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Discussion Starter #41
I'll check the plugs again. The last time I checked them they were fine. I will also check the mixture and see where it's sitting. I do have injector cups, seals and o-rings on order. Previously I mentioned that a smoke test showed injectors 3 and 4 leaking badly. I also have another EHA spare I can swap. I hate dealing with the EHA because I now have a 5th one which 3 leak from the weep holes. I'll see what this 5th one does.
I am reading over the info in that link. Very informative. Is 15-17 a normal vacuum range for the 420sel though? Also, keep in mind that fluctuating is going on while the idle hunts a bit. I'm going to double check both ICM boards to verify there's no bad solder joints. Speaking of opening up the ICM, I've discovered that opening up the black box relays on these cars are done easiest using the pick tools and mini screwdrivers from phone repair kits. :p
 

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Discussion Starter #43
I serviced all of my injectors and they're spraying beautifully and popping at the correct pressure.

I bought a master fuel pressure testing kit and conducted tests. However within the first test I was having incorrect readings. Meaning the pressure test was failed. I did a fuel flow test along with it and that also failed. Also when conducting the test I observed the pressure change higher for a bit and then drop 30-40 psi lower than it should, with the power loss (when I checked it running as well) coinciding with the pressure changes. I am reaching the conclusion that there must be a pump not performing optimally. Or perhaps a clog. I'm betting on one of the pumps though. One of them is making extra noise, akin to that of rattling, which fluctuates. I'm going to take a closer look at the pumps and make a determination. I'll update when I can.
 

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Third time, plug wire set and possibly cap and rotor.
Let's ask the OP:

"Have you already verified that all HT components are 100%?"

Vacuum leaks should be eliminated if not already done (sorry, no time to read entire post).

This BEFORE diving into more complicated, expensive areas.

Bonne chance.

RayH
 

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Recently, my 560SEL began exhibiting very similar symptoms to that of the OP.

My approach was multi-pronged...

First, I had fuel pressure tested. It was fine for a few minutes, then dwindled to damn near nothing. And, this on top of replacing both pumps, filter and accumulator 18 months before. I had not replaced the strainer in the tank, however.

Secondly, I had a feeling my cat was clogged.

In the end, I replaced all of the fuel components again save for the accumulator but this time, did replace the strainer in the tank.

Also had a set of test pipes installed and that crudded up cat removed. It seems the pre-cat had come to pieces on the inside and the guts accumulated in the cat, rendering the whole exhaust rather worthless.

Much better now.

And, I'm withholding judgement on the quality of the fuel pumps for a while yet, although I am aware that they must have been working pretty hard to keep combustion going in an engine that could not exhale properly.
 

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I was pleased with my original, but changed it.
 

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Discussion Starter #50
Recently, my 560SEL began exhibiting very similar symptoms to that of the OP.

My approach was multi-pronged...

First, I had fuel pressure tested. It was fine for a few minutes, then dwindled to damn near nothing. And, this on top of replacing both pumps, filter and accumulator 18 months before. I had not replaced the strainer in the tank, however.

Secondly, I had a feeling my cat was clogged.

In the end, I replaced all of the fuel components again save for the accumulator but this time, did replace the strainer in the tank.

Also had a set of test pipes installed and that crudded up cat removed. It seems the pre-cat had come to pieces on the inside and the guts accumulated in the cat, rendering the whole exhaust rather worthless.

Much better now.

And, I'm withholding judgement on the quality of the fuel pumps for a while yet, although I am aware that they must have been working pretty hard to keep combustion going in an engine that could not exhale properly.


So was it the strainer causing your problems? I don't have a cat on my car, just the precat with the o2 sensor.
 

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Discussion Starter #51
Well guys, I have conducted many series of fuel pressure tests, with varying results. The tests I conducted were according to an instructional a friend of mine wrote up.

In the first set of steps I was instructed to connect the pressure gauge between the cold start valve and the lower chamber of the fuel distributor. Then disconnect the EHA (differential pressure regulator) and then to activate the pump(s). Pressure should read between 75-82PSI. My results per this step: Test condition: engine cold. Pressure:74/75PSI.

