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Sputtering and stalling only while driving

JoeSpit

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Joined
Dec 9, 2020
Messages
63
Location
island of maui
Hey gang, so after replacing my fuel pump (twice) and ignition switch. I am still getting my sputtering/stalling. so let me take you back

-My OEM fuel pump was getting loud and i had to chage it out. did that and it worked well for a week.
-then i wasnt getting proper spark or power to the coil, i noticed after cleaning ignition switch it worked fine here and there but it it had a hard start i would just spray contacts again and it would work.]

Now i'm getting sputters and stalls while i'm driving and it wont start up again until it cools down a bit. I replaced the ignition switch and still no progress. When everything cools a bit it will start up no issue and i can rev it all day in park and its fine, BUT once i start driving for 5-10min it dies.

This makes me think its something to do with wiring and trans heat. I gave the wires a (nightime) visual inspection but they seem fine. The power going to my fuel pimp reads at 10.5-11v So me thinks it must be wiring. Ill post pics of wire loom tomorrow in the day time but does anyone have any thoughts on WTH is goin on here?
 
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JoeSpit

JoeSpit

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Joined
Dec 9, 2020
Messages
63
Location
island of maui
well it looks like the issue is wiring. Even though i have inspected every inch except for what passes over the transmission i cant find a break or nothing, However since i get 12.5v at the distribution box for the fuel pump and 11v or under at the connector to the fuel pump, there must be something up with the wiring, right?

Does anyone have any tips for rewiring? I'm afraid to damage the distribution box or the connector to the pump. I think i'm going to route it differently, like high around the firewall to the driver side and try to avoid any hotspots on the old girl.

I've never really rewired befoire so any special tools i should get to remove pins from distributon box or anything like that?
 

Krusty_tub

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Apr 23, 2022
Messages
92
Location
Ct
Put a test light accross the batt + and ground - pins of the fp connector. Turn key on, if it's dim or doesn't light at all then you'll need to find out if it's the batt+ side or ground side with the test lamp
 
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JoeSpit

JoeSpit

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Joined
Dec 9, 2020
Messages
63
Location
island of maui
Put a test light accross the batt + and ground - pins of the fp connector. Turn key on, if it's dim or doesn't light at all then you'll need to find out if it's the batt+ side or ground side with the test lamp
yeah i checked with my volt meter and at the fuel pump connector it reads 11v or under, Meanwhile at the power distribution box it reads the full 12.5v on the same wires. So i guess i'm going to strip out the wires from the loom, give them thorough inspection and if i can see any crack of copper ill just do a full rewire, hopefully i just find a lil patch of rough wire.

At first i was ifraid, i was petrified. but now i'm kinda excited to solder after many years. Hope its like a bike and im not rusty n make things worse
 

FJQue

TJ Enthusiast
Joined
Mar 15, 2020
Messages
183
Location
Kansas City
yeah i checked with my volt meter and at the fuel pump connector it reads 11v or under, Meanwhile at the power distribution box it reads the full 12.5v on the same wires. So i guess i'm going to strip out the wires from the loom, give them thorough inspection and if i can see any crack of copper ill just do a full rewire, hopefully i just find a lil patch of rough wire.

At first i was ifraid, i was petrified. but now i'm kinda excited to solder after many years. Hope its like a bike and im not rusty n make things worse
You're an animal. Following just because we could all be facing wiring issues by this age of the TJ. I've heard our ECU's are time bombs for sure, luckily there's an aftermarket company that figured out what the weak connections were, fixed it and sells them online. Someone else has to have run into this, I suck with a voltmeter, I know it's time to learn..
 

Krusty_tub

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Apr 23, 2022
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Location
Ct
I wouldn't rewire it unless the whole harness is damaged. It could just be a bad ground or loose pin at the relay
 
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JoeSpit

JoeSpit

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Dec 9, 2020
Messages
63
Location
island of maui
I wouldn't rewire it unless the whole harness is damaged. It could just be a bad ground or loose pin at the relay
Yeah i got ahead of myself. i was trying to do a test by cutting and running one of the fuel wires right to the battery (neighbors idea, i shouldn't have listened) and at some point i got the 12v reading so i figured the wires right at the connector were messed, so my 8 year old and me soldered new wires on there. It didnt work be we had a blast! ( it runs a lil worse now tho)

Later on another neighbor noticed some of my vacuum lines (i think to the evap) are alllll F'd up. Sooooo maybe its also a vacuum problem. Which i did hear a whistle like a week back but everytime i opened the hood it went away, and then i forgot.

