Alright, I finally decided to make an account because I can't seem to find a fix for this anywhere. A little bit of background: 89 Renix 4.0 sat in California Woods for 13 years with my Great Uncle. I got it back in 2021 and have been working on it since. It's had issues from loss of fuel/power while driving to the transmission being pushed into the flywheel (long story). Today's lucky issue is that it won't start without starting fluid. It'll crank and crank till the battery is dead. But if I use starting fluid it'll start and run perfectly.

I've done the Fuel pump (2x), fuel pressure Regulator (3x), TPS (3x), IAC, Fuel Filter (3x), new Plugs and Wires (2x), new Injectors (2x), cleaned the Throttle Body (2x), bypassed the Ballast Resistor, Ignition Coil, O2 Sensor, Vacuum Lines, MAP, MAP vacuum upgrade, Crankshaft Position Sensor, swapped the ECU for a spare I had, replaced the entire fuel tank, Cap/Rotor when I first got it, and a Valve Cover Gasket.

I'm thinking possibly the MAT or the CTS being bad, but I really don't wanna put more money than I have to into this jeep. I love the thing, but boy it's a money pit. Does anyone have any ideas???

I also checked the fuel pressure. It seemed a little high, around 37 idle and 42 when I primed it. Probably from bypassing the Ballast Resistor.

Another weird thing: It'll start when hot, but not cold.

Any and all help is appreciated!!!

 

Go here:

https://cruiser54.com. Do tips 1-5 to start off. Then browse through the rest of the page.

Then go here: https://cruiser54.com/?page_id=365 and get the FSM and the Renix fuel injection manual

39psi with the vac line disconnected is the spec. Should be 31 psi when the engine is running.

You can check the resistance of both CTS and MAT sensors from the specs in the FSM.

 

I'll do the tips and test the resistance on the MAT. Don't I have to remove the intake manifold to get to the CTS?

Also new development: it started with the O2 sensor pulled out. I cleaned the sensor (it was practically pure black), and put it back in. It started right away after that.

(Edit) I forgot to mention, it was idling around 37 PSI with the vacuum line attached.

 

Don't have to remove the manifold to test the CTS. The connector is down by the knock sensor.

Not sure I follow about the O2 sensor. You took it out to clean it and it started right up afterwards?

 

Yeah, so I pretty much took it out, like completely out. And then out of curiosity went to start the engine and it started right up. I shut it down, cleaned the O2 Sensor, and then put it back in and connected it. The engine started right up again. I drove it for a bit and it seemed fine.

This morning I went to start it and it had almost the same issue. Long crank, but it fired for a second before cranking again. Got it running after about 20 seconds of cranking. It smells rich and my dad says it sounds like either the timing is retarded or that it's flooded.

Since the O2 sensor was practically pure black, I'm going to assume something is causing it to run rich. I'm just not sure what. Still have to do some of Cruisers' tips when I get home.

Last time I did the spark plugs they were black. I'm going to bet that if I took one out now, it'll also be black.

 

Yeah, it's running rich. What brand O2 sensor did you buy? I (and others) have had issues with Bosch. Seems like every 2 years I failed smog testing and needed a new O2 sensor. I put an NTK in back in 2020. Not only passed then, but passed in 2022 on 1st attempt.

Also, most of my trips are fairly short. Sometimes it doesn't even get to full temp so it remains in open loop. Periodically, I take it for an extended high speed pass down the freeway to get the cat up to full temp and burn all the crud out.