Fuel Cell Pressure + Miss Fire = ??????

ProjekTJ

Well-Known Member
Joined
Mar 23, 2005
Location
Salisbury
Long story short for now...ask questions and I'll try to answer them.

Fuel cell connected wrong, had the return line hooked up to the wrong connection on the fuel cell...caused a large amount of pressure buildup in the fuel cell. No where for the pressure to go so it decided to escape out of the front of the vehicle through the fuel line going towards the fuel rail. A good bit of fuel on the ground under the jeep...vehicle studderd and hesitated, sometimes completely cutting out at low RPM's both before and after the spillage. I've since moved the return hose to another (now thought to be the correct connection) on the fuel cell. Vehicle through out the codes posted.

What's going on and what should I expect to see when I pull the coil pack and plugs?

This post is to get some ideas before I get into it. I'll know more when I pull the spark plugs-- I know that.

aimg.photobucket.com_albums_v443_ProjekTJ_advanceticket.jpg


Help out if you can.

Thanks,
Staton
 
Station,
I found on my fuel cell that the factory check valve (roll over valve) was not working correctly on the vent line. I ran my vent off the connection without the valve, them just built a 1/4 manual shutoff lever (built from parts at Lowes) in the vent line. Solved my problem. Pressuer stop building in the tank. May be different on the Jeep...just figure i would share my input.

(Manual valve worked great last weekend:driver: )

Seth
 
you may also find that the misfire codes were caused by a lean condition not ignition failure.

Did you have the problem before you swapped the tank for a cell?
 
I did not have this problem before switching over to the fuel cell.

Originally when installed the return hose was connected to the far left connection when looking at the tank from the filler end. I have since moved it to the middle and now currently far right connection after seeing several other identical setups in this same location. It's still doing it as of this afternoon. I checked the spark plugs and everything looks normal.

Explain the lean condition some more Slade.

Thanks for the help guys...

-Staton:(
 
If your engine runs lean, it will misfire, sending codes to your computer making it think you have an ignition component failure. If you did not have this problem prior to switching to a fuel cell its not likely an ignition problem. There is no way that disturbing the fuel system will cause a coil or ignition module to fail.

Greg (BigWAylon) just completed the same install so he can help you verify the correct connections.

here's what I think, try to clear the DTC's (trouble codes) and allow the computer to go thru a "relearn" . simply let it run or take it for a short drive (10-15 miles) and see if the codes reset or if the engine runs properly. I suspect that you unhooked the battery when you installed the cell causing the computer to require a relearn.

OR

You may have damaged the fuel pressure regulator when you improperly hooked up your feed and return lines. Try and check what the fuel pressure is. You stated it built up enuff pressure to blow a quick connect fitting and leak out. This can likely destory the diaphragm inside the vaccuum operated regulator.

Its more likely a fuel pressure problem since thats what you where messing with originally. Hope it helps
 
greg slade said:
Greg (BigWAylon) just completed the same install so he can help you verify the correct connections.
Click to expand...


he actually used the fuel cell I had...and did his the week before...

so, we're just trying to make sure we all have it right...

Greg
 
Pull the sending unit last night after it completely crapped out on me while testing it on an incline and decline. Since I'm not really sure what the TJ stock sending unit is suppose to look like in the first place I wasn't really sure where to start. We did find upon looking in the filler that the sending unit was cocked at an angle (no, not from the fluid distortion) and we were able to straighten it out and check the fuel filter. Everything seemed fine. Started it without the filler bolted down so we could see the internal. Cranked up & ran fine. Bolted up the filler neck and tried starting it again...back to it's old sh*T.
NOW, it will start up completely fine at times and then other times it will backfire, studder, and sound like it's running on 5 cylinders. But once you get it running...it's fine. Drove it home last night, no problems. Get into the driveway - shut it off- restart- same sh*T again.

Really not happy at all about this. I have a hard time believing it is the sending unit after inspecting it and reinstalling. I've got a pic of it I'll post later today. Any other help is welcome.

Thanks,
Staton (not happy) Carter
 
i was messing with this fuel pump with Staton last night, so ill add a couple ofdetails for all y'all

when we first removed the filler neck and turned the key to watch the pump run, we saw that it was pumping gas back into the tank, geyser style, rather than up out of the pump into the fuel lines

im not sure of the exact terms, but the sending unit consisted of two major parts, the plastic top half, and the aluminum bottom half. The bottom half which attaches to the top half with three plastic legs, had gotten cocked forward, one of the legs had become un attached. This caused the tube in the middle, inside the spring to seperate partially, and then gas to leak, leading the the geyser mentioned above

we put these halves back together, and reinstalled the sending unit, turned the key, and sure enough, no geyser, and pressure in the lines, started right up, and seemed to work fine, so we took it as a victory and bolted everythign back down. shortly after, it was back to the same old shit, sputtering and backfiring when we tried to start it. It was getting a little late to keep messing with it, but i had a couple thoughts about it since then.

