blunto

In trying to diagnose what seems to be a problem in my fuel system (no fuel pressure; needless to say my car won't start), I wanted to bypass the relay and other wiring in the fuel system by sending voltage directly to the fuel pump through the fuel pump prime connector.

This process seems simple enough, but before I diagnose a faulty fuel pump, I just wanted to make sure that I was correctly sending voltage to the pump through the connector.

With a fully charged battery, I used jumper cables with one end coming from the positive post and the other end clamped to a safety pin which I inserted into the fuel pump prime connector head. 1) Shouldn't this pretty much guarantee that I am making an ok connection?

Also, once this connection is made, it sounds as if my fuel rail is pressurizing, but my FP gauge shows no pressure. As soon as I remove voltage from the connector, this sound immediately goes away. 2) Is it possible that my pump is sending some pressure to the rail, simply not enough to be seen at the schrader valve, or should it theoretically do nothing at all?

Any experience with this procedure, pump replacement, or anything else related would be greatly appreciated. Again, I just dont want to jump to any premature conclusions before I replace my pump seeing as I'm low on $$$...

Thanks in advance

slopokrodrigez

Are you using a known good gage? Is it connected to the schrader valve or is it some type of inline gage? As long as you have voltage to the prime connector, the pump will be on so don't run it very long. If you have it running and it shows no pressure at the rails, the next place to look is right before the fuel filter. Disconnect the tube at the filter and start the pump. If fuel comes out then you may have a clogged fuel filter, restricted or even kinked line. If fuel doesn't come out, sorry but your pump is dead.

Last question, have you recently run the car real low on fuel and then gotten it filled up?

LPEdave

You don't just have a piece of regular wire you can use (one end on battery, other end on connector)? I presume the above works, but I'm not sure what the conductivity of a safety pin is...

Dave

Mtrhds94Z

Also, since you asked the correct way to do it, I highly recommend a FUSED jumper...

blunto

The gauge I'm using has consistently worked on my cousin's L98 C4; I just assumed it would be fine for an LT1, unless anyone has heard diff...

I am checking for pressure at the schrader valve by the way.

Right after my car stopped running I replaced my fuel filter because it was simple and cheap and my symptoms were a possible match. It was very slightly clogged, atleast compared to the new one, but nothing serious. While I was down there I checked for any visible damage in the lines but didn't see any.

I did run my car low on gas I think 2 days before my car died. I filled up my tank all the way from there and drove it down to about 3/4 of a tank. Good call slopo but what could that mean?

I questioned the safety pin rig-up too but I didnt know what else to use. I saw someone on the forum post saying they used a wire from their multitester--- I fried mine! (the wire) I don't have a fused wire but I'll try to get one if it makes a difference.

I was mostly confused by what seemed to be the trickle of fuel running through my rail when I hooked up to the pump prime connector. I'll check again for a kinked line but if it is my pump, any suggestions on whether to go from the bottom or cut through the hatch?

Thanks all for your patience...

Mtrhds94Z

Just a thought here you DID remove the 'valve' from the schrader valve with a tire valve wrench right?[unless the guage 'depresses' it, which I don't thin kit does..
Won't read anything with that valve in place..

smoknta

Every Fuel pressure guage that i've seen pushes the schrader valve down for you. Maybe not the ones that are ment to leave on.

slopokrodrigez

Well what we see every week is full tanks of gas with dead fuel pumps. When we question the owners, they tell us it had gotten real low on fuel and just filled up the tank. We theorize that the pumps are overheating since there is not enough fuel to cool it, then they blast the pump with cool fuel at the fill up. This ends the life of the pump.

Also, I think Mtrhds94Z is right, try removing the core of the schrader valve before you put the gage on it.

Have you disconnected the line before the filter and tried the pump prime connector to see if you are pumping there?

Replacing the pump from the bottom is not hard at all BUT, it is a lot of work. And when ever you are removing a lot of hardware, you chance loosing or breaking them. I put an inline pump in mine and removed the tank pump by dropping it from the bottom. I vote for cutting the access hole.