crossedfires

Ok.. new fuel pump, both filters replaced, fuel lines open, fuel in the tank, fuel fuse f.p on the fuse block good, voltage spec's to the injectors, injector fuses good, on the ALCL connection block ran a hot wire to the G block which is fuel pump and its not engaging the pump, turned the ignition on and listened and heard nothing coming from the pump. This all started 7 months ago, The car was running fine, I pulled the factory Delco out and ordered a Auto Sound System, Before I ordered the new sound system several weeks had gone by so I decided to start the car to make sure the battery stayed up and I think I heard a pop sound coming from under the dash toward the fuse block so I quickly shut the engine off. yestersay I installed the new stereo but before I put the dash back together I tried starting the car, It cranks but wont start, due the new stereo required that I not use two of the wires in the factory wiring I decided to reinstall the factory stereo and try to start the car, it still wouldn't start. I went ahead and reinstalled the new sound system using the customer service step by step and being assured the wiring is compatible with the factory wiring and shouldn't change anything, the dash is back together. My vette shop manuel is now in my hand but Im lost. According to the manual and its pyramid check list chart 2 page 6E-21 I should "back probe white ECM connector pin 20, CKT 419 with a test light to ground". OK.. does this mean to actually probe the wire on the white plug that connects into the ECM cause if it does theres nothing indicating pin 20 on my ECM not to mention the dang thing is behind the battery and Im guessing the battery has to stay connected to do this test, does anyone know how your actually suppose to peform this test? Any help or advice in figuring this all out would be greatly appreciated.

maxmachz

Look close at the ecm plugs, they are numbered at each terminal / wire on each plug....very tiny nomenclature, but is there. Yes you do test that way, to see if the wire harness is the problem up or downstream from the ecm itself. And to see if the ecm is sending or receiving the proper signal. I pulled the ecm out of it's bracket, left it hooked up, swing it to the right and still have the battery in and active to perform the checks. you can see the plugs and the numbers and letters much better this way as well.

crossedfires

wow.. that blows lol thought I was missing something so you can leave the battery in and still pull the ECM out of the bracket or pull do you battery out then pull the ECM out and place battery back? Is there no screws holding the ECM into the bracket?

maxmachz

Battery out 1st; then take the nuts off the ecm studs, remove it from the bracket, swing it to the right side of the car (pull the storage bin out of course, lids up).

Put battery back in, hook it up. Test. Resolve issue, then pull battery back out, put ecm back in it's bracket, then put battery back in.

Been there, done that. Found my ground to the diagnostic terminal was severed.

crossedfires

good deal.. thanks for the info, seems they'd would have made the ecm as ez to get to as the ALDL test connection if not for us garage monkeys atleast for the dealer shops. anyway thanks again.. hoping friday i can get back on this thing and maybe getr done. have a good week and enjoy your ride!

jdp6000

Will it run if you pour a bit of gas down the TBI's? Just wondering about that pop you heard. Its possible you fried something in the connector behind the fuse block.

When you turn the key to on you say no noise from the pump...do you hear a noise from the injectors?

While cranking are all the gauges working?

crossedfires

I just now had a chance to work on it again.. I poured sum fuel in the tbi's and it cranked right up and ran 3-4 seconds and died, tried it again and it did the same. All the gauges worked, I noticed the engine light didnt come on when putting the key in start position but the battery light came on and went out after it started. I like the fact u picked up on the pop sound as i discribed.. it seemed to have came from under the dash between the steering wheel and fuse block and has kept me woundering, i did check the fuses for injectors, ECM and fuel pump on the block, all checked out ok.. but i still keep thinking about that pop and wounder if theres something else somewhere under there. At this point soon as i get time again im gonna follow the manual testing and see where that gets me unless anyone has any ideas.. boy they couldv'e put that ecm in a better place!! lol thanks for your reply if u think of something I'll give it a shot

jdp6000

I'll look up a few things when I get home. I need to trace the power distribution to the pump.

Check something in the mean time. Key off, touch the top of the fuel pump fuse with red of a meter and run the black to a good ground. Should have no power. Do the same with someone turning the key to on and see if you get ant power even for a couple of seconds.

crossedfires

I've got a voltage meter but being in the middle of moving into a new house I'm not sure where its at so I used a test light and checked the fuse, key off no power, key on got power. I also pulled the plug connection to the fuel pump thats under the fuel door, its a 1 peice 3 plug connector. One for ground, one for power and I have no idea what the third one is for. The middle one is power at which with the key off it has no power with the key on it gets power and that my friend is confussing me.. being that I put a brand new fuel pump in and Im not hearing it prime when turning the key to the on position. I dont know what kind of voltage its getting at the fuel pump connection but it would seem that if its getting power there wouldn't be a blown fuse or relay.. ?

jdp6000

Which one had power on it? One is the feed for the fuel gauge so the voltage will vary on that one. Need to know wire colors you see.

Note that when you unplug the connector the fuel guage should stop working.

I believe you should have power on the other wire too.....its should power up for 2 second intially for system prime....then stop.

There is another fuel pump test using Terminal "G" on the diagnostic plug under the ashtray but I don't remember how to do it. Maybe someone will come along with instructions.

jdp6000

Just reading the book. It says to apply battery voltage to terminal "G" and listen for the pump running...I think you did this. If you don't here it run check CKT120 and CKT150.

CKT150 is the grond coming off the pump.

CKT120 is the power supply wire at the pump. I think you checked this.

I just can't understand how it ran before and not after the pop. But based on the Terminal G test and no power at the pump the book suggests its the pump thats bad.

The key is to determine if its the pump before looking any where else. You need to put direct power to the pump power wire coming out of the tank. But you need to figure out which of the three wires power the pump first. You need to figure out which wire back there is for the fuel gauge. What I would do is first determine the fuel gauge wire....unplug the harness back there and note the fuel gauge pegging and not working. You have 3 wires. The trick is to determine which is the gauge sender wire. With the harness disconnected use a small wire to run between the blacks on the male and female connector....that will be the ground. Now using another small wire check the other two wires (jumping from each connector)....you know you have the right one when the fuel gauge works. Once you have this figured out you will know the other wire supplies power to the pump. I would put power from a battery to that wire (just for a quick second) and see if you hear the pump swirl. If it swirls the pump is good. We can then look somewhere else.

crossedfires

I've already been down this road also, I never heard the pump prime when turning the key on and nor did it prime when i put a hot wire to the "G" on the ALDL test block' I assumed that it was the fuel pump after testing witha hot wire to the "G" and I replaced the fuel pump.. guess what Nothing. The pump dont activate turning on the ignition, hot wiring to the "G" nor hot wiring direct to the wire under the fuel lid. Its like something is cutting off the pump... the connection under the fuel lid to the pump is a one peice 3 prong plug, the left side is a ground the middle is hot and the right side is a sensor as I was told by a vette shop mechanic over the phone.

crossedfires

After checking the fuel system completely all the way from the voltage to clearing fuel lines, replacing filters, fuel pump, double checking wiring, ECM and grounds, scratching my head in confussion several days and reading the Corvette shop manual several nights.. I found the problem and repair for less than 2 bucks. Who would have ever thought that if your "CHECK ENGINE LIGHT" Bulb goes out it would cut power to your fuel pump. Replaced check engine bulb and the car started. Thanks to all that replied and oh, Keep a spare dash cluster bulb in your glove box!!