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Do I need a new IP?
Driving home Friday on the interstate 65mph suddenly noticed the throttle became unresponsive. Looked down at the gauges and see the oil pressure fluttering and falling. Threw it into neutral and coasted to a stop, the engine stalled as I cam to a stop. I kept one eye on the oil pressure as I was coasting to a stop and it never hit zero, maybe 10 seconds to get stopped.
I blew an oil cooler line and dumped most of the engine oil. After the tow home I spliced and patched the cooler line to assess the damage, filled with oil and it fired right up with full oil pressure. I took it around the block and as it warmed up the throttle response became weak and lost power to the point where it stalled when I released the pedal. Next day I started again cold (struggled to start) and once again it seemed to run decent for the first 10 minutes with full oil pressure but once it warmed up, no throttle, no power and stalled (still had full oil pressure), would not start again warm. It seems the engine bearings, cam, etc. survived the oil loss but not the IP. Is there anything else I can check before removing the IP for rebuild ? Suggestions? |
85 300SD
Should say what it is I guess 85 300SD
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As soon as the engine stops when warmed up. Is the starter then able to crank the engine over well? I do not suspect the injection pump died because of the lack of internal lubrication. From what I understand and it is not certain. A pool of oil exists in the base of the injection pump rather than it fed like a crank bearing. That pool is refreshed with new oil but always has the pool present. You want an opinion on the possibility of the engine tightening up as it warms up.
My suspicion is it is inside the engine. At the same time I hope I am wrong. Those oil cooler hoses have been a curse for many over the years. There is no instant warning system like a bright light or warning buzzer on these diesels from the factory. I suspect most look at the oil pressure gauge after the problem is showing the results of inadaquate or no oil pressure. |
The engine is not tightening. As I was waiting for the tow truck I even tried to crank it and it cranked fine right after it stopped hot.
When it gets warm and acts up it still cranks easy. Definitely a fuel related issue, but I agree, my initial thought was that the engine would fail before the IP, but I do not know enough about the IP workings to understand how a broken oil line relates to no throttle response and stalling. Again, engine oil pressure is absolutely normal, even at idle which leads me to believe there was no major engine damage done. Is there a hydraulic governor in the IP that works off engine oil pressure? |
That sounds like a fuel starvation issue to me. Please check both the filters and also try using the primer pump if it stalls again. If you have clear fuel lines between the IP and the spin on fuel filter, check to see if you have air bubbles in the line
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Wait for other opinions. Also see if the engine continues running with the oil cap off. As long as it is not puffing like a steam engine and throwing oil out.
If there is too much base pressure present in the engine from blowby it can shut the engine down. Acts internally to shut the injection pump off. Or try a hot restart with the oil cap off. Personally I just still feel it is not the fuel injection pump itself. Still I hope the additional explanation of how an engine making too much blowby can shut the injection pump down is understandable. Easy to test and eliminate if nothing else. |
Checked the blow-by with the filler cap off when assessing for any damage from the oil cooler line failure. Also pressure checked cooling system.
The engine never overheated, and still had a minimum of oil pressure when it shut down. The engine only has 143K on it and was running like a Swiss watch when the line blew so I doubt if the filters are plugged. Is there a transfer pump in the IP that draws the fuel from the tank first? Just trying to connect why I would loose throttle response in coordination with oil line failure. |
i blew an oil line awhile ago, engine noise changed (a shrill sound) when i was cruising at ~ 65 mph,
checked the gauges and oil pressure was zero, let off the throttle, shut 'er down and coasted to a stop, everything is still completely normal including oil pressure, starts right up, runs great like before, no diff in blowby or smoke when running, has a knock now though, sounds like you had a partial seizure, maybe a piston/ring scenario, i'd check the compression, might as well have a look inside the valve cover also, though mine was fine there |
Did something off the road strike the oil cooler / lines, also striking a fuel hose or fuel system related at the same time?
Are you dripping fuel anywhere? How much fuel is indicated, did you run low at the same time.. faulty gauge? Did you reverse any fuel lines under the hood and now sucking through the return line that goes back to the tank, that is half way up the tank (sipping off the top)? |
Looks like a rub spot finally blew, nothing hit it. No fuel leaks, hoses are in the same location as previous. Tank is full.
I will probably do a compression test before removing IP but still trying to figure out why the first sign of trouble was throttle response and how it can run fine when cold but loose all power and stall when warm. Ring seizure should cause a miss, or blue smoke or something else. Even with my history of luck I cannot fathom and oil line and IP issue at the same time without being related. |
Look for cracked plastic hard lines that may have been bumped during the oil line repair.
If the primer pump is the old white style, is is screwed down? |
Run the car with a separate fuel supply and separate lines. That should vindicate the pump.
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"Run the car with a separate fuel supply and separate lines. That should vindicate the pump".
Very GOOD idea. I was going to ask if that was done but you beat me to it <grin> |
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Thanks for the info
I just tried to start it when I came home from work and no start. I cracked the first three injection lines and cranked, did not seem to have the usual pressure. I pulled all the lines off and did get fuel squirting out of each pump. I guess the next step is a compression test. I looked at all the hoses and lines, the only other thing that could have been damaged is from hot oil splashing on something because it all worked fine until the line broke |
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The next step is to check the fuel pressure between the secondary and the IP. The lack of sufficient fuel is still the most likely culprit...........the reason is still uncertain. |
I'd replace the lift pump before replacing the IP.
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I will not start cold now.
I will rig a gauge between secondary and IP and post results. |
You appear to be determined to blame the IP. They seldom fail like you describe. Removing hard lines etc will only mask the problem.
The idea of attempting to start it with a fuel feed from a bottle is a good one. if it needs a kick to get it going give it a good spray of WD40 in the air inlet while some one is cranking with their foot to the floor. If it does start, dont try & let it idle. 2000 rpm is a good speed for the first 5 minutes provided you have oil pressure. |
Actually I am determined NOT to blame the IP which is why I am here asking questions.
I have been working on MB diesels for 20 years and for the life of me cannot figure the relationship between a broken oil line and a fuel system issue occurring at the exact same time, other than oil feed to the IP. I appreciate any help and all suggestions and will try them all before I remove the IP, been there, done that, no desire to do it again. I will bottle feed her tonight and hope for the best. |
Call me
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TECHNICAL SUPPORT whunter ASE Master Mechanic Mon-Fri 9:00a-6:00p ET Cell phone: 248-850-7027 . |
Maybe the lift pump failed, causing the engine which was running at high rpm's to lurch which was the straw which broke the camel's back for the oil line??????
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Well after a long talk with Ron this afternoon, I checked a bunch of things in the fuel system:
1) Fuel flow test....filled a pint jar in about 10 seconds 2) Fuel pressure between secondary and IP abut 22 psi 3) Checked filters for sludge dirt etc. Fuel system seems to pass all tests. Started it and ran it at 2000 rpm for about 15 minutes, when it was up to temp the oil pressure started fading and it started running rough, let off the throttle and it stalled. Started it again and oil pressure fluctuating more and I shut it down. Per my discussion with Ron, I think I spun a bearing. Although it does not knock or seize he says this is typical. Looks like I'm pulling the engine this winter. I will post an update when I open her up. Thank all for the help! |
Hmm
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Sad to hear that diagnosis. Glad I could help you. . |
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