2nd step instructed a volume test from system side. Target: 0.5 gallons per minute or more. Result: 2/3 gallon per 1 minute. Acceptable per instructions. If pressure is lower than 75-82 replace system pressure regulator (fuel pressure regulator).

Fuel system test continued.

Disconnect EHA connector and close valve on pressure gauge. I did this on the lower chamber side. Target: 2.9 - 7.0 PSI. Result: 11.5 PSI. Fail?

Next, per instruction, move on to volume test at return line. Target: 5 ounces per minute. Result: 1/3 gallon per 1 minute. Fail? Per instructions fuel distributor needs replacement.

Anyone knowledgeable with these tests, procedures and target values? Feedback?

Upon cold start, the fuel pressure was within the target range for the first few series of checks. In one instance when the car was approaching operating temperature the fuel pressure plummeted to as low as 45 PSI and the car ran rough and lost power.

2 days ago after idling at operating at operating temperature for about 20 minutes the car gave no signs of the previous issues that have been plaguing it. I had swapped out the EHA for a spare. I can't make a solid claim on its operating condition, however it did not leak. Made no obvious difference unplugging it while running. Had to be plugged in to get it to start though.

I took it for a spin and made it only around the block before i limped it back into the parking garage. At that point the car was barely running at all.

Today I went and started it, first crank no problem. Idled smoothly and revved effortlessly. Ran it for 30 minutes twice, minimal resistance flooring it to rev limiter.

I have posted a video on YouTube of it idling and revving it. You can hear the way the engine runs change as it approaches opersring temperature. Please watch it and give me feedback. Thanks!

 

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You state the car was running fine then the fuel pressure dropped and it started to run poorly, this makes me think that one of your pumps is crapping out when it heats up.

Also did you measure the system pressure and the lower chamber pressure together to find the proper pressure difference? If
 

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So was it the strainer causing your problems? I don't have a cat on my car, just the precat with the o2 sensor.
I believe the strainer ruined the pumps...or at least one of them.

Couple that with the plugged up exhaust and it was a train wreck waiting...
 

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Discussion Starter #55
You state the car was running fine then the fuel pressure dropped and it started to run poorly, this makes me think that one of your pumps is crapping out when it heats up.

Also did you measure the system pressure and the lower chamber pressure together to find the proper pressure difference? If
That's what I'm beginning to think. Maybe when the trunk ground went bad maybe a pump got damaged.

Is that process any different than what I did for the first step? Do I have to measure that directly from the system supply line?
 

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The lower chamber pressure is set to .4 bar or 5.8 psi lower than the system pressure when The car is running and warmed up.

The manual says your system pressure should be at 90 psi.
 

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Discussion Starter #57
The lower chamber pressure is set to .4 bar or 5.8 psi lower than the system pressure when The car is running and warmed up.

The manual says your system pressure should be at 90 psi.
Ah! Thanks for that. Well now this is now making more sense. At any time my fuel pressure hasn't hit more than 82 psi. Right now it sits at 74 psi. So what I did was order brand new Bosch pumps which I'll have tomorrow. The fact that full pressure isn't there definitely explains why there's no power, etc. When I get the pumps installed I will update you guys.
 

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Discussion Starter #58
I forgot to mention that after having ran the pumps for awhile earlier that I noticed one of the pumps has a lot of chatter, like something grinding, after warmed up.
 

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Maybe to check, if you haven't already done so.

- Timing set advanced to 14 at low idle with vacuum assist plugged for low test gas, maybe 11 or 12 if you are filling with super.
- Make sure both side plugs on the green cable running from the Ignition Control Unit to the Distributor? The plug into the distributor can get damaged by screwdrivers opening the distributor cap, and you never see it. Just seal them with insulating tape. The cable itself costs $180 if you can find one.
- Idle linkage is hardly ever a problem unless the someone fiddled with them. Adjusting regulating linkage 30-300.pdf can usually be easily found and show how to reset. Symptom that this is a problem is the car stalls in a parking lot at 5 mph.
- Remove, soak with carb cleaner and replace the Idle Control Valve.
- Alternator brushes. Unsure if an issue here would actually manifest to low idle problem. Worn out brushes would mean lower voltage going back to charge the system. It's possible to change them without removing the alternator, but you have to loosen it.

Hope that helps.
 
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