staggering, stumbling, but not quite dying--oh yeah the Jeep

[waynestiles]

Since I've had the new engine put in the GW it's been pretty much pure joy. I've put nearly 1K miles on in in the past 2 weeks.

However-------- 2 days ago I had a brief spell---maybe 2 min. or less, a mile or two-- when it started to miss and stumble a bit. I was cruising on some 2 lanes at a solid 70 with nary a problem. after that brief interruption it went back to roaring down the road nice as you could want.
today 2 tanks of gas later it did the same only much more dramatically. I was down to 8/20th of a tank of gas as a later fill up indicated and cruising on the freeway about 70 or so when it started missing stumbling and staggering. by pumping the gas almost frantically I was able to keep it running in a rather herky-jerky manner; though the speed slowly dropped down to about 40 or so. it'd seem to die than my pumping would get it going again for a bit only to repete--with an occasional backfire-ish pop from the exhaust. After a rathery panicy 5 miles of this it suddenly started running better and ran aalmost normally. I got off the freeway heading for a gas station and it did it again for a short while more dying, pumping popping only to slowly run back to normal.

I filled it up, also had an oil change, lube job and transmission check and top-off and drove it home--running faultlessly.

So What Happened?

seems fuel supply oriented to me. something plugging the gas line? I had some issues early on after running a couple tanks of gas treatment/carb cleaner stuff. it'd act a bit this way but it'd flat out die and I'd have to slap on a new fuel filtre and it'd run good for another 100 miles or so only to plug up again but I was never able to keep it running by kicking it in the Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley with the go-pedal like I did today.

Bad fuel pickup, clogged filtre, dying fuel pump? I've got a 1200 mile week next week and right now I'm abit spooked about taking the GW.

[red mistress]

I had this problem with my old bronco.
when the tank was runnin low (like less than 1/4), it would do same as you describe.

The fuel pump went out shortly after it was doing this.
put new fuel pump and never had problem again.

But also- I've had boats that did the same thing when tank was low, and water in the fuel treatment worked it all out.

I would also check all your hose connections as when tank is low the pump works harder to get the necessary fuel.

on my Scrambler's Edelbrock MPFI, the kit supplied a external electric hi-pressure fuel pump. I've got a picture of my wife crying on our honeymoon (that she took) while I was riding mountain bicycle back to truck to get gas.
It would quit sucking fuel when tank was 1/3 full.
In the tank pump fixed this problem.

[firecaptain13]

Start with easiest... fuel filter. Check the old one for clogging. Next, possibly the pump... but doesn't sound quite right. Maybe the sock in the tank is getting clogged. Another possibilty is vapor lock. Also, do you still have your catalytic converter? Mine was giving similar problems. It would take approx 30-40 minutes of hiway spped to get it to get nice and hot, then it would just fall on its face. Anything over 1/4 throttle would make it worse. I could barely feather the throttle enough to keep it at 50.

[waynestiles]

this thing is blessedly cat-free also new edlebrock manifold and carb, pretty much completely emissons free and simplified vacuum system and other that this runs great and strong.

I'd guess a plugged filtre except my previous experience with that did not include the ability to keep it going---if badly and then having it smooth out and run normally for a while. I'm wondering if the lower fuel level somehow effects it. up until today I always filled at the half way mark--10 or almost 11 gal to refill, today it took a tad over 12 thats the only difference I can see as a cause/effect. don't understand what/why that diff yould cause it to drive so ugly.

[GWDriver]

I had the same thing happen to my YJ when in England. Changed the filter and it still happened. Changed everything I could think of that might cause the problem. Still happened. The cat was only a year old so I 'knew' that wasn't the problem. Turned out the 'newer' cat had an internal failure. Factory defect.

Changed the cat & O2 sensor & it worked just fine.

[waynestiles]

dumping the cat and going to a 2 3/4 low restriction exhaust system was about the 1st thing I did after taking delivery of it. whatever it is it ain't a bad cat, thats for sure.

[firecaptain13]

Maybe when the fuel is lower, the pump is having to pull a little harder and colapsing a piece of rbber fuel line either next to the engine or comming out of the tank. Also, check your fuel pick-up tube in the tank. Pull the access cover under the rear seat and it's right there

[waynestiles]

Thats on the list of suspects--ie deteriorating pickup sock blocking the line with low fuel levels.

I'd been thinking about replacing the whole pickup/sender because the gauge is so erratic. But I have come to realize that the long narrow design of the tank leads to sloshing due to inadequate internal baffling and that simply switching to a standard replacement pickup & gauge assembly may be a waste of time and money.

[firecaptain13]

There is a lot of sloshing in my stock tank, but it doesn't realy get to be a problem off rod until well below 1/2 tank. Normal driving I take it down till the light comes on while on a flat surface.
Checking the unit is free (just a little work on your part). It'll tell you if that's the problem. If not, a good cleaning might solve your eretic guage problem

[JeepBountyHunter]

Dang Wayne, while you were here I should have given you a cleaned out tank I have with a new sending unit and sock in it...

[waynestiles]

If I'd known . . . . . .

but the old mini van was pretty well loaded down as it was. when I got it home, the rack unstrapped from the roof, and the engine and bits out of the back, I swear I heard it give a big sigh of relief.

