on my 91 bird, 305 tbi it wont fire now. i had put the car away a month or more ago, and i went to just fire it up recently and nothing, it ran fine when put it, but i left it with very low gas. It runs if you dump a little gas down the throttle body. when i turn on the car i dont hear the pump at all. could the line be frozen or pump be frozen? or cold the pump just could of went out on it? how can i tell for sure before i rip it all apart. thanks

 

also before i put the car away, my oil pressure gage would be really low, even when flooring it. anyone know about this??

 

When mine did that it was the fuel pump. Apparently if you try to start our cars when there out of gas it doesn't take too long before the pump burns out.

 

Check for power to the fuel pump connector, if you are getting power to the pump but it still does not run then there is little else it can be. Make sure you have gas.

The in tank pumps use the fuel to keep them cool, there is a wrapper around them that soaks up some fuel to keep them cool when you are low. If you run them too long on empty, it can and frequently will burn them up. Plugged filters make them run hotter than usual and will shorten their life as well.

 

alright, well i had put 3 gallons in though. another possibility is a mouse could've chewed the wire/s. could it possibly be the oil sending unit that could be causing it to do this?

 

The symptom of a bad sender is that the car dies after starting. Cranking causes the pump to run, oil pressure keeps it running.

Checking the power at the pump answers the question.

 

it never dies. but ill have to do that this weekend, i dont have a manual though. how do i check the wires to the pump?

 

well i did the by pass thing where u find the red wire with a connector on the passenger side. and i put the wire in it and the pump turned on, and then i tried starting it while someone put it on there and it stilll woulnt fire. anyone know what it could be now?

 

Just correction.. the sender is for the gauge.
The oil pump switch is a failsafe for the fuel pump. It has zero to do with the fuel pump running unless, the relay has 'bought the farm' (died).

The oil pressure switch can be omitted from the harness and the fuel pump will run.
The fuel pump relay is switched by the ECM and stays that way as long as there is a tach signal to the ECM (read: the engine is cranking/running).

THe oil pressure switch is a very common misconception about saving the car if the oil pressure drops below 'X'psi (3-5psi is when it closes btw) or making the fuel pump run.

It, the oil pressure switch, is only there to assure the pump will keep running in the event the relay fails.

 

well today i was working on it and i took the gas line off right by the tbi, by passed the fuel pump and fuel sprayed out. then i went and bought a new relay ( the one by teh drivers side firewall, there is two) and put that in and still no start. i also checked the fure down by the batter the 20A one and it was blown so i switched that and still no start. its also got spark and everything. what could be wrong now?

 

anyone have a clue?

 

Did ya change the filter?

 

how old is that gas?

 

no didnt change the filter. but the pump isnt priming when i turn the key so i dont think its that. and the gas was new, it was pretty low, and the car was sitting a month and i tried starting it. no start. so i put 5 gallons of new stuff in adn still no start.

 

Have you tested the pressure ? Pushing it out the unrestricted line and building pressure are two different things.
Have someone crank the engine and observe the spray from the injectors. Or, just make sure the injectors or even pulsing (they are on a fused circuit).

The pump should be priming for 2 seconds when you turn the key to the 'run' position. You should also be able to hear the relay switching. There is no fuse for the relay (excluding the 20A under the hood which is power to the pump & ECM), the ECM controls power and ground for turning the relay on/off.

This just recently happened to a friends truck I put a TPI on. He let it sit for a period and the pump went to the the great beyond. The pump will run just fine (audibly since the tank is in the cab) and fuel will come out the schrader valve on the rail (not impressivly) but, 1-2psi at the rail doesn't do much for a TPI trying to start.

 

alright. well it has no prime when i turn the key. only way it primes is if i jump the red wire for it. and even with it primed by hot wiring it, it still wont start. where is the relay located for the pump, is it the one by itself on the passenger side, or is it one of the two on the drivers side next to each other. yea i just had the line diconnected and it sprayed out. do i just take the air cleaner off and look down there to see if fuel spits out or what?
thanks

 

try reseating the ecm connections. drop the ecm and physically disconnect the ecm for few minutes and reconnect it. see if will prime then.

i had the same problem with the tbi in my 89 and the ecm was at fault.

 

alright, where exactly is the ecm located. i need to get a manual for it.

 

passanger side. right above where your feet would be. there should be (3) - 7 mm screws holding the plastic cover in place. once the cover is removed you will see an aluminum box with a **** load of wires attached to it. that is your ecm (engine computer).

 

ok sounds good, i will try that this week. messed around today with it for a little bit and i had a friend try to start. i took off the air cleaner and look down the tbi and i didnt see any fuel spraying in, is that where you look?

