zim

How do you test your fuel pump? Had the 90 Cherokee quit yesterday. It will start with ether to the throttle, but quit after that runs out. Am checking wires, and thought if anyone had a test for the fuel pump, I'd try that too. Thanks.

freegdr

pressure gauge on the fuel rail

tjwalker

Do you hear the fuel pump "energize" and run for approx. 2 seconds when the key is turned to the ON position? You should. If you don't first thing to do is to verify/swap out your fuel pump relay.

zim

I don't have a presure gauge to put on the rail, so I gotta do it by the process of elemination. First off, It was running just fine, and then just died going down the road. Fired right back up and drove for about 15 minutes, died again. This time it jwould not re-start. I tried it several times over about a half hour period, then started walking home. Drug it home last nite and gave it a shot of ether and it will run as long as you keep shooting the ether to it.
tjwalker, I have always been able to hear the fuel pump "presure up" each time I turn on the key. Not any longer!! Now when I hit the key, all is silent back there. Can you give me a bit more info on the fuel pump relay? Like a good way to test it? Thank you all a bunch, I will get to the botom of this. zim

huntingman2706217

take the fuel line off the fuel rail and bump the starter... if fuel comes out then its not the pump... but if it runs on starting fluid id bet money its the fuel pump... otherwise it would be the fuel pump relay or a fuse keeping power from the pump... the pump can be pulled easily with the tank still in... you can take it out and run the wires right to the battery... if you get nothing then its bad... something then it might be good... but dont know if it gets the right pressure...

tjwalker

If you don't hear the pump run for 2 seconds with the key on, you either have a bad fuel pump or you have a "control electronics" issue that is preventing power from getting TO the fuel pump.

Not sure where the relay is on the RENIX, probably near the firewall somewhere, but job #1 is to check for power on that socket and try a different relay. Simple things first. Also not sure about fusing for the fuel pump circuit, but you need to look into that too.

If the relay socket has power and the relay has been changed, and fuse verified, then you need to ensure that power is getting from there TO the fuel pump. If wiring is good to the pump, then try running direct 12 volts power from the battery to the pump; that always tells the story.

ezab

Start by checking your Ballast Resistor. Pictured below it should be on the driver side inner fender. If the resistor is good I would say it is your Fuel Pump.

huntingman2706217

i have never seen a balace resistor go bad... and from what ive read about trouble shooting the ignition system it part of that system... never heard or read of it having anything to do with the fuel pump except for what you just showed me... all it is is a resistor anyway and they almost never go bad unless you break it...

mike mike

From what I understand about the Renix system the ballast resistor would only have power when the engine is running. 12volts on one side and 6 on the other.

zim

Great information here guys!! Thank you all. I will be starting all of the troubleshooting tests today. Dug out my Haynes book and will start with pulling all the possible fuses, then go to the fuel rail, etc. right down the list.
One other thing about this rig is the steering coulme is shot. Totally worn out and wallows about in the tilt area. I have a new one here in the shop and will take it to town to get a key fitted for it Monday. If this pump and relay pass the test, the problem could possibly lie in the wiring in the old steering coulume I think. None the less it is the weak link in my rig and I am always suspisious of any electrical trouble that may have it's root there. Thanks again, I'm on it!

huntingman2706217

Go in the tech write up section... there is a write up I did on your tilt problem... there common as all get out... Kay be easier then swapping them out... just 4 bolts that come loose... also u can easily pull the ignition from your old column and install in the new... nothing much to it...

zim

Hah! Huntingman, your write-up was what helped me determine that my old column is shot! I bought it from a really, really, large guy who drug himself in and out by hanging on the steering wheel. The drivers seat was also totally mashed with broken welds and tubing everywhere. The new column had no key, and my old one the ignition switch is so worn out that you don't even need a key to start the engine. The ign. lock position doesn't even work. There have been several broken small pieces of metal fall out of the column in the past month or so, that is what is convincing me that it is time to replace it while I am sorting out this lack of fuel problem.

hennigm4

The fuel pressure relay is located on the passenger side engine compartment, its under that black cover near the firewall behind the bat. 4 relays in a row ,all the same, I think the closest to the bumper is the fuel pump, Try swapping them around, they are all the same. Also a fuel pressure tester is a handy item to have 35.00 at an auto parts store. If its not the relays, folks seem to say the cps??? I have an 87, so mine is similar to yours I believe.

Mine was hiccuping and running like crap, thought it was the pump, but ended up being the injectors.

Good luck.

ezab

So you are saying resistors don't go bad? It is in the circuit and it is much easier to at least check before replacing a fuel pump. You should probably at least look at a wiring diagram before trying to give advice.

huntingman2706217

No... thats not what I said at all... you should at least learn how to read before posting...