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Bro-KEN fuel system electric testing

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Lets assume for the sake of conversation you ONLY have a test light.

Test #1 IS THE DAMN PUMP WORKING?

Key Off/engine off

If you have a fuel pressure meter now would be a good time to install it.

Get a heavy gauge wire #16 or better and jump from pin G ( lower left hand of ALDL connector ) to +12 volts. You can go direct from the battery. When you complete this circut the fuel pump will be Whizzing away.

This circut will check the wiring from the fuel pump relay ( swinger=output ) down to the fuse panel and the wiring all the way down to the pump in the tank.

Test #1 ALT ( dont have a long piece of wire )
Key Off/engine off

If you have a fuel pressure meter now would be a good time to install it.


Next to the brake booster is the fuel pump relay
( inbetween the booster & wiper motor)

there should be 4 wires on the connector
Big Orange PIN A ( +12 volts battery power )

Big Red PIN E ( switched power to pump)

Dark Green/White PIN D
( Relay control to coil from ECM +12 @ start & run)

Blk/White Pin F
(Ground for relay coil)

And another BIG RED Pin C
This is the connection from PIN G of the ALDL connector.

Check that PIN A is HOT with the test light.
then Jump pin A to pin E

Pump SHOULD be whizzing away again.


If no pump action is happening....
Remove the license plate on the back.
Find the 3 PIN connector with
TAN WHITE PIN C Pump power from Relay
PURPLE PIN B Tank sender
(90 OHM's when full 0 when empty)
BLACK PIN A Ground

The male connector is the one going to the tank!!!
Seperate the connector(s)

Check that pin A on the female side is in fact GROUND ( if you have a OHM meter)

Take a 12 volt battery and hook the
TAN/White to +
The Black to -
ON THE MALE CONNECTOR

Pump whizzing away????
Disconnect.......

Now take the test light and put it on the female connector between the TAN/White & the black
Put the light where you can see it while your in the drivers seat.

Turn the key on to crank, the light SHOULD COME ON for 2 seconds.. If not.....Turn the key off
( you will need an assistant for this one, some scantilly clad bikini babe.)

You grab the fuel pump relay still connected and have the assistant crank the car...you should feel a click when the relay goes.

If no click.......

Either the ECM is goofed OR the relay is BAD or the relay socket is goofed.

We need to perform these tests BEFORE we can go any further.


You have the number...you know what to do!

Mike
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
Hey Mike, I was fooling around with it today and thought of something that in all honesty, I'm surprised nobody's brought it up before. ;)

One of the things that will shut down the fuel pump is lack of oil pressure, or at least, lack of a signal from the oil pressure sensor.

fuelpumprelaydiagram.jpg


I also discovered that the reason I'm not seeing a "Service Engine Soon" light is due to the fact that the light is not lighting. It doesn't light when the self-test is performed when you first turn the key, and when I tried to retrieve codes to see if there was something I missed, the light never lit. Now I gotta start working at it from that angle. Sounds more and more like a grounding issue after all. :eyerole

fuelpumprelaydiagram_A3.jpg


Maybe I'll just re-wire the whole frigging car! :L

_ken :w

(I've just been back looking at your description here and trying to decipher it. ;))
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Tres Bean mon Frer'

Ok

Here's a question
Does the car light off everytime you crank it..then dies ( when you can crank it hahahahahaahah)

Or no fire in the hole at any time?


You shoulda called today!

The oil pressure switch hardly fails but I needed you to do the tests first!!!

Electrical is hard enough...but Via remote..thats a challenge


Mike
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
There is spark at the plugs. :D

It seems that there is no juice to the pump. Not only that, but there is no "SES" light coming on -- ever; it's no wonder I'm not seeing trouble codes.

Me suspects the other ground, of which you spaketh once before. :gap

_ken :w
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Further

The oil pressure thing Keeps the fuel relay in AFTER start, not during.

The Check engine light....
We will need to dig for that one

But.....

The light gets its power from the Inj #1 fuse in the panel

The other side of the light
Goes to the ECM connector
The A connector pin 5 ( Brown/White)
The connector with A & B( rows ) is the smaller connector( C-2 )

ECM
C1 is the BIG connector (16 pin dual) Series "C&D"
C2 is the small connector (12 pin dual)Series "A&B"


If the connector lock is on your right
Row A is on your right
Row B is on the left
1 is the top
12 pins total in each row.

