Troubleshooting fuel system, no start

    • Troubleshooting fuel system, no start

      I have been rebuilding a 1997 TJ over the last couple months, I got the motor back together and finally fired up last night. I turned the engine off and went to start it again and it cranks but does not fire. I have a new fuel pump in it and have checked that injectors work, replaced the few that were not functioning. I crawled under the jeep and noticed the "Fuel return Evap Line" looks to be rusted and wet over top of the rear spring mount. I guess I'm wondering if that evap return line could be causing no pressure at the fuel rail? I have not put a gauge on the rail i just know when i push in on the valve on the rail little to no fuel comes out. I saw one video where it was a grey connector located next to the PCM that ended up needing to be removed and wires splice to each other in pairs.

      I do not know if i have power at back of jeep yet, i plan on checking that tonight to see if the pump is still getting power. rely seemed to click and fuses looked good.


      -Matt
    • u need air, fuel and spark for it to run. I asshme u have a new air filter so confirm u have fuel pressure at the rail and then we can help some more.
      '88 YJ with not much '88 left. :)
      Team Mall Crawler #609
      Werock Stock Class we-rock.cc
      Werock '06 - 2nd East Coast, 5th overall Werock '07 - 3rd East Coast Sponsored by: The Drive Shaft Shop driveshaftshop.com Delaware Jeep Assoc. delawareja.com
    • I realize that last message was confusing. I do not have pressure at the fuel rail. I pulled the connection off at fuel pump and I have a hot to ground (frame with test light) but that’s about all I can come up with. I can hear the pump kick on, at least it sure sounds like the pump. Odd
    • This pump is only 25 minutes run time old, I’m guessing you have experience with new pumps going bad even after it just ran the vehicle. Guess I’ll buy a new one. The crank position sensor doesn’t tell the pump when to send fuel? I’m just struggling with a brand new pump being bad. I guess it could happen and it would happen to me.

      Cheers astape thanks for the reply
    • the pump will cycle for 3-5 seconds when u first turn the key. U do not have to start it. This will be enough to pressurize the rail. U can pull the quick disco near the harness plug or off the motor, hold up a bucket and have someone turn the key. U should hear the pump and fuel should pour out with a lot of force. U may want to put a larger hose over line to direct it. It will make a mess if its working.


      If its working at that point the then the auto shut down relay may be killing the pump circuit. There r several causes for this. First determine if the pump is pushing.

      I have also seen the feed hose internal to the tank in the pump assembly come loose. U will have to drop the tank to inspect.
      '88 YJ with not much '88 left. :)
      Team Mall Crawler #609
      Werock Stock Class we-rock.cc
      Werock '06 - 2nd East Coast, 5th overall Werock '07 - 3rd East Coast Sponsored by: The Drive Shaft Shop driveshaftshop.com Delaware Jeep Assoc. delawareja.com
    • Thanks,

      So I was able to push in the schrader valve(stem) on the fuel rail and turn the key and gas went everywhere. When I cycle the key like you said just on not started; and checked again at Schrader stem no pressure. The only way i can get fuel to the rail is by holding in Schrader stem and turn key to on not start.

      As far as the feed hose coming loose i did end up dropping the tank just so i could have a better look at things.

      I have a question you might know something about; the gas tank has two lines Fuel to rail and another smaller line which runs to the Ash-can, do you know if it matters which stem i hook it up to, the ash-can has a port on left and right i was not sure if internally it matter which one the fuel vapor line went to. the other port on ash-can comes from a solenoid or something so hard to explain and my manual does not show my jeeps configuration for the evap and air system. I was just trying to rule out me having the evap line hooked up wrong or not hooked up being the issue.