So i probably have more than one single issue.

Tomorrow i plan to get new vacuum hoses, if that dont remedy things nicely, i was going to cut the fuel wires a foot at a time until i get that good 12v reading, as i type that it sounds like a bad idea but seemed like a goodin at some point.
 
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JoeSpit

JoeSpit

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Dec 9, 2020
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island of maui
So far today i checked all my grounds (at least i think i got all of em all .they're all in the engine bay, yeah?), fixed my vacuum leaks (didn't work) and noticed that my issues could be a bad TPS. My line of thinking was a) i'm getting improper voltage readings when i back probe the sensor and b) it gets sputtery when things get hot and that sensor is near exhaust manifold. I was wrong

The new TPS did nothing, it still puttered out when it got to temp (so ill be saving $60 when i return that)

So my issue still seems to stem from what i assume to be wiring issues, The wires to the fuel line read under proper voltage, and now same with the TPS (unless my safety pin back probe is shit)

I really dont know where to look next. At the power distribution box i seem to get the right voltage for the fuel pump, so it's probably not the wiring from the ECU, or should i crack that harness open and see?

i think next ill recut my fuel line wires and test to see if i can find good voltage (since i forgot to reassemble a plastic piece when i put it back together

any thoughts yalls?
 
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JoeSpit

JoeSpit

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Messages
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island of maui
welp its not the wiring to the fuel pump. I didnt realize it only pulses on start up (me not know) and that 10.5-11v reading was coming from the fuel gauge signal

So i know a lot of what its not, but i still have no idea what it IS!

I know it something that has to do with it getting hot. maybe a wire shorting... somewhere else? Something heat related. but now i am fully stumped.

ITS NOT: fuel pump wiring, TPS, ignition components (still pretty sure its not the coil) vacuum leaks, i tested the crank sensor and i didnt get anything on the ohms test (but maybe it fails when it gets hot?)

Any thoughts?

HALP MEh JESUS
 
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JoeSpit

JoeSpit

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Dec 9, 2020
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island of maui
just switched out crank sensor and no difference. Aside from cam sensor, i have basically changed out everything and i'm back to thinking its a faulty fuel pump. So tomorrow ill pull and swap out for another one. That was my original problem so maybe its just that. After all it was running like a champ for about a week.

My first replacement didnt putter outthere was just a day when it wouldnt start. That issue was the ignition switch but i figured that out after i put in a second pump, by cleaning the contacts on the ignition switch. Now I've a new ignition and i get the putters so hopefully a new newer pump will solve it

otherwise i guess ill have to acquiesce and tow it to a mechanic.

quite the stumper... any thoughts?
 
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JoeSpit

JoeSpit

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island of maui
so looking deep into the forums archives someone had a similar issue because of a cracked exhaust


then i noticed this...crack in my exhaust... i didnt notice my exhaust being any louder but i would get a whistleing i thought was vacuum. Probably this? which would make more sense than 2 faulty fuel pumps and everything else i thought it was. The problem gets worse as the engine gets hotter. i think this checks all the boxes

exhaust.jpg
 
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FJQue

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Mar 15, 2020
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Kansas City
o_O - these kind issues are so frustrating, wish I was more help but that's why i am following, to learn. Could you putty this up real quick just to check..?
 
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JoeSpit

JoeSpit

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Dec 9, 2020
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island of maui
i did and nothing different 🙃 however i'm leaning towards (another) bad pump. But i figured i would also check my PCM to make sure thats not fried and i get proper reading on all the important pins buts pin 2 which says it's "fused ignition switch output" supposedly i'm to get a 12v reading from this but i aint I only seem to muster .10v when key is in on position, .50 when i crank, and then -.15 while running. i'm trying to research now what dat do?

