88 Cherokee Crank but Not Starting

Hey everyone, I have an 88 XJ with a 4.0 and the AW4 Auto with some issues here.

Last ran November 2012. Previous owner said it would not start. He has since replaced the ignition coil, distributor, cap, spark plugs and wires. He was under the impression it was a bad fuel pump.

Once we got the Jeep, we noticed it might be low on gas. Put 4 or so gallons in. Didn't get that lucky. A new CPS sensor came with it, has not been installed yet. The Jeep would crank and crank but no start. Got a new battery and now have a much stronger crank.
Tried testing the existing CPS sensor based on resistance, and voltage when cranking. Resistance appeared to be between the range we've found it should be in. Voltage may or may not be, not sure on that.

We took the air intake tube off to get to the throttle body. We checked fuel pressure at the rail, and there was none. Turned the Key to the on position and no fuel pressure. You could hear the pump prime for 3-5 seconds when you turn the ignition to ON. We turned the key to the on position a few times to see if it would push fuel to the rail. Also tried cranking to see if fuel would get to the rail. It was apparent there was no fuel pressure.

Out of curiosity to see if fuel appeared to the the main issue, we sprayed starter fluid into the throttle body. Upon cranking, the engine actually ran for a second or two. That leads us to believe that the Jeep has spark, and all the new spark/ignition components are in working order.

Next we pursued the no-fuel issue. Down at the gas tank, we disconnected the fuel line from the fuel filter. Some old gas spilled out of the line. We turned the key to ON to see if the fuel pump would prime and send fuel through the line (If it may have been the case that the fuel filter or a line was clogged). No fuel came out.

We decided to remove the fuel pump from the gas tank. We got it out. Just for kicks, we jumped the fuel pump to see if it would pump some water--but it was clear that the pump was not in working order. It was very corroded and had no screen on the intake.
Today, we got a new fuel pump. Got the fuel pump installed, plumbed, and hooked up. Upon turning the ignition to ON, the fuel pump primes, and there is instantly fuel at the rail. So, we now have fuel.

Unfortunately, the Jeep will still only crank. We are not sure if the injectors are clogged, or if it is just not firing, or if it needs some cranking for a rough start (since it has not started for a year). There is a tiny hose that ends around the throttle body that is not connected to anything at the moment and I was wondering what that was. It appears to be the MAP vacuum hose? I am not sure where to connect that too.

The CPS is also a toss-up. Under the hood, there appear to be two plugs that the CPS sensor can plug into. One is at the back of the head and runs into the main wiring harness. The CPS was connected to another plug which went directly into the firewall at the drivers side.
Upon some research, I guess 88 and 89 XJ's had issues with the main harness connection with the CPS, and there was another wiring kit which was offered to remedy the problem. We are not familiar with this and would love to hear any more about it. We just want to make sure the existing CPS is connected to the right plug before proceeding.

Any advice or troubleshooting tips would be greatly appreciated.

The Renix system has to crank until it reaches 300 RPM BEFORE the CPS will send a signal to the PCM (ECU) to trigger a spark.

If the battery is poor condition, or the starter is poor condition, or the main cables are poor condition, or the ground strap from the head to the firewall is poor condition--your are dead in the water.

HOWEVER, you know that it would fire with starting fluid into the TB--now that you have fixed the fuel pump, REPEAT shooting starting fluid into the TB while cranking.

Hey, thanks for the reply.

I replaced the battery a day ago, has a real strong crank now, in my opinion.

So my friend and I have been working on this and did hear a sign of life with the starting fluid before we did the fuel pump. Just have been hesitant with the use of starting fluid. The most recent attempts at starting, with the new pump and now good fuel pressure, didn't result in any sign of life. (No starting fluid added). A few times however, we did get an odd, brief, pop out of the throttle body that produced a little flare up. I don't know what would be causing it to "flare up" out of the intake like that. Something is igniting but spark order may be off? (Previous owner did ignitions stuff and could have put it back in the wrong order, it is on the list of things to check).

