Little or NO power after bottoming out suspension- 1981 300SD - Page 5 - PeachParts Mercedes-Benz Forum

whunter · #61 02-18-2013, 05:29 PM

Quote:

Originally Posted by ROLLGUY

My friend was driving his SD on a dirt road and hit a dip, bottoming out the suspension and denting the oil pan. About a mile later, the car died. He tried putting on new filters, but still could not get the car to start. He got it towed home and called me. I replaced the dented oil pan. I also replaced the old style (leaking) primer pump thinking that is the reason it would not start. After about an hour trying to start it, I suspected something was wrong with the injection pump. I decided to pull the IP and replace it with a known good one. After trying to get the start of delivery set (removing/replacing the IP three times), I figured something was wrong with the timing device, or something else. I decided to just put the original pump back on. After successfully getting SOD set, the engine finally started. However, it barely had any power. It would only rev up to maybe 1,500 RPM. I don't want to pull the IP again. I thought that maybe the muffler was clogged, so I pulled the downpipe off the turbo, and still no power. It seems to idle perfectly, but barely has enough power to move the car in gear (I can walk faster). I also found out that the turbo was worn out, and thought that it might be bad enough to keep the engine from getting any air. I removed both manifolds and the turbo, and started the engine to see if the turbo was restricting the air (had it bolted to the oil feed tube and drain tube to prevent an oil spill), but still no power. Having ruled out he entire exhaust system, the only thing left is the fuel system. The filters are both new, and the primer pump is new (new style). I even tried pumping the primer while it was running to help pump fuel, but still no change. I also tried clamping the return hose, but that did not change anything either.
Anyone have any ideas? Like I said, I really don't want to pull the IP again. There is the possibility that something broke inside the IP from the suspension bottoming out, but I would like to rule everything else out before trying another IP (for the second time). I already have over 8 hours invested in trying to repair my friends car (his only transportation), and don't want to needlessly invest any more. Thanks in advance for any ideas or help...Rich

The symptom is (limited) fuel starvation

If I understand what has been done thus far (with no results).

#1. The injection pump has been run directly off a fuel bottle.
#2. The throttle linkage was disconnected from the injection pump, and lever worked by hand.
#3. The exhaust - intake manifold was removed, oil line capped and engine run.
#4. The injection pump has been replaced several times.
#5. The valve timing and chain have been inspected.
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If this is correct ?
Here are some of my thoughts.

Injectors clogged by sediment stirred up in the impact.

I hope you have looked at the following possible issues, and forgot to mention them.

The lift pump has two valves that fail.
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Fuel injection pump starvation with a good lift pump
Fuel injection pump starvation with a good lift pump - PeachParts Mercedes ShopForum

Fuel pressure relief valve adjustment
Fuel pressure relief valve adjustment - PeachParts Mercedes ShopForum

lift pump test
1979 300td -- Can anybody walk me through a lift pump test? - PeachParts Mercedes ShopForum

fuel pressure
fuel pressure - PeachParts Mercedes ShopForum

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tiger64 · #62 02-18-2013, 09:54 PM

When you ran on separate bottle, did the rpm go above 1800 or did the same limitation exist?

kerry · #63 02-18-2013, 10:26 PM

Same limitation according to an earlier post.

barry12345 · #64 02-18-2013, 10:43 PM

If when trying your various injection pumps you used their lift pumps instead of only the original lift pump?Then generally the lift pump has already been substituted. You of course would not have several lift pumps with the same exact issues. Did you do the bottle test again with any of the replacement lift pumps and injection pumps after the injection pumps changes?.

While slamming through moderate snow drifts on the way to town this afternoon this occured to me. Mr hunter in the last post was interesting. A serious source of dirt dumped into the injectors might have been residual garbage sitting in the bottom of the injection pump The injection pump sediment if there got shook up like never before.

Although this would be strange as there are continious strong pulses there in the base of the injection pump all the time when running. The secondary fuel filter perhaps dumping junk during the slam would seem more sensible for injector contamination. There is a differance between lightly bottoming out and a real hard slam. It would have to jar his bones to disturb things this much I think.

This totally quitting a mile after the slam still gets to me. I would think if the injectors were that jammed up with contaminates to totally kill the engine they would not self clear. Or not enough to let you run even as it is now. Although nothing in that senario is certain at least in my mind.

Then there is pure applied logic. If you have substituted the injection pump and lift pump. Both fuel filters, and are running on a bottle.. Plus you have fuel pressure in the base of the injection pump at 1800 rpms.

The last item is still important. As there could be an unknown obstruction from filter to filter or filter to injection pump for example. Running on a temporary fuel supply once again would also be mandatory.

