TJ won't start: Could it be my fuel pump?

[Chris]

So it's a gorgeous day out today and I decide to take the TJ out. I go outside, start it up, and it runs fine for a minute.

After a minute it starts sputtering very aggressively, then dies. I start it up again and it starts, but it sounds like it's running on 3 cylinders. It's sputtering like crazy, and then 15 seconds later it dies. I continue to start it, and this continues to happen. It will run for 15 seconds max, but sputter out and die.

Eventually it just stopped starting altogether. It will turn over and crank, but it won't actually start.

No error codes or anything.

My immediate assumption is the fuel pump. Why you ask? Well when I cycle the ignition, I no longer hear the fuel pump priming at all. I checked the fuse for the fuel pump under the hood (as well as the relay) and it's good.

I'd love to test the fuel pressure at the rail, but they got rid of the Schrader valves on these things sometime in 2002 (screw you Chrysler!).

What do you guys think? Is my train of thought on track here?

UPDATE: I lied. I guess all that sound deadening material made it impossible to hear the fuel pump priming inside the vehicle any longer. I just had my neighbor come over though and he cycled the ignition while I sat under it. The fuel pump is indeed priming after all.

 

[Jerry Bransford]

If it starts after spraying starting fluid into the throttle body my first guess would be the fuel pump crapped out. Especially since you no longer hear the fuel pump priming and its fuse is good. See if you can hear/feel the fuel pump relay clicking on-off each time a helper turns the ignition switch on-off-on. If you can that would further make me believe the fuel pump has gone belly up.

 

[Daryl]

Does your Jeep have skim? If it does, try another key. If that doesn’t work, I’m with Jerry on this one.

 

[Jerry Bransford]

Does your Jeep have skim? If it does, try another key. If that doesn’t work, I’m with Jerry on this one.

The SKIM system will at least let it start each time even with a bad key, it just kills the engine something like 1.5 seconds later if the key doesn't respond to the code check.

 

[Chris]

If it starts after spraying starting fluid into the throttle body my first guess would be the fuel pump crapped out. Especially since you no longer hear the fuel pump priming and its fuse is good. See if you can hear/feel the fuel pump relay clicking on-off each time a helper turns the ignition switch on-off-on. If you can that would further make me believe the fuel pump has gone belly up.

I lied. I guess all that sound deadening material made it impossible to hear the fuel pump priming inside the vehicle any longer. I just had my neighbor come over though and he cycled the ignition while I sat under it. The fuel pump is indeed priming after all.

I'll still give the starter fluid a try though to see if that does anything. The fact that it was sputtering and then dying makes me want to think it's fuel related.

Does your Jeep have skim? If it does, try another key. If that doesn’t work, I’m with Jerry on this one.

No SKIM on this one.

 

[Jay MacLeay]

This sounds similar to the symptoms I was having with my timing chain being too loose. Cel would flicker as the engine sputtered and died, but no codes stayed stored. I think you can check the timing chain if you take off the cap on the OPDA and look down at the gear while someone turns the crankshaft with a ratchet. Most likely this isn't your issue, but it kind of sounds like it might, and it is fairly easy to check out. Good luck!

 

[jjvw]

A sensor with a poor connection might be triggering the ASD.

 

[Jay MacLeay]

A sensor with a poor connection might be triggering the ASD.

Wouldn't that leave a stored code?

 

[jjvw]

Wouldn't that leave a stored code?

Not when it happened on mine. I wasted a lot of time thinking it was the fuel pump. I unplugged/replugged everything I could reach. As best I could tell, it was an o2 sensor that I had replaced several months earlier.

 

[Chris]

The real pain in the butt here is of course that there is no CEL or stored / pending codes. That would make life a lot easier if there was some stored codes.

 

[Chris]

Not when it happened on mine. I wasted a lot of time thinking it was the fuel pump. I unplugged/replugged everything I could reach. As best I could tell, it was an o2 sensor that I replaced several months earlier.

So yours ended up being O2 sensors? And it wouldn’t start at all?

The post cat O2 sensors are disabled, but I suppose it could always be the pre-cat sensors.

 

[jjvw]

So yours ended up being O2 sensors? And it wouldn’t start at all?

The post cat O2 sensors are disabled, but I suppose it could always be the pre-cat sensors.

On mine specifically, the engine would sputter and shut off if the Jeep was twisted up just right, but I also noticed it when hitting a bump hard and fast enough to jostle the connection.

