Jeep will only start when I jump the fuel pump relay with a paper clip

charleschoplin

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Tennessee
Jeep will only start when I jump Fuel Pump Relay with a paper clip. changed fuel
pump last week using Delphi, brand new injectors. Pulled the main fuel line off and fuel comes out but not a lot can also hear pump buzzing every time the key is turned to the on position. Cycle the key without the relay jumped and it almost starts but doesn’t. Swapped relays and nothing. Checked for power at relay and it’s good. Almost seems like it’s loosing its ground for the relay but when started it runs and it is grounded off. If i’m not mistaken the ground for the fuel pump relay is in the PCM pin 19 i believe the brown wire also know that the ASD Relay is in line with the fuel pump relay. Need help.
 
The PCM provides the ground connection that turns the fuel pump relay on, there's always 12 volts on it so long as the key is on. The fuel pump relay only receives its required ground connection from the PCM for the initial 1.8 seconds right after you turn your key on. After that 1.8 seconds is over, the PCM will only continue to provide the ground connection to keep the fuel pump relay energized if everything else is ok like a good signal from the crankshaft position sensor.

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The PCM provides the ground connection that turns the fuel pump relay on, there's always 12 volts on it so long as the key is on. The fuel pump relay only receives its required ground connection from the PCM for the initial 1.8 seconds right after you turn your key on. After that 1.8 seconds is over, the PCM will only continue to provide the ground connection to keep the fuel pump relay energized if everything else is ok like a good signal from the crankshaft position sensor.

View attachment 265173
It is throwing a P1282 code which is fuel pump relay circuit control. I have checked the cps with an oscilloscope and the breaks are even everything checks out pulled up a diagram of how they should look and they look just fine. haven’t found anything else wrong so kind of moving towards bad PCM
 
I don't suppose your Jeep has the SKIM system installed...
When you turn the ignition to run and crank the engine; is there an amber circle illuminated with an inset key on the top left of the instrument cluster ?
 
Alright fellow TJ owners, I'm going nuts and deeply need advice. I have a 2004 TJ Sport with the 4.0 and automatic transmission. I started getting code 1495 which is related to the EVAP system. I've changed everything under the hood and behind the passenger side rear tire, and even used a Snap On smoke machine to check for leaks. And yes, I've changed the gas cap ! I'm still getting the 1495 code. I've installed the anti plug foulers in the downstream cat converters and the 420 codes are gone. I'm out of my league here. Any ideas or past experiences with your TJ similar to mine ?
 
Alright fellow TJ owners, I'm going nuts and deeply need advice. I have a 2004 TJ Sport with the 4.0 and automatic transmission. I started getting code 1495 which is related to the EVAP system. I've changed everything under the hood and behind the passenger side rear tire, and even used a Snap On smoke machine to check for leaks. And yes, I've changed the gas cap ! I'm still getting the 1495 code. I've installed the anti plug foulers in the downstream cat converters and the 420 codes are gone. I'm out of my league here. Any ideas or past experiences with your TJ similar to mine ?
did you change the evap cannister ?
 
Alright fellow TJ owners, I'm going nuts and deeply need advice. I have a 2004 TJ Sport with the 4.0 and automatic transmission. I started getting code 1495 which is related to the EVAP system. I've changed everything under the hood and behind the passenger side rear tire, and even used a Snap On smoke machine to check for leaks. And yes, I've changed the gas cap ! I'm still getting the 1495 code. I've installed the anti plug foulers in the downstream cat converters and the 420 codes are gone. I'm out of my league here. Any ideas or past experiences with your TJ similar to mine ?
DTC P1495 identifies a Leak Detection Pump solenoid circuit problem....
Malfunction is detected when the Powertrain Control Module (PCM) detected the pump solenoid did not change status when activated,
You need to test for voltage and verify the solenoid is functioning....
 
Was already done, and the solenoid was changed along with everything else connected in the system. But thanks for your input. I appreciate it.
 
I've changed everything, checked voltages, ran smoke test for leaky lines, but it's still popping up as check engine light. I've heard it could be something in the gas tank all the way to the CPU being defective.
ok just checking i know if you just change the purge valve and dont change the vapor cannister also the charcoal in it will just stop up the new valve
 
I don't suppose your Jeep has the SKIM system installed...
When you turn the ignition to run and crank the engine; is there an amber circle illuminated with an inset key on the top left of the instrument cluster ?
no it doesn’t have SKIM i believe the key would be like dark green or tan whatever that color is if you have SKIM
 
2 years later and now It starts, but only on the second or third try after turning the key off and on about 3 times. once it does start, it runs and drives just fine
 
2 years later and now It starts, but only on the second or third try after turning the key off and on about 3 times. once it does start, it runs and drives just fine

Check valve in the fuel pump is no longer working. You'll need to replace the whole unit or install the Bosch pump into your existing Fuel Pump Assembly.
 
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Just thought I would add my recent experience with fuel pump woes for anyone who may be searching for a solution.

This is on my Son's 2005 TJ 4.0. He had a cylinder misfire code (can't remember the code), a warm up catalyst code P0431, Evap small leak code P0456, and Evap lose fuel cap code P0457. We replaced the spark plugs, ignition coi,l and fuel cap. Jeep started and drove great for 2 days then suddenly had trouble starting to the point where he called me to bring the trailer. He was able to get it started running roughly for the first few minutes to get it home. The jeep over the next few days ran great.
We needed to drop the fuel tank to address the evap leak on one of the lines on top of the tank as well as the hard to fuel situation (the hard to fuel situation from the plunger inside the tank connected to the filler neck). The plunger was sticking and we took it out to sand it slightly to make it move and not stick. We removed the tank and cleaned it up. In the process of putting the fuel pump back in trying to get the clamp to seat, the punch slipped and broke the plastic nipple that connects to the fuel line (crap). We installed a new fuel pump and the jeep started right up after cycling the pump a few times. We let it run for about 5 minutes then shut it off. When we restarted the jeep cranked and died. Upon further start attempts the jeep would struggle to stay on more than a few seconds - obviously to us a fuel starvation issue. We could no longer hear the pump come on with the key. We pulled the plug off the pump and put it on the meter with the key on I was getting 11.65 volts. Battery showed 12.5 volts. We looked at the pinouts in the factory service manual and found the orange wire with red stripe OR/RD providing power came from the relay box. We swapped relays with the fuel pump relay and no dice. We tested continuity on the OR/RD at different points and found it was testing ok. That OR/RD wire runs through the C102 gray connector at the fire wall, we disconnected C102 and checked continuity there and had it. We then tested voltage across that wire at the C102 connector and were getting 11.65-7 volts. So we cut the OR/RD wire as close to the relay box as we could in the harness that runs on the side of the battery. Stripped the wire and tested voltage there and we got 12.5 volts. We then ran a new wire from that point all the way to the fuel pump connecter about 2 ft from the connecter and spliced into it there. That gave us 12.5 volts and made the fuel pump come on with the key! Hell yes! We then routed that wire through the harness and inside of the wire loom as best as we could.
Jeep cranked right up without stumbling or mumbling. We think we found the source of several woes this jeep was having. The cylinder misfire code we were getting (still can't remember the code) claimed as one of its causes a faulty fuel pump and in our case it was the wiring.

Hope this helps someone out when they search for a similar issue. OH, and I realize this is an older thread.