The only thing left in that supply circuit then is the injectors themselves. It could be nothing else as long as the issue is inadaquate fuel supply to the cylinders. Plus overall that does seem to still be the ongoing issue.

vstech · #65 02-18-2013, 11:02 PM

how does the car run if you remove the oil cap?

kerry · #66 02-18-2013, 11:26 PM

I don't think the test I suggested has been performed. A fuel pressure and flow test between the secondary filter and the IP would rule out a problem with the bypass valve (if such a problem is possible.) We know it's not a fuel flow problem upstream from the pump but downstream from the lift pump to the IP has not yet been tested. Maybe even a piece of crud came loose and plugged the line from the secondary filter to the IP.

funola · #67 02-18-2013, 11:33 PM

If the IP let loose debris and clogged the injectors, wouldn't it make the idle rough and erratic? The engine idles and sounds good according to OP.

ROLLGUY · #68 02-19-2013, 12:44 AM

Quote:

Originally Posted by barry12345

At this point I have become very interested in what it may prove to be. This was to me the only really significant indicator of the original fault. Something drove the engine into a fuel starvation mode. If this was not so the engine would have still been capable of maintaining at least an idle even then as it is now in my opinion. That is where I got into suspecting you may have introduced something else. There is no certainty in that just a remote possibility.

From reading this whole thread over. I can only think of one thing I would do first personally now if the car where here. Either with a pressure gauge or by some other method it would be important to me to find out if the fuel pressure in the base of the injector pump was remaining at 1800 rpms or falling off to nothing as that speed was approaching. The lack of apparent linearity from the linkage at the injection pump could be another indicator that this might be occuring. Sorry about the long post but I suspect this issue may be seriously concerning you at the moment.

Under load the car has absolutly no power is another strong indicator of this as a possibility at least to me. That lift pump might have got a load of something from the bump if pressure is not maintained. Does manually pumping the primer pump as well help increase rpms while at 1800 rpms or so? I know from your posts you know more than average but still are missing something.

Long post or not, a lot of good info here. As far as the lift pump, I used the one that came on the used IP I got from the wreckin' yard, so it has been changed as well. I can only assume that either BOTH IP's and BOTH lift pumps are bad, or both of them are good. I am sure that when the problem is solved, we will all learn something.

ROLLGUY · #69 02-19-2013, 01:02 AM

Quote:

Originally Posted by kerry

I don't think the test I suggested has been performed. A fuel pressure and flow test between the secondary filter and the IP would rule out a problem with the bypass valve (if such a problem is possible.) We know it's not a fuel flow problem upstream from the pump but downstream from the lift pump to the IP has not yet been tested. Maybe even a piece of crud came loose and plugged the line from the secondary filter to the IP.

I have not tested the fuel pressure in any way. However, I do have some interesting info that we all can think about concerning the pressure relief valve. On the original IP on the car (1981 300SD W126), the hose on the side of the IP (toward the engine) on this IP only had a banjo bolt, and not one with the relief valve in it. The replacement IP had the bolt with the relief valve in it. When I replaced the IP, I used the banjo bolt that came with the IP (original-no valve, replacement-valve on bolt). I am not sure that would make any difference, as the engine still runs the same, and the engine ran for years with the banjo bolt without the valve and on the original IP.
I am going to call whunter on Tuesday morning, and have a chat with him. I won't be able to work on this car until Friday anyway, so maybe I can get some good tests to do before then. Thanks for all your suggestions everyone. This is the greatest forum on the www, and I am thankful to be a part of it..Rich

whunter · #70 02-19-2013, 04:28 AM

Quote:

Originally Posted by funola

If the IP let loose debris and clogged the injectors, wouldn't it make the idle rough and erratic? The engine idles and sounds good according to OP.

I am most concerned about semi solid sediment (wax) jelly that accumulates in the bottom of the injection pump.

The impact description is violent enough to shake lose any internal sludge, and feeding it to the delivery valve suction ports.

There would be a delay, using up the fuel volume in the injector, steel line, and delivery valve.

The symptom would be similar to the most abrupt/extreme plugged secondary fuel filter.
Continued attempts to start, and flushing the system with fresh fuel might clear some of the trash.

I have encountered this before, most often in winter.

If the owner is lucky, the car is hauled into a nice warm 70° F shop overnight, and the engine (wax) jelly melts = little or no issue found in the morning.

If they are not lucky, clumped semi solid sediment (not wax) plugs (obstructs) the injectors, until they are cleaned, replaced, or the car is junked.

