Ok I have a 87 camaro that came from the factory with the LG4 carbed engine. My fuel tank has an electric pump in it and I read somewhere that this is used in conjunction with a mechanical pump that is attached to the block.

1st: What PSI does this electric pump put out?
2nd: Does the mechanical pump and the electric pump work at the same time?
3rd: Can the electric pump be used alone without the mechanical pump?

The LG4 is long gone and my 305 TBI engine from my 92 RS is sitting in its place. Stupid me didn't know there were actually 2 pumps being used and thought that I could run my TBI off this pump that is in the tank since carbs and TBI run low pressure. Will my TBI run with just this pump or will I have to drop the tank (pain in the a$$) and install a TBI pump?

Thanks

If I remember I'll take a look in my manual tonight, but I believe they only put out about 3 psi.

Mark

1st: Doesn't quite work like that. The mechanical pump has a bypass mechanisim with a return line that keeps it ar abour 3 or 4 psi.

2nd: Yes they do.

3rd: Nah not really.

Ok, so if I put a mechanical pump on my TBI engine, will it work just like the LG4 did? Would I be able to go that route instead of dropping the tank and installing a TBI pump? Do you think that would casue problems with the TBI computer?

Thanks

lol no...you can't run a mechanical pump on a TBI motor. You're gonna have to drop the tank and put in a TBI pump.

isnt the dual fuel pumps over kill? Could I use an ordinary mechanical on my carbed lg4 it to is a 1987

yeah..it is. not entirely sure why GM did it that way.

might be able to. try it..if you have fuel starvation problems them replace the in tank pump with a piece of hose.

I think they had a mid year change and went to tbi and had the redundancy of having too pumps in other words it would have cost too much to remove the the mechanical pump I guess

nah TBI came after...and they did eliminate the mechanical pump.

Did all lg4s have the electric pump? I have an 85, and wasnt sure if it had an electric or not. I never heard it when I turned the car on, but never really paid attention.

Ben

Momar - I think it was only the 87's. I know mine doesn't. I've seen numerous LG4's in junkyards and 2 had electric pumps - both 87's. Then I saw a LG4 buildup awhile back in a mag with one, and this guy has one...

Jester - the more modern TBI (not CFI) was introduced in 87, not 88. 87 TBI's were California cars, BUT most cars ordered out of CA come with CA emissions.

mark, thats true about the TBI, but you cant really count that as when TBI debuted. i mean, the iron duke was available in canada for 2 years before it was in the US. in 86 they had 50 L98 cars but the L98 was not made available until 87. the RS was available in 87 in california only...it became available everywhere else in 88....though technically it was available in cali in 87...

do you guys know if a TPI pump will fit the sender from an electric LG4 pump?

I want to revive this only for the sake of the previous question. Can anyone answer this: will a TPI pump fit in the LG4 sending unit (with the electric assisting pump)?

Yep, I put in a Walbro TPI pump and it fit the LG4 sending unit. The only modification I had to do was cut the hard line a little shorter to accomodate the longer pump. I made a little page about it here:
http://ukrainetrain21.tripod.com/ukrainetrain/id21.html

Excellent, thanks for the great info! I was 99% sure it would work, after cross-referencing parts from this HUGE book on fuel pumps at autozone (the kid was actually very helpful, I was impressed for him working at Autozone ). Anyhow, I'll be using a stock intank pump, but not for a TPI. It's actually from a 2000 350 truck, I think the specs were something like 60 or 65 gph at 90-100 psi, I think they had a TPI pump rated at around 30-35 gph at 65-95 psi, IIRC. And for them being just about the same price I think this pump will work fine!

Anywho, thanks again!