Jeep Wrangler Forum banner

1 - 20 of 37 Posts

·
Registered
Joined
·
26 Posts
Discussion Starter #1
Jeep was running great until Tuesday, it shut off while running twice. Restarted without any problems both times. The third time was not the charm, it cranks then backfires.

I checked the distributor cap...pitted. Spark plug electrodes were down to needles. Changed all including spark plug wires and cables. It would crank but backfired louder. Then replaced coil, now it cranks but will not start. About to try and see if the coil is bad. Anyone had this experience and could provide some help? Thanks!
 

·
Registered
Joined
·
14,311 Posts
First check basics

Spark at plug end of spark plug wires with cranking and wire on spare plug with plug body grounded?

Fuel rail pressure?

Injectors clicking or checked with noid lights

If have good rail pressure, injector pulse and spark then the history you related sure sounds like a timing belt jumped some teeth

Especially if engine is high milage

Sudden not running never runs again and backfires all fit with that possibility but first things first so check spark and fuel


Sent from my iPod touch using Tapatalk
 

·
Registered
Joined
·
370 Posts
When it was backfiring, was the backfire out the exhaust or did it backfire through the intake?

As the rule goes, three things are needed: air, fuel & fire.

[EDIT] Digger's got good stuff for you. Run with his answers first.

Backfiring through the intake can be an indication of fuel delivery problems. Backfiring out the exhaust could be timing related. Crank position sensors go squirrelly on some and cause issues with firing, but generally if you have a spark, you have a good crank position sensor.
 

·
Registered
Joined
·
14,311 Posts
These crank timed spark vehicles act a little different then traditional distributor cam timed spark vehicles when crank and cam get out of sync

Typical old style engine spark timing would change off normal with crank marks but since your spark is timed off the crank position sensor even if chain jumps spark stays timed with crank position/timing marks


Sent from my iPod touch using Tapatalk
 

·
Registered
Joined
·
26 Posts
Discussion Starter #5
Please excuse me if I get this wrong...new to this forum. learning how to post/reply. To Digger84, thanks! I checked the coil and zapped myself a little even though I was holding with insulated pliers so yes lol the coil appears good. Rail pressure is good. Couldn't hear the injectors but they were replaced about 8 months ago. I went to disconnect the battery and noticed the battery was loose in the box. That's when I realized my new battery has been replaced with an older marine deep cycle battery and the lock-down is missing...go figure. Could that have something to do with it? Anyway, I disconnected the battery for a few minutes and it started, ran rough, blew a little black smoke then back-fired and died. Didn't try to restart, that was enough for the night. Oh the back-fires are out the exhaust. I'm going to get a new battery and try to see if timing is off tomorrow. Thanks for the ideas.
 

·
Registered
Joined
·
473 Posts
What codes are you getting?

Misfires on all cylinders?

The only time I had a misfire on any of my jeeps was from a faulty crank sensor.


Before anything else, I would do a visual inspection of all wires and check the codes. Then it's time for the volt meter.

If it's not the CPS. There could simply be one cylinder not getting spark. Have you tested for spark? Pretty easy to do with your distributor setup.

Other than that I'm thinking blown rings or something blown in the valvetrain. Wouldn't hurt to inspect under the valve cover. Any smell of fuel in oil?
 

·
Registered
Joined
·
26 Posts
Discussion Starter #7
Hi Mattaeus,

No codes, Doesn't sound like all cylinders. I haven't checked all plugs, guess I will do that next. The two I did have spark and the plugs, rotor, distributor cap, and coil are all new. It was running perfect then just not. No smell of fuel in oil and old spark plugs weren't fouled.
 

·
Registered
Joined
·
14,311 Posts
If you have spark rail pressure and injectors clicking or pulsing noid lights unless fuel bad it is likely jumped timing chain

How many miles on engine?


Sent from my iPod touch using Tapatalk
 

·
Registered
Joined
·
26 Posts
Discussion Starter #9
Hi Digger84,

I have about 75K since rebuild. Total miles 230K. I checked all the brand new spark plugs today. They all have fire but are a little fouled and they are brand new and haven't ran for 3 minutes so it appears fuel is not the issue. I guess I will look up how to check jumped timing chain on the Jeep. On my older cars it was just bring to TDC and count the links between the marks. On the Jeep, I don't see any marks so this may be fun.
 

·
Registered
Joined
·
14,311 Posts
https://www.justanswer.com/uploads/supermechanic/2008-10-22_161605_3.gif


To verify correct installation of the timing chain, turn the crankshaft to position the camshaft sprocket timing mark as shown in Fig. 7 . Count the number of chain pins between the timing marks of both sprockets. There must be 15 pins. NOTE: Installation of the timing chain with the timing marks on the crankshaft and camshaft sprockets properly aligned ensures correct valve timing. A worn or stretched timing chain will adversely affect valve timing. If the timing chain deflects more than 12.7 mm (1/2 inch) replace it. The correct timing chain has 48 pins. A chain with more than 48 pins will cause excessive slack.