Most examples of this issue that I have seen effected all injectors.
For diagnosis: I suggest pop testing the injectors, with special attention to the spray pattern and pressure.

My best advice at this point:

If you are more interested in getting the car on the road:
#1. Swap in a spare set of injectors.
#2. Clean the injectors.
vincewaldon.com - HOW-TO: Rebuild Diesel IDI Injectors

Have a great day.
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barry12345 · #71 02-19-2013, 10:27 AM

Quote:

Originally Posted by ROLLGUY

Long post or not, a lot of good info here. As far as the lift pump, I used the one that came on the used IP I got from the wreckin' yard, so it has been changed as well. I can only assume that either BOTH IP's and BOTH lift pumps are bad, or both of them are good. I am sure that when the problem is solved, we will all learn something.

The faults if any between different lift pumps and injection pumps would not be identical even if they existed. Certainly both could be bad in some way but it is again almost certain the faults would be different.

Since Mr hunter has seen jelly like substances hit injectors before as long as you have fuel pressure indications in the injection pump at 1800 rpms. Having the injectors checked and cleaned out if the need is indicated makes sense. I am all too familair with straight waxing of the fuel at really low temperatures so the concept is not alien to me. The rule is never buy fuel from a pump that has a heater on it in cold weather especially. Unless you have one load of fuel thinners in the trunk.

Or grab a set of injectors out of one of the engines you pulled the injection pumps from if cheap and give them a try. Turn the engine over with the starter with the injectors out as this may also clear any residual junk that may also be present in the injector lines.

Since it is now a different injection pump I assume there is no impariment of it's delivery valves with junk as might be the case with the original injection pump.Although this is not much of a consideration if any because the engine is running almost the same except a little better in some ways now.So I would still flush those injector lines as well before installing either your current injectors once dealt with or a test set from a wreck if cheap enough.

There should be a relief valve present somewhere there. I have seen it mentioned that it was further along the system on one car. Right or wrong I do not know. There was one situation where the relief valve was on the input to the pump as well I think. A misteak of installation. Either way whatever was the situation previously it did not stop normal running in your cars case. Unless when you changed pumps there was some change relating to the relief valve. Again any form of real pressure present in the base of the injector pump at 1800 rpm deals with this issue. Or during the process to correct the low pressure if present will.

I have nothing but respect for Mr.Hunters abilities and experience. It is a wise decision to converse with him. I have not had the need to yet for one of my own issues but that day will probably come. His helping people out goes way beyond the norm. Also it is not all that simple in some cases to do so. Human nature being what it is people do things like leave important information out when describing their issues.

ROLLGUY · #72 02-19-2013, 10:32 AM

Although it seems odd that all 5 injectors would go bad at once, the injectors are the only thing in the fuel system that have not been replaced. As stated before, I have a set of rebuilt injectors, and I think I will try them on this engine. The only thing that I may loose, is just the labor. A benefit would be that I can test the rebuilt injectors before I install them in my engine. If any leaks occur, I can fix them before I install them in my engine. I may get a chance to try this on Friday, so stay tuned!

funola · #73 02-19-2013, 10:47 AM

Quote:

Originally Posted by ROLLGUY

Although it seems odd that all 5 injectors would go bad at once, the injectors are the only thing in the fuel system that have not been replaced. As stated before, I have a set of rebuilt injectors, and I think I will try them on this engine. The only thing that I may loose, is just the labor. A benefit would be that I can test the rebuilt injectors before I install them in my engine. If any leaks occur, I can fix them before I install them in my engine. I may get a chance to try this on Friday, so stay tuned!

I think it's odd also that all 5 injectors would clog equally and idle smoothly. Before you pull the injectors, start the engine then pull the return cap on #5 injector return barb and see if it is blocked. Wrap a white tissue around it and see what comes out.

I've asked this question before but do not remember an answer:

Is the engine starting immediately or does it take extended cranking to start?

DeliveryValve · #74 02-19-2013, 10:50 AM

I have not read through the whole thread and not sure if this has been suggested, but it seems like you not getting a boost signal to the ALDA causing it to starve the engine of fuel. Check the condition of the line for obstructions and leaks. Also you might want to temporary bypass the switch-over valve as it maybe faulty.

ROLLGUY · #75 02-19-2013, 10:53 AM

Quote:

Originally Posted by DeliveryValve

I have not read through the whole thread and not sure if this has been suggested, but it seems like you not getting a boost signal to the ALDA causing it to starve the engine of fuel. Check the condition of the line for obstructions and leaks. Also you might want to temporary bypass the switch-over valve as it maybe faulty.

Yes, been there, done that. ALDA is getting a good signal with the OPV bypassed.