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Another No Spark, No Start, but . .

BlackRock

NAXJA Forum User
Location
NorCal
Hi All,

I have read dozens of posts on here and went through multiple troubleshooting steps. But, let me back up.

I drove the 1989 Jeep XJ (4.0) into the garage 2 months ago, it was running great. Put a new 6" lift with coils, shocks, transfer case drop, SYE, rear shackles, add a leaf and rear lift blocks.

Installed an improved headlight wiring harness and new headlights, they work great.

Changed the rear diff cover and serviced both diffs.

Changed rear main seal and oil pan gasket.

Changed transmission (auto) pan gasket and filter screen.

Installed new tranny cooler lines.

Installed a new, right side engine mount.

And, lastly, completely overhauled all of my roof rack holes to plug leaks.

All of the new fluids are in and there is 1/2 tank of gas.

After getting all of this done, went to start it and I have a no spark issue. When I turn the key on, the fuel pump is not turning on, however when I crank it, it comes on. I installed a brand new CPS. I have another 89 XJ here so started swapping parts, all relays, coil, ignition module, cpu and refreshed all grounds. Still no spark and the fuel pump is not engaging with the key in the on position.

Obviously, something I did to it when I did all the work caused it. The only thing that I noticed electronically speaking is that the battery remained connected throughout the entire 2 months of down time and went dead quickly when trying to start it. I put it on a deep cycle charge and it seems fine now. Plenty of cranking amps. Another weird thing, when I crank the engine now, the temp gauge is pegged! It has never done that before.

Does any obvious ideas come to mind? or maybe I should try swapping some other parts of of the other 89' XJ?

Any help would be sincerely appreciated!!

Thanks, Mark
El Dorado Hills, CA
(Gold Country)
 
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Have you tested the battery?

No, I did check it with a DVM and it shows a higher voltage (12.96) than the one in my other 89' XJ (12.64) (That starts right up) and this battery does crank real strong. But to answer the question, I did not have it tested in any other way. Tomorrow I will swap batteries to make sure. :)
 
The way it works is basically, when the key is turned to run (on the way to start) the ECU (computer) shuts (activates) the fuel pump relay for a few seconds to prime the fuel rail. You can often hear the fuel pump run for a few seconds.

When the key is turned to start, the starter relay supplies power to the fuel pump directly, bypassing the ballast resistor, the ECU and the fuel pump relay. Kind of a kick in the butt for the fuel pump.

The ignition switch supplies power to the ignition module and the fuel pump relay when the key is in the run or start position. The fuel pump relay is closed by the ECU on the ground side. The ignition module makes spark on the ground side triggered by the ECU.

Best place to start is to check the larger yellow wire at the ignition module for voltage when the key is in the run position. This can tell you if the problem is a power supply problem or maybe a sensor problem and the ECU isn't doing it's job for whatever reason. ECU rarely fails, it is most always a sensor input issue or a wiring issue.

If you are getting power to the larger yellow wire at the ignition module with the key on, we can work from there. Basically the same wire, through a splice, that supplies the main power to the fuel pump relay.

If the ECU doesn't detect a pulse from the CPS during cranking, it will shut down the fuel pump relay and the ignition module on the ground side. No pulse signal and no fuel pump relay or spark. But you should still have the three second prime, fuel pump relay closes for a few seconds, when you turn the key to the run position.

If you have no prime it is likely to be a power issue, prime, but no spark is likely to be a sensor or wiring issue.

Likely to be the CPS, new or not. It can be hard to get them in there just right (the clearance between the CPS and the tone ring in the bell housing is critical), the connector pins may be oil covered, you may have pulled a connector or wire loose. The CPS puts out a tiny electrical pulse signal, it doesn't take much to screw it up. The bolts for the CPS are special, threaded half way and a larger diameter near the head of the bolt, any old bolt won't do. I had one CPS that was marginal right out of the box.

It may be something else, but likely to be a power supply issue or the CPS itself, a connector, the mounting of the CPS or the wiring.

Hope this makes sense to you, it is easier to do than to explain.:)
 
BlackRock;245653687Another weird thing said:
Try this simple test to help isolate. Disconnect the crank sensor at the connector near the firewall.

NOW crank the engine and watch your temperature gauge. If the temp gauge is not pegged with the crank sensor out of circuit, you have a shorted crank sensor. A faulty crank sensor can screw with the gauges, but usually it is the fuel and voltage.
 
LOL, 8MUD, if you can recall all that detail, you can remember to zip it up too, LOL!!! But it could be worse, you could be forgetting to unzip it, :eek: LOL!

Sounds like a possible bad CPS right out of the box, that is getting to be common! Ask me how I know!

It sounds like a bad or missing Renix ground to start with!!!!
 
LOL, 8MUD, if you can recall all that detail, you can remember to zip it up too, LOL!!! But it could be worse, you could be forgetting to unzip it, :eek: LOL!

Sounds like a possible bad CPS right out of the box, that is getting to be common! Ask me how I know!

It sounds like a bad or missing Renix ground to start with!!!!

I've had a few close calls with that too, those just in time runs to the bathroom.