 

Yes, you should see some fuel spraying (in pulses) at the throttle blades.

 

well even with the pump prime jumped, i still didnt see any fuel spray in. im thinking its the fuel pump.

 

alright well i pulled the ecm down and unplugged it for about 5 minutes. i plugged it back in and still no prime.

 

when you turn the forward watch the ses light carfully. does it blink once before staying on solid? or does just turn right on without blinking?

 

sorry i went down to see the light what it did, but i left the hatch open so the battery was almost dead. which light is the ses. i was getting the securty light and another red one. which one is the ses?

 

SES = Service Engine Soon(Orange Colored Indicator). if it's not even coming on at all, and ALL the fuses have been checked then the ecm is bad.

 

well i know right before i had put the car away. the light would come on sometimes and go off. i dont have a cat though so it could be from that. last night even though the battery was almost dead. that light wasnt coming on.i know there was a 91 or 92 firebird at the junkyard with a 305 tbi in it. would that ecm work?

 

i got a different ecm and put it in my car and still has no prime. i also checked again and no fuel spraying out of the injectors at all. when i primed the pump fuel shot out of the hose when i disconnected it from the tbi, so could the injectors be plugged or what?

 

im going to try putting a new fuel pump in on tuesday, so i will see what that gives me.

 

keep us up to date. i would hook up a test light to the injector harness and see if the ecm is even pulsing the injectors.

 

i took the plug in off the injector, and i put a light on it and had power. but with the pump primed, im getting fuel up to the injectors, but i think the pump is bad where it isnt pushing fuel through the injectors.

 

you will ALWAYS get power to the injectors. The ecm just pulses the ground. The pin with no power to it should pulse to ground as you crank. Verify this with a light.

 

alrigth so when i try to crank it have a light on it?

 

im ready to take this car to the scrap yard lol. i put a new fuel pump in it tonight and still nothing. i checked alot of stuff and here is what i came up with. i am getting power at the back of the car at the pump connection, but i am not getting power at my relay. in my manual it shows it could be a wire, or a oil pressure unit. anyone experience this? the new pump sounds ALot stronger

 

I'm in the same boat, everything is in good working order but the injectors are not pulsing. Is it true the vats will not let the motor turn over if it is bad? Some where I read the vats controls the injector pulse and the starter. good luck

 

well i have no clue, i was reading in my book and i see on teh diagram and i saw this "Fuel pump/Oil pressure switch sender" and a guy told me it could be that and when that fails you dont get power to your fuel pump, which i am having troubles with cause of the no prime. only when its by passed i get power. how much do these cost?

 

Refer to the first post I made in this thread.

If you have no power at the relay (on the lead, 12-14ga wires, in or out), you shouldn't have power at the rear, unless you're cranking the engine.
Then, while cranking, if your oil pressure switch is working, you will have power to the pump even though the relay is dead.

If you put a test light (or analog multimeter) across the wires on the injector(s), it should pulse while cranking the engine.

Have you checked your ECM fuse under the dash btw ?

 

I wonder if perhaps your injectors are dirty or clogged. Try taking them out and cleaning the filter.

 

where is the ecm fuse, i didnt know there was one. if i can remember right i was getting power to the back of the car when i had the key turned on, i was getting it at the middle wire.but none at the relay. i i will look at it tomorrow and write down what im getting, sorry about the confusion. thanks

 

ECM fuse.. (check attached image)

I'll admit, I am a little confused as to where the power is comming from in the wire to the FP. The only branching it does is under the hood.
From the bulkhead (at firewall) to the pump, there is just one wire.

 

thanks, ill test this out today and see before i go to work. is it a problem with the 91/92 305 tbi cars. i see alot of people that have issues with almost the same stuff i do.

 

the ecm fuse was good. i didnt mess with it to much because its in the -'s right now. i am going to give it a few weeks when it gets warmer, and let it get off my mind cause its pissing me off.

 

i was having the same problem i changed the fuse and my injectors are pumping but it still doesnt want to run

 

i changed the opsu today and still no prime when i turn the key. it must be a wire??

 

im having the same damn problem

 

are you sure it isn't the vats ,cuz that what mine did ,it cranked over and everything but the injectors wouldn't fire.i bypassed the vats and it started.

 

I have an 88 305 tbi and have the same problem.no injector pulse and no fuel pump prime.what is the vats? how do i by pass it?

 

To clear up any confusion - VATS (Vehicle Anti Theft System) disables the injectors AND starter. So if you CAN crank, it's not VATS.
And if your fuel pump doesn't run, it's not VATS either because it doesn't control the fuel pump.
So those would be unrelated problems.

Lou

 

i did not know that thanks