Is the bottom of the sending unit supposed to be touching the bottom of the cell? because i didnt think to look at the time, but i dont think it is, and this could lead to the two halves wanting to seperate? trying to remember, it seems like there was maybe a quarter inch gap under it.

also, staton, my roomate and i agree that the way its running could very well be attributed to low/intermittent fuel pressure, so i dont think its quite soon enough to rule out the sending unit as the problem, possibly just pull the filler again and glance in there to see if the can has gotten sideways like it was last night again?
 
in the factory setup...the pump sits on the bottom of the tank...

it does not in the cell Staton has...

I've seen discussion on other sites of people bouncing hard enough off road to have the pump fall apart into the two pieces...

one guy "fixed" it by putting 2-3 small screws to hold the two pieces together...


Greg
 
Behold, I give you the TJ sending unit.:confused:
DSC00331.jpg


Is the sending unit suppose to look like this while in the tank? With the seperation between the two pieces? Or are they suppose to be pushed together, filling the void?

Apart, the unit touches the bottom of the fuel cell.

Together, it would have about 1.5" to 2" between the sending unit and the bottom of the cell.

AND, the GRAND QUESTION OF THEM ALL...

Would the seperation cause these above mentioned faults?

Help...
 
Where are all the people that know shit?!???! This is bugging the hell out of me. I've followed other people posts about adding this exact fuel cell and they don't seem to be having these problems.
What can I check to find out what the back pressure damaged?
Is the sending unit suppose to have the exposed parts?(see photo)
Could it be the TPS or CPS?
I don't want to shell out for a new unit when that's not the issue.
And if anyone would like to make a trip over to my house I'll provide whatever you'd like (beer/food)...as long as we figure the problem out.
paging Mr. Zuber...hello?
 
The seperation between the two pieces of the sending unit is normal. When in the TJ fuel tank it is spring loaded against the bottem of the tank. It doesn't matter if its spring loaded or not in the fuel cell as long as you don't land hard enough to make them seperate which is pretty hard to do. If you have taken the two halves apart you may have ruined the O-ring between the two halves and will most likely need to buy a new sending unit. I don't understand the problem with the return line. When using the stock TJ sending unit there is no need to run a return line from the engine. When doing the swap the only lines you need is the one going into the sending unit and a vent line so pressure doesn't build up in the tank. I did this swap so let me know if you need anything else.
 
Are you referring to an O-ring between the white plastic piece and the black plastic piece where the spring is located? When we looked in the filler neck at the pump it was geysering fuel inside of itself...that was while the 2 pieces were cocked sideways. After correcting that everything seemed fine. I think I may have to put some screws in the "feet" connecting the 2 pieces to avoid seperation again.

Currently I have a return line running into the tank into one of the open fittings on the cell. Last one on the right if you are looking at the cell from the filler end.

I'm going home now to check to fuel pressure at the rail...just to see if I'm getting a good reading.
 
Staton, you shouldn't have a return line on that system, the TJ pump is a regulated pump, so Im a little unsure of where you are getting your return from... When we built Dan4Jeepin's tank, we dropped the stock pump into it, and ran a seperate vent line and haven't had a single problem yet... Also, if you seperate the 2 halves of the pump, there is a 2 o-rings if I remember correctly as well as a spring in between, if you seperated those pieces, then there is a chance you have a broken O-ring and are loosing pressure within the pump itself, causing a lean system and a misfire... I personally have never pulled a pump apart that I could get to work properly after reassembly, and a new pump from the dealer is about $300...

Where exactly is your return coming from? This may also be part of the problem since you should not have an external return line seperate of you pump....


And a secomd thought (or 3rd?).... If you seperate the two halves, some of the internal clips may have cracked, allowing the pump to seperated from the sending unit after you install it in the tank... And you cannot buy the O-rings or the pump or sending unit seperately from the dealer (I already tried a few times)... And no, the pump does not "need" to sit against the bottome of the tank, but it does need to be held together somehow, be it screws or whatnot... The stock tank and pump configuration actually presses against the bottom of the pump, to keep them from seperating... This is why you'll see a smashed tank on a TJ and it won't run so well, because it will crack the pump housing and cause a pressure loss in the system, often times its enough pressure to start the vehicle, but will only occasionally lose pressure...
 
well, its not a return, but we were referring to the vent line, which was hooked up wrong by whoever did it first, to the port which extends down to teh bottom of the tank, so when staton first got the cell, pressure would build up in the tank, and then force gas out through the vent and he had gas dripping out the charcoal canister

he has since fixed this by attaching this vent to teh correct port, and the only issue now is the pump had seperated itself in the tank, so i guess there is no telling if these o rings were lost when it came apart or what, he might have a little more info
 
yeah, and like seth said, ditch the rollover valve that comes stock in the fuel cell, and go off one of the other open ports, and use a manual rollover valve... That tank will need to breath properly. If its not right now, you could be starving the pump as well, and it will run just fine until the pressure is too much for the pump to work against...
 
