timhall1999

New to 4.0. Anyone have a picture detailing what’s what in the engine bay ?
Also to my surprise. After driving for 4 days and no issues
parked Jeep for 15 or so hours
now cranks but no start

pushed the schrader valve to drain fuel
cranked and then checked to see if more fuel came out and yes

so I’m assuming it’s a spark issue

battery seems to be good
had it hooked to another vehicle and crank and crank and nothing


any advice would be appreciated as I’m used to 6.0 power strokes.
left those pain in the asses for a 4.0 and seems like I’m stuck under the hood on all my vehicles lol

timhall1999

1993 Cherokee Sport
4.0 2WD
auto

tjwalker

1. Check all fuses. Don't forget about the critical fuses in the power distribution center (the black box) under the hood!

2. Listen for the fuel pump. Turn the key to the ON position (not start). The fuel pump should energize and run for approximately 2 seconds by design. If you don't hear that, you need to address the fuel pump circuitry.

3. Check for spark. Remove a spark plug. Keep it attached to the plug wire. Place the plug electrode near a good engine ground. Have a buddy crank the engine while you watch. You are looking for a strong, BLUE, snapping spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine (weak spark is usually related to the ignition coil, your coil can be tested for both primary and secondary resistance with a manual and a meter).

4. IF spark is good (and ONLY if), then introduce a small amount of gas or starting fluid into the intake. If the engine starts and runs for a short period of time with this technique, you have identified a "fuel delivery" problem. Your 93 4.0 engine needs approximately 31 psi of fuel pressure to start, that can only be accurately tested with a fuel pressure gauge which often can be rented very inexpensively from local parts stores, call around for availability.

timhall1999

So the only thing I did before this happened was I remove the air box to clean filter and dust the box off
and the PCV fitting and plastic the seem loosed and didn’t go back together that firmly
idk if they were like that before removing air box.
but could that cause the no start issues
if the pipe isn’t sealed causing a vacuum leak?

timhall1999

But when I put it back it
I started it and moved it in my driveway back about 5 feet
so idk if that could be the cause
after moving it
I let it sit for a day and then tried to start and drive and then issues arose

timhall1999

Fuel pump seems to to turn on when key is in run position
pulled the fuzes in the black box all seem good
oulled the relays in the box
and all seem good
when cranking
no lights are on except parking brake
coolant gauge maxes out
oil pressure gauge is Steady at 20 and slowly climbs while cranking and bat voltage reads about 10
but I’m about to check the battery
that pcv valve rubber attachment is cracked and the breather hose seems loose
rheres two unconnected plus one is by the ECm and air box
adj the other comes from the main harness and out by the washer fluid



bought the Jeep 4 days ago
ran it fine for 150 miles or so
Topped off coolant
cleaned air filter
and plugged in a damn car charger and sits for 15 hours plus and doesn’t start
eben when jumping with another vehicle

timhall1999

timhall1999

Tested starter battery and alternator with oreillys tester

alternator had volt regulator fail
Could that cause my no start issue

replaced ignition coil before test and didn’t help

timhall1999

Bump, I know I’m an idiot with diagnosis
any help would be appreciated
Having a mechanic come look at it tomorrow
idk if a alternator that tested bad with voltage regulator
would cause my issue ?

Ricthewrench

Batt condition can definitely be your huckleberry! Jumping it will not repair a bad cell. Hook up a good battery and try it. R

tjwalker

I haven't seen any reply yet on you doing some preliminary testing for "spark" and "fuel". Doing so will very likely point you as to which of these components isn't there or if both of them are missing.

Review my post #3, numbers 3 and 4. This is testing you can easily do yourself in about a half hour..Spark, fuel, compression and air are involved with starting of any engine. Yes, timing too can also be involved. But for the vast majority of crank but no start conditions, what you are most likely missing is either spark, fuel or BOTH. Your job is to narrow this down and your suspect list will become much, much shorter. Finding out what is good is a really big part of finding out what is bad. This is a process of elimination!

First out of the gate testing for spark and fuel. Seriously consider doing this. This is how I have started diagnosing a crank but no-start condition for the last 47 years, and it would likely be the way any shop technician would approach it if your XJ was in their shop.

Good luck and keep us updated!

DFlintstone

Trust TJ. I could be mistaken but think your V regulator is in the puter? Maybe not. Don't forget flooded happens. Holding it floorboarded will cut injector pulse and provide max air as it cranks. Cranking over a 10 count your starter will get hot. If Tom agrees pulling one plug around then to see if it's wet or dry and checking spark is a thought.

timhall1999

Installed battery after charging it up
cranked and started right up
drove it 10 feet and died

waited a minute or so and started again
and has been good ever since

timhall1999

Drove it about 120 miles and frequently stopped and turned off and it would always start again

thrstone

The good news is it cranks; all the starting problems I've had with mine were ones of deathly silence, even with a new, fully charged battery. The comment above about fuel starvation makes me wonder - I agree that the Jeep fuel pump has a very distinctive whine. You hear it clearly in the cabin just before you start the car....when it's working properly! I hope you solve your starting woes.