brjazz

I recently bought my 1984 XJ, 2.5L 4-cylinder, manual 4 speed, 83,000 miles.
I drove it home a little over 100 miles with no issues other than some hesitation during acceleration. After changing out the fuel filters (previous owner put a clear one near the gas tank, and there is a metal one next to the carb). I was still having the hesitation issue until it died while driving and wouldn’t start. I had it towed home, and after realizing fuel was not getting to the clear fuel filter near the tank, I decided to replace the mechanical fuel pump. After reading the instructions, the old one came off and the new one went on very easily. It started up after a few attempts and idled well for a few minutes and then died.
After that, I wore the battery down trying to get it to start, but it would only start when pumping the accelerator. One time it started seemed to run ok with with the accelerator pressed a little, but died as soon as I let off. All the other times it started, it ran really rough and blew smoke (mostly clear) and fumes out the tailpipe.
I tried pouring a little fuel into the top of the carb, but it still wouldn’t start.
I put the battery on a tender overnight, and am trying to figure out what to do next.
Any suggestions would be greatly appreciated!

Jeepwalker

Sounds like a decent jeep despite the recent issues.

I guess you should first pull off a spark plug and lay the plug tip on the engine (connected to the wire), have a helper turn the engine over and see if it has decent spark. Make sure the plugs aren't fouled. If no good spark, then chase down spark issues.

If the spark is good, you might pull all the plugs out and watch them spark in sequence. Maybe the distributor sensor is crapping out. And I think there might be a start-shaped inductor too ...and on GM vehicles they can degrade and crack. Verify all the wiring is good and connectors aren't corroded.

You should find an older guy who used to be a mechanic in the 80's/early 90's. Mechanics these days won't know how to fix it. This thing 'should' have 'codes' which can be retrieved with a paperclip, but those codes back then weren't very helpful. Still you could try. I wouldn't blame the computer out of the chute b/c those old computers almost never died.

Then let's go back to fuel. Have you replaced the fuel filter? Is there a filter up by the carb? Verify, bc usually on old carb vehicles there are. It's a small 2" filter that slips in the carb as I recall. They clogg easily. If there's one up by the carb, you might want to remove the one you installed so you don't introduce more suction pressure ..at least till you get it running right. It would be good if you rented a fuel pressure tester and if it has fittings to make a T ...to get your fuel pressure. Then a hose to a bucket and check fuel flow. Maybe your new pump isn't any good? So, try to get the filter and fuel situation figured out.

You might ohm out the temperature sensor. And compare it to a temp/ohm chart. Make sure it hasn't drifted.

You might consider removing the distributor and looking underneath it and checking the integrity of the star-shaped inductor. That's if you don'thave good spark. Don't forget to line the engine up (before removal) ...and know exactly where it goes, because you'd be messing with the timing.

https://www.quadratec.com/products/917241_02.htm


In the old days we'd slowly dribble fuel out of a small cup down the carb and if it ran fine a guy knew it was probably the carb. But don't do that bc if it backfires it'll ignite the fuel and burn down a hand or garage. Ultimately, if all that checks out good, you might end up digging into the carb and cleaning out passages. And if you're young and never did that job, there's like a crapload of tiny parts, (esp if it's a Rochester), springs and check ***** in a carb and they all need to go back in the exact 'right' spot in the exact 'right' way. Don't let any springs go 'Doooiingg!!" and bounce across the floor.

But make that the last thing you do. Check all the other things out FIRST bc people always want to blame the voo-doo parts first and skip over the basics (which are usually the problems)

Jeepwalker

Fuel filter. That's like actual size ..or maybe larger than actual size....

brjazz

Jeepwalker,

Thanks for all the advice! I have a friend that is an incredible mechanic that mostly works on classics and specializes in Mopars… he is backed up on work, but is hoping he can come by next week.
In the meantime, I am trying to learn and do what I can…
I replaced both fuel filters about a week before replacing the fuel pump. I am thinking about replacing all the fuel lines, so I will do like you said and remove the clear filter next to the tank when I do that.

I will follow your advice on checking for spark and fuel issues!

I have rebuilt a carburetor before (Holley 4-barrel), but thanks for the warning! The previous owner also gave me a brand new carburetor, so that may be some indication of the state of the current carb! Ha ha.

Thanks for the info on the small filter in the carb! I did a quick internet search and can’t find where it is specifically located or how to change it. Any additional info would be appreciated!

Jeepwalker

Ok.

Don't replace the fuel lines till you do your flow and pressure tests. Why replace the lines? You might have received a bum fuel pump. Did you install the pump right? The lever has to be under the driving cam. In the old days some people would 'somehow' get the lever *above* the cam...

Really, the thing to do is do basic troubleshooting starting from the ground up, not a scatter-gun approaach:
-Is it 'Timed' properly
-What is the compression
-Are the electrical grounds good
-Are *all* the vacuum hoses good and routed properly? This was a big issue on older vehicles.
-What is the engine Vacuum (when you do get it running)? This is a really important metric.
-Are the plugs 'good' (I've even had new plugs out of the box that weren't good)
-Are the wires good? Esp the coil wire if there's a coil. That one wire (if this jeep has a 'single coil wire' (I don't remember)) can cause problems. ....and those old coil wires had to be a special coil wire, not just any wire, in some.
-What's the fuel puressure? Flow good?
-Is there excess exhaust backpressure?
-O2 sensor working properly?
-PCV good?
-Carb base gasket leaking?
-Computer-related issues? What are they? Don't just rip it out.
-Is the carb solenoid working properly?
-Is the float shot? Maybe there are carb issues. But don't jump to conclusions. Do proper troubleshooting not guesswork.
-EGR? Test the EGR. EGRs can cause operational problems. Easy to clean, but may need replacing. Put your fingers underneath the egr to feel the diaphragm. Have someone start the vehicle, and feel if it lifts up. Remove the EGR and clean the carbon and crud off the pintle and engine bore. I bet it's all loaded up. If the diaphragm work, then remove and clean. A bad EGR shouldn't prevent it from running but would make it run like crap.
-Choke ...that's a whole nuther thing.
-The whole entire emission system can be trouble-shot with a volt meter and vacuum gauge and a couple jumper wires. Not that difficult, but you need to learn some new stuff (see link below).

