240zip Posted May 13, 2011 Share Posted May 13, 2011 I have a set of triple webers, a filter king fuel filter, and some fuel pump which I don't know the name of, but it makes a rumbling noise in the back. I have a wideband A/F meter and also a fuel pressure gauge in-line after the fuel filter. At idle, the gauge shows 3psi and then when I start it drops nearly to zero. The A/F ratio is about 9.8 at idle and then under load it can jump to 14 or even 16 / 18. I pull off the gas if it goes up that high. The filter has a glass bowl so I can see it's only getting 1/2 full. My gut tells me the fuel pump is bad. It's the only thing in the set-up that's old. But I'm not sure if those filter king fuel filters are supposed to be 1/2 full. I'm pretty sure they'll work with webers as I've seen them in pictures of vintage race cars with triples. Any recommendations on where to start? Quote Link to comment Share on other sites More sharing options...
mark Posted May 13, 2011 Share Posted May 13, 2011 Check the voltage at the pump. Quote Link to comment Share on other sites More sharing options...
mark Posted May 13, 2011 Share Posted May 13, 2011 (edited) double post Edited May 13, 2011 by mark Quote Link to comment Share on other sites More sharing options...
30 ounce Posted May 13, 2011 Share Posted May 13, 2011 Does your Z have the filter by the tank (next to the electric pump) like the 260z has? Mine would get clogged often with rust before I had the tank cleaned and coated. 9.8 is exremely rich at idle and 16 is pretty lean... Quote Link to comment Share on other sites More sharing options...
twofouroh Posted May 13, 2011 Share Posted May 13, 2011 If you have the stock electric pump in the back there are 2 filters back there - 1 before the fuel pump, and one IN the fuel pump. Also, the stock rear electric pump was not meant to pump enough gas to run on. It is there to help get the mechanical pump primed - long story short, you need another pump up by the motor if it's the stocker in the back. Quote Link to comment Share on other sites More sharing options...
240zip Posted May 14, 2011 Author Share Posted May 14, 2011 I'm going to get the Holley red and replace the pump in back. Quote Link to comment Share on other sites More sharing options...
30 ounce Posted May 14, 2011 Share Posted May 14, 2011 That's what I'm using with the stock electric pump in back. Works great! Quote Link to comment Share on other sites More sharing options...
240zip Posted May 14, 2011 Author Share Posted May 14, 2011 I'm not sure I get what you mean. You have the Holley Red AND the stock electric pump (both)? Why do you need both? Quote Link to comment Share on other sites More sharing options...
30 ounce Posted May 14, 2011 Share Posted May 14, 2011 I replaced the mechanical fuel pump with the holly red in the engine bay. The stock electric pump was not meant to fuel the carbs by itself. In stock form it sent fuel to the mechanical pump which fed the carbs. Quote Link to comment Share on other sites More sharing options...
240zip Posted May 15, 2011 Author Share Posted May 15, 2011 So if I block off the mechanical and then replace the OEM with the Holley red, shouldn't that work? Quote Link to comment Share on other sites More sharing options...
30 ounce Posted May 15, 2011 Share Posted May 15, 2011 Yes. If you are only going to use the holly red (without the electric pump by the tank) you'll need to mount it in back by the tank lower than the pickup point. It likes to push better than pull. You'll want to isolate it with rubber mounts as it's a bit noisy. Mine is mounted in front right wheel well and I can hear it. Quote Link to comment Share on other sites More sharing options...
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