The intake tube is currently removed so I could get some starter fluid down in there. However, there is also a loose hose by the throttle body that appears to be a vacuum hose for the MAP sensor. I just don't know where to attach it to the throttle body.

Near the base of the throttle body on the passengers side, an oval rubber stopper with two holes in it (hopefully still there) plugs into two holes (top and bottom or stacked vertically). The Map vacuum line goes into the hole that goes all the way through, one is a blind hole, one is a vacuum hole. I usually clean that hole out with a drill bit and blow through the vacuum line. Inspect the vacuum line closely for cracks or rub through spots.

I'd check the fuel rail with a fuel pressure gauge, it is possible to get good pressure with the prime when the key is turned to run and to loose most of the pressure as soon as the motor is cranking over, if there is an open circuit between the starter relay and the fuel pump. The power for the fuel pump comes directly from the starter relay during cranking.

I read someplace that no reference signal from the MAP (unplugged, no power etc.) and the injectors won't work.

Might also want to ohm test the number one injector ground to battery negative. Various sensors and all of the injectors use the same ground path. If that ground is flaky things are doubtful to work right. That ground eventually ends up at the engine dipstick brace.

If you are getting good spark while the engine is cranking, your CPS is likely OK.

You might also try 1/8 th throttle (just a little throttle) while cranking, just in case the IAC is stuck shut, you need little air for it to run.

A Little late now, but when starting an XJ that has been sitting for awhile I usually go to the starter relay, unplug the Orange and Black wire from the spade connector (usually marked/etched "BAL" on the relay face) and hold the wire connector to the large stud on the relay, with all the red wires attached (battery power). This supplies power to the fuel pump and purges the fuel lines and injector rail of the gas that has been sitting in there slowly turning into jelly. You pump the old fuel out (before cycling it through the injectors) and any new fuel that moves up to the fuel rail has been through the filter.

Our goal for this afternoon are as follows:
- Check for correct firing order in the rotor
- Connect the CPS to the "Upgraded" harness that leads into the firewall.
- Recheck the CPS for Ohms and AC Voltage. I believe we are looking for 0.5 AC Volts?
- Reconnect MAP Vacuum hose to the TB
- Check fuel pressure during cranking
- Check ground resistance via the #1 injector and the negative terminal on the battery.

I had what looked like good fuel come out of the shrader valve to check pressure. However, I did not flush the old gas out of the rail before we tried cranking it over. As you mentioned, a little late but, we could still try and get some fresh gas up there if it has not already reached the fuel rail.

Accomplished this afternoon
- Checked the firing order, looks good there.
- Connected the CPS to the firewall harness
- Retested the CPS and read 0.235 AC Volts. This could be too low.
- Connected the MAP vacuum line back to the throttle body on the bottom opening.
- Had fuel pressure during cranking.

So we are getting this odd backfire or "cough" from the intake along with a quick flame.
Seen here --> http://www.youtube.com/watch?v=Je9KKoazwlM

I've got no idea why it'd be doing that. What do you all think?

Also found a loose what appears to be a vacuum line. (I have it sitting ontop of the air box for the picture) Haven't seen an obvious place where this should go yet.


Thanks everyone.

That back flash can be a lot of things. Most common is the inside of the distributor is dirty (cross fire), bad plug cables (cross fire), fuel puddling near the valves or the firing order. The bad firing order can be at the spark plugs or the distributor cap. May also be a hanging valve or burnt valve, but that is rare, more likely to be excess fuel from a misfire building up and igniting. I've had them do that when they get water in the ignition parts.

Another possibility is the distributor is set up wrong. Look closely at the distributor locking bolt and see if it has wrench marks on it.

Double check the rotor is pointing near number one, when number one cylinder is at the top of the compression stroke and the timing marks are aligned. If it doesn't point *near* number one, then we can fiddle with the distributor if need be. Don't pull it on a hunch, definitely don't pull the distributor if the motor isn't at number one TDC (makes it whole lot easier to get back in correctly).

