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Old 04-20-2001, 04:10 PM
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Join Date: Feb 2001
Location: Saint Marys Ga
Posts: 103
I have a 1972 300 sel that is pumping out so much gas that the crankcase is filling up! several mechanics have tried to diagnose the problem (pressure regulator.elec problem,"brain box".no solution yet.any ideas?
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Old 04-20-2001, 04:48 PM
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Join Date: Dec 2000
Location: Long Island, NY
Posts: 3,677
Fuel gets in from exactly 2 places...

1. The cold start valve.
2. The injectors.

Most likely, you have something stuck open. Alternatively, you have a wiring problem.

Tools-wise, you have to invest in

1. 2 fuel line cut-off clamps. About 6$ at the nearest pep boys.

2. A pressure guage that will read up to 40psi. About 20$. Be sure it has (or be sure to also buy) the appropriate fittings to handle 5/16" fuel line.

3. A multimeter. If possible, the fancy digital automotive one from sears. I like that model. It's also available from JC Whitney.

Now that the weather is warm (at least here it is), disconnect the fuel line from the cold start valve and put the fuel pressure guage in its place. Turn the key to activate the pump (no, don't start the car) and then turn it back off. The pressure should hit 32psi the instant you hit the key, and it should stay there for a while.

If the pressure drops "quickly" (as in less that 30 minutes), the next step is to block the return line with one of the clamps (the return line is the one that comes off the damper). If it still drops quickly, use the other clamp on the other line.

If the pressure STILL drops, you have a leaky injector.

The problem may be electrical. For that, you need the dianosis procedures in "the book" (engine manual).

Long ago, I prepared a .zip file with scanned pages from several print sources. I send this file to anybody in your shoes. Send me an email ( and I'll reply with the file attached.

Your last shot is to start swapping parts. That's expensive and will not get you far.

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Old 04-23-2001, 04:32 PM
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Join Date: Nov 1999
Location: Matthews, NC, USA
Posts: 133
I had a fuel pump relay malfunction (shorted out) and then burned the wiring harness. The burned wiring harness caused the fuel pump to run continuously until all the fuel was pumped into the crankcase on my 1986 300E.

Hope this helps
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