Little or NO power after bottoming out suspension- 1981 300SD - Page 7 - PeachParts Mercedes-Benz Forum

pgringo · #91 02-19-2013, 06:32 PM

I just have to say, this thread is better than anything on tv this week. I can't hardly wait for the exciting conclusion.

ROLLGUY · #92 02-19-2013, 08:03 PM

Quote:

Originally Posted by pgringo

I just have to say, this thread is better than anything on tv this week. I can't hardly wait for the exciting conclusion.

Exciting indeed, especially for me! There is so much knowledge and experience here, why go anywhere else to find out how to fix your Benz?

turbobenz · #93 02-19-2013, 09:05 PM

Have you tried running the car without the vacuum shutoff valve plugged in?

I highly doubt it would be the injector IP pump wax theory. These arent 30PSI gasser injectors, these are 1600PSI steel injectors with a powerful spring AND their screwed into a hot head. Unless actual particulates got stirred up I doubt some varnish would really affect them.

Check for actual air pressure blowing out of the line going to the alda when your revving it. Inspect the old hardline for cracks

ROLLGUY · #94 02-19-2013, 09:16 PM

Quote:

Originally Posted by turbobenz

Have you tried running the car without the vacuum shutoff valve plugged in?

Check for actual air pressure blowing out of the line going to the alda when your revving it. Inspect the old hardline for cracks

Again, been there, done that. As far as I am concerned, the only thing left to replace is the injectors...Rich

ROLLGUY · #95 02-22-2013, 01:33 PM

Well, I installed the rebuilt injectors, heat shields, and return hose. After getting all the air out of the lines, it started. BUT, it still runs the same as it did before, with the exception being that it smokes a little more than it did (grayish). I am at a loss as to what could be the problem. It was suggested by a friend that the lift pump is bad, and/or the injection pump. I told him they were both replaced with one from the JY. I find it hard to believe that the car in the JY had the same problem, and that both pumps are bad. It was also suggested by another friend that the timer went bad from bottoming the suspension. He suggested that I at least advance the IP a little and see if it runs better. If that makes a difference, then we are on the right track. What say you?....Rich

funola · #96 02-22-2013, 02:44 PM

I didn't think clogged injectors were it, for the unlikely reason they would clog equally and still produce a good idle.

Have you done the fuel pressure test http://mercedes.thatchermathias.com/w123CD2/Program/Engine/617/07_1-145.pdf

I thought you had the IP timed with the drip method. If it was timed correctly, doesn't that rule out a bad timer?

mach4 · #97 02-22-2013, 03:38 PM

Time for some serious troubleshooting.

If you're sure the timing is spot on then I'd move to Plan B, or C, or D or whatever letter we're up to.

My recommendation at this point is to swap in the entire fuel delivery system from a known good engine that is currently running - IP, lift pump, filters, injectors, hard lines, etc Call this engine B Your original engine is A

If engine A runs good with engine B's fuel delivery components, then start swapping back the components until you find which one is the problem.

If engine A runs the same as it did with its own fuel delivery components, then I'd go ahead and install the engine A components on engine B and verify that the fuel delivery components are good or bad on that engine.

This will give you data on the engine itself and on the fuel delivery components. It's a lot of work, but I'm not seeing many other options.

We've got to eliminate some variables and this is one way to eliminate a lot all at once and start to narrow the causal components.

For example, if there were something in the engine itself that was creating some huge friction that prevented the rpms from building, this process would eliminate fueling as the cause and allow a different focus. If the problem migrates to the new engine, it's got to be fuel.

Good luck

kerry · #98 02-22-2013, 04:13 PM

Quote:

Originally Posted by funola

Have you done the fuel pressure test http://mercedes.thatchermathias.com/w123CD2/Program/Engine/617/07_1-145.pdf

Yes, as far as I can tell, the fuel pressure/flow test between the secondary filter and IP has not yet been carried out. There is a possibility (perhaps quite remote) that there is a problem in the secondary filter assembly hindering the flow from the secondary filter to the IP.

Swapping in a complete secondary filter assembly from a pick n pull might be a feasible alternative way of ruling an issue with the assembly itself.

funola · #99 02-22-2013, 04:25 PM

Quote:

Originally Posted by kerry

Yes, as far as I can tell, the fuel pressure/flow test between the secondary filter and IP has not yet been carried out. There is a possibility (perhaps quite remote) that there is a problem in the secondary filter assembly hindering the flow from the secondary filter to the IP.

Swapping in a complete secondary filter assembly from a pick n pull might be a feasible alternative way of ruling an issue with the assembly itself.

As I recall, the owner changed the secondary in the field in an attempt to get the car started. Not sure if something got messed up there in the process. Replacing secondary with another is worth trying.

kerry · #**100** 02-22-2013, 04:35 PM

Just to be clear. I wasn't saying just put in a new filter, but swap in a whole different filter assembly. I don't know how exactly the assembly works but I know there is a bypass valve in the assembly because one of the ways of knowing if the primer pump has provided pressure to the IP, is when you can hear the bypass valve open in the assembly. I'm speculating that if that bypass valve is stuck open as a result of the shock from the bottoming out, it could be diverting enough fuel back into the return system and the IP is getting inadequate flow.
Can anyone else comment on whether this is a real possibility or not?

funola · #**101** 02-22-2013, 04:57 PM

Was the return fuel captured in a bottle and how did it look? May want to take the fuel lines/ injector pipes, banjo fittings apart and blow everything out.

funola · #**102** 02-22-2013, 07:29 PM

Did you put the injector return hose in a bottle and observe the flow? Compare the flow to a normal running 617 engine and that may give a clue?

KarTek · #**103** 02-22-2013, 07:37 PM

Is it possible that something has happened to the transmission/broken bellhousing or some such thing that's putting the engine in a bind?

Probably very little chance but I'm just trying to think out of the box.

Delibes · #**104** 02-22-2013, 07:47 PM

I still suspect the mystery lies somewhere in the linkage...

W126 - 300SD - Throttle Linkage Adjustments

Could anyone provide a nice, well-lit photo of a good one in a 300SD?

ROLLGUY · #**105** 02-22-2013, 08:48 PM

I am pretty sure the problem is solved, but not totally fixed. By solved, I believe the injection timer is bad. After replacing the injectors today, I discussed the problem with the local expert. He believed that the timer is bad, because of the excessive gray smoke, and the lack of RPM's. He suggested an easy test, and I performed it. I removed the hard lines from the injectors and loosened the IP. I advanced the IP about 10 degrees (just a guess). I tightened the IP bolts and bent the hard lines enough to tighten the nuts. After getting it started and the air out of the system, it revved much better than before (almost like it should). However, it was much noisier than it should be, which suggests that the IP timer is not doing it's job. That being said, I will replace the timer. It totally makes sense now, that that is the problem. I believe that if it was a fuel delivery problem, the engine would not run smooth at the highest RPM for a long time. If fuel was starved somehow, it would gradually run slower and slower. I am convinced that the timer is the problem, not fuel starvation in any way.....Rich