i have an idea that my fuel pump needs to be replaced, but i dont want to replace the pump to realize that it was never broken in the first place.

i have an 87 305 LG4 firebird, electronic pump...

can someone just tell me the things to check, like fuses and relays, and where its all located? i would like to check all that and then replace the pump...

thanks in advance for any imput!!!!!

 

ever find your answer?

i'd like to know myself.....

 

First why do you have a feeling it needs to be replaced? We need more info and symptoms in order to give you suggestions.

 

well i could tell you mine and maybe it could help him.

at idle the car holds at 45 with no problems. when you go to give it throttle especially when the car is under load it drops alot more then the normal 3-5 points.

i personally had two pumps. an in-line ati booster and a upgraded in-tank. however i think the in-line has been acting up working and not working without knowing it since the old engine didn't require alot of fuel i never noticed.

because of the in-line not working i think it caused the intank pump to work harder possibly burning it out. when i put the new engine setup in requiring alot more fuel i think the pumps just weren't able to handle it.

i removed the secondary inline pump and tried it with just the in-tank pump but the same thing happened. as much as i hate to see two 1 year old pumps have to be replaced i can't think of anything else that would cause the pressure to drop like that under acceleration if the pumps weren't bad.

 

no, i never got an awnser....

but, car starts, but wont turn over, and i am getting spark, so I figure im not getting fuel, so thats why i want to check everything like fuses and relays to make sure that its all correct or working before i replace my fuel pump

does that help any?

 

are you possibly missing a ground on the engine?

i had that problem on mine and was missing a ground........replaced the ground and she fired right up.

 

In order to see if it is indeed the fuel that is causing your problem, hook up a fuel pressure gauge to the fuel rail. Mount the gauge inside the car or on the wiper temporarily. Now drive and see what happens when u stomp it. Is your fuel pressure dropping? If your fuel pressure is not dropping then it is another problem. If the pressure drops, then the pump may be bad OR you may be losing voltage to the pump at open throttle.

 

That's a carb. It better not have 45 psi of fuel pressure. It should have about 3-5 psi.

What are you talking about?

 

do you have to drive the car (put it under load)? like i said with mine i could hook up a gauge and it held the 45 pressure nicely at idle but when you go to give it throttle by hand, especially when it's a decent amount of at least 2,000+ rpm then it drops considerably.

is there any way to tell the voltage on a pump without dropping the tank. it seems as if all indications are pointing towards a bad pump but i'd like to try all the easy stuff first before going through all that work again.

 

Does your '87 LG4 not also have a mechanical pump in conjunction with the electric pump?

 

i know i have fuel lines going down to the rear of the car and into the tank, so im sure i have an electric pump, but i never really looked to see if i ALSO had a mechanical pump too

what is the ground to the engine? is that the negative (black) battery cable on a battery by any chance?

my engine is a carb, so i should look, if i can, to see if i get readings of 3-5 psi?

well, i cant put the car under any load, i cant get it to turn over, at all. it will start and chug and chug, but just wont turn over.

but i would really like to know where are the fuses located at, stuff like that, so like kandied91z said, i can check the easy stuff and then start on replacing my pump, (or ground, what ever might cause the car to not turn over.)

i replaced the tiny fuel filter by the carb a month ago, but someone told me i might have a second filter, where the hell would that be located?

also, as somewhat of a side note, my younger brother tried helping me set my idle speed about a month ago, but instead he twisted the idle mixutre screw, and since the idle never adjusted, he turned it like seven times, the car ran fine for a little while, then a week a go it stopped turning over. i never returned the idle screw back to its orginal position, i didnt know where back was, 4 turns, 7 turns 12 turns.... might that have ANYTHING to do with the car not turning over? i also think that if i dont set the mixture screw back soon, other problems may arise, how do i adjust it to optimal mixture, how would i know?

thank you very much for the input!

 

Of course there are, that would be the usual way that fuel gets from the tank to the engine, regardless of whether the pump is electric in-tank, or mechanical on the side of the block.

