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  #1  
Old October 7th, 2020, 10:56
TricolorXJ TricolorXJ is offline
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1991 XJ SE - Crank no start problems

Hey all, new here and I thought I would throw my hat in the ring.
I have a 1991 Cherokee XJ SE that has been sitting for years.


I'm able to get it running with starting fluid, so I'm pretty sure/ hope the only problem is that it's not getting gas.


I just found out that I checked the power to the fuel pump wrong. I had to have someone crank the engine when I checked, and I had just turned the key to the on position and got little to no readings on the multi-meter. I will be going to recheck the power tomorrow.


I can't find anywhere that tells me where the Fuel pump fuse is. The fuel pump relay is getting power (around 12 volts), replaced it with the AC fuse and it still didn't start.



It has fresh fuel, enough coolant and oil, and I cleaned the spark plugs.


I don't have a way to post images, but there is an electronic harness to the right of the air filter box that isn't connected to anything. Is this to access the computer? Would be happy to know what that goes to/if that is normal.


Thanks!
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Old October 8th, 2020, 22:11
TricolorXJ TricolorXJ is offline
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Re: 1991 XJ SE - Crank no start problems

As an update, I still didn't get a power reading on the multimeter going to the fuel pump. But the relay is for sure working. Still couldn't find the fuse for the fuel pump.
Any ideas on why the fuel pump may not be getting power? I may have checked it wrong, I'm not a mechanic unfortunately lol
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  #3  
Old October 9th, 2020, 19:07
Unclewolverine Unclewolverine is offline
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Re: 1991 XJ SE - Crank no start problems

If you got power at the relay and not at the pump its a bad connector or broke wire. Have you tried hotwiring the pump?
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Old October 9th, 2020, 21:59
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Re: 1991 XJ SE - Crank no start problems

I may be wrong, I'm old three relays control the fuel pump. ASD relay supplies power to the whole sytem, the ballast relay is power to the pump while cranking and bypasses the ballast resistor, the fuel pump relay supplies power while running through the ballast resistor.

The black green (?) wire at the ballast resistor should be hot both during cranking and running. I may be wrong on the color, one end of the resistor should be near battery voltage the other end noticeably less than battery voltage, but hot none the less. A quick check for both the fuel crank and fuel run relay.

Unclewolverine may be onto something, seen it before, the fuel pump wire/harness goes through multiple connectors (5-6?) which increases the chance for one to cause issues. The fuel pump ground can also cause issues.

If you have power at the ballast resistor, at the pump in the rear, a good ground and still no fuel try wacking the outside of the fuel tank near the pump hard a few times with a rubber mallet. When the pump sits idle for a long time, the varnish in gasoline can cause them to seize. It is sometimees possible to free the pump with a sharp blow to the side of the tank.

Another quick test, when the key is first turned to/or through the run position the fuel pump should run for a few seconds to prime the fuel rail. Turn it to run a few times, then push in the shrader valve on the fuel rail, you should get a squirt of fuel. On mine I can hear the pump run for 2-3 second when I turn the key to run, it's subtle but noticeable.

Lastly when they have been sitting for a long time the fuel filter gets gunked up. Have some extra fuel line handy and take the filter off, wash it in some solvent or gasoline, blow through it backwards. Make sure to keep track of in and out on the filter. Have something handy to plug the line from the fuel tank, it may start to siphon drain the tank with the filter removed. A new filter isn't really very expensive, I usually put one in after I've had it running for awhile, I reuse the old filter until things have cleaned themselves out some with fuel flow.
I don't have a 91 schematic, but the basics transend multiple years.
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  #5  
Old October 10th, 2020, 09:44
TricolorXJ TricolorXJ is offline
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Re: 1991 XJ SE - Crank no start problems

Thank you both for the replies,


I have not tried hotwiring it, I don't think I have the tools or the know how to do that. I'm sure there are plenty of how-tos around the internet. Not sure what you mean by "Bad connector". Do you mean the male/female power connectors that are near the fuel pump?



I will be trying to bang on the tank haha, a neighbor suggested doing that.


