fuel pump electrical issues

[Kenny Calhoon]

i have a 1993 grand cherokee and the fuel pump will not come on all the time. when the check engine light comes on then i hear the pump. also weird clicking coming from the front of the motor right before the relays trip and the pump comes on

 

[BGMacaw]

I recall another poster having a similar issue including the clicking. He said it mostly happened when the vehicle was cold but would start fine after it was warmed up/hot. His turned out to be the ECM. As a test he said he used a hair dryer to heat up the ECM while the engine was cold and after doing so the pump would engage normally.

i have a 1993 grand cherokee and the fuel pump will not come on all the time. when the check engine light comes on then i hear the pump. also weird clicking coming from the front of the motor right before the relays trip and the pump comes on

 

[jimbob2001]

IHi. Guys ! (And. Girls!). Let's. Tackle. This. FUEL. PuMp. Electrical Issue! Need. A. Couple. Of. Things to. Troubleshoot. This. Problem. You will. NEED. A. HELPER. And a. DVM. (Multimeter). Can. Be. Purchased. At a. Radio Shack or. FRYs Electronics! Have. Helper. Sit. In. Drivers. Seàt. - While. You REMOVE the. Gas. Cap! LISTEN. For. The. Fuel. Pump to. COME. ON while. YOUR. Helper. Turns KEY ON. Remember. That. With the. ENGINE. NOT. Running - ECM. Only. Turns. Fuel pump on. For. TWO or Three seconds at. A time!! (Needs. CPS signal to stay on) Do. This a. COUPLE. Of times - WAIT. About. 5 or 10 Seconds. Between. KEY ON. Times. - to allow ECM to RESET. Did you. HEAR The. Pump come on each time the Key was turned. ON??? If not - CHECK : Fuel. Pump Fuse. Make SURE. Fuse for PUMP is OK! Is the. Fuel Pump RELAY coming:. ON. For. Two or three seconds - when your. Helper TURNS key ON?? You Check-it-out : while. HELPER cycles KEY ON. Next - Is there Power on the. - FUEL. Pump? Jack-Up back of. Jeep (if not enough clearance) Unplug connector from Back of Fuel Tank - Verify. Voltage for two or three seconds with DVM (set on DC Volts) Have Helper Cycle Key ON - while you check power to Connector - If there. IS. Power (12V) and pump still does not come on (while plugged in) THEN you need a new pump! Simple - Huh? Also - Does. Jeep ever. START? Check Engine lite. ON? JB

 

[Kenny Calhoon]

IHi. Guys ! (And. Girls!). Let's. Tackle. This. FUEL. PuMp. Electrical Issue! Need. A. Couple. Of. Things to. Troubleshoot. This. Problem. You will. NEED. A. HELPER. And a. DVM. (Multimeter). Can. Be. Purchased. At a. Radio Shack or. FRYs Electronics! Have. Helper. Sit. In. Drivers. Seàt. - While. You REMOVE the. Gas. Cap! LISTEN. For. The. Fuel. Pump to. COME. ON while. YOUR. Helper. Turns KEY ON. Remember. That. With the. ENGINE. NOT. Running - ECM. Only. Turns. Fuel pump on. For. TWO or Three seconds at. A time!! (Needs. CPS signal to stay on) Do. This a. COUPLE. Of times - WAIT. About. 5 or 10 Seconds. Between. KEY ON. Times. - to allow ECM to RESET. Did you. HEAR The. Pump come on each time the Key was turned. ON??? If not - CHECK : Fuel. Pump Fuse. Make SURE. Fuse for PUMP is OK! Is the. Fuel Pump RELAY coming:. ON. For. Two or three seconds - when your. Helper TURNS key ON?? You Check-it-out : while. HELPER cycles KEY ON. Next - Is there Power on the. - FUEL. Pump? Jack-Up back of. Jeep (if not enough clearance) Unplug connector from Back of Fuel Tank - Verify. Voltage for two or three seconds with DVM (set on DC Volts) Have Helper Cycle Key ON - while you check power to Connector - If there. IS. Power (12V) and pump still does not come on (while plugged in) THEN you need a new pump! Simple - Huh? Also - Does. Jeep ever. START? Check Engine lite. ON? JB

the jeep does start but only after the check engine light comes on. i have checked the voltage at the elec connection and only had 6.3 volts on a couple of wires with key on not enough elec i know but where do i go from here?

 

[jimbob2001]

Wow. - - this. Is a. Wierd. Problem! You. State. That. The. Jeep. Starts. - But the Check. Engine. Lite. Comes. ON! Correct? Have. You managed. To. DUMP the. Codes Yet? Need. To. KNOW. What Code(s). ECM. Is. Putting OUT?? Also, you say - Your only. Getting. 6.3VDC. To. Connector. For the Fuel Pump. Right? Should be around 4. Wires. On. (Going to connector) - which. Two wires have 6V? First things FIRST! Have you. Replaced. ANY. Parts? Fuel Pump Relay? The Fuel pump? Fuel pump FUSE?? Just trying. Get a. BASELINE. On. The. Problem!! Are you. Hearing. The. Fuel pump. COME. ON. - for. Two or. Three. Seconds - when YOU. JUST turn. KEY on for 3 or 5 seconds? (dont stArt it) The Fuel pump should have. 12 v. On it for two or three. Seconds.- when you turn key ON! OK - let's. Back up. The problem sounds like - BAD wiring or a BAD ground! TRY THIS- - Turn. KEY OFF. Measure Battery Voltage - Should be - - 12V to 12.5V. With Car NOT running, THEN. - REMOVE. Fuel pump Relay - Measure ALL. Terminls. In. Fuel Pump Relay. SOCKET! One. Terminal Should. Measure 12VDC - with KEY. OFF! DOES IT? This is. The. Voltage. That FEEDS the Pump! ( When relay energizes). Have you replaced Relay? Do. You. Have a Jeep Service Manual? Handy to. RUN. DOWN. Electrical ISSUES! GOOD LUCK! Keep us Posted! - JB