The idle mixture screws are pretty much inaccessible on one of these carbs, unless somebody has removed the plugs that cover them. They are locatd on the front of the carb, in the base, almost touching the intake manifold. They have threads that are about as fine as frog hair, and they do almost exactly nothing. I don't even know why they bothered to put them there and put a plug over them and all that. They aren't how you adjust the idle mixture. If those are the ones you're talking about, tighten them all the way GENTLY, and back them out 7 turns from there, and then forget they exist.

If the fuel pump is the problem, then all you'd have to do to get it to start and then run halfway normal for a couple of seconds, would be to dump some gas down into the intake through the carb, and it will start right up and run until that is used up. Try that and see if it starts. Something tells me from your description that it won't though. If you can't make it run by supplying an alternate source of fuel, then the problem isn't the pump.

"Crank" is the same as "Turn over" and is what the starter motor does
"Start" is the same as "Run" and is what the engine does when it works right

So it turns over normally, but has trouble starting, right?

What is the choke doing? Does it ever open, after the engine has been running for a few minutes? Does it close normally when the engine is cold? Does the "Choke" light on the dash come on when you first turn the key to "On", and then go out when the engine RPMs get above 1000 or so?

 

Any large conducting metal body is ground. If you're asking how the pump gets ground, it may either connect to the chassis or come from the fuel pump relay which should be located in the driver's side corner nearest the windshield.

These carbs don't need any pressure to start. I have only an electric pump that I can operate with a switch for anti-theft purposes. Occasionally I forget to turn the switch back on when coming back to the car and it starts just fine but idles erratically, sometimes as long as 10 seconds depending on how much fuel is in the carb.

If you do have a mechanical pump, it's unlikely that both pumps are not working. Check and see if you do, it would be located on the passenger side of the engine near the front and the bottom.

Come back and tell us what happened after you've done what RB said.

 

well, i have four fuel lines going into the tank...
thats really all i can say for now, because it seems that i might have a mechanical pump and not an electric pump like i thought, so then how do i know if i have an electric pump? can someone tell me or am i going to have to take off the tank to check?
what does the mechanical pump look like? on the passenger side i have fuel lines and then it meets into a bunch of parts then the fuel lines go into the fuel tank.

well, the screw he tightend was on the passenger side of the carb, the car ran normal after he turned it, so i left it alone, if you say thats not the idle mixture screw, then do you know what it was? ill turn it back just for turning it back though anyways

i sprayed starter fluid into the carb and the car almost STARTED, so i will pour gas into the carb tonight after work

so i will also check up on the choke tonight to, see whats it doing.

and yes, the car CRANKS up fine, but it wont start, just crank...

sorry if i caused any confusion

 

Did he turn screw #1 or screw #2?

 

4 lines....

Main feed line, return line, line to the canister, and line to the little relief valve right in front of the left rear wheel.

You certainly have a mechanical pump. You may or may not have an electric one, I don't know that. The only difference from outside the tank, would be an extra wire, and a relay under the hood to power it.

Here's what a fuel pump looks like. The top pic is from above, looking toward the bottom of the block in between the coolant recovery bottle and the strut tower. The round thing at the upper left is the AIR system management valve. The bottom pic is from below, looking up at the front corner of the block.

 

I think i might have a different problem than i thought....

i diffenatly saw that i have a mechanical fuel pump, under the passenger side of the block, and now i am sure i DONT have an electric pump too.

i guess that makes replacing the pump easier, but now it might not be the solution to my car not starting...

i didnt see what the choke was doing, i was by myself, but i poured some gas in the carb and it still didnt start, infact, it flooded, most likely because i put to much in, so tomarrow night i will try again, and see if i can get a pressure reading and see if the lines are plugged or something.

but really recently, i rebuilt the carb, the water pump blew up and i replaced that, and then the check engine cable wire blew up, most likely because it shorted, which i never fixed

so could any of that be related to my car still not starting? this all happened with in a month ago, and a week ago is when my car stopped starting....

oh yea, and he turned screw number one, exept for my carb, the screw is on the top, not down towards the base, but it still looks the same

 

Sounds like the vacuum break screw. The next time you try to start your car, use a screwdriver or some other means to hold the primary air valve open while you crank it.