Pull your spark plug cables off one at a time, clean the poles on the distributor cap, inside the cap, blow out the bottom of the distributor under the sync sensor plate, the inside of the spark plug cable boots and the plug tops. Ohm the cables and check for cracks. Use an old plug, open it to 0.60 and hold it on a ground and look at th spark, should be crisp blue white that you can hear go crack, A yellow spark, wide spark or one that even splashes on the plug electrode is weak.

Do a compression test. I always do one on a new to me motor, just to check out what I've got, before I sink a bunch of money in it (or put my money into the wrong parts).

Click on the link below and review posts # 7, 12, and 13.

http://www.jeepforum.com/forum/f140/cruisers-mostly-renix-tips-1304879/

cruiser54 said:

Click on the link below and review posts # 7, 12, and 13.

http://www.jeepforum.com/forum/f140/cruisers-mostly-renix-tips-1304879/

Click to expand...

Cruiser accurately describes the TDC 1 procedure and explains it better than I can. One point, the cylinder can build a little pressure on the exhaust stroke ( and my fool you). Getting a hand and thumb behind the A/C compressor and bracket, on the number one cylinder, is doable but not easy. I always use a compression gauge. Multiple reasons, one is you can do it yourself, you can watch the gauge while turning the harmonic balancer bolt. Two the compression gauge is more responsive than your thumb, you can turn the motor by hand slowly and still see the pressure, which may or may not be the case with the thumb method. Using a compression gauge, you are less likely o confuse the exhaust stroke with the compression stroke. Either method will work.

Update for 9/18

We started off by taking off the wires and spark plugs. Tested the resistance in the spark plug wires and they were within specification. Took the spark plugs out and smelled fuel after cranking. Lead us to believe that injectors were firing. Spark plugs looked new with little to no fouling.

Did a compression test on the cylinders and the results were as follows:
#1 - 160 PSI
#2 - 155 PSI
#3 - 150 PSI
#4 - 140 PSI
#5 - 135 PSI
#6 - 135 PSI

We had gathered that the variation of compression pressures were within tolerance, 15% of the highest pressure. Nothing stood out as being too low.

Next we addressed the possible timing issue. We aligned the #1 TDC from the given instructions while using a compression gauge instead of the thumb. Noticed that the distributer was approximately ~180° off from #1. We indexed the distributor so that #1 TDC aligned with the #1 on the distributer. Connected all the components back together and fired right up! Surprisingly with very little hesitation.

Now it has a very high surging idle from the initial start up. On the second start up it had a high idle and then came down to what appeared to be a normal idle then would randomly pop back up to a high idle.

Lastly, I do not think that there is any coolant in the system. Nor could I find a radiator cap, assuming the fill is somewhere else.

So that is where I am at now, she lives! Need to address the high idle and the coolant at the moment.

Thanks everyone!

Get the cooling system filled. Have a bottle in the passenger side rear of the engine bay?

Right, obviously don't want to run it without coolant!

Fortunately we didn't run it nearly enough for it to "overheat"

Yes, it has the bottle on the pass side near the firewall. I believe it has the Renix Closed Cooling system.

Fill the bottle until the level is at the top of the little nipple inside the bottle. Use a Napa 703-1396 cap on the bottle. Run it.

I believe the system may be empty or near it. Do I repeat the above procedure if necessary? Also I was considering doing a flush of the system with distilled water.

Flush it first if you want.

Repeat the fill process as needed.

Great!

Thank you for all the help everyone has provided me! I am very happy to see that it is running now!

What would you suggest doing for the high idle?

Snobrdrkid07 said:

Great!

Thank you for all the help everyone has provided me! I am very happy to see that it is running now!

What would you suggest doing for the high idle?

Click to expand...

Coupla things. Click on the link below and do what's described in posts # 1, #2, #3, and #5. Report back and we'll go from there.


http://www.jeepforum.com/forum/f140/cruisers-mostly-renix-tips-1304879/

Have you figured out where the loose vacuum line goes? It may be affecting your idle.

Haven't Figured out where that particular loose vacuum line goes.