hey guys i bought this 82 trans am with the 305 cfi about a month or so ago , i was running great no problems then a it started to feel like it was loseing power while im driveing i step on the gas an it kinda bogs down then slowly starts to pick up rpm's then goes , i did a complet tune up cap rotor wires , fuel filter air filters , even when its sitting idleing it seems slightly hesistant , i hook up my obd scanner to it an it links up but tells me theres no codes , i just replaced the distributor with the ingnition module an pick up coil but it didnt help at all o also cut the cat off an added a straight pipe an still no luch , u guys got any ideas ?? i need some major advice

 

Check fuel pressure, spec is 9-13 psi.
Check the ignition timing, make sure it advances when you rev it.

 

if it where the fuel prssure wouldnt it act like that even when its sitting in park ?

 

Dont take anything for granted, if you work on an efi car you need to have the ability to check for proper fuel pressure.

 

yeah your right well ill check the timeing an the fuel pressure , i just dont think it could be the timeing seeing how when its in park it runs great just when im moveing it seems like theres no wpower then it slowly gets up

 

Definitely check fuel pressure.

 

well ill defenitely check the pressure , u guys really think that ,that would cause this problem ?

 

ell guys i checkt the fuel pressure an it way off it barely makeing 6 psi , so ill be droppen a new pump in on thursday , thanks for the help

 

If you can pinch off the return line at some point in the system, then test the fuel pressure again, if its high, then you probably have a bad regulator.

 

well actually both pressure regulators are new along with the injectors

 

I would be leaning towards changing the pump but you need to check the fuel pressure with the return line open and then pinched off. Just like ex-x-fire has a been telling you.

 

Excuse me chiming in here. The regulator(s) determine fuel pressure. The return line carries the excess fuel from the regulators. Pinching off the return line will dead head the pump. While this is useful for testing the maximum pressure capability of the pump, it has nothing to do with the regulators. The pressure reading with the key on engine off, and with the engine idling, then at throttle snap are tests of the regulators and a general function test of the pump.

To test the pump itself, first test pressure on the supply line as described above, then detach the supply line, attach a hose to the open end, and perform a free flow test. The pump should flow 1qt in a minute with no decrease in flow over time. I cannot find a dead head pressure spec for the low pressure TBI pump, but I would expect the TBI pump to support at least 25PSI. Do not run the pump dead head for more than 20 seconds.

 

ex-x-fire's advice was sound. Pinching the return line IS doing a "dead head" pressure test of the pump...and it's WAY faster and easier to do than the way that you described. Furthermore, IF the FPR has failed and that is causing your low pressure (unlikely in this case), then pinching the return like will reveal that with an instant spike in pressure. It's proof that the PUMP is capable of building a head...and that the regulator must not be providing the proper restriction to flow. Fact is, Statistically CFI pumps are shitty and that is the MOST likely problem given that the OP has already verified lack of fuel pressure.

TO THE OP: when you are satified with your diganostic process that it is indeed the fuel pump, please replace with a pump designed for use in a multi-port EFI system; they are a better design, will last far longer, and also meet future demands of upgrade/mods...all while costing about the same amount. A "TPI pump", an "LT1 pump", or any pump built for those or similar applications.

Lastly, yes, an engine can and will idle fine and even cruise fine with a bad pump/low pressure; these are operating modes that use the least amount of fuel and tax the fuel system the least. Acceleration is when the most fuel is consumed and that is when lack-of-fuel symptoms will present themselves...just as they have here, in this case.

 

The only problem with pinching the return line to test the regulator is that it will overlook a restricted supply line or a partially clogged pick up. These are both common causes of low fuel pressure. That's why we test the pump for flow and dead head pressure, before we condemn a regulator.

 

I don't agree at all.
1. A clogged return would give you a high pressure problem, not the problem we have here.
2. The only way to diagnose a clogged pick-up is to remove it from the tank. Otherwise, you don't know if it's a pump or a pick up -volume test or otherwise.
3. A restricted pick-up/filter etc would still likely meet the pressure spec KOEO, and not under load. Proof that you have pressure (Regulator and pump working), but failing a "flow test".

There is more than one way to skin a cat. Your way is by the book. Ex-x-fire's is the fastest way and it still gets you answers that matter.

 

hey guys i dropt the fuel pump in the other day an that was it , well its all fixed an the bird flies now lol , thanks for everyones input on the matter , hey i do got one more question when i had the hanger out there was a small "noise filter " on the hanger does it need to be there ?

 

Good job! As far as how I do things, not everyone has to agree with me. I know what I know from decades of experience, some great training early on, and continued study. I test fuel systems the way I do because I have been bitten by not doing it this way. If what you do works for you then go with it. If at some point it doesn't work, then I'm here to help.