I have a hard time believing i got two bad pumps. My first replacement worked for like a day (granted i unbeknowst had a bad ignition swith then), and the 2nd one for a week. As it is, it will start up and run fir about 10 minutes and then sputter n putter itself to death.

but perhaps my 1st pump was fine and my ignition issue made me think it was bad and THEN maybe i replaced it with a bum pump?

So after i figure out what the "fused ignition output" has to do with (btw all my fuses seem fine and my circuit tester lights up when i put it on a2, just no 12v reading) I'll probably just pull and replace my pump
 
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JoeSpit

JoeSpit

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island of maui
okay the PCM is fine, i was either reading the wrong pin or my back probe wasnt inserted all the way.

I did however notice another small crack on my exhaust near the engine mount. It's in such a cramped spot I'm not sure if i can JB weld it.

So now do i bother rere-replacing the pump i suspected, or just get a new exhaust manifold. I would just really hate to replace the exhaust if its not my issue... granted it IS cracked in at least 2 places so I gus i'd have to replace it eventually

Whats your thoughts replace the pump or exhaust? ...or both
 
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FJQue

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Mar 15, 2020
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Well, I’m not worth a shit at electrical diagnostics nor am I Jeep mechanic at all, but you have done a lot of checking, probing, sealing testing, replacing, etc..
I’m on my 4th TJ and once had a square light. I’ve never had a lick of trouble with my Wranglers, except, twice had fuel pump issues. So that must be a thing.
Last time I replaced one, cleaned tank, all that jazz.. One thing stands out to me from all my research. Apparently there’s no real replacement for our Wranglers’ pumps and it’s become a total shitshow of getting a new one that doesn’t suck. That’s what I remember most. Unfortunately, I didn’t keep either of those Jeeps for a long time after changing pumps. There’s some fuel pump threads where Jerry & the like name their preferred replacement pump to gamble on, that’s the one I bought. Point being, I’d be looking real hard at that aftermarket pump you already put in..
 
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JoeSpit

JoeSpit

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island of maui
yeah im gonna check to see if my jb weld remedies in the am. if that aint it, i know its the fuel pump. Good thing is i'll probably be able to switch in like 40 minutes i've done it soo often and recently lol

but one forum post was getting similar issues because of cracked exhaust. so i'm pretty sure i puttied all the cracks and once it cures i'll know for sure. Good thing napa has a good exchange policy.

It's been fun and frustrating, but i think mostly fun... unless i cant figure it out and have to bring it to a mechanic like some hay seed
 

sycboi

Hemi ‘97
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Jan 19, 2021
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The one and only time I had very similar drivability issues in my TJ it ended up being the upstream O2 Sensor. The cracked manifold definitely isn’t helping the situation…
 
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JoeSpit

JoeSpit

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Dec 9, 2020
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island of maui
welp sure enough i should have trusted my 1st instinct... it WAS a second bad fuel pump. Now for better or for worse, i couldnt get a third delphi as it seems i used all of napas hawaii supply of them. So i have a NAPA branded one, which already the fuel level sending unit didnt work from the get go, which doesn't instill confidence. But she's running!!!!!

Napa said they would NOT trade out if this 3rd one dies on me, does that sound right to any of you's? Anyone know their warranty policy better than me (or the clerk i delt with)?

It just goes to show tho, always trust your GUT! All of my neighbors and friends said it couldnt possibly be 2 bad pumps in a row. which sent me down the rabbit hole of: inspecting wires, probing PCM, changing out (and then returning) every sensor, JB welding cracks in my exhaust (which i will still need to replace after a good vacation of wrenching), needlessly replacing vacuum hoses (i;m sure there's something i'm leaving out that i tried) It was a crash course in learning how a lot of these systems work, as most of my previous experience I delt with even simpler systems on old 60's Cadillac's.

Lets see how long this napa brand pump lasts now

Thanks for all the support gang!
 
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JoeSpit

JoeSpit

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Dec 9, 2020
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island of maui
Aaaaand my now 3rd replacement pump is dead and I’m waiting for aaa …again. This time it’s not even sputtering it’s just dead. I was driving and it just cut out. Of course I had filled it up last night so now I’ll have to removed the tank full weight 😩