Fuel and Ignition Fuel Pumps and Systems, Ignition and Spark Systems

Fuel delivery problem

Old 02-17-2010, 01:29 PM
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Fuel delivery problem

I have a 1984 Z28 w/a 350 SB (300 HP) & Edlebrock carb. I purchased a new a fuel sending unit locally (O'Reilly's) for a 1985 model as 1982 - 84 are not available any longer from a Chevy dealer (considered absolete for these years). The tank is also new & holds 15 gal. but I can only get about 10-11 gal. used (approx. 3/4 empty) and the cars acts like it's out of gas. I've tried a few things and am stumped as to the cause.

Also, anyone know why Chevy used block mounted mechanical AND tank mounted electric sending units at the same time? It is to get ready for the EFI systems that eventually came to be standard equipment? Just curious.

Anyway, all suggestions/troubleshooting techniques would be greatly appreciated. Thanks.
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Old 02-17-2010, 05:52 PM
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"Sending unit" is the term usually applied to the level sensor. Is this what you are asking about? Or are you calling an electric in-tank fuel pump a "fuel sending unit"?

Looking at my Chilton's it shows the the carbed 3rd Gens use only a mechanical pump, bolted to the block. MPFI, Cross-Fire and TBI used in-tank pumps. Is it possible your setup was converted to a carb at some point?

Last edited by Injuneer; 02-17-2010 at 05:55 PM.
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Old 02-19-2010, 03:51 PM
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The sending unit (I'm referring to the whole in tank "assembly") has an electric pump as well as the float arm and what not as an integral assembly. I'm wondering if the arm's sensor mechanism might be bad in some way. The block mounted mechanical pump is also brand new and I don't suspect it to be bad at this point. Problem is taking it (the tank mounted unit) out. I have to cut out my new muffler and part of the exhaust line to drop the tank. At this point, however, I'm stuck and not real sure what to do.

I've done a lot of research prior to listing this problem and from what I've ascertained, Chevy did not have fuel injection for the Camaro in 1984. I believe some of the late 85's had it as an option and I know it was either optional or standard from '86 and beyond. This is actually my 2nd '84 Z28. I had one when I was younger and it too had the same setup, block mounted mechanical (& carbed) and in-tank electric pump included with the sending unit assembly.
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