My 98 has developed an issue with starting. Normally, when I get in to start my car I will just turn the key to the on position for about 5 seconds (having driven a diesel for many years its just a habit) and allow the gauges to sweep and the fuel pump to run up a little pressure, (the pump would normally would stop in about 4 seconds, and was easily heard making its whining noise). Now, intermitantly, when I try to start the car I will not hear the pump and when I go to the start position with the key the engine will spin normally but will not fire. I will get a P1518 code most of the time, have also gotten U1255,U1016,P0356,C1276 randomly.

Now that I have been dealing with this for a couple of days, if I turn the key to the on position and I don't hear the pump, I can turn it back off and back to on and back to off several times and eventually the pump will come on for it's ussual 4 seconds and the engine will start normally with no codes.

I have cleaned the contacts in the ignition switch per Bill C's write up and I put in a brand new battery. This has not cured the problem. My next move is to buy or borrow a fuel pressure gauge to see if I'm in the 55-60 lb range per the service manual. But like I said the car runs and accerates normally once it starts so I'm doubting at this point that is the issue, but not sure. So if my pressure doesn't check out I'll be buying a pump. If my pressure is good, does anybody have any experience with this issue??? Please help me out here.

(Note to moderator: if this should be in C5 tech please feel free to move it)

 

Try swapping the fuel pump relay with one of the others in the relay box. The computer sends out 12v to trigger the relay. The relay sends voltage to the pump. Could also be the fuel pump ground or electrical connections at the pump or inside the tank. A volt meter would help a great deal in isolating the problem. Measure trigger voltage, then relay output voltage at the relay then at the pump, looking for voltage drops. If your voltage is good everywhere, then put your meter on the ground and measure the resistance to the frame. If it is higher than a few ohms, 1/2 tap the ground, solder a 10ga wire to it and ground it to the frame rail with a good ring connector, star washer and bolt with the paint removed from the connection point.

 

1518 is a throttle body code, it will put the car into a limp mode.

 

Update...

I have checked and cleaned the chassis grounds, all good. I have checked the f/p fuse, the B+ connection at the underhood relay panel is tight and cleanI have checked the inside of ground splice pack 122, all clean, no corrosion. To do that of course I had to pull the battery tray. No sign of acid corrosion on the wiring or anything. The PCM? was corroded on the outside but I think thats just from water not acid. Checked the connections to the TAC module and all the gaskets were good and the connections clean inside.

My service manual says DTC P1518 is "PCM to TAC module serial data circuit". The TAC module is the black box attached to the side of the PCM under the battery tray.

I'm about to go back out to check the wiring through the door accordians and the BCM under the toe board for serial bus issues.

I would like to check the Throttle body next, any tips?