loss of power

[garwoo]

I have a 1967 230SL The engine starts easily and runs fine. lately tho' it has been losing  power after about 5-10 minutes of driving. Any kind of up-grade will slow it down. The only maintenance done recently was an oil and filter change plus a new fuel filter was installed. The engine sounds like it is missing under power.
Any ideas what may be wrong?
Thank-you all

[mrfatboy]

Any chance of the linkage being touched during the “maintenance”?

Stuck WRD?

[Bob G MN]

I had something similar.  It was caused by a clogged fuel filter.  there is one at the bottom of the tank and another for the injection system.  It may have something to do with the filter you installed.

[Jonny B]

There is also a third filter at the inlet to the fuel pump.

[garwoo]

Thank-you all  or your Suggestions. Mr Fat Boy I was intrigued by your suggestion of a stuck WRD That is something I know nothing much about. If you could give me a few more clues please. I read all the info in the technical manual but......... something else I did, was drain the fuel tank which I cold not do before. Ever try to find a 22MM Allen Wrench? they don't exist. With the help of my mechanic. I took 22MM. socket down to  my local hardwear store and found a Bolt that fit the socket plus a couple of nuts that fit the bolt. We screwed on the nuts (not too far) and found a welder to spot weld the nuts so the nuts couldn't turn. the head of the bolt then became the Allen Wrench. The plug in the bottom of the  tank is solid brass with a fuel filter attached to the bottom inside the tank. and very tight but my new allen wrench unscrewed it easily.

[mrfatboy]

Anytime I hear a car runs better or worst after 10 minutes (avg time of complete warmup) I immediately suspect the WRD. However, the suggestion of checking for a clogged fuel filter (main, fuel pump, fuel tank) is just as valid. I always forget that one because it’s the one problem I have not had.....yet🤣

Make sure all the fuel filters are clean, and check for fuel flow before and after you lose power. Search this forum/tech manual how to do test. If lower or not to spec after you have the problem you probably found your issue.

There is tons of info on the WRD on this forum. You can remove the small air filter on the back. You should feel suction (When finger placed over hole) and loud hiss when engine is cold. As the engine warms the suction/sound diminishes to almost nothing. This is normal.

Regarding draining the fuel tank. You can make a tool. Instructions are in the tech manual. I just bought some 22mm nuts and bolt to make mine.

Report back with your test results. 

Good luck👍

[Alex D]

Don't forget to check the gas tank vent lines.  Huge improvement in performance once cleaned them out. 

[garwoo]

Sorry, ran out time yesterday. I did changed the main fuel filter twice, drained and flushed the tank and cleaned the tank filter. could not find a filter on the fuel pump.
Thanks Alex for the vent lines info. its on my list.
Earlier when I took the car out for a test run It started right away, as always. but after 10 minutes the engine became more labored so I turned it off for about a minute then turned it back on without doing a thing. The car started right away and ran perfectly all the way home.
Will report back after I check the WRD and tank vents.

[mrfatboy]

The fuel pump has a internal screen/filter right at the inlet fitting.

[garwoo]

Thankyou all for your advise. As some of you know, I changed the main fuel filter twice, I also emptied the fuel tank and flushed it out.
2 days ago I made a decision to run the fuel pump with what I thought was the return line disconnected to capture fuel that had been thru the system. As it happened the line I disconnected at the tank was some kind of overflow fitting which squirted fuel out of the tank. I finally captured a couple of Quarts. after a few minutes the fuel cleared up and showed dirt at the bottom of the container. This a.m. I changed the fuel filter for third time. On my test run the car ran perfectly. This tells me the tank is still contaminated! Has anyone had any experience with Tank Cleaning?
As always I appreciate your help.
Ed

[wayne R]

Ed ,If your car has been sitting  in storage or not used for a period of more than about  five years or more,
then yes, tank needs to removed and cleaned correctly, if old gas, petrol, has turned to jelly inside tank.
Let me know if this happened in its history,then ill tell you how to clean it out.    regards.

[garwoo]

Thanks Wayne,
The tank looks clean from what I can see and after being drained and flushed, plus 2 new main fuel filters. I'm on my 3rd filter now. I was trying to collect some fuel from the return line to the tank but I disconnected the tank overflow? line by mistake and collected a 1/2 gallon by the time i was able to cap it off. this sample had black flakes on the bottom.
The car has not been sitting too much in the 5 years  its been in my care. It runs perfectly immediately after a filter change but goes down hill pretty fast after.
 thanks again Ed

[enriquegarcia]

Ed,
I had a similar problem with my 68 280SL, and like you, I chased dirty fuel filters, clogged fuel lines, clogged vents, dirty tank, electric fuel pump, etc. The problem turned out to be the electric pump. It checked out OK--initially, so it threw me off. But apparently, after running for a few minutes, or sometimes several tens of iminutes, it would either quit or just run weak. A new short pump (with my old one as a core trade in) solved my problem. In fact, my car ran much better than it ever had before. And the problem has not reappeared in over a year. Good luck!
-Enrique Garcia

[garwoo]

Enrique, thanks for sharing your experience, I am going to look into the fuel pump being the culprit.
Ed

[BaronYoungman]

Yes you will find that the fuel pump will start running with gusto but when it heats up it reaches a steady state and that  could be substantially lower in volume. Usually this is due to having shorts in the Armature, glue just getting old and being eaten away by ethanol in gasoline causing some of the commutators to be dead spots. Bob

[jim 56]

yes the pump on my car would start fine then would decrease in flow after awhile.Had the armature rewound works fine now.One thing I have seen on this site is people saying that it is hard to find a 22mm hex wrench.I have seen people make one out of a bolt which works fine.I bought a 22mm hex socket with a 1/2 drive from Summit racing that worked fine.

[garwoo]

Thank-you all for sharing your Pagoda experiences. I did not redrain the tank or put in a third main fuel filter. I found a guy who could rebuild my pump. The pump has a problem, the impellor is warped. If anyone knows a source for a replacement impellor please let me know, otherwise a new modern (less expensive) pump is the only other answer I can think of.
Thanks again
Ed

[mrfatboy]

Contact BaronYoungman. He posted above in this thread.

[garwoo]

Hi Bob, thanks for your reply's and all the other advice given. I am at a point now that I am looking to replace my original fuel pump with a new pump, at least for the immediate future. if any one can recommend a reasonably inexpensive substitute pump, I can at least drive my 230SL Until the original is fixed.
Thanks again
Ed