Fuel pump, again. For now I'd like to just simply switch out my electric pump/sender and put in a mechanical sender out of a carb'd monte. Again the car is an 87 LS w/a fuel injected 4.3. I cant find anything to tell me if my exsisting fuel lines will hook right up to a mechanical sender or not. I did a little research and figured out my electric pump won't run without the ecm. And I also can't find any different part numbers for with or without fuel injection. Does anyone know about this?
What exactly are you trying to do? Are you trying to run a 4.3 V6 with TBI on a mechanical fuel pump, or are you trying to swap something else into a TBI car or just eliminate the EFI on the V6? Your post is not very clear.
Well, I can try to take a stab at this from several different angles. First off, you CAN run the in tank electric TBI pump with a carb. You will need to run a regulator like the cheapie Holley regulator they package with the electric "Blue Pump". This is necessary because a carb needs 5-6 PSI, and the TBI is 10-15-- too high for the needle and seat. Without the regulator, it will flood the carb. The pump will work just fine with the computer removed, it is after all just an electric motor, so it needs current to run. How I would wire it would be to use a 2 pronged pressure switch that is on under pressure and off without pressure. This way, you do not need to switch it on manually, and you can have either the ground side or the positive side of the relay's electromagnet switch. (If you run it as positive, have it as a part of a switched circuit that is hot both in run and crank. Just don't combine 2 circuits together to get this effect or you will not be able to disengage the starter!) The car will start fine with no fuel pressure, and you can jump the switch with a wire (or add a switch to a secondary power or ground source so you can do it on demand) if you need to prime the engine. It also would shut down the pump if the engine loses oil pressure from either a engine malfunction or an accident. All you need now is a filter, some hose and a hard line to get fuel to the regulator, and then on to the carb. This sounds like a big PITA, but it is not really that bad. In fact, Chevy offered a kit a while back that did this in a 3g F body with a ZZ1 350. If the fuel line is on the passenger's side of the car, you could do a similar setup with hose and such to make it pure mechanical as well. The in tank pump presents the biggest issue as I do not know if a standard pickup will fit in the place of the TBI pickup. I am sure someone else will know and post it though, if you do not like my solution. I tend to believe keeping the TBI's pump will require the least amount of work and modifications. You don't need to touch the gas tank, or the chassis lines that way, and you are just left with some simple plumbing and very minor wiring. If you need me to, I can post how to wire a standard DIN relay.
If you buy a new Covette what does it come with.. thats right an in-tank electric pump because its better safer quieter and more reliable. Its an all win no downside situation. Don't spend more to do more work to go backward as some do just because they don't make the effort to educate themselves. Which in this case won't take a lot. I recommend the Malory MAA-4309 adjustable return style fuel regulator as seen on www.jegs.com or Summit websites. (just do a search on maa-4309) That and and an electrical power supply switch as mentioned by 85Cutty should be all you need. You can also check out www.racetronix.com Click the Buick Grand National link. It shows a drop in replacement pump etc but also lists a keyed hot wire switch (G-body upgrade wireing harness) for saftey and a dramatic improvement as to what your pump can & will supply fuel wise. They sell that for $40. The Mallory fuel regulator is $78 but you are done and its safer, quieter, less expensive, and more dependable than an out of tank electric with sump or cell and will easily supply a constant supply of cold fresh fuel. Almost none of the old school cars run an in tank electric because they did not come with baffled/bucketed tanks, the needed hanger, return line etc. but some G-bodys did. I have run this system on my Cutlass with a 509ci motor and Q-jet carb for years.
alright, I told you I'd be back. So I ordered the fuel pressure regulator you recomended and the fuel pump harness with the upgraded body ground. For now I'm just going to get everything working, and togeather I'll prolly just have a Q Junk to get it all going. What kinda psi do I need to make it happy and not blow it apart???
FWIW IMO their is not a better carberator for a street car than a professional rebuilt Q-jet. I had an 800cfm electric choke unit redone by The Carb Shop in Ontario Calfornia. It was done right for my car/setup was inexpensive and was almost perfectly dialed in out of the box. (They always set them up a little rich as its safer so less warranty work for them) The car weighed 3840lbs with me a full size spare fuel etc ran 110mph in the quarter got 17mpg feading a 509 and is very responsive even at part throttle.
I put a T fitting between the regulator and the carb with a short hose going to a fuel pressure guage. This way I could set the guage under my wiper to check my fuel pressure while driveing or slip it back under the hood when I don't want it under my wiper. Through the whole quarter mile blast it would hold steady at the 5.75lbs I had it set at. Have fun and keep us posted.
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