I'm confused between what I'm reading on various sites, talking about pulling the sending unit to get to the fuel pump vs the Chilton's which says the 88 requires you drop the tank to replace it.

Anyone have direct experience with this so I can know what I'm in for?

 

It's one of the easiest. Remove the fuel door (four torx). Remove the rubbher gasket (carefull not to tear). Remove the three lines off of the assembly. Unplug. Remove the 10mm bolts and lift the assembly out by tlifting and turning.

 

I am so glad to hear that...the frickin Chilton's manual has me taking the tank out to get to it. Unreal!

Though I have decent pressure while sitting still, once it warms up and I get moving, it bogs down and my pressure drops. My father in law says he replaced the pump and filter but I'm skeptical it was done correctly.

Any insight to how it "done incorrectly" can cause stumble on acceleration?

Thanks again!

 

Get the FSM or Factory Service Manual. You can find em' on Ebay. They are far better than the Chiltons. You might want to check the fuel filter too. That's underneath the car, behind the front wheel on the passenger side. You'd be amazed at how clogged they can get. What you have may be ok for idling, but imagine trying to pull through a clogged soda straw?

 

First thing you need to do is throw the Chilton's manual in the trash and by a Factory Service Manual....WW

 

What "filter" was replaced? The sock at the pump inlet or the one under the passenger door? If both were not replaced that might be the problem. I'm not aware of a wat to improperly replace the pump. It is a pretty straight forward job.

 

He said he replaced the sock when he did the pump but didn't get to replace the one under the passenger side floorboard until weeks later, after it had been driven for awhile. The bogging problem has gotten progressively worse. It runs fine sitting in park but once in gear, blah during acceleration.

The old fuel filter he took out was disgusting and could not blow through. Is it possible the fuel pump and sock were clogged by sediment making it back into the tank due to the dirty filter?

And, we were getting code 54, Low Fuel circuit voltage. Replaced the Fuel Pump Relay, cleared the code and it hasn't returned but the bogging continues.

 

Fuel pressure is 41 ignition on, 36 at idle, when revved, it goes up but sometimes it goes down to low 30's then bounces back up to 36. Also, pressure goes up to 43 while running and the vacuum line is pulled off of the FPR.

 

dropping to 30 is some what low but if it is maintaining 43 while vacum is unpluged doubt if anything is wrong with the pump. What do you mean by bogging you may be describing a clugged converter. Tell us more describe what is happening.

 

Starts fine cold, when I take it out it even drives ok for a minute or two until I'm guessing when it goes into closed loop and relies on the sensors. When I say bogs, I accelerate, it gets to 2k RPMs and I lose all power. I think they call this "limp home mode." I first thought it was fuel related so that is when I replaced the fuel pump relay (code 54 did pop) but still bogs down when it gets warmed up. Code has not returned.

I've done the following: my father in law replaced fuel pump, fuel filter, and sock about a month ago. I since have replaced the fuel relay, cap, rotor, Ignition coil, Ignition control module, plugs, wires, serpentine belt, O2 sensor.

I've set the timing and reset the idle which was 200 RPMs high as PO set it higher to smooth it out. Cleaned MAF sensor, even tried the disconnect trick and it still bogged.

Disconnected the EST and the ESC at separate times to determine if knock sensor circuit logic was forcing it to limp mode; same behavior. Still not sure about knock sensor as I can't reach it. Following the troubleshooting flow from AgentMan86, I did try the knocking on the block with a wrench and it did not change the idle at all. Disconnected the ESC while running, got the SES light on and it didn't change the idle either.

Found a vacuum line broken but it was the one on the brake pedal side of the cruise control unit near the battery. Fixed but no idea if that would affect overall vacuum pressure.

I know this was alot but that is what I've done over these last few weeks. I am absolutely frustrated to insanity.

Any insight/help you can give would be greatly appreciated!

Tony

 

NO,NO, don't throw it away. They make excellent door stops and are great for starting a fire. In honesty both Chilton and Haynes can be useful but if you are to do any even semi-serious wrenching you gotta have the FSM.

Allow me to back off any comments about Chilton. I do not have one. I'll stick to my belief that Haynes can help the novice wrench bender.

 

This is why you're replacing your fuel pump again.....the low voltage killed the pump. Low voltage created excess heat.

Ensure you have a solid 12V at the harness, replace the pump / sock / pulsator, replace the fuel filter, all should be well.

You did test the regulator, correct? (pinch off return line during a low pressure event).

As others stated, changing a fuel pump on a C4 will take 30 minutes the first time you do it. Piece of cake.

 

I'm a noob so where can I pinch off the return line and under what conditions and what am I looking for it to do? Also, the pulsator is just a chunk of hose, right? Where does it go and how is it oriented? I think PO may have not installed it right.

So this behavior I described above is typical of a fuel pump that has been strained by low voltage? It seems to starve for fuel but only after it has been started for a minute or two. I'm a first time vette owner and admitted amateur mechanic so still learning....thanks by the way for taking time to reply, all of you.

 

Hell you don't drop the gas tank to replace a C4 pump. The guy who wrote that nonsense in the Chilton's manual should be kicked in the nuts.

I just wonder how many poor bastards read that and unnecessarily dropped the entire tank when I could all be done right from the top though the gas lid opening.

 

That is exactly why I asked the experts. Earlier models show the method you all outline here, but they say the 88-89 must pull the tank; long and unnecessary method for sure.

 

It's all BS. There's plenty of room once you remove the gas lid and rubber spill matt to do it all from the top.

Here's a how to with pictures:

L98 procedure is the same even though thread title says LT1:

http://forums.corvetteforum.com/c4-t...s-of-pics.html

I've found a few other mistakes in the Chiltons book. The Haynes is better in my opinion but what you really want is the GM Factory manual for your specific year as already mentioned. Check ebay.

The problem with the Haynes and Chiltons is they try to roll the entire C4 generation into one book. The wiring diagrams are pretty generic and not entirely accurate. You also have to weed and sort though information that is not applicable to your engine or year for example. With the year specific factory manual you don't have that problem.

 

 

Both fuel lines run under the passenger side frame rail. The pressure side is the larger of the two, and the return line is the smaller. Any place where there is rubber hose will work....the closer to the fuel rail, the better....or faster it will react. You could just pinch it off at the filler neck as well...would just take slightly longer to react. When your pressure drops, pinch off the return line and see if it rises. If it does (which I doubt) the regulator is faulty. I don't think this is your issue, but I hate replacing parts (and doing work) until I'm sure what's at fault.

And yes, sustained low voltage will overheat and kill a fuel pump. Same thing that happens in home appliances.....say the power company experiences a serious voltage drop....it can damage air conditioners, refrigerators, any high load motor driven item.

The pulsator is just a piece of hose between the fuel pump and the hard metal fuel line assembly on the sending unit. Replace it with a section of FUEL INJECTION hose of the same diameter.

Your fuel pump is operating fine cold, but once it heats up (heat = electrical resistance) it starts to malfunction. I've seen several behave exactly like this.

 

I've got a new ACDelco fuel pump, sock and filter ready for pickup today. I've found some fuel injection hose -

http://shop.advanceautoparts.com/web...A|GRP2024_____

Will this stuff do it?

And thank you [all] for taking the time to help! I am dying to get in it and go!

 

That'll work just fine.