As a guess, I pulled most of the plugs anywhere near the trans tunnel, which included the o2 sensors I had replaced earlier. I suspect it was them because I had messed with them. But I'll never know. This was over 2 years ago with no sign of it happening again.

 

[jjvw]

Go back and look at any sensor you or anyone else has messed with.

A friend of my dad was a Chrysler TJ tech way back when. This was his recommendation to me.

 

[Chris]

Go back and look at any sensor you or anyone else has messed with.

A friend of my dad was a Chrysler TJ tech way back when. This was his recommendation to me.

I haven't messed with any of them, though the shop may have. Of course I've driven it quite a bit since I had the mid-arm installed, so if it was something they touched, there wasn't a problem initially at least.

I'm going to swing by AutoZone tonight and pick up some starting fluid just to see if that trick does anything at all. Obviously I can rule out the starter and the battery since it has no trouble turning over. Seems like it's going to be something either fuel or sensor related.

 

[toximus]

Does it fire at all when you turn it over?

 

[Starrs]

So it's a gorgeous day out today and I decide to take the TJ out. I go outside, start it up, and it runs fine for a minute.

After a minute it starts sputtering very aggressively, then dies. I start it up again and it starts, but it sounds like it's running on 3 cylinders. It's sputtering like crazy, and then 15 seconds later it dies. I continue to start it, and this continues to happen. It will run for 15 seconds max, but sputter out and die.

Eventually it just stopped starting altogether. It will turn over and crank, but it won't actually start.

No error codes or anything.

My immediate assumption is the fuel pump. Why you ask? Well when I cycle the ignition, I no longer hear the fuel pump priming at all. I checked the fuse for the fuel pump under the hood (as well as the relay) and it's good.

I'd love to test the fuel pressure at the rail, but they got rid of the Schrader valves on these things sometime in 2002 (screw you Chrysler!).

What do you guys think? Is my train of thought on track here?

UPDATE: I lied. I guess all that sound deadening material made it impossible to hear the fuel pump priming inside the vehicle any longer. I just had my neighbor come over though and he cycled the ignition while I sat under it. The fuel pump is indeed priming after all.

Yikes. Worst luck for sure. Hope that’s an easy fix.

 

[Chris]

Fixed it!

So I am by no means the smartest guy in the world, but I like to think that after all these years, the wisdom is finally starting to come. I'm a very firm believer in the Occam's Razor principle, and I find in most cases, the most difficult answer usually has the simplest explanation. When people post about no-start issues, the first things I always think of are the simple things like batteries and such.

Well in this case, I took an hour and thought about it. I started it, it ran fine, and then it sputtered out. It continued to start, but each time it would sputter and sputter until it eventually just wouldn't start anymore at all (only turn over).

The fuel gauge showed it was at the 1/2 way mark, but if that was the case, why did it mimic that "out of fuel" experience when all of this happened.

I decided to run down to the gas station with my 2.5 gallon gas can. I filled it up, came home, filled up the TJ, and then cycled the ignition a number of time to make sure there was fuel in the lines.

I went to turn it over, and BOOM, it started right up just like always.

So, what does this mean? It means that my fuel level sensor in the tank is stuck again (if you remember, I had a problem with this before when I initially installed my GenRight aluminum tank). So this entire time I've been thinking I had gas in the tank, but I didn't.

I'm just glad I was smart enough to rule out the most simple explanation first, otherwise I'd probably have been chasing this like a mad man, replacing sensors, and who knows what else!

This is yet again another perfect example of Occam's Razor at it's finest.

Anyways, I'm just glad I solved this. Now I'll need to probably replace the fuel pump, as that sending unit has given me trouble once before. Again, I'm just glad it didn't end up being something much more difficult to track down.

The moral of the story here is to ALWAYS rule out the most simple explanations first, even if they seem stupid and silly.

 

[bobthetj03]

Sucks that you missed on a nice day to go for a cruise, but glad it was an easy fix. You're getting good at dropping that tank!

 

[Chris]

Sucks that you missed on a nice day to go for a cruise, but glad it was an easy fix. You're getting good at dropping that tank!

When I drop the tank again this time, it will be the 4th time I believe.

For something so easy (only help on by a few bolts) it's really a pain in the ass to have to remove, mostly just because of all the evap lines and fuel filler neck.

Though I guess now I really have an excuse to remove the tank, because now I can cap off my evap lines once and for all, since I disabled the evap system.

 

[Boinked]

I can only imagine what your wife called you after you told her you ran out of gas.........

I would make up a story about a relay to save the harassment.