Now we're talkin' -- got some real action.

Alright, I'm back from checking the pressure at the fuel rail. 41 PSI, checked twice.
I now understand that the sending unit does not have a return but DOES have a vent line. When my fuel cell was hooked up originally it was wrongfully connected to the one with the alum. pipe to the bottom of the tank. This caused the venting into the tank, back into the gas which was forced back out through the hose to the front of the charcoal canister. Thus, a gassy pool under my jeep while at work. Since, this has been corrected. No more high pressures in the tank.

Onto the sending unit. When the seperation of the sending unit happened ---I don't know when??? The area with the possibly now broken O-ring is most likely the guilty party.
I'm going to take a look inside the filler neck tonight to see if it's seperated again. If so, I'm going to reconnect it, possibly with some type of screws.
And if it's not seperated...you'll be hearing from me again.
A new sending unit may be on the way.

To shops or individuals doing this install --pay attention to what connections you are using. I was under the assumption that mine was installed properly since it had been driven prior to my arrival for pickup and no mention of problems was made. This is a headache waiting to happen. Literally, when the back pressure fills the cabin and you are stuck in a jeep full of gas fumes you WILL have a headache. It could possibly turn into a costly mistake and ruin a good sending unit. $$$

-Staton
 
Staton, there is no Vent directly off the stock pump that Im aware of... I'll see if we can get some pics of Dan's setup tonight for you to compare, and i'll follow out the lines so youll know exactly where they should go, I wouldn't buy a new pump or anything until you know for a fact that your lines are properly run...

Hugh
 
Take some pictures if you are able. They always help me out way more than words. Thanks Hugh...you da man.
I think everything is connected properly now. I don't have a dedicated vent tube connected to the cell though. That could be a problem I guess, but I've seen many others running this exact setup with no problems. Of the 3 connections on the fuel cell I'm using the one to the far Right if you are looking at it from the filler neck end. It's labeled Vent I believe.

Thanks,
Staton
 
Afternoon Update 2/20: Series of Events

I opened up the filler cap again and peaked in with a flashlight and found this little guy with a pimp lean...
DSC00337.jpg

Notice the vibration in the fuel...it's running like this. Pretty good to I might add. I don't know if this is enough pitch to make a difference, but if the vehicle were to be on an incline/decline could this be a problem? It stalled completely and terminally the other night on an uphill incline of less than about 30*.

I corrected the cylinder lean without removing the sending unit...
DSC00344.jpg

...and at the same time I pushed it up from the bottom and acheived some clearance on the underside of the filter. I'd figure about an 1" to 1.5", enought for my fingers to fit underneath. Notice the placement of the plastic arms now, less exposed and the tabs in the cylinder are exposed. I then cranked it up like that and it ran fine. Did I fix it, it seems ok...Fu(K NO, it stalls out after tapping the gas a couple of times. I messed around with starting it a couple more times and got it running again. Took probably 3 tries full of backfiring, hesitation, and stalls. Then on the 3rd it just fires like it's my bitch.
Here is it running...
DSC00347.jpg

Notice the lovely fountain effect showing that it's not at the end of the retaining arms. Very straight and looks good.
Poof...stalls...check engine light on...trolls jump out of the glove box and club me with a manaquins arm...wouldn't have been so bad but the arm had one of those damn sequenze (sp?) bags on it that all the ladies want attached to it.
Luckily my attack helper dog was nearby -
aimg.photobucket.com_albums_v443_ProjekTJ_DSC00332.jpg


Anyway, nothing is really new...I just thought I'd post up some pics of what I'd been talking about. It still runs fine one minute and like crap the next. I'll probably just buy a new sending unit to piss some money away. Hopefully I'll win the contest.
I'm pissed, I've taken in too many gas fumes both thru my nose and through absorption thru the skin. Sorry for my language in the post. I'm just not happy about this stupid setup. And if one more person tells me they don't understand why it's not working correctly because they are running the same setup I'm going to contact the trolls.

Here is my connections currently.
DSC00335.jpg


If you'd like to see anything else or need any info I'll be glad to help. Offer still stands on coming down to kick the tires with me.
 
Those stains on the ground under the dog are troll bashings. Fuel cell helper Dog took no prisoners.

Damn greenies.
 
twas leaning the other way on saturday when we first found it, thats interesting

i wonder if those o-rings they spoke of on that center tube are just long gone now, because it was completely seperated
 
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