Author Topic: Anybody had this behavior from the fuel pump?  (Read 3796 times)

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Anybody had this behavior from the fuel pump?
« on: February 09, 2015, 21:32:34 »
I have a '67 250SE. Yes it's an SE but I became a member here because I couldn't find an SE forum and this forum is a treasure of technical information in addition to the BBB. Anyway, except for the body and some other minor parts the SE and SL are cousins.
I have the tall fuel pump. A few months back I had no problem, you could hear it whine the moment I switched the ignition. Lately I had problems starting the engine and I spent a lot of time checking injection and distributor. The problem was only the starting, once started the engine was fine doing it's warm up and running at idle and under load very well. That's why I didn't suspect the fuel pump. Finally I checked the fuel flow and pressure. I barely had a quart after 1 minute and the pressure wouldn't get higher than 5 PSI. And all of this only after a few minutes from switching the ignition on. I noticed that when I switch on I hear a short gurgling and then quiet. After about 2 minutes I hear more and more gurgling for 10-20 seconds that slowly turns into the normal whine. After that the car starts almost immediately. I had a voltmeter on the battery which shows a drop of about 0.5-0.7V when I switch on. That tells me that DC voltage gets to the pump motor. The fact that once started it runs fine makes me think that the pump part is relatively OK and not gelled up. It wasn't gelled up in September when it was starting fine, although it is in the 30's in the garaj now. I don't have any leaks at the pump. I have a feeling that maybe the windings or the brushes. I would have to get it up and replace the pump with a temporary pump from eBay while I see what's going on.
Anybody had this problem?


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Re: Anybody had this behavior from the fuel pump?
« Reply #1 on: February 16, 2015, 21:35:44 »
I haven't seen this exact situation, but it sounds like a blockage, possibly in the tank strainer.  There may also be a small filter in the pump's inlet that's blocked.  That would make the car hard to start until there's enough pressure to get a good squirt from the cold start valve.
Chuck Taylor
1963 230SL #00133
1970 280SL #13027 (restored and sold)
1966 230SL #15274 (sold)
1970 280SL #14076 (sold)
Falls Church VA


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Re: Anybody had this behavior from the fuel pump?
« Reply #2 on: February 17, 2015, 02:20:55 »
Welcome to the forum.

Like Chuck, I would suspect a dirty filter. Check also the one in the engine bay. Though a dirty filter would create problems mostly under load.