Pull the ecm fuse
disconnect the ECM connectors
Locate C-2 ( connnector2, Row A pin 5) A-5
Ground that wire Brown/White
replace the fuse
Turn key to run position
If the light lights
Your ECM is toast ( for the lamp driver transistor)
Serial communications will still be good however

If you have a scanner
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Gettin grounded C-4 1988

FRAME GROUND POINTS


G-401
Pass side door behind seat, behind plastic trim
About where the top of door line is.. ON THE BODY
10 mm bolt into frame metal, single wire.
This goes to the splice for grounding the entire ASS end of the car.

G-320
Left side of cargo compartment about where 401 lives on opposite side. ABS ground (total system)
& left side hatch strut for rear window defogger.

G-201
Is the ground for the entire cabin area. Behind instrument panel, left hand side, near steering column.

G-125
Pass side by toe kick panel,Dash grounds etc.

G-109
The Frame ground point for the AC Blower motor sensors & relays, spark ESC module, Washer pump.
On the frame rail, pass side, below the hi pressure
A/C cutout switches.


G-104 MAS IMPORTANTE'******************
The big gorilla from the Neg side of the battery
to the drivers side of the engine block with the ground braid & other Grounds!!!!
ECM,Fuel pump relay, Mass sensor & relays, tranny position Etc.

And

G-101
The little wire off the neg side of the
battery to frame rail & to Ground braid.This is the the ground strap.. the braided chunk of wire connects FRAME to ENGINE!!!!

G-115
Drivers side, foward frame rail, By horn.
Ground for headlight, horn, evap cansiter, turn & marker lights.

G-116
Mirror of G-115

G-117
Ground for Fan(s) & fan relays
By fan on frame rail twds pass side
on the cross member between the left & right frame rail on top.

This should be very similar for all c-4's but it's out of the 88 book.

Mike
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Yet More!

Your schematic is not the same as my GM one.
Where did you get it?

The ECM issues a 2 second pump on ( read prime ) command IF the VATS is cool ( or bypassed in your case ) and the Ign is ON or in START.

That should start the engine. once OIL PRESSURE is sensed by that switch it closes and bypasses the ECM & fuel pump relay via this circut.

Try this
on the oil pressure switch (2 pin connector)
there is an

Orange on pin C +12 direct to battery
(via fusible link H)

Red Pin D
Home run to fuel pump fuse and out of the fuse to the pump.

Pull the connector
get a test light
C should be hot

now get a paperclip
use one end of the paper clip and jam it into the Red side of the connector.. hook that up to your test light clip
use the probe side of the test light to go to the Orange side.

If the light lights you have a circut.
If not there is something OPEN in the fuel pump circut or high resistance.

If the light lights... jump Red & Orange
and see if you get fuel pressure..( pump should be whizzing away) Don't need the key here.

This will confirm that the pump is ok ( a different way then before).

Does your brain hurt yet?

Mike
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Further again

If you spray Quick start down the Throttle body
does the car start?

And

If you jump the Oil pressure switch (and the car idles)

Take your ohm meter and go across the two pins of the switch... witht the car idleing.. the switch will be closed!

In a perfect world!


Mike
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
I printed this too Mike,. Thanks, I'll let you know what I find. :upthumbs

_ken :w
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Your schematics

I found them... there in the BIG book, not the electrical supplement. I use the ones in the supplement..better..colors...bigger.


Mike
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
Saw someone viewing it earlier, this comment caught my attention...

Ken said:
Maybe I'll just re-wire the whole frigging car! :L

Who'd have thunk it! ;LOL

unwrapped0002.JPG

unwired0005.JPG

unwired0003.JPG


unwired0001.JPG

Painlessharness01.JPG
 
C

c4ever

Guest
Hey Ken,
I can't believe they got all that wire in that teeny weeny box!

Carlo;LOL ;LOL ;LOL
 

jmccloud

Well-known member
Joined
Feb 1, 2003
Messages
694
Location
Maryland
Corvette
1995 White Coupe LT-1 Auto
SES light

Have you checked the bulb? Or what ever illuminates?
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
The problem I had a year ago, is a moot issue at this point Happy; I'm way beyond those problems and into more. :L

_ken :w
 

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