Daily Driver, Go Where I Want To Build
- Thread starter jjvw
- Start date
The very quick synopsis of what has kept the Jeep out of commission is that at least two, maybe more fuel related problems happened an at once.
It started about a year ago with a sporadic weak idle. Something about that led me to replace the throttle position sensor with a new Mopar unit. There was a slight improvement.
Shortly after, I started having to give it throttle to start and keep the engine running until it warmed up. I replaced the Idle Air Control valve before the trip over Red Cone earlier this summer. That solved the startup problem.
But on that trip, the engine would very briefly loose power. Once while sitting at idle and at least once while driving home. And something just wasn't quite right in how the engine ran.
A short time later, I intended to drive the Jeep into work. But the engine did not start. And I very quickly noticed that the fuel pump did not prime when the ignition was turned on.
This led me to believe that the fuel pump had died.
It started about a year ago with a sporadic weak idle. Something about that led me to replace the throttle position sensor with a new Mopar unit. There was a slight improvement.
Shortly after, I started having to give it throttle to start and keep the engine running until it warmed up. I replaced the Idle Air Control valve before the trip over Red Cone earlier this summer. That solved the startup problem.
But on that trip, the engine would very briefly loose power. Once while sitting at idle and at least once while driving home. And something just wasn't quite right in how the engine ran.
A short time later, I intended to drive the Jeep into work. But the engine did not start. And I very quickly noticed that the fuel pump did not prime when the ignition was turned on.
This led me to believe that the fuel pump had died.
Knowing that Mopar fuel pump modules are long out of production and the Bosch units are only sporatically available, Blaine suggested a Walbro to rebuild what I have.
Walbro 255LPH Fuel Pump - 1997-2004 Jeep WRANGLER 4.0L (S) E.F.I. https://walbrofuelpumps.com/1997-2004-jeep-wrangler-high-pressure-255lph-fuel-pump-6-cyl-4-0l.html
More on the rebuild later as this is a very good thing to be aware of. I rebuilt mine only to find out that the problem was not the fuel pump.
Walbro 255LPH Fuel Pump - 1997-2004 Jeep WRANGLER 4.0L (S) E.F.I. https://walbrofuelpumps.com/1997-2004-jeep-wrangler-high-pressure-255lph-fuel-pump-6-cyl-4-0l.html
More on the rebuild later as this is a very good thing to be aware of. I rebuilt mine only to find out that the problem was not the fuel pump.
Throughout most of this ordeal, something else seemed odd beyond the more obvious describeable problems that I could never make sense of when the engine was running.
When the Walbro pump arrived, I rebuilt my original Mopar fuel module that I had replaced about 90k miles ago with a Bosch module.
Back when I decided that the pump has died, I checked voltage at the connector and would get a brief pulse of 12v with the ignition on. Before I dropped the tank, I plugged in the rebuilt fuel module and got nothing with the ignition on.
I check the connector again between power and ground and now suddenly have no voltage. I check power to the body and have 12v. That suggests a bad ground in the wiring harness.
I start checking continuity throughout the ground wire all the way to the engine block. Each time I have continuity. I test voltage at the plug again and find 0v again.
Desperate to find something, I hook up each fuel pump modules to a M12 battery and both turn on.
I do all of this over and over and over again trying to figure out what I am missing because nothing makes sense.
When the Walbro pump arrived, I rebuilt my original Mopar fuel module that I had replaced about 90k miles ago with a Bosch module.
Back when I decided that the pump has died, I checked voltage at the connector and would get a brief pulse of 12v with the ignition on. Before I dropped the tank, I plugged in the rebuilt fuel module and got nothing with the ignition on.
I check the connector again between power and ground and now suddenly have no voltage. I check power to the body and have 12v. That suggests a bad ground in the wiring harness.
I start checking continuity throughout the ground wire all the way to the engine block. Each time I have continuity. I test voltage at the plug again and find 0v again.
Desperate to find something, I hook up each fuel pump modules to a M12 battery and both turn on.
I do all of this over and over and over again trying to figure out what I am missing because nothing makes sense.
Okay! For a guy that gives people grief about precision, that's out of character. And I won't comment about your intentional contraction problem either.
I keep digging and soon have the entire engine harness pulled out and opened up looking for a damaged wire. Nothing. I keep checking things over and over again.
Eventually, during yet another continuity check, I notice a very brief loss of continuity when I moved the growing tangle of a wiring harness. I start poking at stuff and soon discover a splice I made to the ground wire several years ago would lose continuity if I moved it just right.
That was the problem.
Eventually, during yet another continuity check, I notice a very brief loss of continuity when I moved the growing tangle of a wiring harness. I start poking at stuff and soon discover a splice I made to the ground wire several years ago would lose continuity if I moved it just right.
That was the problem.
Without have the schematic in front of me, could it be a switched ground problem? As in the fuel pump relay isn’t latching to ground with the ignition on (rather than ground being constant)?
I replaced that splice with a non-insulated butt splice and adhesive heat shrink. No more loss of continuity.
After cutting open the old pink splice, I found that I had crimped over the wire insulation. That compromised the connection and it took about 5 years to become a problem. Just to be safe, I cut out and re-did all the other splices from that time.
After cutting open the old pink splice, I found that I had crimped over the wire insulation. That compromised the connection and it took about 5 years to become a problem. Just to be safe, I cut out and re-did all the other splices from that time.
My guess is his response meant he didn’t have a spelling mistake near the top of his priority list when describing a much more interesting issue with us. Not that he’s happy to make communication mistakes.
Having opened up the entire wiring harness, I decided to clean up the SpeedoHealer installation from about ten years ago while I was at it. Originally, I spliced it in by the transfer case and ran 4-5 feet of wire forward into the engine bay eventually up to the glove box. The cleaner way is to tap into the wiring harness at the firewall.
And I added a connector for convenience, in the event that I need to remove the entire engine harness again.
And I added a connector for convenience, in the event that I need to remove the entire engine harness again.
That is the condensed version of a long, miserable problem solving effort. A quick drive yesterday and 45 miles today and the Jeep appears to be right back to where it should be. Which means I can get back to a small pile of half finished projects now that the Jeep is drivable again.
And I have a nice spare fuel pump module ready for the future.
And I have a nice spare fuel pump module ready for the future.
The fuel pump ground is a direct line to the engine block that picks up several other grounds along the way. I found that out the old fashioned way. All switching is on the power side. I could have made a new ground on the body near the gas tank and solved this long term. By shear luck, this also would have bypassed the bad splice. But at the time nothing was making sense and the problem was inconsistent, so I kept looking for something in case this was the start of a even bigger issue.
Similar threads
