I have 95 with LT1. Don’t think there have been many mods. Only had the car for about 6 weeks. I have read a lot of post about this and think I have narrowed it down to a weak fuel pump, but wanting to get feedback if I am missing something.

When at idle the car is great. When driving at all speed ranges the car is fine. The problem comes in when I open the throttle up.

(What I have done to diagnose the problem)
The first thing I did was the cheapest-changed the fuel filter (it did not help). So today I bought a fuel pressure gage. Turn the ignition on and I have 42psi. Start the car and it drops 10psi and holds at 32psi. After shut down it jumps back up to 42psi. There is no immediate pressure loss and after 30mins it is still at 42psi. So I taped the gauge to the window and went for a drive. Normal acceleration it stayed about 30psi. But when i opened it up and tried to punch-it it dropped to 10psi and if i stay on the gas it dropped all the way to 0psi and would not come back till I let off the accelerator, at what point it immediately jumped back to 30psi. The check engine light came on and when I got home the code that was stored is 55(fuel lean monitor).

Am i correct in assuming a weak pump or should I look towards the pressure regulator or O2 sensors? Just not wanting to spend $$$ that I don’t have to.

 

Correction--I left the pressure gage connected and moved the car into the garage, 30 mins after being parked the pressure has dropped to 16psi.

 

My fuel pump symptoms were a persistant high speed misfire; bought an AC/Delco fuel pump from Rockauto for $100, a 45 minute install and it ran like it was supposed to! They are cheap and its an easy job.

 

Sounds like you may have found the problem on your own.

 

Might as well check the fuel pressure regulator. Just take off the vacuum hose and see if it smells like gasoline... Its too simple to not do... Good Luck

 

All the pressure was gone within a few hours. The vacuum line smells like fuel but it is not real strong and not wet. I have now pinched off the fuel supply line after getting the pressure back to 40psi. At least i think it is the supply line. I have to do it back at the tank because the rest of the lines are all metal.

 

Yeah, pinch off that line by the fuel filler and see if the pressure drops off...
If it does it is most likely a check valve in the pump or the pulsator tube (or whatever its called) that runs like 1in up the fuel pump...

 

Ok I have pinched off each of the lines one at a time and it still looses pressure. Can a leaking injector cause the lean fuel problem and no pressure under hard acceleration? Or can both the pump and pressure valve be bad? Starting to get puzzled.

 

Quote:

Originally Posted by sfcbishop

Ok I have pinched off each of the lines one at a time and it still looses pressure. Can a leaking injector cause the lean fuel problem and no pressure under hard acceleration? Or can both the pump and pressure valve be bad? Starting to get puzzled.

So u pinched off the fuel line and the return line?

See I have a feeling its not a leaky injector because the pressure is going down to 0psi when you are flooring it but when you drive normally its is relatively ok. Injectors leaking that bad would probably cause a poor idle, and you dont have that symptom. I am thinking more fuel pump or fuel pressure regulator.
Did you try running the engine without the fuel pressure regulator vacuum line connected? See your pressure at idle and at wot... maybe it will lead you to the problem.
When you start the car does it start right up or does it turn over a few times before it starts?
Did you put your fuel filter in the right way? Did you inspect the fuel lines for leaks or pinches or anything like that?
Just throwing things out there, I am really not sure. It can still be a few things...

 

No have not tried running without the vacuum line connected. It starts right up even after the pressure leaks back out. I have pinched both lines at the same time and the pressure seems to be holding. I am starting to think it is a combination of a weak pump and the regulator. Might just replace both of those and see where it puts me. Thinking about the C44 kit from racetronix. Should I just stick with the stock 190lph or for $18 more go ahead and get the high flow 255lph. Will it hurt anything? And is there a certain pressure valve I should be looking at or is the OE replacement from O'Reillys sufficient?

 

Like Dogfish said check regulator, you don't want to buy a pump you don't need.
BTW I replaced fuel pump on my 84 once and I am still thinking that it could be just rubber hose leaking.

 

I was not getting a good sqeaze on the fuel hose. I did it again and as soon as I got a good sqeaze on the supply line the pressure held steady. So I am sure it has to be the fuel pump. I removed it to look at it and there is not a strainer attached. I felt around in the tank the best I could and looked with a flashlight but dont see it. I am assuming that if someone else changed it in the past they left it off. It still has what looks to be the original pulsator on it. So I am looking at the C44 kit from racetronix. Should I just stick with the stock 190 lph or for $18 more go ahead and get the high flow 255 lph. Has anyone else had a problem with this setup from racetronix?

 

You'll be fine with the racetronix. I had problems with one of there fuel pump (Leaking valve), they honored the warranty right away..

 

yes it's your fuel pump...I had headers put on mine and right whiel they were pushing it wide open on the dyno they called me and said my psi drops to a low 12psi. saying it was really lean. They threw a fuel pump on it and its good to go back at 43..

 

I'd go with a fuel pump too. As long as the vac line is clear on the fuel pressure regulator and your not seeing gas leaking, I believe your good. Whichever pump you chose will be fine.

 

Thanks everyone. I am going to order the pump and will let everyone know how it turns out when it comes in.

 

I see you're in Killeen. My son has been assigned to Ft. Hood. He'll be there right after he graduates from West Point in May.

When I had a fuel pressure issue on my 86 L98, I traced it to the pulsator. I replaced it with a length of fuel hose and that solved the problem.

Hope you're able to cure your problem.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day 21 May 2010!!!

 

What he said. I purchased a Racetronix complete kit for about
$99.00.

 

Racetronics gets my vote, but I would buy directly from them and not a supplier.

 

Just FYI, I am having the EXACT same problem and came up with the same conclusion. Im in the process of ordering a racetronix fuel pump. Let me know how your fix goes.

good luck