Fuel Pump?

[noboundaries.jd]

just got from  hpneymoon and it is officially over. Jeep running like shiiiza. let dad borrow while gone and he informed me this was happening. said gas looked like 1/4 tank and i informed that i was pretty sure 1/4 = 0/4 so he put 5 gals in and it ran fine...in the driveway. i got home and hardly made it oyut of the neighborhood before it went to crap. idled fine at startup but then acted like it was missfiring and running rich. i had already swapped wires so i did plugs, cap and rotor. ran fine at startup but went to crap before it could get to temp. even stalled once. ignition is solid so I'm thinking fuel delivery. fuel rail has pressure but I'm questioning the pump and/ or filter. when i got the Jeep i topped it off before heading home  and it leaked a fair amount of fuel out of the tank where the pump mounts. don't know if that would be related but, I'm sure i could benfit from pulling the pump and replacing that gasket, may as well do it all while I'm there. any thoughts?

[Geonovast]

Fuel rail has pressure, but how much?

[Myron]

I  had a similar problem with my 4 cylinder. It ended up being the vacuum line that runs to the tank was burnt in two. Fuel tanks not getting proper vacuum can do some strange things. The seal on your sender may be to blame, letting your vacuum escape from there. Just a thought.

[noboundaries.jd]

I'm not sure how much pressure the fuel rail has. ive read many threads about similar issues that all suggest checking it. is it 39psi vacuum disconnected and 31psi connected?

[cruiser54]

Last time fuel filter was replaced? Perhaps it's chock full of crud from the bottom of the tank?

[mvusse]

I would start by replacing the filter and putting a new sock on the pump. If that doesn't solve it get a fuel pressure tester and see what the pressure is at idle and at WOT, because the most likely next candidate is the pump.

[noboundaries.jd]

well, that wasnt it. for $71 i could get a pump with the sock and all the fixins including the sending unit gasket so i got it. i also swapped the filter and cleaned the harness connections. she purred like a singer until...went to crap again. kind of burped and then it stalled. i fired it right back up and it was really rough so i cut it off. on the plus side i got home and jumped straight in the shower where my wife promptly brought me a shower beer!

[noboundaries.jd]

bump.

guys i really need some help with this. it sucks that the Jeep is stuck at my folks. i went by after work and pulled all my harness disconnects topside and cleaned them out. double checked my vacuum lines and clocked the battery voltage. wish my phone had not been dead as i had planned to make a video of it doing it's thing. i did not expect much from what i did today but i fired it up anyways. she ran beautifully for probably 3 minutes and then started to buck so i shut it off. i loaded my socket set into the Subie and plan to hit up my JY after work tomorrow for a MAP and whatever else i find.

what could this be? what would allow it to idle perfectly cold and then turn to shiiza?

[ComancheKid45]

O2 sensor.....when it gets up to a certain temp and goes into closed loop a bad O2 sensor can cause all kinda of weird problems on these trucks.

[noboundaries.jd]

thanks ComancheKid. i did seafoam it a few times when i first brought it home and have heard it can eff up an O2 sensor however, that was at least a month ago.

charging phone now. will get a video of it later to post up.

[87MJTIM]

:hijack:

 

I need a new fuel pump etal.  I am replacing the tank on my 87 Larado.  The guy at the body shop tells me that NAPA has pump in stock.  However, from the other members here, most of these over-the-counter pumps won't fit the 23 gal tank.

 

Is the body shop guy correct?  Will these pumps fit?

 

I checked on-line with Advances Auto and read the prod reviews.  They all said the same thing: pump did not fit. (Airtex Elect. #E7006, Bosch #69302, Denso #950-3024).

 

Advise?

 

 

[HOrnbrod]

I have the same 23.5 gal. tank in my 91 and used a Bosch 69302 pump, no problems.

[87MJTIM]

I have the same 23.5 gal. tank in my 91 and used a Bosch 69302 pump, no problems.

 

You say you have a 91.  That's a Chrysler HO.  Mine is an 87 Renix.  Will the sending unit wiring match? 

[HOrnbrod]

 

I have the same 23.5 gal. tank in my 91 and used a Bosch 69302 pump, no problems.

 

You say you have a 91.  That's a Chrysler HO.  Mine is an 87 Renix.  Will the sending unit wiring match? 

 

No, the sending units are different and send a different polarity signal output to the fuel gauge, but both the 87 and 91 4.0 MJs use the same Bosch fuel pump from the factory.

[BillyFry4x4]

I would check to see if your crank position sensor is loose. That thing caused me problems for a week straight just being loose. Your issue sounds really similar to mine.

[noboundaries.jd]

negative. shes good and tight but, thanks! i just backed it out onto the street and am waiting for a buddy to come give me a tow. I'm back and forth about whether or not he towing me to the mechanic, or to my house. i have not used a mechanic in 10 years, was a hell of a run. i need this thing running. 

[BillyFry4x4]

What about the connector for it? Maybe try cleaning that and making sure it's secure. If that doesn't work I would suggest testing the MAP sensor and IAC.

[BillyFry4x4]

 

 

I have the same 23.5 gal. tank in my 91 and used a Bosch 69302 pump, no problems.

 

You say you have a 91.  That's a Chrysler HO.  Mine is an 87 Renix.  Will the sending unit wiring match? 

 

No, the sending units are different and send a different polarity signal output to the fuel gauge, but both the 87 and 91 4.0 MJs use the same Bosch fuel pump from the factory.

Would the 91 sending unit work in an 87 if the gauge from the 91 was put in to replace the one in the 87 cluster?

[HOrnbrod]

Would the 91 sending unit work in an 87 if the gauge from the 91 was put in to replace the one in the 87 cluster?

 

The 91 fuel gauge will not mount in a Renix cluster; completely different circuit board and mounting points.

 

HO Fuel Gauge

 

 

Renix Fuel Gauge

 

[BillyFry4x4]

 

Would the 91 sending unit work in an 87 if the gauge from the 91 was put in to replace the one in the 87 cluster?

 

The 91 fuel gauge will not mount in a Renix cluster; completely different circuit board and mounting points.

ah, okay. Thanks.

[noboundaries.jd]

got it home tonight. i'll be digging into all of the connections for all of the sensors with my ohm meter tomorrow. will be doing many of Cruisers upgrades as well. hopefully i'll get it figured out.