67 GMC

Don't think that's the problem. Were the plugs wet with gas? One injector might leak but then you would see that with your built in fuel pressure gauge on the rail. After you shut it off, you would see a quick drop in fuel pressure if an injector was leaking.


Just a thought-I'm not sure how you are measuring the CPS voltage at the ECU? Typically, you disconnect the sensor and probe the connector and can only measure it while cranking (not running) since the engine won't run when un-plugged. I've never heard a CPS running as high as 0.95V. If you can't tell, I still think it's the CPS (unless you have already changed that ).

DFlintstone

Not to disagree GMC....smelling gas and having it start faster holding it floored, (at least for a bit), had me leaning towards flooding. Agreed on checking a plug or two. Also seeing if the tailpipe is black might say something. A guy could always try starting fluid, that could rule out being lean. Less than $3, might be worth a shot.

The same two wires off the CPS can be checked right at the connectors on the ECU. This rules out any bad connections on the way.

matt0106

Hey guys. So, I did get it to start last night, just to drive it home. But this morning when I was trying to leave for work, it wouldn't start again. I have been pulling the plugs to look at them when it won't start, but they're always dry, whether I hold the pedal or not.

That's why I'm so confused and stumped, it's like it starts when it wants. I haven't had much time to look at EVERYTHING that I need to, I've been working with no days off.

DFlintstone

MMMM well then GMC was on the right track. You verified spark. Myself, I'd try starting fluid for diagnosing. See if that makes it fire. You might google "noid light". It checks power to the injectors. I actually McGivered one with a bulb from a 3 cell mag light. >>

https://www.youtube.com/watch?v=nPdk...ature=youtu.be

cruiser54

Grounds "upgraded" but has my Tip 5 been done?

DFlintstone

Getten pretty busy here! Pete, he adjusted his TPS (post 57). Hopefully you saw about an ohm there Matt? (for ground). Do get it that that TPS really matters.

I'll try to "bug out" since Cruiser showed up, but do try the starting fluid.

67 GMC

Like you said-Starter Fluid is pretty cheap! Hang in there.

matt0106

So, I checked all the injector connectors with a homemade noid light and they are all getting a signal. The bulb flashed while cranking on all of them.
So far I've only checked two spark plugs for spark while cranking. They were both good. I'll check the other four later.

And yes cruiser, I've done 1-8 of your tips.

cruiser54

Good.

matt0106

All injectors are spraying. I checked while cranking.
All spark plugs are getting spark while cranking. Five of the spark plugs looked like the spark was weak, the other spark plugs spark looked fine. It was brighter than the others.
Bad distributor cap? Bad wires?

matt0106

After I checked the injectors and spark plugs, I cleaned the distributor cap and rotor. It started after I did that.

But the way it's acting, I bet it won't start tomorrow morning.

2heapjeeps

My 90 4.0 started right up when I first got it, but ran like dog 💩. After new plugs and clean grounds it ran better but with a long crank start (not as bad as yours) I learned it was an xj thing. Since then I had many start issues. I've discovered many times simple solutions solve big problems with my renix. You said it seems to start when it wants to. Likely a bad connection somewhere. Free checks are cleaning any corrosion not on just batt terminals and connectors, but the wires themselves. Once at work a jump would even work. Cleaned the exposed copper of battery cables and I fired right up. Check the connections on starter motor clean and tight! Check those spade connectors on starter relay if loose add a tiny piece of tin foil till can fix properly. I've been running with the to foil for years though. Just on the green wire terminal cuz every morning I had to take it off and touch it to the positive terminal with the key on just to start my jeep. That's what the tin foil fixed lol. But if that connection is bad your jeep wont even crank. If you have flooding issues maybe its due to poor spark, you have no gas issue, but since the spark isnt strong enough your developing too much fuel which just adds up....maybe. In all the prior maintenance n checking its easy to forget to tighten one nut that causes major headaches. I'd guess your stuff all works, but some loose connection is causing this hit n miss issue. But then again I learn as i go. Dflinstone and many other including cruisers list has helped me tremendously. Best of luck.

DFlintstone

Plug gap get's a little bigger each mile. You need and knock them back to .035 now and then. They can last a very long time. I'm making up some numbers...Gap them every year, or 10K, change them after 30K. That has to be close. I clean my cap, rotor and wires right in the kitchen sink now and then. Like a dish, Dawn soap and a brush, dry well. If you get new (NTK's), Be sure to check that they are gaped to .o35

2heapjeeps

Been over a year in my xj. I'll have to try that. I'm looking into fully sealed terminal connectors to the batt posts. If that helps the crank issue ill mention it.

matt0106

So, like I said. It didn't start this morning. This is what's pissing me off. Not sure what to replace or check when it's not starting. What sensors does the ECU need to get a signal from to start?