Problem: crank the car in the morning and w/ a couple pumps of the gas pedal, it fires up. runs a lil high at first then idles way down. as the day goes on, it starts to run rough. rough, as in, its hard as hell to crank and once i get it cranked, it dies. i have to pump the **** out of the gas pedal for it to crank. only time it runs good is in the morning. i've set the timing and did a complete tune up: cap and rotor, plugs and wires, changed oil twice, fuel filter, coolant temp sensor, fan relay, thermostat, rad. cap, coolant flush, fan switch sensor. any ideas? thanks in advance.

 

BUMP

 

im not too sure about this year but i have the same issue with my 83,if its not yu pump going out then the only thing i can think of is that you are vapor locking win the engine gets hot,basically the fuel line runs near the hot spot of your engine block and over time the fuel line thins out and win it does every time your engine gets hot it turns your fuel in the line into actual gas b4 it can reah the engine so now your driving on fuems basically and once you shut her off u gotta go thu hell to get her to fire back up.alot of hot rod drivers use wooden close pens to seperate the line from the block because they ake in heat

 

Actually, doesn't sound like it could be anything like what happened with your '83.

You say you have the TBI system. If so, pumping the accelerator does absolutely nothing. It's not like a carb that squirts fuel into the intake manifold when you pump the accelerator.

Problems that develop when the engine is warm/hot almost always involve electronics. The ignition module and coil are the two most common culprits. Next in line is the fuel pump.

You didn't mention it, but can we assume you aren't getting an SES light when it starts acting up? The ignition module, coil, and fuel pump can go bad without turning on the SES light.

 

im not getting an SES light when its acting up.

 

module is good. tested 5 times.

 

Tested hot?

Coil tested?

 

it wasnt hot. i hadnt cranked the car all day. after he tested it, it was hot. havent tested the coil yet.

 

Just turn the key to "ON" and listen for the fuel pump to hum for 2-3 seconds, THEN, and not before, turn the key to "START". This allows the fuel pump to prime the TBI for starting. If all else is good , the car should fire up in 2 or 3 cranks and idle at 1200-1500 until it warms up (open loop).
If the car starts to run poorly when the idle is low (closed loop) you have a problem with your O2 sensor. If it's original, replace it with a GM unit.
Get back with the results.

 

fuel pump kicks on and car NOW Cranks up right away. before i took the module off to get it check, it didnt crank up right away. the module tested fine so its still the same one. weird!!

 

ok, back at it. the module is fine, the fuel pump is fine( i hear it kick on). havent tested the coil. I'm not sure it is the coil. my problems are when i first crank it in the morning and start to drive it. by that i mean it studdords on take off and takes a few minutes to catch and go. after a few hours of driving, its hard to crank. I know five7kid that you said pumping on the gas doesnt do anything because of the tbi, but when i do pump on it i can tell that it is helping. it really seems like it is pumping gas. could the problem lye with the injectors or fuel pump (even though i hear it kicking on).

 

BUMPer

 

BUMP

 

http://www.chevyhiperformance.com/pr...5ci/index.html

Check out that article on here. I dont know much I assure you!

There was something in that article that they changed the mechanical pump! I would check to see if you have a mechanical and electronic pump. I do have experience with replacing a fuel pump in my friends 89 Firebird.

My friend checked his pressure to make sure the fuel was getting to the engine. It was such a low pressure that he not only replaced the pump but the lines also all the way to the injectors to account for the upgraded 350 we put in the Firebird to replace the weak 305.

Maybe this helps but let us know what you come up with! Maybe a throttle sensor or air flow sensor or fuel filter or something dunno GL!

 

well, i bought a fuel pressure gauge from auto zone and hooked it up. this particular one, you have to plug it "inline from the tank to the fuel filter". anyways, i turned the key on and off 3 different times, a couple seconds in between each one to reach max fuel pressure(40-47 according to manual). i heard the pump kick on each time. the needle in the gauge didnt get above 4 psi. then i cranked the car thinking it would go up. it didnt get above 5. week *** fuel pump. solution: get a new pump. . anyways, thanks for all the advice folks. i really appreciate the help. part number for pressure guage i bought, cp7817

 

40-47 psi is TPI fuel pressure. TBI is more like 8-12.

But, 4 psi is too low.

 

thanks for the correction. i just double checked it and your right. ok, with it being just a lil low on the psi, could it be the pump still?

 

That's not a little low, that's very low.

Yes, fuel pump (assuming it isn't the fuel filter causing the low fuel pressure).

 

the adapter from the fuel pressure kit screws inline before the filter(tank-adapter-filter). the 4 psi reading was strait from the pump. i can always put the adapter inline after the filter(filter-adapter-engine) but i'm sure the reading wood be much lower. i'm starting to wonder if there was enough gas in the car. its just below an 1/8th tank, that is if the gas needle is right. i'll put some more gas in it later and try again. i'm leaving that adapter screwed in from now on. i just have to find something to cap it off with. it was a pita to install. i came real close to bending the fuel line so i could get them to line up.

 

Let us know how she runs once you get a new pump in her! I think she will run like a champ!

 

FYI
Pumping the pedal doesn't do anything thing for computer controlled engines. Holding the pedal down cause the ECM to disable the injectors to clear flooding condition.

Vapor lock doesn't happen with in tank fuel pumps, the fuel keeps the pump cool.

 

If the pump ends up being fine I would check a couple more things. The starter may be affected by heat; usually though I think this was an issue on cars with headers. The other thing would be if the sock in the tank is sucking up crap as the day progresses, and overnight the debris disperses back into the fuel/tank.

 

well, i added some more gas, almost a half tank. checked pressure again and it is still reading about 5psi. like i stated before, the inline valve is between the tank and filter so the reading is strait from the pump. weak pump, trash on screen? so as i have the time and another set of hands, i'm pulling the pump so i can see.