Beware: Your old-timer mechanic might be the "Let's rip off that emission crap" kind of guy. Most of them were. I don't trust old mechanics bc I knew a lot of those old mechanics in the day. The VAST majority of them were ignorant of early computer controlled carb systems. It was rare to find a guy who really knew how to trouble-shoot one. Hopefully your guy is good and knows how to work on that older stuff, *understands* it. But I doubt it. And you should too. If he starts grumbling about "rip it off" "You don't need that EGR..." you know he doesn't. And politely stop there. Or focus on the 'why it doesn't run' and restore the emissions later on, on your own. Um, when ya rip that stuff off they usually run worse! Choke doesn't work right. ****-poor idle, worse acceleration. And worse fuel economy. Don't fall into that trap. You'll end up worse off. I had a few buddies who didn't understand emissions and did that and they ended up with POS'. It was real common to do that back in the day bc people didn't understand how to work on them.

If your mechanic does that, put a hard STOP to it and find a different guy. Or be your own guy. You should be able to get it to run right and well. Very few guys know how to de-bug those old CCC systems (Computer Controlled Carbs). Or maybe that's the problem, it's already half-bastardized. A good-running CCC system is like an early form of electronic fuel management. Those engine's would sit there and idle rock-solid smooth for an hour like an EFI system. It's just mechanical fuel control. The computer actuates a solenoid in the carb to meter the fuel. And I have had cars with that system go to almost 300k miles w/o troubles. But your Jeep should still start and run even if the carb solenoid was unhooked. So, something else is going on, like fuel or spark. If he tries to talk you into pulling that stuff off you'll have a rich-running screwed-up system. Or maybe half of it *is* already pulled off and you need to restore it back to how it should be. Guys would do that and end up with a POS and eventually sell the rig.

Read through this and the Spark, fuel & emission systems:
https://jeep-manual.ru/index.php?page=XJ-2


_

brjazz

Thanks again! I will follow your advise!

So, funny development… I pushed it out of the garage and decided to turn it over, and it fired right up! It sputtered a bit like it had some bad fuel or something, but I drive it around the block, and it idled quite a while before it died and wouldn’t start again.

It seems like when it was cold, it started right up, but once it got warmed up, it died and won’t start.

Does that indicate anything that I could specifically start on?

Jeepwalker

Yeah ...fuel issues. Did this thing sit for a long time before you bought it?

1) I wonder if there's water in the fuel? That'll spoof a lot of things and super easy to overlook. Might be worth pumping some fuel into a bucket and looking for water on the bottom (after it's had time to settle out). Not that difficult to Lower the tank and dump the fuel out. It can take many bottles of HEET to clean out bad water issues.
2) Could be fuel in the carb leaking down. Like a leaky needle valve. Then when ya to to start it, the fuel bowl needs to fill up. So it doesn't start right away. Just a thought. Did the fuel filter you put in ..was it the right one? Did it have a one-way valve inside the filter? (if it was supposed to have one). Did you put it in the right way? It's supposed to hold pressure so when you go to start it there's fuel ready to go.
3) Weak fuel pump.

That's why checking fuel pressure and flow is important, so you have actual readings.

brjazz

It did sit for a while, and was just recently driven semi-regularly. I am starting to think there could be multiple issues at play (fuel tank contamination, spark issues, vacuum lines not connected properly, carburetor issues, etc.)

I am positive the fuel filters are on the right way. They were both clearly marked with a “to carb” arrow. Also, this afternoon I was able to confirm fuel is flowing to the carb, so I know the fuel pump and filters are at least working minimally, but I am going to borrow a fuel pressure tester line you suggested.

Thanks again for all the advice! I have my list of things to do! tomorrow I plan to test the fuel pressure and also check the quality of spark I am getting.

You have given me a great roadmap to follow and lots of great advice. I will start working on things in the order you have recommended and let you know how it goes!

cruiser54

Make sure the intake manifold bolts aren't loose. Very common on the 4 cylinder engine.

2k2 GJC LMT 4.7L V8 VIN=N

he's not wrong about that in addition to a 2002 jeep grand cherokee that turns over but won't start (quite different from your '84 I'm sure) I also own a 1983 Nissan 720 pickup which turns over and starts and even runs (I've been driving it while the jeep is down) but that poor little 4 cylinder pickup has had (nearly) every deletable system deleted and it gets about 9 miles to the gallon. Needs a new carb but until i found it on Amazon for 125 bucks I was looking at spending 500-600 on rockauto and that's twice what I gave for the truck 5 years ago and probably 1/1000th of what I've put through it in gas. I love that truck I've been all over her tinkering and fixing. If I don't touch her for too long she will break just to feel me under the hood again. But yeah I plan to eventually restore most of her lost insides. Everytime someone advised me to just delete that you don't need it anyways she ran a little worse. I repeat 9 miles to the GALLON. she should do twice that in mpg on her worst day if I never cared for her at all