The heavy 6-8 gauge red wire.
It connects back to the battery + positive post.

It may be covered up with a small rubber boot.

Pry the boot back with your fingers.
Not a screwdriver or pliers.
The alternator output lug is wired HOT to the battery........You don not want to short circuit to chassis ground accidentally.

You fingers will get burnt badly if you short circuit there.

brian

 

Short circuit with metal that is.

There is only 12 Vdc present at the battery with the engine off.

No danger of electrical shock.

But if you dead short circuit an auto or large truck battery,
You immediately have 1,400- 3,000Amps present to make your wrench, screwdriver, or pliers glow red hot to 4,000 degrees + F.

The heat will climb through your metallic tool in your hand(s) in a flash.
You get burnt like that.

Enough current to burn a Snap On wrench or ratchet in half in just one second.

Why I said pull the protective rubber back with your bare fingers only.

Brian

 

ok the volts at alt are 14.65 and at distributer 14.08

 

Ok.

Its troublesome yet then,.......

Time to remove the fuel door on your Vette and get access to the fuel pump electrical connector.

There are 4 torx head srcerws holding the fuel door on.
T15 torx size.
Remove them, the gas cap lid, and the stiff rubber insert.

Be careful so you don't scratch the paint.

Find the fuel pump connector.

You want to check voltage on the 14-16 gauge Gray wire and the black wire .

Gray to your + positive voltmeter lead.
Black is ground to your meter.

Take a reading with the key on engine running.

Backprobe with 2 paperclips.

Be careful so they do not touch one another or the bare steel gas tank.

You should see around 12.6 to 14.4 vdc again with the engine running.

Let me know your measured Volt reading.

 

I'll do that test tomorrow I'm kind of beat up after spending all day on that fuel filter. If that checks out ok is there another thing i should look at? You guys sure have been a lot of help Thanks

 

Defective electric in tank fuel pump.

Make sure that you have 12.6-14.4 vdc present at the fuel pump before you call the pump bad.

I have seen at least 2 dozen electrical power feed problems on GM cars and trucks over the last 10 years.

Other shops replaced electric fuel pumps and the driveability problem not fixed.

I repaired a ground or a bad electrical splice, pump voltage went from 4-8 VDC back to 14.4 VDC and Engine Power- rear tire spinning performance was back.

Nearly all modern or GM mechanics miss this check.


I was taught by an old school mechanic from the 1950's to 2007 when he passed on.

Not taught by Autozone or the like.

Brian

 

You are doing great by the way troubleshooting Your 1988 Vette yourself.

I am just guiding you.

Tomorrow is a New Day.

I will help you till you find & repair the problem(s) with your Corvette.


BR

 

Thanks Brian,
When we get this monster running i'm going to melt the friggen tires off of it LOL. So your saying if i don't have at least 12.6 at the pump i've got an electrical problem

 

I applaud the way you continue to tackle this problem as well....

While you are back at the fuel tank unit, if the voltage checks at the pump connector are found to be ok, there is one more check you might want to try if you still have the fuel pressure gauge.... You may need an assistant..

You can pinch the rubber fuel return line at the tank, (it is the one on the right hand lower side of the filler hole which attaches to the rigid metal line that goes back in to the tank below and to the left (7 o'clock) of the filler. Then turn the key on and see if the fuel pressure at the rail increases to around the 40 psi and holds steady or slowly bleeds down. If it does, the problem may be with the fuel pressure regulator.

If your pressure is still way low and the voltages Brian said to check are good, you may have a clogged fuel sock on the end of the fuel pump, a leaking fuel pulsator, a bad check valve on the fuel pump, or the pickup tube could have cracked. These are all in the tank on the tank unit..

And yes, if you have low voltage to the pump, it may be an electrical problem, but the circuit is pretty easy to troubleshoot....

But, one step at a time... Hang in there....

 

awesome thanks by the way did you get any of those storms that went through OK. As i said my daughter lives in norman but i haven't talked to her tonight. I've still got the fuel gauge so i will do that check also.

 

No, another day of no rain in Norman... Every storm seems to be setting up about 25 miles to the east of us this year.. and we need the rain.. The lakes are anywhere from 2-7 ft below normal..

 

I do not like big voltage drops.

Neither does your Corvette.

