Engine/Transmission (1994 - 1998) Blowing Fuel Pump

[C_Power]

TRuck runs but no gauges and trans stuck in third gear. The 20amp fuel pump fuse is blown and blows when replaced. Any help would be great. .

 

[hsmith]

Tell us what you have. ie. year and so so so.

 

[C_Power]

96' 4wd 3500 auto stock

 

[hsmith]

Call me stupid, but the '96 does not use a fuel pump fuse. The pump runs off the cam. Mechanical for sure. Mine is like yours but only 2wd and manual. Which fuse are you referring to?

 

[C_Power]

As far as I can tell it goes to the PCM, Fuel Pump Relay, and the Trans Relay. I tried scanning the PCM and it won't link. If stick a fuse in it blows. The truck run fine and punched it, all the gauges dies and all the lights came on. It fuse #8 in the PDC.

 

[tp0d]

You have a rubbed-thru wire somewhere. Or, have you done any work to the truck lately? Pinching a wire between a bolt/etc can be easily done.



I`ve had 3 wires rubbed thru on my truck so far, seperate occasions. They can be a real bugger to track down. A good place to look is around the intercooler, at the bottom by the frame. I had 2 wires go bad there.



good luck



-j

 

[Howard Durand]

The manual is probably referring to the fuel pre heater which is mounted along with the fuel pump.

Try disconnecting the cable to it, they do have a tendency to go bad.

The relay for it is the small one of the two that are mounted on the firewall above the engine.

 

[C_Power]

Update, Went through disconnecting sensors and checking wires. Figured out if I unplug the Trans Relay in the PDC my short ground was gone. Can anybody tell me what the relay does and what it powers.

 

[Howard Durand]

I only have a service manual for the 94 which is different from the 96. In mine there is no transmission relay. There is a fuel pump relay but that is for the gas engines only.



Not knowing if the #8 fuse feeds the relay coil or a circuit that passes through the relay it is a guessing game as to what may be the trouble.

If pulling your transmission relay eliminates the short, I would try a different relay. The relay coil itself may be shorted. If it still blows the fuse, then it must be the circuit passing through the relay, which I believe is the one that carries the 12 volt feed for the overdrive and torque converter solenoids. Try unplugging that cable at the transmission. You may have a shorted solenoid or internal wiring.

 

[EBansberg]

did you try driving it with the relay disconnected? Any lockup or OD? Only things I would think the transmission would have a relay for.

 

[Joe G.]

Is it the relay shown on this page that is replaced by a jumper wire in order to install a manual lockup switch? http://www.tstproducts.com/Torque Converter Lockup Switch.pdf



If it is, then put the jumper in and see what happens.

 

[C_Power]

Update... I took the trans. pan off and found the rocker arm that shifts for second gear had broke in half. The pieces had tore the wiring on the solenoids. Which caused the shorts in the wiring. Now its off the transmission shop for a rebuild. Thanks for your input and suggestions.