But as I mentioned previously, the power not getting to the pump is concerning. 8Mud, can you clarify a few things, I'm new to XJ's and car mechanics:


Is ASD the Auto Shutdown Relay? Where is the Ballast Relay located? In the relay box in the engine bay? Still haven't been able to find the fuse to the fuel pump itself.


I'll be checking the power to the ballast resistor but what does "A quick check for both the fuel crank and fuel run relay" entail?


Sorry for the 10 million questions, thanks again!


Some additional info: The 1991 XJ is a 6 cylinder 4.0, and 4x4.
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Old October 10th, 2020, 11:27
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Re: 1991 XJ SE - Crank no start problems

Quote:
Originally Posted by TricolorXJ View Post
Thank you both for the replies,


I have not tried hotwiring it, I don't think I have the tools or the know how to do that. I'm sure there are plenty of how-tos around the internet. Not sure what you mean by "Bad connector". Do you mean the male/female power connectors that are near the fuel pump?



I will be trying to bang on the tank haha, a neighbor suggested doing that.


But as I mentioned previously, the power not getting to the pump is concerning. 8Mud, can you clarify a few things, I'm new to XJ's and car mechanics:


Is ASD the Auto Shutdown Relay? Where is the Ballast Relay located? In the relay box in the engine bay? Still haven't been able to find the fuse to the fuel pump itself.


I'll be checking the power to the ballast resistor but what does "A quick check for both the fuel crank and fuel run relay" entail?


Sorry for the 10 million questions, thanks again!


Some additional info: The 1991 XJ is a 6 cylinder 4.0, and 4x4.
I'm not real familiar with the 91 and don't have a schematic handy so some of this is guesswork.
The ASD relay is the auto shut down relay, the ECU (engine control unit/computer) gets a pulse signal from the CPS (crank position sensor) as the motor turns over and closes the fuel pump relay when the engine fires up. The ECU closes the Ballast relay (in the PDC power distribution center just behind the battery). during cranking, this bypasses the ballast resistor and gives full power to the pump to compensate for the power drain needed to run the starter motor. Under normal running the power from fuel pump relay to the pump goes through the ballast resistor which cuts down the voltage a bit. I hope my explanation is clear.
The ballast resistor is located on the inside of the drivers side fender well on most models, not sure for the 91. A white ceramic block maybe two inches long. There should be power there during both cranking and running. You can bridge or jumper the ballast resistor, it is largely useless anyway, it was installed to quiet the feul pump some for sissy drivers.
You have spark so the CPS is likely good, when bad you will have no spark or fuel, the ASD relay won't close. You have spark so the ASD relay is likely good, it also supplies power to the ignition coil.
The harness for the fuel pump and other stuff runs down the drivers side under the inside door sill. That harness has many connectors along it's length any one of which can be corroded, loose or have a poor contact inside a connector that can generate enough heat to discolor or partially melt the plastic connector (happened to me). The connector that melted on one of my XJ's was the one just before the rear fender well, but there are others just as vulerable to failure.

I have no idea where the fuel pump fuse is on the 91 on some later models it was the "2" fuse. But most years the PDC fuse layout changed most every year. There should be a fuse and relay diagram in the cover for the PDC. Or in the owners manual.
Sorry about typos, spilled coffee in my keyboard, makes typing interesting.

No problem with the questions, I just hope my explanations make sense. XJ acronyms and part names can be confussing, expecially because some have evolved over the years. I still use ECU (Engine control unit) the new name is PCM (powertrain control module). I learned automotive electrical on main battle tanks in the military, enough wiring in one tank to build a fleet of XJ's . I've been working on XJ's since 87. Things that seem common to me might be greek to you.
If you have a wiring problem this can turn into a real can of worms, can be labor intensive and may take hours (or days). I always found it to be challenging and interesting, some people get frustrated.
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  #7  
Old October 10th, 2020, 13:13
TricolorXJ TricolorXJ is offline
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Re: 1991 XJ SE - Crank no start problems

Thanks for the next plan of action and wealth of info 8Mud!


I'll get a chance to work on it early this week. What I'll plan to do is check that ECU fuse (which I believe is the fuel pump fuse among other things).


Then I'll check to see if the ballast resistor is getting power going to it and from it.