Sent from my iPod touch using Tapatalk
 

·
Registered
Joined
·
14,311 Posts
But I would use the marks in the first image not the pin count as that method was good in 87 but by 98 pretty sure they went to larger gears with a longer chain and pin count is more like 20

So just verify marks then rotate crank two full rotations and verify marks again and skip the pin count


Sent from my iPod touch using Tapatalk
 

·
Registered
Joined
·
26 Posts
Discussion Starter #13
TJ won't run follow-up

Hi Digger84,

The marks wouldn't quite line up so it appears it did jump a tooth. The old chain would move about a 1/2". The new one is very tight. The "damper" in the crankcase cover was busted and it recently started using a little oil which I now know was the timing chain cover.

I rotated the marks until they were as close as possible on the old chain and aligned them before I put on the new chain. Hopefully that will cure the issue. I'll let everyone know after I get the new seal in tomorrow.

Thanks for the help!
 

·
Registered
Joined
·
26 Posts
Discussion Starter #14
This "adventure" is taking a long time. Taking it apart, and I'm not sure if it's from the prior rebuild but the screws holding fan shroud bottom were missing...wouldn't matter they broke the plastic. The right side radiator bottom bolt was not tight. The left bottom bolt was missing. The clips to hold the radiator were all rusted and broken (found replacements from O'Reilly's). It would help if every other bolt wasn't a different size, lol.

Make sure you check the replacement radiator. I didn't until it was installed. When I started to attach the fan shroud the new radiator (CARQUEST) didn't have the nuts built into the radiator frame for the bolts, just a hole. Always love that extra trip going back for nuts and bolts for parts. If it says it's an OEM replacement I should be able to use same bolts!

Finally, got it back together, filled up the radiator and watched it run out almost as quickly as I put it in from the water pump and thermostat housing. Took off the thermostat, gasket it appears to be fine (felpro, no rtv used). The water pump gasket came apart when I removed the pump (also felpro, no rtv used). What the heck? I spent an hour cleaning the block (after getting all the old gasket off, used 800 sand paper to ensure it was down to bare metal) and used new parts. Found a note in another thread where folks had a similar problem but no resolution. ideas?
 

·
Registered
Joined
·
5 Posts
My 99 stopped running too, just kept turning over. My gas gauge didn't work for a couple of weeks prior so it turned out I needed a new fuel pump. Hope that helps.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #16
Hi deak88,

I have fuel pressure and the pump and injectors were changed about 8 months ago. I went old school with the water pump and thermostat gaskets used the gray permatex. So much for Jeeps recommendation not to use sealant. Finally got everything buttoned back-up. Tried to start, won't start. No fire at the coil which was new and working. Stuck a replacement in, still no fire from the coil. What next? Any Ideas? There was a fuse under the hood that sparked which goes to the fog lights and now the driver side fog light doesn't work but there is 12 volts going to the light so it just appears the bulb blew.
 

·
Registered
Joined
·
14,311 Posts
If no spark at coil three possibilities

Missing constant plus 12 check with meter (if bad fix harness or fuse or relay or key switch)

Missing pulsing ground check with meter

Bad coil test with you directly supply plus 12 and a pulsed ground (if bad replace)

If missing pulsesd ground we next move to crank position sensor and its 5 volt supply from the pcm


Sent from my iPod touch using Tapatalk
 

·
Registered
Joined
·
26 Posts
Discussion Starter #18
If no spark at coil three possibilities

Missing constant plus 12 check with meter (if bad fix harness or fuse or relay or key switch)

Missing pulsing ground check with meter

Bad coil test with you directly supply plus 12 and a pulsed ground (if bad replace)

If missing pulsesd ground we next move to crank position sensor and its 5 volt supply from the pcm


Sent from my iPod touch using Tapatalk
Hi Digger,

How do I check those? I have a multimeter but not sure where to check. I plugged the odbc up to see if it threw a code but now it won't connect and I noticed the gauges aren't coming on when I turn the key on.

I also checked fuel rail pressure. I have none. So, I had spark and fire before I changed the timing chain. Replaced coil, wires, distributor cap/rotor, spark plugs and now I have nothing. This is a little more than frustrating. If the crank position sensor is bad or if it's not at TDC would that cause the problem? I hope so and it's bot the
 

·
Registered
Joined
·
14,311 Posts
CAS needed for spark but not needed for rail pressure

Check grounds and check fuses


Sent from my iPod touch using Tapatalk
 
1 - 20 of 37 Posts
Top