94 Z-71 5.7 Need help troubleshooting the fuel system.
#1
04-19-2011, 08:58 AM
94 Z-71 5.7 Need help troubleshooting the fuel system.
I went out to start my truck after about a week of sitting and she just wouldn’t go. It turns over great with plenty of spark and if you put a little go go juice in the TB it starts right up.
I can’t hear the fuel pump priming with the key on engine off. But there is a (click) sound at what should be about the end of the prime cycle, 4 or 5 seconds.
I had a hole in my gas tank so I thought this would be a great time to change the tank and pump. So Off with the bed! Put in a new tank and fuel pump and (click) nothing. Same **** different day. Both the new and the old fuel pumps will run with 12v applied directly to the motor. On the 94 the fuel fuse and relay are located on the passenger side firewall under a black cover. According to the Haynes manual I have the fuse should be a pink wire. I have a gray and gr/wh strip. I’m getting about 11.50V on the gr/wh strip. I’m also getting about 9.somthing volts on the pinkish/ orangeish wire of the relay.
Im thinking there is an electrical problem somewhere inline. So if this makes sence to anyone please lend a hand in the proper way to test the system from one end to the other.
I keep running across posts referring to testing the ALDL somehow. Any thoughts on how to do this?
Any and all help is greatly appreciated.
I can’t hear the fuel pump priming with the key on engine off. But there is a (click) sound at what should be about the end of the prime cycle, 4 or 5 seconds.
I had a hole in my gas tank so I thought this would be a great time to change the tank and pump. So Off with the bed! Put in a new tank and fuel pump and (click) nothing. Same **** different day. Both the new and the old fuel pumps will run with 12v applied directly to the motor. On the 94 the fuel fuse and relay are located on the passenger side firewall under a black cover. According to the Haynes manual I have the fuse should be a pink wire. I have a gray and gr/wh strip. I’m getting about 11.50V on the gr/wh strip. I’m also getting about 9.somthing volts on the pinkish/ orangeish wire of the relay.
Im thinking there is an electrical problem somewhere inline. So if this makes sence to anyone please lend a hand in the proper way to test the system from one end to the other.
I keep running across posts referring to testing the ALDL somehow. Any thoughts on how to do this?
Any and all help is greatly appreciated.
#2
04-19-2011, 09:58 AM
Not uncommon for these years of trucks. I've found rub throughs ahead of the rear axle. This after condemming the fuel pump and replacing it. $200.00 misgiagnosis.
#3
04-26-2011, 08:07 AM
Ok I’m narrowing it down. The fuel pump isn’t getting any power. I retraced the line all the way back to the relay and fuse and still don’t have any juice. I can (hotwire) the fuse next to the relay and get the fuel pump to work and the truck starts fine.
The question I have is where does the fuse normally get power from? It looks to me like it goes to the computer. Could my computer be shot or does it get a signal from somewhere telling it when to power?
#6
04-27-2011, 06:04 AM
Found this online.
the computer will supply voltage for the first 2 seconds to the fuel pump then shut off intill the engine is turned over. the sensor that tells the computer the engine is turning over is in the distributor.so if you have voltage for 2 sec it could be the pickup in the distributor. other than that it could be the computer.?
Reply
How would I test the pickup? also I dont have any service/ check engine light on at any time.
the computer will supply voltage for the first 2 seconds to the fuel pump then shut off intill the engine is turned over. the sensor that tells the computer the engine is turning over is in the distributor.so if you have voltage for 2 sec it could be the pickup in the distributor. other than that it could be the computer.?
Reply
How would I test the pickup? also I dont have any service/ check engine light on at any time.
Last edited by crazy_dave; 04-27-2011 at 07:45 AM.
#8
04-27-2011, 07:45 AM
Yep. I got a new one just for $hits and giggles but still didnt have any power. I bench tested both the new and the old relay and they seemed to work fine.
#10
04-27-2011, 01:08 PM
I know where the fuseable links are but I wasn’t sure what they would look like when there bad. Is there a way to test them?
