Author Topic: Intermittent fuel starvation problem, found something  (Read 6204 times)

geezer

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Intermittent fuel starvation problem, found something
« on: August 24, 2009, 16:29:12 »
I've been chasing an intermittent fuel starvation problem in my M130 engine for a few weeks now.  I found that there was quite a bit of sludge and goo in the gas tank, had that cleaned out, replaced the fuel filter, cleaned the screens in the electric pump & fuel tank.  Next I suspected that the gas flow out of the electric pump was weak.  The pump delivery is weak at 3 quarts per minute.  But the dang thing would just runout of gas.  I took one suggestion and topped up the tank.  I checked for proper voltage at the pump, OK.

Each time I thought that I had it fixed I'd have to walk home.  When I get the car home all is well again. %$*^)**%$@#&

I finally decided to just let the car run in the driveway until it dies and check it out the moment that if croaks.  After a bout 1/2 hour of running at 2000rpm it died and would not restart.  With the key on I could feel the pump running.  Cracked the fuel line at the cold start valve and gas squirted out.  Cracked the line at the return port on the injection pump and nothing.  I suspect that there is some sort of bugger either at the inlet fitting or something is floating around in the passage in the injection pump.

From what I see the fuel passage is straight through the inj pump from front to back.  Will it foul anything up if I blow air into the return port in the injection pump?  Hopefully that will blow any guck back out the inlet port of the inj pump.  
« Last Edit: August 24, 2009, 19:00:24 by geezer »

geezer

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Re: Intermittent fuel starvation problem, found something
« Reply #1 on: August 25, 2009, 18:56:11 »
Well I dug into the problem last night.  Ultimately what I found was some guck in the return check valve, on the injection pump, which made the valve stick open and at another time it would stick closed.  Got the check valve cleaned up and now it operates freely. 

Unfortunately I have to finally condemn the electric fuel pump.  Though it free flows a bunch of gas through an open hose I can put my finger over the hose and stop the flow.  Clearly the pump still cannot consistently produce enough pressure to overcome the spring tension in the return check valve on the injection pump thus I am not getting any return fuel flow to the tank nor am I getting enough flow & pressure for the engine to operate properly.

geezer

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Re: Intermittent fuel starvation problem, found something
« Reply #2 on: September 02, 2009, 20:39:56 »
FYI a new electric fuel pump did the trick.

Peter van Es

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Re: Intermittent fuel starvation problem, found something
« Reply #3 on: September 02, 2009, 21:11:33 »
Congratulations. How is it running now?

Peter
1970 280SL. System Admin of the site. Please do not mail or PM me questions on Pagoda's... I'm not likely to know the answer.  Please post on the forum instead!

Iconic

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Re: Intermittent fuel starvation problem, found something
« Reply #4 on: September 04, 2009, 17:23:59 »
Excellent, I'm thrilled for you.
Now you can do what it was created to do,  ...DRIVE IT !
Enjoy.
1970 280 SL Automatic, USA version, Grey-Blue (906G/906G), Blue leather (245)
1968 SS396 Camaro Convertible (owned since 1977 -- my first car :D)
1984 Porsche Euro Carrera coupe, LSD, SlateBlueMet/Blue
1998 BMW M-Rdstr Estoril Blue
1970 280 SL Automatic, Anthracite Grey-173G, Red Interior-132 - sold

thelews

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Re: Intermittent fuel starvation problem, found something
« Reply #5 on: September 04, 2009, 17:57:03 »
Last summer, on a beautiful summer days drive, my car quit...early '67 250 SL.  Had it towed home and the fuel pump (tall version) was not running.  Not having anything to lose, I removed the pump and then started dismantling the motor on the bench.  What a mess of filth after 42 years.  I blew it out, cleaned it out with carb and electrical cleaner, in general, spiffed it all up inside.  The brushes were worn, but still making contact.  Reassembled, attached a 12V external source and I was in business again.

Last Saturday, 900 miles later, things were getting funny on the throttle while on the freeway.  I exited as soon as I could and the car died.  Pump out again.  Towed home, removed pump, took a quick look and decided the brushes were probably too worn.  Took it to a local electric motor shop.  He confirmed my brush theory, custom fit a set of new brushes and said all is well.  $78.  I reinstalled a nicely humming pump and went for a spin.  While my car has always been a pleasure to drive and is very smooth, it seemed to hit a new level of smoothness and responsiveness.  With the pump operating at full capacity, the injection pump is now most likely getting a consistent flow of fuel at full volume allowing it to operate even more efficiently, while before, without the new brushes, it may have been flowing at a slightly diminished capacity.
Enjoy some pictures at this link:
http://www.flickr.com/photos/8292359@N06/sets/72157603240571101/show/

John - Wisconsin
1967 Early 250 SL Red/Caviar, Manual #1543
1961 190 SL 23K miles
1964 Porsche 356
1970 Porsche 911E
1991 BMW 318is
1966 Jaguar XKE
1971 Alfa Romeo GTV 1750

geezer

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Re: Intermittent fuel starvation problem, found something
« Reply #6 on: September 07, 2009, 10:53:04 »
The car runs great now.  I am amazed at how much better it runs.  Heck I even did a burnout at a stop sign (there was a little gravel that helped).