Question about 1991 Jeep Wrangler

3 Answers

1991 Jeep Fuel Control Issue

Recenty while driving my 91 Wrangler the engine started idling roughly, I noticed the fuel gauge went from about 1/2 tank to past full, the Jeep cut off. After sitting a few minutes it started up and made it home. Where it shut off again. I suspected a short in the fuel pump.

This weekend I replaced the fuel pump and fuel filter. The Jeep started up fine and ran for about 15 minutes and the same thing, the fuel gauge spiked up past the full mark, the jeep started sputtering and then shut off. After about 30 minutes it started ran for a few minutes and shut off again.

Posted by on


3 Answers

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 20 achievements.


    An expert that got 10 achievements.


    An expert that got 5 achievements.

  • Master
  • 1,498 Answers

Hey Mudkicker,

Who ever thought of putting an electric fuel pump inside a tank of gas........

Check your other gauges for accuracy. They do that when a ground is loose.

Check the wiring from the fuel tank along the longitudinal frame for frays and shorts. Plugs are secured.

Under the hood, passenger side, check the fuel pump relay. Switch it with one of the others to test it.

Bring the vehicle to an auto parts store. Ask them to break out he code reader. Check for diag codes

Comment me back

Posted on Aug 26, 2009

  • Level 1:

    An expert who has achieved level 1.

  • Contributor
  • 1 Answer

I had a similar problem for years. Spent a ton of money on fuel pumps, electronics, etc.
Finally a man put in a new coil, then Lo, and behold it was fixed. Don't hold this as gospel for you, but do check the coil out.

Posted on Aug 20, 2009

  • Level 2:

    An expert who has achieved level 2 by getting 100 points


    An expert that got 5 achievements.


    An expert that has over 500 points.


    An expert who has answered 200 questions.

  • Expert
  • 224 Answers

Need to chane the fuel gauge sending unit

Posted on Jul 20, 2009

1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi there,
Save hours of searching online or wasting money on unnecessary repairs by talking to a 6YA Expert who can help you resolve this issue over the phone in a minute or two.

Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.

Here's a link to this great service

Good luck!

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

Rough idle, gas fumes, sputters while driving

You have an air leak around the throttle body

Sep 21, 2017 | 1988 Jeep Wrangler

1 Answer

1990 Jeep Wrangler 2.5l idles rough/ black smoke/ fuel odor

You could pay a garage to diagnose the problem cheaper than throwing more parts at it.
The problems may be connected or they may be different issues.
Yes I would change the oil and filter, but first I would make sure the fuel system is not dumping too much fuel into the cylinders.
The O2 sensor helps the computer decide on how much fuel the engine needs, along with the other sensors. And you said you have already replaced the O2 sensor.
A mechanic would take a scanner and "read" the sensors and look for something out of normal range.
The fuel pump and fuel filter are off the list as far as causing a rich mixture goes.
I would start with the rich mixture and then see if fixing that issue takes care of the no start when hot issue.
Change the oil and filter first, and see if the injector is on too much.
You can watch the spray and tell - at idle it should be very light.
Also look at the engine temp - is it warming up to normal 195 degrees? Can you tell if the fuel pressure regulator is blown and pouring fuel into the throttle body ?
Without a scanner its going to be more difficult, but not impossible to diagnose.
Let me know what you find out.

Jul 23, 2012 | 1990 Jeep Wrangler

2 Answers

1990 Jeep Wrangler 2.5L Idles Rough/Black Smoke / Rich Fuel Odor

thrown parts never fixes cars. 50 causes, can be 49 time guesing wrong or worse added a new defective part to the mix.
yes finish the tune up, why did you do it last>? odd no?
vacuum leaks cause, high idle on all jeeps!!
and then the ECU sees bad idle and tries over and over to reach
700rpm (spec) and cant so hunts it (that hunting today is deemed ******* , ask toyota why , fines)
all vacuum leaks do that , if it sucks AIR , illegally it will do that.
illegalll means air not from the ISC stepper drive device.
bad hoses, bad gaskets what ever.

does engine reach and hold 180f coolant temperatures???
this is first. it must, does it?
ill not guess, I propose doing a thing called TESTING.
lots of thoughts, really .... here are mine, plus RENIX facts.
I owed 2 , 1988s, with dang REnix french EFI? a horrid system.
TBI is yours TBI not MPI? (count the injectors there) mpi is 4.
no sold scan tools work on it and no CEL lamp. on RENIX.
nor does the key on 3 times trick. work before 91, dang!
1991 it changed to far better and the 3 key trick works then...

black smoke is: (rich)
high fuel pressure. (id be all over this)
injector leaks, (do a leak down test )
ECT bad, e (old name CTS)
on a hot engine, it reads (ohmmeter tests)
25,000 ohms is wrong, for 0degr. F.
317 ohms is about par for 180f normal temp , is yours 300 hot unplugged??????. a simple 5 min test.
if not the thermostat is bad or CTS bad. (IR gun it to learn this)

i see that rough idle , its MISFIRING and its really flooding .
and black smoke is always results of that, and most CATcons this old are now dead, (cat converter on all mine broke-up to bits and gone inside, and stinks any time it's rich or misfiring) par for 90s./:

the 1990 wangler books are rare, but can be found on ebay
buy one is my best advice,

its and old jeep
and its best to check compression on all old cars.
did you? x5 warm or hot, and WOT tested, (throttle open)

the 2.5L most 1990(not 91)
have TBI and ****** RENIX EFI (French junk)
only jeep dealer scan tools work here, not you.