      Thanks again,

      Matt
    • its just really hard to diagnose over the internet. Is the fuel pump getting power as u try to start or does power to it turn off? U may have to use a paper clip and some wire to make a lead off the plug. If it turns iff then the auto shut down relay is killing the pump circuit.
      '88 YJ with not much '88 left. :)
      Team Mall Crawler #609
      Werock Stock Class we-rock.cc
      Werock '06 - 2nd East Coast, 5th overall Werock '07 - 3rd East Coast Sponsored by: The Drive Shaft Shop driveshaftshop.com Delaware Jeep Assoc. delawareja.com
    • No worries I appreciate the input. I pulled the asd relay and numbered from 12volt supply to center wire. Tried to start it didn’t fire. I read that means it’s either crank or camshaft sensors. The camshaft sensor is the disc inside distributor correct? I’ll install the jumper as you said off fuel pump today.

      Thanks again.
    • Hey Astape,

      I’m wondering if you know of any information out there about ways to bypass the ASD circuit. I’m beginning to believe whatever issue I have is in the asd. I say that because I don’t have power to fuel pump when cranking engine over. Also looks like I do not have the 5volt supply to injectors as well.

      Thanks again
    • i would have to review the diagrams. There r only a few things that can cause the auto shut down to activate.

      Does the check engine light turn on when u turn the key to start? This will tell u if the computer us turning on.

      Does the tach bounce a little when cranking? Will tell u if the cps is sending a signal


      There is a 10amp fuse in the under hood fuse box i think labeled iod. It will kill the relay power, double check it.


      Pull the bottom off the under hood fuse box and look for chaffed or brocken wires.
      '88 YJ with not much '88 left. :)
      Team Mall Crawler #609
      Werock Stock Class we-rock.cc
      Werock '06 - 2nd East Coast, 5th overall Werock '07 - 3rd East Coast Sponsored by: The Drive Shaft Shop driveshaftshop.com Delaware Jeep Assoc. delawareja.com
    • Astape,

      1) Check engine light comes on when key turned to start. Turns off after a few seconds.
      2) The tach DOES NOT bounce when cranking motor over.
      3) Looking for the IOD fuse. What does that stand for if you don’t mind.
      4) I have the under hood fuse box detached everything under it is attached and no brakes or burns.

      I’m looking through the service manual I found online to figure out how the fuel injectors get power. I have crank, fuel at least to rail and spark. I believe I have no power to injectors. Checking that tonight.

      Is there anyone in the Dover area you recommend working on Jeeps?

      -Matt
    • i doubt it. How do u know u have spark. Do u have an in line tester and u can see the light turn on? The fact that the tach doesnt bouce screams cps or dist sync sensor. The lack of these signals will keep the computer from firing the injectors.


      Can confirm spark.... shoot starting fluid down the intake it should fire up if u have spark. If it doesnt it goes back to those 2 sensors being am issue.
      '88 YJ with not much '88 left. :)
      Team Mall Crawler #609
      Werock Stock Class we-rock.cc
      Werock '06 - 2nd East Coast, 5th overall Werock '07 - 3rd East Coast Sponsored by: The Drive Shaft Shop driveshaftshop.com Delaware Jeep Assoc. delawareja.com
    • astape wrote:

      i doubt it. How do u know u have spark. Do u have an in line tester and u can see the light turn on? The fact that the tach doesnt bouce screams cps or dist sync sensor. The lack of these signals will keep the computer from firing the injectors.


      Can confirm spark.... shoot starting fluid down the intake it should fire up if u have spark. If it doesnt it goes back to those 2 sensors being am issue.
      don't know if this was covered but i had same problem was on trail ride jeep died got it home no fuel to rail bought new fuel pump i believe bosch pump and still no pressure to rail? changed fuses sill nothing?towed it up to my work and had avtec guy look at it he had it running in 20 minutes it turned out to be pump wireing was different then mine so he flipped two wires in plug started right up! good luck
    • Confirmed spark... pulled plug wire hooked up loose spark plug grounded to motor turned key. Watched spark plug fire twice stopped turning key.

      Tach no bouncing... replaced both distributor and crankshaft sensors.

      Leads me back to pcm. However the check engine like lights up and turns off after a few seconds.

      Fuel injectors are not getting 5volt power. Ever.

      Leads me back to pcm.

      I’m working on checking all grounds and wires now. So far everything looks great.
    • Id bet its the PCM, your gonna have to find a used one. The check engine light comes on for a few most every vehicle and shuts off. You could check the harness as well.