Then I will do some wire following from the fuel pump up to the engine to see if I can find any corroded connections and to check the power on those connections.


If the ballast resistor IS getting power how might I bridge that? I don't mind a loud fuel pump if I can get this baby running! Plus I can't even find ballast resistors on Oreilly's, etc. Would I need to get some splicing tools and learn to use them to bypass it?



Any website recommendations on finding OEM XJ parts or at least quality parts? Kind of considering buying fuel pump and filter anyways since its probably gunked up.
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  #8  
Old October 10th, 2020, 20:38
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Re: 1991 XJ SE - Crank no start problems

I usually buy off rockauto, I look on this site for part manufacturer recommendations.

A crimp connector kit doesn't cost much at the auto parts store. It takes a little practice to use crimp connectors. Don't get the cheapest crimping pliers. Shrink tubing is also handy, to seal the splice and avoid corrosion over the years.

Three ways to troubleshoot electrical systems, start at the beginning, start at the end or start in the middle. I often start in the middle and/or the easiest spot to get to. Middle eliminates half the circuit as being the problem, upstream or downstream. The ballast resistor is in the middle but unlikely to be your problem in this case, but a handy place to test for voltage.

Sitting for years increases the chance some rodent was chewing on the wiring. Happened to me and has happened to many others. A good high intensity flashlight is a must, it illuminates hard to see spots and also helps to focus your attention on possible trouble spots. I'd have a plan to quickly disconnect the battery if the wiring starts to smoke. Rodents chew off the insulation and leave naked wires right next to each other. Another big issue is corrosion, corrosion in connectors and at connections causes issues. And there is always the chance somebody else working on the vehicle screwed something up. Swapping components is usually my last resort after troubleshooting. I'm cheap and the component, sensor or relay is often not the issue.

Four wires going to the fuel module, two are for the fuel gauge, one is a ground and one the hot wire for the pump. Having a wiring diagram or schematic handy can save time and can help with an overview. If you plan on keeping the XJ, acquiring a year specific FSM (factory service manual) is almost a must.
I'm not going to swear to it but I seem to recollect the wire you want at the pump module connector is the black green stripe wire. Check it with a volt meter while cranking, make sure you have a good clean ground spot on the body to test for voltage.
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  #9  
Old October 11th, 2020, 11:21
TricolorXJ TricolorXJ is offline
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Re: 1991 XJ SE - Crank no start problems

Is this the type of tool and kit you were referring too? https://www.lowes.com/pd/Utilitech-B...tors/999953686


I know you said not to get the cheapest but it looks good and is cheap haha.


Thanks again for the information. I think I'll probably have time to work on the XJ tomorrow and will come back with updates.
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  #10  
Old October 11th, 2020, 23:30
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Re: 1991 XJ SE - Crank no start problems

Check the lateral movement of the two jaws, the hinge play. If the hinge isn't tight you are likely to have issues. I have at least four crimping pliers I've discarded over the years just because they were a pain to work with. One of those tools where luck plays a roll in how they are going to work, price has little to do with it.
After you make your crimp pull on the wire and make sure it is in there tight.
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  #11  
Old October 12th, 2020, 18:34
TricolorXJ TricolorXJ is offline
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Re: 1991 XJ SE - Crank no start problems

Hey I have some updates from working on it today.


ECU Fuses looked to be in good shape. The Ballast resistor ceramic was actually broke in two pieces. However, the plugs coming off of them had about 10-11 volts and they both showed power when one was plugged in. So even though the ballast is broke I don't think that is my problem as power is still going through it.


I made my way back to the power harness to the fuel pump under the driver's side passenger seat and rechecked the power at that harness. It actually got power, I changed my grounding location to a more cleaner metal spot on the frame and bingo, power readings. I don't remember how much but substantial, maybe 5 and 9 volts on two of the three prongs.



BUT...that third prong on the harness was not reading power. It was the black wire. The other two getting power was a green and blue wire.


I'm making an order for a fuel pump and fuel filter since the XJ has been sitting for so long it's sure to be gummed up. Plus, I know that it is getting some power, unless there is a short in between the short distance between the harness and the pump.


Ballast resistor is $15 on Amazon so I may get one of those too.