I've been running it around today and nary a bumble. I'm heading out for a week on the road tomorrow. I think I'll fillup a 5 gal can of gas and then run it down a ways again and see if it does the same thing---starts missing and choking when the I'm down below half a tank. maybe plumb in an inexpensive see through in line filter before the regular cannister filter in the morning so I can see if any crudniks are blocking flow at that point. IF it starts misbehaving again and nothing shows in the filter I'll have to assume it is the tank and setup. IN that case another run over to Cardington may be neccessary

[waynestiles]

2nd installment: Had it out on another road trip for this week---all this flooding here in central IN and more rain predicted made me feel it'd be a better vehicle than my fiero.

yesterday it was doing it again, even after a fresh fillup. and a fuel filter change. However someone suggested "vapor lock" and I'm wondering????
what is it? what causes it? and how does one prevent it?

when it happened the other day it was after maybe a 2 hr steady run at highway speeds in hot humid weather. the 600 miles prior to that were all stop and go--maybe 30 or 40 miles than a pause for an hour or two of work. Yesterday it was after 2 or 3 hours at freeway speeds in hot high 80's low 90s and high humidity. 1st time I stopped and changed the fuel filter. it took about half an hour with the hood up (I had to move a bunch of stuff to get to the tool box and then find the extra filter) the filter I removed seemed to be clear, no obstruction at all when I blew through the little tubes. while working the engin got to cool down a bit of course. when done it fired right up and ran well for another 50 miles and started the whole dying, chugging sputtering slowing down thing. I got off the freeway and popped the hood and let it cool down for 45 min or so while eating an early dinner. then back on the road smooth as silk for another 30 miles to the motel.

Does this sound like vapor locking?

[Gambler68]

Could be!. Check the routing of your gas lines to the carb and see if they are in a high heat area. I remember seeing a large aluminum intake and plenty of air space around the carb which is good. Most vapor lock happens at high altitude but if you're getting engine bay temps high enough..

[Treeshark]

Wayne, I know this is late in the game and I didn't check, but have you changed your ignition module? On the engine fender well?

Do This: Get a small bag of ice from 7-11 or wherever. Go for a ride. Try to get it to spit and sputter. If it does, pull over, and put the bag of ice under the hood on top of the ICM. Close hood and drive on. I know this sounds stupid, but it works. If it stops your problem, you know it's the ICM. I learned this trick from a friend of mine who has driven these things his whole life. I would try it even if you have replaced it already. As everyone knows, they are pretty un-reliable. It's heat that makes them fail. The cold seems to be a temporary fix for them.

[JeepNOFEAR]

My Jeep did the same thing. New motor also.

I put about 1/4 of a gallon of crappy gas from a "racetrack" gas station and it started sputtering, backfiring, and huge loss of power. I drove to a BP and filled it up the rest of the way with their gas and it stop and never did it again.

[firecaptain13]

The vapor lock is essentially the gas boiling in the fuel line and making vapor in the line not allowing it to pass into the carb. You said hiway speeds... what kind of temps were showing on the guage? Sometimes at higher speeds, these beasts build up air pressure under the hood and that doesn't allow enough cooling air to circulate around the motor. All the accessories heat up, including the fuel pump and fuel lines. On mine, there is a sweet spot around 65 where my underhood temps stay constant... when I'm at 75, there is a noticeable difference in temps.

[waynestiles]

My hard gas line comes up from below to the filter up over the driversside valve cover then rubber fuel lines run across the intake to the pax-side of the carb. KInd of seems the long way around the barn to me. Seems like a lot of rubber hose exposed to engine bay heat. I know you have to have some to allow for engine movement.. Has anyone worked on a more logical or efficient routing or insulating it; or is this a "non-standard" issue?
I'm thinking of the rubber hose run over the engine and some sort of heat shield between the hard line and the drivers side exhaust manifold etc.

right now I'm running it with the hood loose on the safety catch and a bungee threaded through underneath for safety---just to get a bit more air in the bay.

of course I may be "baying" at the wrong moon here too!:confused:

The module is new, maybe I could put some spacers under it and rais it up so air can get to the under side.

[JeepBountyHunter]

I once heard of someone putting wooden clothes pins on the metal lines to dissapate the heat???

[waynestiles]

I've heard that too but it sounds real illogical to me---wood is a real poor heat conductor---and you'd think it might pick up even more heat from the engine bay. but then whaddaIknow about it.

maybe it worked in Model T days or on tropical zone military jeeps in WW II or something. doubt vapor lock was a big issue in Korea or 'Nam

[ComancheRob]

IIRC The ICM in your Jeep is a Motorcraft or Ford style one. Go get a new one. Doesnt cost much and its overlooked from time to time.

[J4GRAND]

Do you have a spacer between the carb and the Edelbrock manifold? I was told it was crucial to do this to prevent vapor lock with the aluminum manifold.
Also, I had a similar miss/spuitter that was driving me nuts. Turned out I had a small piece of crud in my float bowl that would plug one of the jets until I got a backfire then it would clear up for a while.

[waynestiles]

velly inta-lesting-----drove it all day today, 2 tanks of gas. not a bobble---BUT it was about 10 degrees cooler, mid 80s instead of 90s and the humidity was down noticably.

we'll see how it goes the rest of the week. when I get back home I may look at doing some rerouting of the fuel line in the engine bay. see if I can bring it up the pax-side and heat shield it somehow. I may also put some short spacers between the inner fender and the module.

abnbout that carb spacer; Is that an Edelbrock recommendation?

maybe that should go in another thread

WS

[JeepBountyHunter]

Wayne, somehow I thought maybe it'd run better in cooler temps...
Pm'ed you about something.
Aaron