Hey y'all, I have a T/A with a factory LG4 which is, as far as I know, stock.

I had a no-start issue that I fixed with some new battery leads (thankfully), but as we were fixing some vacuum leaks... the mechanical fuel pump gasket blew and sprayed gas everywhere. Well, we decided to replace the mech. pump and after several struggling hours of getting the pushrod to stay up it was in. Tried to start the car and heard no electric pump noise... This is where the fun begins.

What I have found so far is:

• A disconnected small lead from the battery that was stopping what I think is the fuel pump priming (rapid clicking when you key on). Re-connected that and hear the clicking again.

• No power going through the purple wire to the fuel pump relay. I can send 12V directly into the tan wire to the pump and hear it kick on, this makes me think the elec. pump is still physically good. The issue is that I read 12V on the battery (duh), batt -> starter lead, and the little wires on the starter that go to other parts of the car. I do not read 12V on the pins for the "CRANK" fuse that sends power through the purple wire to the relay. I read 12V on every other fuse (iirc), just not that one. First question: Where the hell could I be losing continuity here that the fuse box doesn't read 12V only on this one fuse??

• The car will start and idle high with the choke after priming the elec. pump a little bit. But after about 10-30 seconds the RPMs will drop pretty fast and it dies, no saving it. It also does not respond well to throttle inputs. So aside from the electrical issue, I know the elec. pump is good and can send fuel up front by holding 12V to the tan wire while a buddy starts the car. But even while holding it the car will die after 10-30 seconds. Second question: Could this be a sign that we somehow installed the mech. pump wrong still? Or is the fact that it'll fire up proof that at least that pump is okay?

We replaced the spark plugs in 6 out of 8 cylinders before the mech. pump blew, but said screw it to the two impossible ones in the back for now. Surely this can't be a reason it dies after starting, right? I haven't pulled a plug to see if it sparks, but I don't hear misfire for the short while that the car is alive.

Apologies for the word count, but I figure it's better to get the info out there than leave a bunch out. I appreciate any help with this that anyone can give! I can also clarify anything that isn't clear.

 

I think with the lg4s with the dual pumps the electric pusher pump in the tank is just designed to push fuel to the inlet of the mech fuel pump. I think if the electric pusher pump is completely not working, the mechanical pump still is able to pull fuel through the electric pump and give fuel to the engine properly, it is just much harder on the mechanical pump without the help of the pusher and shouldn’t be left like that permanently, some people replace the electric pump with a rubber hose to the bottom of the tank, so the mech pump isn’t having to suck fuel through a non working electric pump, but the engine should still be able to run and drive properly with just the mechanical pump. If the engine is not running properly like you said, I don’t think it would be an issue with the electric pump not working unless the pickup is clogged or something like that. Cause as said earlier, the mechanical pump should be able to pull enough fuel through the electric pump.

 

Also did the car run fine after you replaced the battery leads, but before the old mech pump started leaking fluid?

 

If the pusher pump quits the mechanical pump cant pull enough fuel through it. Remove the stupid pusher pump from the tank run an old style pickup line and problem solved. Went through this years ago

 

Yes after we replaced the battery leads we were fixing some vacuum leaks and it ran great! Better than it has since I bought it. Then the mech pump starting leaking and after replacing that it won't stay running. I have to check if it's pumping fuel because I guess the pushrod could have fallen, even though I was sure we got it right.

 

The issue is that I can put power directly to the pusher pump and hear it kick on. But when we start the car even keeping power to that pump the car won't stay running.

 

Its wore out most probably so dont go through the trouble replacing it when you pull it. Manual fuel pumps by themselves have worked forever.and you dont have to pull the whole rear end and fuel tank out to change a manual pump so save yourself some trouble down the road. Possibly something wrong with the manual pump you put in also but thats a rare occurence..Could be though..