Please let me know if you have any suggestions like benefits of bypassing the resistor or not.
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Old October 12th, 2020, 21:38
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Re: 1991 XJ SE - Crank no start problems

The balast resistor is unreliable in normal circusrances, cracked or broken it is likely to get you stranded. What you can do is buy a spade connector designed to add a pole to an existing connection. Two male poles on one end of the resistor. If and when it screws up you can jump it quickly for a test and/or to get you home. Typically when the ballast resistor goes bad the motor will start and run for a few seconds then die. But it can cut back voltage in other circumstances and make the pump sluggish during normal running (happened to me).

I may be wrong but I think you are checking the wrong wires. Side note a solid black wire is always a ground wire and if it has voltage it means the ground connection to the body somewhere on the harness (usually near the end of the harness) is faulty.

Time to go back to the pump connection right at the front of the gas tank, Hard to crawl under there, your best bet is jack it up under the center of the rear axle or even one side of the axle and use a pair of jack stands. Test that connection at the fuel pump for power while cranking or even a few seconds of power when you first turn the key to the run possiton (purge function).

But like I said I'm unsure of which wire to test, one is pump power, one is ground and the others are for the fuel gauge. The wire color for the pump power chnages over the years it is pink for an 88 and I believe dark green and tan for a 93. Side note; the wire changes color right at the last fuel unit connector, It is one color going to the connetor and another color to the pump.

The color of the wire at the ballast resistor (one end or the other) is likely to be the same color at the pump connector going into the connector, the pump power wire going out of the connetor is likely to be a different color.

You also have to test your battery voltage, make sure the battery is changed up to near 13 volts (or as high as possible). You may need all that power to turn over the pump after it has been sitting for a long time. You might also want to test the battery voltage while you are cranking it over, some drop is normal, a drastic drop is going to cause issues.

You also want to ohm test the ground wire at the pump connector, the closer the ohms get to "0" the better. That ground (black wire) is a known trouble spot.
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Old October 13th, 2020, 10:17
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Rob Mayercik Rob Mayercik is offline
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Re: 1991 XJ SE - Crank no start problems

Quote:
Originally Posted by 8Mud View Post
The balast resistor is unreliable in normal circusrances, cracked or broken it is likely to get you stranded. What you can do is buy a spade connector designed to add a pole to an existing connection. Two male poles on one end of the resistor. If and when it screws up you can jump it quickly for a test and/or to get you home. Typically when the ballast resistor goes bad the motor will start and run for a few seconds then die. But it can cut back voltage in other circumstances and make the pump sluggish during normal running (happened to me).
The ballast resistor was put in by Chrysler because they got complaints from owners about the fuel pump "being too noisy"; there was no "technical" reason to have it, it was purely "aesthetics". I replaced mine with a jumper wire something like 15 years ago, and have never looked back (if that made the pump any louder, I've certainly never noticed).

Tricolor, since your resistor's cracked now, I'd recommend just throwing it away and replacing it with a jumper wire before it does leave you stranded.
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Old October 14th, 2020, 18:26
TricolorXJ TricolorXJ is offline
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Re: 1991 XJ SE - Crank no start problems

Thanks for the replies and info.


I need to get some crimpers and a wiring kit and I can take care of that. Is there a way to wire those connectors together without cutting the connectors off?

Just in case the fuel pump is crazy I would like to keep the possibility of using the resistor in the future. I'm new to XJs so I don't have any idea what it sounds like on or off the resistor.



Getting a new battery and replacing the fuel pump and filter friday so hopefully she'll be running this week!


BTW I've been using a surrogate battery so not sure if that would cause my issues, it may not be fully charged but starts up the car its currently on.


Completely unrelated but are 30" tires ok on stock XJ? It's a 1991 SE (Special Edition) which from what I understand is a package more geared towards offroading but not sure.
The wheel wells are cracked so if it rubbed at all there I think it would just fall off.
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Old October 14th, 2020, 20:29
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Re: 1991 XJ SE - Crank no start problems

The standard crimp-on spade connectors should match the terminals on the resistor, so making a plug-in jumper should be easy. I just cut the harness connectors off and used a butt splice.

30s stock should work ok, but may need a couple washers under the steering stops.
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