SMChevy7

Hi all. 98 c5 no work done to it outside of suspension and axle back exhauxt.

died on my way into work about a month ago. Full tank of gas, engine was bucking and sputtering. Was lucky enough to keep revving it crazy high and limped off to a side street. First thought was fuel pump because it had been very loud with normal driving, which it had never done before.

Spark was good, ignition pulse was there, would turn but not start. Relays are good.

Replaced fuel pump, started and ran around the block then died again. Would not start again, and yes I had enough battery voltage.

Know I had gas because I heard the jet siphon turn on and pump over gas, also had to take the fuel pump out again to sit the gasket better and had 3 gallons of gas come out.

when i jumped the relay the pump would not turn on, then I unplugged the pump and plugged it back in and it kicked on. so I turned my key off, plugged the relay back in, and started the car and it idled fine.

then I let it idle for a while and it died after about 5 minutes. Before it died I got my wheel back on and lowered if, when I lowered it the engine revved like someone was stepping on the gas peddle, not sure if this is a sign of anything.

I unplugged it and saw the connector was all messed up, so I replaced it with a new connector. I can still here the pump turning on well for two seconds when I turn key to on position

I can clearly hear my pump turn on, and I know I have a solid 2 gallons of gas that I poured straight into it.

I am lost and don't know what to do next. I read other posts and have checked the ground and it is not loose, and the pump still turns on. I still have low fuel pressure, even when cycling the key, and even when jumping the relay there is low fuel pressure. Should I try a new pump? It sounds good when it turns on, i am just at a loss and am not sure what to do next.

Robrote

Hopefully someone can provide a wiring diagram of the fuel pump circuit and you can work your way backward. It's got to be a wiring issue somewhere. Just thinking out loud, corrosion in the underhood fuse box where the relay is?

SMChevy7

I have had this car for a little over a year now. I had put a new battery in it, and never had any issues with electrical stuff. So I don't think there's any problem under there

ZZ06

8VETTE7 or Bill would have the diagram. Post your codes.....

SMChevy7

Hey guys so I have the codes but they are written down at home, I will post them when i get home tonight. A lot of electrical codes like door modules not communicating.

I was taking the pressure right off the fuel line that was above intake manifold, opposite the battery

69

Troubleshooting effort from back in the day schematics showing pump circuit

https://www.corvetteforum.com/forums...ng-unit-2.html

Cheers,
Goose

69

The fuel system used on the 1997-98 LS1 engines uses fuel rails that are equipped as a return (dual line system). The fuel pressure regulator is built into the fuel rail and is vacuumed controlled. Now it’s be awhile since I worked on this system, but if I recall correctly, under high load, low manifold vacuum (near atmosphere), the pressure regulator would raise the fuel pressure slightly for the higher fuel demand.

Your above comment really got my attention!>>. Before it died I got my wheel back on and lowered if, when I lowered it the engine revved like someone was stepping on the gas peddle, not sure if this is a sign of anything.


I suspect that your fuel pressure regulator is leaking fuel into the vacume reference line and when you lowered your car off the jack, fuel migrated into the induction system inducing the high rev of the motor.
To validate this condition, proceed as follows;

Step 1) Remove the driver side coil cover and attach the fuel pressure test gauge to fuel rail.

Step 2) To pre-pressurize the fuel system, place key in ignition and cycle key from OFF to RUN to OFF (DO NOT CRANK THE ENGINE). Cycle key five (5) times to build fuel pressure. POST UP your actual fuel pressure indicated on the fuel pressure gauge
.
Step 3) WARNING MAKE SURE THE ENGINE IS COOL (NOT HOT) AS FUEL LEAKING COULD CAUSE YOU CAR TO CATCH FIRE!!!!! With the engine cool to the touch as to not catch on fire from fuel leak, proceed as follows;
Disconnect fuel pressure vacume line from fuel pressure regulator port, see below, -pressurize the fuel system, place key in ignition and cycle key from OFF to RUN to OFF (DO NOT CRANK THE ENGINE). Cycle key five (5) times to build fuel pressure.

Result> You should have NO fuel leaking from the fuel pressure regulator vacume line port.
Post up your results.

Cheers,
Goose

SMChevy7

Hey guys so here are the codes I got off my car prior to changing my fuel pump
Kind of mind blown there are so many lol.
P1571 h c
B2578 h
B2583 h
U1160 h
B2282 h
B2284 h
U1064 h
U1096 h
B2283 h
B2285 h
B0851 h
B0856 h
B2605 h
B2606 h
U1016 h
U1160 h
C2120 h c

I also appreciate all of your help. Goose, I am going to check my fuel pressure like that this Saturday, I am getting a brand new battery tonight and starting with that cause my battery got completely discharged from checking all these voltages.

