alienxj

My XJ has been occasionally not wanting to start, when it does this I don't hear the fuel pump priming or it only primes for a short burst. I replaced the fuel pump relay and fuel filter (for the hell of it) and it was working for awhile but now the problem is back. When it starts it runs fine no stalling or hesitation. Could I possibly need an auto shutdown relay? Thanks

nickxj94

check your grounds on the fuel tank and under hood.. make sure there all getting a good conection,, if the asr was bad it wouldnt run at all..

cruiser54

Try this. can't hurt and can only help. Pay particular attention to the ballast resistor connections.

I suggest unplugging EVERY electrical connection in the engine bay you can find, whether engine related or not, and spraying it out with a good electronics cleaner, visually inspecting the terminals, and adding dielectric grease before plugging it back together. Be sure that the connectors to the ballast resistor mounted near the air cleaner housing are clean and tight.
ALL of the relays should be removed, the terminals wire-brushed until shiny, and the receptacles sprayed out with contact cleaner. Then dielectric grease should be added before plugging them back in. I do this on every Renix era Jeep I purchase or work on for someone else.
Revised 03/15/2012

alienxj

Thanks for the suggestions, yesterday I cleaned all the contacts and used dielectric grease with reassembly, I also added a 4ga ground to the battery. It still does the same thing sometimes. What's the best way to check the ground to the fuel pump will I have to drop the tank? Can I just drill a hole in the corner of the metal tank and run another ground?

freegdr

renix does not have auto shut down relay try installing the old fuel pump relay where the power latch relay goes see if issue continues...

cruiser54

To check the ground, probe the black wire at the fuel pump/sender plug with an ohmeter and touch the other lead to a good chassis ground.

DFlintstone

You might see if it has power to ,(and through), that ceramic ballast resistor on the inner fender by the air cleaner. It gets battery voltage from the front and sends a little less out the rear to the pump.

cruiser54

Why didn't I think of that, too? My wife complained a few weeks ago that her XJ was acting like it did last summer when the fuel pump went out. Thought I'd check the connectors and stuff. Sure enough, the spade terminals were loose on the ballast resistor. Been fine since I took care of that.

DFlintstone

Funny! No that's where the 220 goes.---------

Cruiser. you did! (mine had bad contact once as well, it also failed once) Only had power at the front.

alienxj

I cleaned the contacts on the ballast resistor yesterday and that helped a lot. It happened once since then, it just won't prime or start for 10 minutes then works. I'm going to go over the connections again tomorrow and try to sure up the grounds. thanks for the great suggestions.

DFlintstone

Well, hold on, I hadn't seen that ^. The pump DOES come on for 2 sec or so when you turn on the key? It will do that twice or so then, no mas? I mean, you do know, the pump won't keep running when you turn on the key, it will stop in about two sec.

That would be normal, (for sure). If that's the case, try this, (it's actually pretty easy, 3 minutes with a $5 HF meter).

C/O Cruiser;

Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
　
Revised 11-29-2011

cruiser54

Glad to hear it. Now do what is outlined in Post #3 and see if that helps.

alienxj

figured it out!

What are the 2 relays on the drivers side of a renix 4.0? One of the relays looks like it used to be mounted on the sidewall but it was just hanging out. I swapped those and it's been working flawlessly for a week now.

cruiser54

[IMG]file:///C:/Users/Owner/Pictures/Jeep%20Tech%20Photos/Relay%20location.gif[/IMG]

AC, Power Latch, Fuel pump, O2 heater relay in order from front to back.

alienxj

The bank of 4 relays is on my passenger's side by the battery, the 2 I was referring to that got swapped are on the driver's side, there's only 2 that side.