine would be burning lots of oil and making agonic noises).

I don’t know if you have done a diesel purge, but is one of the first thing you should do (specially considering that is cheap, easy and quick) and very recommended when you have performance and smoke issues on a diesel. Over time dirt builds up inside lines, IP, injectors and the diesel purge cleans that restoring performance. If your injectors or pump are worn diesel purge won’t improve things, though.

Next, you have to adjust the valves and inspect the condition of the timing chain. Tight valves produce uneven compression, which in a diesel is a big problem. A loose chain can change IP timing. Adjusting the valves is “easy” (once you acquire practice) and the tools needed are cheap. IP timing can and should be adjusted every certain millage to compensate for wear.

After the valve adjustment and chain inspection, do a compression test. If compression is uneven, for example 380PSI on one cylinder and then other is 300PSI, that engine is worn and is never going to idle smooth again until you rebuild it.

In fact, a valve adjustment and compression test are the first thing you have to do before spending any money on one of these engines. If compression is even, then your problem is most likely an injection problem.

Just for your information, replacing the rack damper bolt on my car made a lot of difference, not perfect, but much better. Still needs further adjustment since I adjusted it very conservatively. You can try that as well, specially if you have the silver version. For 36 dollars and half hour of your time, you don’t have much to lose.

I know this is frustrating, especially if you are trying to keep the diagnosis and repair cost low by doing it your self, but I think there are a few things left on the list that you can do for not that much money before throwing the towel or paying and injection shop to fix it.
 

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Discussion Starter #17
Well, that sucks.

There are lots of things you can do, you decide what to do, but this is my opinion.
Thank you for your time and your opinion. I’m here on the forum asking for opinions, and I certainly appreciate yours and the others who have commented.

I read through and evaluate all of the comments and suggestions, and try to figure out what correlates most closely with my observations.

So...
The car may need a valve adjustment, and when the local mechanic that is next to my business has some time it’s going to be done, but that may be a few weeks out though.

I’m going to order a lift pump.
I’m going to look up how to adjust the IP timing, and the Alda and try to get to those in the next two weeks.
For the turbo, I was just thinking out loud. If the bearings in the turbo are getting old, they may have increased friction, and only spin/ create boost at higher exhaust volumes which would explain why it feels good and sounds good at slightly higher rpms as long as there is no big load.
Also thinking out loud...if it were a compression/valve/ cylinder, wouldn’t it run rough at all rpms, instead of smoothing out at slightly higher rpms?
Yes, I have drained the tank, new good fuel, and the car has brand new injectors. I was in accord with all of those ideas at the very beginning. It makes sense.
I’m not giving up on the car. And it’s more of a time issue versus money , but I certainly appreciate your consideration for the financial aspect of repairs.

Thank you again. I look forward to everyone’s opinion/ suggestion, even forcedinduction’s.
That’s why I’m here on the forum.
 

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Discussion Starter #18
[email protected]#*&#@!!!! All is well now, purrs like a kitten, and pulls up the hills like it was new. Maybe if I would have listened earlier....

Thanks for all of the info, advice, and recommendations from everyone!!!


Maybe your engine needs a valve adjustment to restore compression to all cylinders? Maybe you need to adjust the injection timing?
 

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Yeah, it is always the simple thing we keep putting off, insisting that it must be something much more complex.

When you hear hoof beats, think horse, not Zebra.
 
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