Should have left a battery charger on it -_-

SMChevy7

So I got the fuel pressure gauge on and tested it like goose said and got 0

jumped the relay and had 12 v at the relay

checked voltage at the fuel pump and had
12 v, 0v, 5v, ground on that 4 pin connector

69

To help you troubleshoot this problem;
Do you hear the fuel pump running and you got 0 psi fuel presser on the test gauge?
Did you disconnect the fuel pressure regulator vacuum line to see if there is the presence of fuel?
When you replceed the pump, did you replace the complete fuel module assembly inclding pipes and fuel level sensor or did you just replace the pump only by disassembling the original module and replacing the pump?
GOOSE

SMChevy7

Goose, thanks so much for being so thorough.

I replaced the entire thing, fuel filter to fuel lines came as one piece, and it was basically bolt in and go.

The fuel pump audibly is on for 2 seconds, and when the relay is jumped it is constantly on

I did disconnect that vacuum line and there was no fuel it was completely dry.

I added 4 gallons of gas just to be sure I had enough
And tenllhen
I disconnected the fuel line from the black port, an no fuel even came out from the pump even though the relay was jumped and I heard it on, maybe just a bad pump?

69

OK, troubleshooting long shot here…
as you hear the pump running and you have 0 Zero fuel pressure on the test gauge and as you replaced the fuel module connector and to ensure that the pump is not running backwards, do to the power and ground wire being crossed during connector replacements.

NOTE as there are two (2) GRAY wires in this connector, one (1) gray wire to power the pump and one (1) gray wire for the fuel level sensor, it is extremely important to NOT mis-pin these wires as you may risk damage to your PCM!!!

Proceed as follows,
Disconnect electrical connector for the Left Fuel Pump module.
Remove Fuel Pump Relay as you did in the past and jumper wire pins to send voltage down the line to the Fuel Pump Module connector.
Using a volt meter, set meter to voltage, probe pin “A” on connector to chassis ground >Result you should have approx 12 Volts or battery voltage. If you have approx 5 volts, the plug is miswired. If you do not have voltage, cycle voltage meter to “continuity” and if you have “continuity” then the plug is mis-wired.

Using the below schematic for a 1998, probe all four (wires) to ensure you have proper voltages coming from the proper pins in the connector.

Below I have color coded the wires for a better understanding of the wire colors vs. wire positions in the connector. When looking at the connector/electrical pins, the lock tab should be in the up position for proper orientation when probing with the voltage meter.
Hope this info is helpful and post up results.
Cheers,
Goose

SMChevy7

Goose,

you nailed it. I wired the new connector backwards like a fool! Ran out of daylight after work today. Gonna rewire it tomorrow and will report back

SMChevy7

So I rewired it this morning, and got it running with a fuel pressure of 58!

then turned it off, took a shower and was ready to test drive it. Tried to start it again and got no fuel pressure again, and security system turned on (remove key for 10 seconds) wouldn't turn back on. Pretty sure my wiring job is messed up. Gonna try again friday

SMChevy7

Checked all my voltages again and they were good. I unplugged it and plugged it in and it was running again at 58 psi, and again by the time I got it lowered to the ground it died. That happened twice today. I checked that vacuum hose and it was dry. This is 100% something with the pump because when it won't start it's cause the pump isn't turning on. But I definitely have power there and now have the connector wired the correct way

Robrote

I'm no Ben Franklin, but if you have 12v to the pump and it's not running, I'm thinking the pump is no longer a pump.

C5 Diag

If you think your problem "might" be electrically related I'd back probe both negative and positive terminals at the FP connector and do a voltage drop check...just unplugging the connector and checking power and ground doesn't give an accurate condition of your wiring...should have a voltage drop of less than .5 VDC for both...you have to have the fuel pump running to do the test !!...good luck !!

SMChevy7

Okay so I can't get a reading back probing it no matter how far I push in the prongs on the voltmeter....

but if jacked up on the left side it's running at a solid 58 psi, then as soon as I lower it it dies, then if I jack it back up it'll jump back to 58 psi. Even if its a super slowdrop to the grkund this happe s and i can literally jack it back up and it'll stay running....

as soon as the tire starts to hit the ground is when it dies. Every single time. I tested it like this multiple times now.

what the heck could this be????

C5 Diag

Sounds like you have a broken wire somewhere in the harness near the tank...the harness flexing might be causing the pump to shut off...I'd start shaking down the harness...you can work from the harness out and start the "jabbing" process...if you do make sure you use liquid electrical tape to cover the small holes in the wire !!

C5 Diag

DVOM probes are way to thick to back probe if that's what you used...Lisle make a nice kit...real thin and they work great !!