the injector must not leak. just 1 injector here,
(key off running does it dribble now? must not) looking with eyes./
(the SM is in my hands) service manual..
2.5L (NOT 4.2L)
conducted a tune-up last
cap,rotor, wires, sparks and filters is a full tuneup on any neglected 90s jeep.
good engine first
good spark
then fueling last.
order matters, on old cars,
new cps.
yes all injectors tick but yours has only 1.
and takes a stethoscope to hear. (or my mag sensor tool)

this AMC spark system uses and ICM 2.5L only
and 50 tooth CMP sensors in the Distributor. (CPS you called it?)

my guess you replaced the TDC sensor
TDC sensor (mounted at the rear of the engine on the flywheel housing) CKP its called today. (yes names all changed long ago)

in a real shop we sCOPE the spark to see if its ok.
then check
Fuel pressure, the EFI in this car can not correct bad fuel pressure
its blind to it.
this engine has a very odd TBI
it has a pressure test port
and a FPR pressure adjustment screw.

here are the SM words on this, and I quote.
Fuel pump operating pressure is 14.5 psi (100 kPa). The fuel pressure regulator is adjustable by means of a Torx® head screw on the bottom of the pressure regulator.
  1. Remove the air cleaner assembly. Remove the screw test port plug on the throttle body, then install a fuel pressure test fitting. Pressure test fittings are available at many auto parts stores.
  2. Connect an accurate pressure test gauge to the test fitting.
  3. Connect a tachometer to diagnostic connector terminals D1-1 and D1-3, then start the engine and accelerate it to 2000 rpm.
  4. Read the fuel pressure on the gauge. If necessary, turn the adjustment screw on the bottom of the fuel pressure regulator to obtain 14.5 psi (100 kPa) of fuel pressure. Turning the screw inward increases the pressure and turning the screw outward decreases the pressure.
  5. Once all adjustments are complete, install a lead seal ball to cover the regulator adjusting screw. Turn the ignition OFF, then disconnect the tachometer and remove the fuel pressure gauge. Install the original plug screw into the throttle body, then install the air cleaner assembly.

top is test port
bottom is adj screw. (this is like 1st test on rich fuel)

1: cyl compression at spec, WOT.
2: a real tuneup completed ,not just spark plugs. (ICM bad?)
3: ECT reads 300 ohms hot (CTS)
4: fuel pressure at spec. 14.5psi.
5: injector not leaking. (had bad fuel in the last year, or now?)
6: there are no sold scan tools work here, so id have to scope
all ecu pins to find cause. sorry but its sticking RENIX.

has the car sat unused for a year, ? no history
when was car a good daily driver, ? last decade? last week?

Mar 14, 2017 | 1990 Jeep Wrangler

2 Answers

My 1991 wrangler the fuel gauge is pass full line .is the gauge bad or the fuel level in the tank?

The porblem under discussion here is not related with my expertise. Please get helped from any other. OK.

Dec 13, 2011 | 1991 Jeep Wrangler

1 Answer

I am hoping that some of you jeep brainiacs out there can help with a suggestion of the problem with my 1992 Jeep Wrangler 4.0 hi-output. Symptoms: backfire from time to time....cuts off when driving, cuts...

i would recommend you connect a fuel pressure gauge to the engine fuel rail port and watch the fuel pressure as you drive it note fuel pressure should be between 31 and 39 psi and stay there while vehicle is being driven. if it drops check the wiring to the pump in many cases the pump connector is burned and losses connnection. also try watching the egr see if its diaphragm keeps surging try disconnecting the vacuum hose to it see it any change is noticed, common problem 4.0 engines of that year EGR's cost about 90 dollars but help stalling and emissions problems greatly.

Dec 19, 2010 | 1990 Jeep Wrangler

1 Answer

1999 jeep wrangler idles rough almost dies out now has a slight miss or hesitation while driving

Please be fast about checking your fuel pump. It is not giving enough fuel pressure.


Rate this.

May 25, 2009 | 1999 Jeep Wrangler

2 Answers

Jeep wrangler stalls out

check maf and tps sensor

Feb 18, 2009 | 1988 Jeep Wrangler

1 Answer

91 wrangler

The fuel pump ground wire is loose. If you have a loose parking brake pedal or recently had it worked on, check the black and yellow wire that's on one of the screws that holds the Pk. brake assembly. It's hard to find, but it's up there. I guess it could be elsewhwere on the ground wire between the fuel pump and the grounding point by the Pk. brake.

Nov 01, 2008 | 1991 Jeep Wrangler

Not finding what you are looking for?
1991 Jeep Wrangler Logo

511 people viewed this question

Ask a Question

Usually answered in minutes!

Top Jeep Experts


Level 3 Expert

79865 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22326 Answers

Kevin Daniels

Level 3 Expert

1455 Answers

Are you a Jeep Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides