Fuel Pump (questions about what i have found via search)

[XJ-Mayhem]

Okay, story goes...90 xj 4.0 aw4... and about 2 months ago i was having a problem where i would randomly die on the freeway, but i just could throw it into neutral and start it right back up again and keep going. Happened about 2-3 times and every time I had my stereo playing rather loudly to compensate for road noise (after market head unit and front speakers, stock wiring) and just figured it had something to do with those few times i cranked it up real loud at my favorite part then died. So i stopped listening to music all together, and the problem stopped for the past month.

The other day, I drained the jeep completely of gas on my way home from school and made my way to a gas station with my 1gal tank, filled her up, drove there and filled the tank and was good to go. It was a rough start after the 1gal red tank, and i had to flutter the throttle a little to get it to start but it roared to life.

Now two days after i ran out of fuel, and had driven about 45 miles on that new tank, i am on the free way and it does the shut off thing again (no music at all this time) and it feels exactly like it did when i ran out of fuel, sputtering but if i flutter throttle it runs rough. got it to the side of the road, managed to start it for a few seconds with a super rough idle and then it died. wouldnt start again.

now its home, and it cranks fine, but i don't hear the fuel pump prime like i normally do. I don't have a fuel pressure tester, but when i push in the little needle on the valve on the fuel rail, absolutely nothing comes out and very little to no resistance pushing the actual needle.

in my search here, i found a very useful post by Joe_Peters about this situation...but i do not know where to find the things like the "B Latch relay" to test with my multimeter, or really any of the other things he says to test.

I am going to start tomorrow by cleaning all the ground he mentioned, and see if that helps.


Pretty much it seems i have my diagnostic procedure already, but i just need it put into idiot terms so i can go through it tomorrow

Ok.

Renix, B Latch relay instead of ASD relay, essentially the same function. B Latch relay provides 12 volt power to the coil on the 3-wire connector at the ICM, pin "A", pin "B" is ground, pin "C" is tach. Check for pin "A" 12 volts and pin "B" ground. The B Latch relay also provides 12 volts to the fuel pump, bypassing the ballast resistor, when the key is turned to ON. After 3-seconds, when the ECU has received no signal from the crank sensor, the ECU cuts the ground to the B Latch relay and cuts off the fuel pump. Before we go any further, GROUNDS are CRITICAL to the Renix system. Three extremely important system grounds are at the DIPSTICK TUBE--the ICM, the ECU, and the o2 sensor. Clean down to bare metal, treat with anti-corrosive agent, make the connections TIGHT. Also, there is one and one only unibody ground--the POS braided strap from the head to the firewall. Replace with a 4 or 2 gauge cable, strip the surfaces to bare metal, anti-corrosive agent, and make the connections TIGHT. Now would be a good time to talk about the ICM to coil clips--they corrode overtime and need to be cleaned and treated with dielectric grease.

Ok. The 3-second prime is from the B latch relay bypassing the ballast resistor. Once the key is turned to START the 12 volts to the fuel pump is provided by the starter relay, again bypassing the ballast resistor. Once the engine starts, and is running at idle and all the way up to just short of WOT, the fuel pump relay sends 12 volts to the ballast resistor on the driver's side fenderwell--white ceramic piece, two wires--and then 6 volts runs to the fuel pump. You can jumper the two wires together eliminating the ballast resistor. The pump might be a little noisier. When the engine is running at WOT, 12 volts is sent to the fuel pump bypassing the ballast resistor, from the oxygen heater relay.

Cranks, won't start questions to be answered:

Is there spark?

Is there spark to ALL cylinders--is the rotor turning?

What is the spark's condition--blue and snappy (good), or yellow and weak (not good)?

Is the fuel pump running?

Is the fuel pressure correct?

Is there a firing impulse to the fuel injectors?

Do you have spark, and is it going to all cylinders? If yes, go to fuel. If not determine what needs repaired.

Is the fuel pump running? Yes, then test pressure. If pressure is good, then test for firing impulse.

Fuel, air, compression, spark, all in the right quantities, at the right time, in the right place.

Post back what you find.

 

[joe_peters]

Howdy!

Good use of the search feature.

Ok, Both the B Latch relay and fuel pump relay are energized by a ground from the ECU--engine control unit. Both relays get power from the ignition switch when you turn the key to ON. If the ECU has not sensed a signal from the crank sensor it cuts the grounds for the relays.

Now, let me jump around a bit here. The fuel pump is inside the tank, and it is LUBRICATED by the fuel running through it. Each time you run out of fuel the pump is damaged by dry starting. So, I would be a little suspicious that a weak pump bit the bullet.

Back on track now relay layout (shown under the fair use rules):

Now, as the fuel pump gets power from multiple sources, depending on key ON, START, key ON (engine running) and key ON engine running at WOT, and you seem to be getting no pressure, I would go to the connector at the fuel pump and test for voltage there while cranking. Test the ground too.

 

[XJ-Mayhem]

Thanks sounds like a good start for tomorrow.

I wouldn't doubt the fuel pump biting the bullet either :/ do i have to drop the tank to replace it?

Also, I do have some shotty wiring on this thing, the brake lights don't light up with the running lights but work when i press the brakes...and the instrument cluster lights don't work either (except the brights indicator) so i wouldn't doubt an electrical issue either.

I will report back tomorrow.

 

[joe_peters]

No, you can access the 90 tank pump/sending unit with out dropping the tank, but you will have to pump some fuel out to keep it from spilling if its full.

Test fuse number 15, RED color 10 amp fuse for the instrument lights.

Can you clarify on the brake lights? Headlights full on--do you have taillights? What about when "parking" lights are selected--do you have taillights?

Curious if someone switched wires and has the brakes turning on the taillights.

 

[XJ-Mayhem]

No, you can access the 90 tank pump/sending unit with out dropping the tank, but you will have to pump some fuel out to keep it from spilling if its full.

Test fuse number 15, RED color 10 amp fuse for the instrument lights.

Can you clarify on the brake lights? Headlights full on--do you have taillights? What about when "parking" lights are selected--do you have taillights?

Curious if someone switched wires and has the brakes turning on the taillights.

Okay cool I thought this might be the case after looking at the tank as well.
I am waiting on a friend to come help me with key positions while I test if there is power going to the fuel pump via the connector right near the fuel filter.

Alright, I seem to remember pulling it and giving it a look and it looking fine...but I'll give it a once over again and try putting a new one in if I have it.

Yea, when i pull the headlight knob out one notch, nothing goes on, one more notch to its full-out position and just the head lights come on. If I push the brake pedal, the brake lights do light up though, but only while pressing the pedal. I got a fix it ticket for this the other day :doh:

 

[kastein]

Test first with the pump disconnected and then again with the pump connected - any significant difference in voltage at the connector between these two readings indicates an issue further upstream - i.e. wiring harness, fuel pump relay, etc.

 

[Pelican]

Joe, I know you have used the term "fair use rules" a couple of times in referring to what I assume is something copied out of an FSM. What does this mean?

 

[kastein]

Exact reproduction of information is permitted to a certain extent under "fair use" - the extent you're allowed to copy to is what I forget. Generally quoted material is OK as long as it's like a single diagram/figure/table/paragraph, iirc.

EDIT: http://en.wikipedia.org/wiki/Fair_use

1. the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
2. the nature of the copyrighted work;
3. the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
4. the effect of the use upon the potential market for or value of the copyrighted work.

I would consider this nonprofit educational use, and a single diagram from a new york phone book sized manual is certainly in line with #3 as well.

 

[XJ-Mayhem]

Test first with the pump disconnected and then again with the pump connected - any significant difference in voltage at the connector between these two readings indicates an issue further upstream - i.e. wiring harness, fuel pump relay, etc.

How can I test the connection if it is plugged into the fuel pump and no terminals are showing?

 

[kastein]

There are generally ways of back-probing the connectors (paper clips, etc usually fit between the wire and the rubber weather seal if you are careful.) I generally have a pile of assorted chunks of wiring harness around and splice up an extension cable that goes in between the two connectors and has enough bare wire in various spots to measure what I'm after though, when I'm doing something like this.

 

[Pelican]

Thanks, Kastein. I've always understood the principles involved but didn't know the practice had a specific name. Glad to see the powers that be have relaxed the rules as respects posting from FSMs.

 

[XJ-Mayhem]

There are generally ways of back-probing the connectors (paper clips, etc usually fit between the wire and the rubber weather seal if you are careful.) I generally have a pile of assorted chunks of wiring harness around and splice up an extension cable that goes in between the two connectors and has enough bare wire in various spots to measure what I'm after though, when I'm doing something like this.

Thank you for the help...


Now onto my next issue... I called my local jeep parts dept and fuel pumps aren't manufactured any more and there MAY be ONE in NY...I live in CA...

He said to check after market, what are my options? I would rather go new, than used from a JY.


seems like this is my best bet?

http://shop.advanceautoparts.com/we...10944&ci_sku=18770046-320996&vehicleId=320996

 

[XJ-Mayhem]

or i found this from local NAPA so i don't have to wait for shipping and can be on my way sooner...

http://www.napaonline.com/Search/Detail.aspx?A=NFPP74057_0202919177&An=599001+101990+50038+2038004

 

[90cherk]

The stalling and rough idle etc. sound like how my '90 was when the original fuel pump died on it last year. It had been making high pitched whining noises off and on for about a year or two so it was expected. My mechanic was not able to find a replacement pump from his supplier and he modified a later model to work in the '90. Glad you found a pump.

 

[XJ-Mayhem]

The stalling and rough idle etc. sound like how my '90 was when the original fuel pump died on it last year. It had been making high pitched whining noises off and on for about a year or two so it was expected. My mechanic was not able to find a replacement pump from his supplier and he modified a later model to work in the '90. Glad you found a pump.

I have never noticed it making any noise, i can't hear much over the tires, the rattling interior, the un-muffled exhaust, and the wind rushing past my open windows in my un-air conditioned cab...so it could have been screaming at me lol.


So you think either of those fuel pumps are fine? The one I found at Advance looks better...but I like the ease of being able to go pick up the NAPA one tomorrow... or possibly tonight if I am assured I wont be replacing it in a few months :wow:

 

[kastein]

they are probably talking about the whole fuel pump, level sender, and mounting bracket / bulkhead assembly. That isn't made anymore (by them) and in some cases (MJs) is not made anymore by ANYONE. However, a replacement pump that fits into the assembly should be easy to find. The "universal" ones that auto parts chains sell will often not quite fit into the bracket but generally will work, just make sure you get one made by one of the good brands, Bosch preferred above all others.

 

[joe_peters]

BOSCH Part # 69302

Electric Fuel Pump Kit

$95.79

I only use the Bosch 69302 in my 90. This is from rockauto.com

The last one I bought cost me $72 delivered to my door--rockauto.com has awesome sales at times. I only bought it because it was such a good deal.

 

[XJ-Mayhem]

BOSCH Part # 69302

Electric Fuel Pump Kit

$95.79

I only use the Bosch 69302 in my 90. This is from rockauto.com

The last one I bought cost me $72 delivered to my door--rockauto.com has awesome sales at times. I only bought it because it was such a good deal.

Thank you for the exact part number. From the looks of the picture, I will be reusing some of the old fuel pump parts?

 

[joe_peters]

Thanks, Kastein. I've always understood the principles involved but didn't know the practice had a specific name. Glad to see the powers that be have relaxed the rules as respects posting from FSMs.

Fair use rules have always been in effect. Where the line gets crossed is when people put up a link to materials that are clearly not "fair use"--FSM, parts catalogs, training manuals when they are in their entirety or other wise outside of the "fair use" guides.

Think of it like this: go to the library, look something up, make a copy of a couple pages, leave a happy patron. Fair use. However, if you copy an entire work--book or magazine--you have broken the copyright laws. Next time you are at a library look around the copy machine, there will be a sign posted warning you of this.

 

[XJ-Mayhem]

So am I just going to re-use the filter when I order that Bosch 69302?

And the same goes for reusing the brass looking thing that goes on the outside of the tank, that my lines actually connect to?