Looks like I may be replacing a fuel pump soon. Car is an 87 Z-28 with a 5.0 TPI. The car has been running rough lately. When it is able to go it surges alot. Has a jumpy idle. Took about 10 minutes to start today. Ran good for a little then it started acting like it was going to die. I checked the fuel pressure and when I just turn the key it was at 20. Once I shut it off the pressure was holding fine for the minute I watched it. I started the car up and the pressure bounced aroudn between 27-29. Do you guys think the fuel pump is to blame here? I replaced the fuel filter last week also.

 

Maybe the pump. Sounds like it tho. You might want to upgrade to the Walbro pump which is cheaper and better than stock.

 

I agree. Could very well be the fuel pump. Are you checking your fuel pressure with the vacum line disconnected? These cars are very sensitive to fuel pressure changes. Has your car thrown a "Check Engine" light? If your fuel pressure is low, you could be running lean.....this is what my '92 Z28 was doing.....as well as sputtering and idling rough.

If you replaced your fuel filter, then its always a ggod ides to go back and double check your work.

Aklim hit the nail right on the head. Get the Walbro. Whatever you do, dont buy a no name brand form your local parts store. The money you may save now won't be worth it when it goes out a year from now....or sooner. I learned the hard way.

Its a pretty straight forward install once your get the fuel tank out.

If you really want to nip this in the butt for good, you can pick up a package from Racetronix.

Frat

 

Thanks for the tips guys. Do you think it could be the fuel pressure regulator? How would I check that.
Fratsit-I did get a lean code the last time it was driven. I did not disconnect the vacum line. I will check the pressure again with the line disconnected.

 

You could clamp off the return line and cycle the pump. That will get it up to whatever pressure you want till you take the wire off the battery. If you let it go and the pressure drops quickly then you might start with the regulator.

 

27-29psi with the car running is not normal. In fact, it should have been struggling to run at that pressure.

You should verify fuel pressure with the vacum line disconnected and the car running. In my 92, with the line disconnected and the car running, I have a steady 44psi, connect the vacum line and it drops to around 34-36 psi. Throwing that Code, should definately steer your into your fuel system. As a heads up, if your Ignition Module starts to go, you will get the same symptoms you are getting now......only your fuel pressure wont be low.

If your gage line is long enough, run it under the hood, up to a spot on your windshield that you can se while driving. Tape it there and go for a spin. Pay attention to what your pressure is when it starts to sputter and look for that "Check Engine" light. Even if you don't get the light, if your pressure is down, it could be the pump. When mine was acting up, I could hear it start to cavitate while running at idle. I would throw a Code 44, and my pressure would be around 20 psi.

If your really into that hotrod, I would suggest buying a factory servce manual for your model year. DONT get a Hanes or Chiltons, they are not as thourough and cover the entire Third Gen. model run. A good servivce manual can be found on EBAY for pennies on the dollar. Its one of the best investments I made for my '92. It also discuss's using the clamp to check your regulator, like Aklim suggested.

Frat
Bremerton, Wa.

 

Cool I will look into those service manuals, they should come in handy. Yesterday I tested the fuel regulator and with the fuel return line pinched off and the fuel pressure did not change. So now we definetly know its the pump. You are right about it struggling to run. I could barely take it down the street. Hopefully after the pump it will run strong again

 

If you pinched off the return line and pressurize it and the pressure doesn't rise, assuming your gage is right, your pump is not able to provide fuel. In that case, I suspect that the pump is bad. Also, when youa re there, check the wiring to make sure it doesn't have rust or the ground is bad. In fact, the racetronix kit should have a bypass to make sure it is right.

Also, after this, check the regulator too by making sure it holds pressure for a while after the pump stops priming.

 

Right on,

Hope everything works out for you and good luck.

Frat