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#1
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1972 350 Mercedes sl fuel pump issue
Recently, while charging the battery, the fuel pump apparently activated and pumped gas until the engine was full and began leaking - out the rear main seal, I assume. The gas leak led to an explosion in the garage where the car was stored causing some damage. What could have caused this to happen?
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#2
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Quote:
When fuel pump runs, it pumps gas into the injector rails and then back to the tank via a fuel pressure regulator. It could run for hours that way. There is nothing to "fill". It just recirculates. However, there are a number of hose clamped connections throughout system including the ones that connect the injectors to the rails. It is quite common for those connections to leak. It is also possible that a hose, like the front connection between the rails, could be weak or damaged. With gas leaking around the engine and a charger connected to the battery (also under hood?) all you need is one spark. I am assuming an original pump. If an aftermarket or later model pump was used, it could overpressure the system if the return line is somehow restricted. I really can't see how the pump would run by itself. It requires the ignition to be turned on but then only runs for a few seconds unless the starter is engaged. Were you trying to start car with charger hooked up?
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Graham 85 300D,72 350SL, 98 E320, Outback 2.5 |
#3
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There is no question that gas entered the engine and is now in the crankcase. This was easily verified by checking on the dipstick - both by sight and smell. The gas leak was not caused by poor connections. Also, no one was trying to start the car. It would seem there had to some sort of malfunction, but the question is what.
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#4
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If your pump can run on its own, then I guess your injectors could somehow open too. But they should both be closed/off if ignition is off.
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Graham 85 300D,72 350SL, 98 E320, Outback 2.5 |
#5
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Sounds like a short somewhere - possibly in the ignition circuit, sending power to the D-Jet system and maybe other systems. The pump runs during the first key-on for a few seconds to pressurize, so an intermittent short could cause that cycle to occur a lot - as well as the opening of the cold-start valve for cold starts - which can cause gas to go into the manifold and then eventually into the engine. Same if the injectors leak or are getting a false signal.
Check your wiring, starting with the ignition switch. Then check the EFI harness. Check all ground connections, also.
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Current: 2021 Charger Scat Pack Widebody "Sinabee" 2018 Durango R/T Previous: 1972 280SE 4.5 2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi" 1999 Chrysler 300M - RIP @ 221k |
#6
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good points guys, this COULD not happen without power to the pump and CSV, Key left on or ignition switch short
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Ron 2015 Porsche Cayman - Elizabeth 2011 Porsche Cayman - Bond,James Bond Sadly MERCEDESLESS - ALways LOOKING ! 99 E320 THE Queen Mary - SOLD 62 220b - Dolly - Finally my Finny! Sadly SOLD 72 450SL, Pearl-SOLD 16 F350 6.7 Diesel -THOR 19 BMW X5 - Heaven on Wheels 14 38HP John Deere 3038E Tractor -Mean Green 84 300SD, Benjamin -SOLD 71 220 - W115-Libby ( my first love) -SOLD 73 280 - W114 "Organspende" Rest in Peace 81 380 SL - Rest in Peace |
#7
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You need fuel pressure to make any of this happen so the pump would need to be running. Once the pump is shut off ( assuming that it is ) fuel pressure starts to drop slowly if all of the check valves are working, or rather quickly if they're not working. It wouldn't be a lot of fuel if it happened one time but repeated cylcles would add up.
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#8
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Waiting for the NHTSA recall to be issued on 1972 350SLs.
All 24 owners of running cars will have to be notified.
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Looking for Early 108 windshield surround wood in decent-to-good condition. |
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