So I bought this 1988 wagoneer limited about a month ago, it ran like a top.... for about two weeks. Then I'm driving down the road and it quits, hit the key it starts right back up and I drive home, next time I go to start it, it starts then stalls after a second or two and has been that way since except twice out of about fifty tries it starts and runs great, drive it around the yard, shut it off and back to start stall.
I check for spark and it seems fine so i check for fuel and it seems to be not getting fuel so I put on a new fuel pump and filter (six hours later) I try to start it and same problem, ouch!. It still doesn't act like it's getting fuel so I go buy myself a fuel pressure tester, sure enough 32 to 40 llb pressure, no prob except I can keep it running (roughly) by squirting a little fuel down the throttle body, and more oddly by running a hot wire from the battery to the balast resistor but once again roughly. If I bypass the resistor completely it doesn't help and when I pull the hot wire off the resistor the engine smooths out for the prescibed two seconds and then stalls.
It seems like the fuel injection just stops injecting. I've checked all the connections on the sensors, ohmed out the crank shaft position sensor, cleaned contacts and prayed for a sighn from god. I'm stumped! any suggestions?

Maybe a short somewhere off the pump..? Idk man, you've been doin the right stuff..

Just a suggestion, not to expensive, and worth it to try. You can upgrade the fuel injectors, and EVILXJ sells them here. I put the 703's in, took me all of an hour, and evened out my idle. I have an 88 Laredo, but that way, maybe its just something wrong with the injectors. could be an intermittant (spelling error....lol) random issue with in the injector.

Good luck.

Only takes three minutes to rule out this trickster;


Renix CPS Testing and Adjusting C/O Cruiser54
　
　
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.

I believe your Renix ECU controls the injectors with the CPS signal as well as the spark. I changed mine as the signal dropped below .3 and got improved starting and it ran smoother. The wires were funky and I'm sure it was 10 years old, so I didn't try saving $45 by drilling it.

The ohm test on the CPS is a pi$$ poor test IMHO. You need to do an AC volt test as Flintstone suggests. Another sugggestion: Check the wire connectors at the ceramic ballist resistor over near the air filter housing. If they are loose fitting, the fuel pump will not operate at all times.

possible fuel pump getting tired ....

Could be. But after my wife complaining that her Jeep was acting like the fuel pump was going out again, I checked the terminals at the ballast resistor. They were not grasping tightly. I repaired that and it's run like a champ for over two weeks. Who knows?

RCBRC= Refresh Connections Before Replacing Components.

he said he by passed it and no difference though

Wiggle the injector harness back near the rear of the valve cover and see if anything changes.

Have you ever refreshed your grounds? The injectors and ECU, among many other critical sensors/components ground at the engine dipstick tube stud.

Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011

He put a new one in per his first post.

Pull the 3 or 4 relays on the passenger inner fender. Wire brush off their terminals and spray contact cleaner down into their receptacles. Then, reinstall them all in a different position. See what happens.

missed that whole line there ...wow im getting old

I was getting even for post # 9. LOL.

I once had trouble with those resistor connections as well. I'd still check the CPS though!

Wagoneer got a c101 connector? Might check that next.