Be careful when making fuel pressure checks and custom rubber hose hookups to the fuel system with worm gear hose clamps.

A fire fueled by 40- 100psi spraying gasoline will burn your Vette down and you down to the ground.

My boss Jack about burnt me down and his sister's 2002 Ford Explorer.

He lifted up the fuel rail after removing the upper intake plenum, with the Bosch 3 injectors intact.

Said to me Brian crank the engine over I want to see if the all 6 injectors are spraying properly( nice cone highly atomized fan spraying pattern.

I said "Jack I do not think that is a good idea!!"
Do what I tell YOU!! I sign your paychecks don't I ?!!!.

Ok, so I hit the key and cranked the engine over.

Watching from inside the Explorer, I cranked the engine over for 2 seconds..........

The engine backfired up through the intake and caught all 6 highly atomized fuel spray injector patterns on fire............

The a huge ball of fire shot out about 10 feet from under the hood...........

I dove out of the truck onto the ground and ran to a nearby fire extinguisher.

Ran back pulled the damn lock pins out and sprayed the fire out in the next 30 seconds.

White powder everywhere.

I looked at my boss & he looked at me........

Then I looked at the engine...........

the #6 fuel injector popped out of the fuel rail.......

The big source of the gasoline fire explosion that took place.

I said "Hey Jack the fire is out..............That was a Bad Idea like I told You..........
See how fast i got the fire extinguisher from 20 feet away????

Took me about 1.5 seconds..........LOL

Be careful around gasoline.

Static electricity can ignite gasoline vapors too.

Brian

 

the volts at the fuel pump was 13.96

 

i also blocked the return line at the pump and i still only had 12lbs presure with the key on

 

You're doing great! Hang in there and somebody will chime in. If it is indeed the fuel pump, that is one of the easiest things you can do on a C4 Corvette!

 

i'm really puzzeled as to why i can't hear the fuel pump run. But yet i still have 12lbs at the rail and it will start

 

The fuel pump will only energize for a few seconds to pressurize the system, then it will stop until the car stops. Have someone turn the key on, while you're standing by the fuel pump (with the fuel door open). You should hear it come on for about two-three seconds with a 'whirring' sound, then go silent until the key cranks.

 

Its time to remove the fuel pump from the gas tank on your Vette.

The sending unit and pump hanger assembly is bolted down to the top of gas tank.

You already have access to it.
Remove the 9 or 10 bolts fastening it down.

Pull the sending unit assembly straight up and then turn it left or right to clear the attached gas float.

If the fuel sock is intact and clean,
call the electric fuel pump bad- defective.

Buy a new electric pump from Napa, Carquest, or O'Reileys.
They each sell quality fuel pumps.
Purchase a new fuel pickup sock too.

Install the new fuel pump.
Button everything back up and try starting your Corvette again.

Recheck the fuel pressure.
It should be now 41- 47 PSI with the vacuum line off the fuel pressure regulator.
Your Vette should run much better.

The internal carbon brushes and commutator segments in your old fuel pump are shot.
Causing the electric motor to spin over very slowly,
Thus only 12psi of fuel pressure at the present time.

Brian

 

ok i'll get one tonight and install it tomorrow thanks

 

Just one more bit of advice. Unplug the battery before doing anything. First, you remove fuel filler door, then the gas cap. Next, you pull the big rubber catch-tray from around the fuel filler neck. Just bend the sides inwards, as it is a press fit, no bolts or fasteners. You'll find that getting the fuel lines off are the hardest part of removing the pump, because of their age, they stick to the metal, really hard and it was tough for me to wiggle, pull and work them off the metal lines. Get them off first, before you unbolt the pump from the top of the tank. Then the electrical connectors. There are tabs that you can use a small screwdriver to depress, so you can disconnect them. Finally, you will have to rotate and tilt the fuel pump assembly to get it out of the fuel tank. Be careful, as the fuel level float is built-in and you don't want to bend it. Cover the hole in the fuel tank with some tape, because you may have to transfer parts off the old pump, onto the new pump. Take pictures of what it looks like during the process, so you have a reference. PS: Get a fresh gasket for the tank, if the new kit doesn't have one.

scroll down and you'll see what the assembly looks like.

http://www.corvettepartsblog.com/vettetag/c4-corvette/