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Old 04-17-2010, 11:34 PM
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Join Date: Feb 2008
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84 190D low on power when warm?

I have a 1984 190D with about 150,000 miles. It has been running good for me until about a week ago when it started to loss power and shut off at stops (unless I keep feathering the throttle). When it is cool it starts right up and runs fine however once I get about 15-20 miles away it starts to loss power pretty bad.

So far I have:

1) Pulled fuel tank and strainer and cleaned (it was already pretty clean)
2) Blow out fuel line and installed new primary and secondary filters
3) Installed vacuum gage between filter and lift-pump (pulls 5" H2O)
4) Pulled off lift-pump to pump by hand (seemed fine)
5) Installed clear fuel line to make sure there is no air in the fuel
- There originally was some air and probably has been for a long time
6) I installed an electric boost pump just to make sure injection pump gets enough fuel

Whatever is happening seems to be temperature dependant. Next I plan to check timing and pull injectors to visually inspect and do a compression check. My fear is the injection pump plungers are starting to seeze when warm or something like that.

If you have any thoughts are advise please let me know and I'll be providing updates as I check more things.

Also, does anyone have the PDF dealer manual for this car. I get it from here: but the fuel system link is down...

Thanks in advance for the help...
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Old 04-18-2010, 01:18 AM
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Join Date: Nov 2004
Location: Nova Scotia, Canada.
Posts: 6,510
Well make sure the tank vent blocked is not an issue. Try running with the fuel cap loose. Or when power drops hop out and undo the fuel cap for a second. Big whosh and engine is then normal for awhile is equal to blocked/obstructed tank vent.

At 150k I doubt the injection pump is actually worn out unless it has had a pretty good water diet. Also make sure your relief valve on the pump is overflowing when this occurs. You may have sagging pressure with the fuel supply.

First do the test with the car cold and then again when the difficulty is there. With no relief valve overflow at the pump with the engine cold the fuel is not acting to cool the injection pump where it is important to do it. Also indicates something is wrong.

Or drive the car until the problem occurs and clamp the return line from the injection pump off. Power increase a lot or not? The results of that one test alone would indicate something. A badly obstructed vent hose from the valve cover might cause some difficulty with a hotter engine as well. Easy to check.

The electric boost pump you installed. Location and psi? This is or is not a wvo car?

Last edited by barry123400; 04-18-2010 at 01:41 AM.
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Old 04-18-2010, 10:39 AM
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When I had the tank pulled out I pulled the vent off the bottom of the tank a blew in it to make sure it relieved pressure. I also pulled the cap off the tank and it did not make any difference when it was running bad.

The injection pump relief valve I'm assuming is internal and the best way to check it would be to check the flow at the banjo fitting on the secondary fuel filter?

I will check the valve cover vent line and the boost pump is something I just put in for the sake of troubleshooting but it is a 4-7 psi pump I placed between the secondary fuel filter and the lift pump.

This is a wvo car, two tank setup running that way for the last 25,000 miles. I run dewatered 2 micron filtered oil 165 F at inlet to lift pump. The interesting thing is that the car has the same powerloss symptoms running on wvo but it runs much better on oil than on diesel. The car will bearly even run on diesel but I can at least drive it home on oil and ALMOST get up to the speed limits of the road. I have tried not using the oil at all but that has no positive effect during a 20 mile trip. It seems to loose power even faster on diesel alone.

Thanks for the quick reply!
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Old 04-18-2010, 12:15 PM
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Location: Nova Scotia, Canada.
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I think the relief valve is part of the output fitting itself on the injection pump. I guess about the last test is to examine the fuel flow from the relief valve when you have little power.

Just submerge your clear fuel line from the return valve into a container and watch for air and fuel flow. If you have no air and fuel flow with no power in your case it very well can be the injection pump.

To be really valid because of your description the test has to have the clear hose fed back into the passenger compartment to verify the same senario is occuring at running loads. If It passes the test your injection pump is almost certainly going to be the issue. I imagine this kind of driving test requires two people to preform.

This type of issue is not that uncommon on cars running used vegatable oils from what I have heard before. You could check this out on one of the sites that is more slanted to running wvo. You would not be the first to have a twenty thousand mile approxamate lifespan on an injection pump running wvo. At least there are still good used pumps around if it comes to it.

If you have the time available and indications during the driving test are good. For the time and effort involved I would introduce laquer thinner into that pump and let it soak for a day.

We have always assumed the bores and pistons get abnormal wear. This may still be true but I do not know if it has ever been proven. What if accumulated fats or substance clumps get warmed up a little and reform somehow into element intake port restrictions?

Do the test and if indicated soak the pump. This is important enough to the majority of us for you to post back. The opportunity of purchasing non running used wvo cars is there sometimes.

We really are not aware if the injection pump will respond to an internal cleaning. Odds are certainly not good but at least one person had the solvent break up stuff and spew it out of the pump. It actually fixed his compaint.

Also since the viscosity of the wvo is heavier. Clamping off the return line when you have no power is also indicated. We know these engines will run diesel fuel at very low base injection pump pressures.Yet have no knowledge of the minumin feed pressures required with wvo. If for example the relief valve where totally defective. The addition of the electric pump could have been totally meaningless.You would lose any pressure instantly through the open relief valve back to the tank.

Now for example if your return valve has failed somehow and there is really next to no operational pressure in there. It would be subject to fuel starvation easier than a car on diesel fuel.

The clamping off of the return line will do not harm and will let the pressure rise. The placement of your 4-7 pound booster pump is not the best even for testing. Usually it is at the back to attempt to get the thicker viscosity fuel up to the the lift pump.

I also think there is a definative test but allow that I do not follow the wvo thing very much. If the car will run on wvo and will not on diesel fuel it is pretty clear there is really too much wear in the element bores. This last statement is considered to be the most current belief. Again proven or not I am not sure. To us non wvo users it sounds okay.

There has been so much issue around the use of alternative fuels something could have fallen through the cracks. I personally doubt that though. Once again let us know how this problem works out and what you do.

Last edited by barry123400; 04-18-2010 at 12:49 PM.
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Old 04-18-2010, 10:59 PM
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Join Date: Jun 2002
Location: FL
Posts: 777
Have you checked the butterfly in the air induction system? If its frozen or disconnected, it will cause the same problem, and is soooooo easy to fix.

Good luck
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Old 04-20-2010, 10:31 PM
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I don't think this engine has the butterfly spoken about is a non-turbo model. It goes air filter, intake runners (all separate) and cylinder head.

Can anyone tell me what the flow rate FROM the injection pump and also the injectors should be?

I had almost nothing coming from the injector returns and pretty low flow from the pump but flow non-the-less. Just would like to know if there is a spec or even a rule-of-thumb on this?

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Old 04-20-2010, 10:46 PM
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It sounds like you have a fuel system that has been clagged up with WVO. If it was mine, I would return everything to standard & see if the problem was still there.
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
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Old 04-21-2010, 01:18 AM
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Join Date: Jun 2002
Location: FL
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Actually there is something like a butterfly on the driver's side of the air intake. It opens and closes, limiting the air when warm or cold. The reason I know about it, when they put my engine back together after the head was redone, they forgot to reconnect that flap, and I had similar symptoms, until we figured out what happened and reconnected it to the outside levers.
1983 300D, the "Avocado"
1976 240D, 4-spd the "Pumpkin", SOLD to Pierre
1984 190D, 2.2L, 5-spd, my intro to MBZ diesels, crashed into in 2002
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