Seeing as how the temperature gauge sensor wire sounds like it is grounded someplace, and has spark and/or fule issues, I'm going with some wires grounded someplace, likely to be at the number six exhaust manifold exit. I've had CPS bad out of the box before also. Those grounds will kill you, one of the first things I ever found on my 88 was the head to firewall ground was sitting on top of the paint, looked good. it didn't ground anything.

His is an 89 so it shouldn't have the C-101 connector, maybe the wires from the CPS to the CPU, a connector is oil covered or came loose. But his temp gauge acting that way, makes me suspect cooked wires on the exhaust, maybe. I'm not really sure if the temp gauge senor wire will reach the exhaust manifold, I'm sure from experience the CPS wires will.
 
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Mine did this a couple years ago.I pulled the CPS and cleaned it and also sanded the mounting area an bracket before reinstalling it. I found mine full of dirt and crap from a old oil leak i guess.
 
I would pull the temp sensor wire off the temp sensor, and see what happens.

Look everywhere for damaged wires, from all the recent work. Get the meter out and check the grounds at each sensor, and disconnect the CPS and test it for AC cranking voltage, needs to be .50 V minimum it seems.

Also check the fuel pump ballast resistor. The fuel pump not working while in run, but working in start sounds like a bad ballast resistor? But if it is good, then I would suspect something is grounded that should not be, or not grounded that should be, with the fuel pump, temp sensor-n-gauge and no spark all involved.
 
Also, a remote chance the ignition switch and wires at the ignition switch are going bad, shorting out right there!
 
Mine did this a couple years ago.I pulled the CPS and cleaned it and also sanded the mounting area an bracket before reinstalling it. I found mine full of dirt and crap from a old oil leak i guess.

I did the same, mine was covered in oil and crap from a leaky main bearing seal, cleaned it and the issues disappeared.
 
Thanks to all who have offered help!! I have no voltage across the A & C pins on the MAP with the key in ON/RUN. Also, no prime to the fuel pump. I have checked for burnt or broken wires near #6 exhaust manifold area and all over exhaust, nothing obvious. The water temp sensor is clean and intact and appears to be ok (will find out how to test it or replace). One big clue is, I drove this into the garage and it ran fine up till then, after 2 months of sitting and lots of upgrades, went to start it and nothing, so I am not thinking it would be the types of failures we get while running it, burnt wires, etc. I am wondering if maybe I hit a wire with a wrench while changing the motor mounts or maybe something got disconnected. Or, maybe something was damaged when it sat and the battery drained itself down to nothing (new battery installed now).

Thanks to Mike (Ecomike) I have the electrical tech manual for it and will start checking each component.

Done so far in troubleshooting:

1. Replaced CPS twice with brand new ones, the last being an OEM from Jeep.
2. New Battery
3. Refreshened all grounds at firewall/back of head and dipstick tube area. (Will check for others).
4. Replaced distributor, Cap, Rotor, Plugs.
5. Took a working ECU, MAP Sensor and Realys out of a running 89 XJ and swapped them all, NO HELP.
6. Checked the A & C pins on MAP for 5volts on key to Run = no volts.
7. Swapped out ballast resistor and tested it, works fine, no help on swap.
8. Disabled aftermarket alarm system.

Does anyone know about being able to reset the ECU by doing key On/Off 55 times? Or codes after 5 times On/Off?

Any and all help is enormously appreciated!! I need to get the XJ running before my week long desert trip this weekend.

Thanks!!

Mark
 
Sounds to me like a bad wire possibly damaged during the work, or bad relay. I will dig into the wiring diagram tonight and post some ideas, but no power to the MAP is a BIG, HUGE Clue!!!! It means no power to the ECU, or bad wire output wire(s) from the ECU, as the the ECU needs 12-14 volts, to produce the 5 V that goes to the MAP sensor!
 
Thanks Mike! Please lmk if anything comes to mind. I spent an hour today using electrical contact cleaner on all connectors and visually inspected all connectors, sensors and looms.

It's a mystery :confused:
 
Thanks Mike! Please lmk if anything comes to mind. I spent an hour today using electrical contact cleaner on all connectors and visually inspected all connectors, sensors and looms.

It's a mystery :confused:
Have you checked all the fuses, and checked the power to the ECU, with ignition in the on position?

Note, that if the engine is not cranked within a certain period of time, the ECU shuts down power to the sensors on the 89 IIRC, but not the 87. Cycling the ignition switch resets the timer on the 89.
 
OK you have two interesting symptoms other than the no start. No fuel pump when you first turn on the key and a pegged meter.

First off I would check the Fuel Pump Relay. After that I would check the ground from the head to the firewall and the grounds on the tranny dipstick stud.

I can't remember if the 89 has the C101 connector, but if it does, that is most likely your culprit. Worry about the fuel pump relay first.
 
Good advise!

89 had no C-101.

What about the B+ relay, is it involved at all at that stage, or just the Fuel Pump Relay.

Try pulling the temp sensor wire off the sensor and see if the meter is still pegged, and report back!
 
Note from DJ
In your post #12 you stated QUOTE: “Checked the A & C pins on MAP for 5volts on key to Run = no volts”.
My question to you is what you were using as ground source for your meatier when checking for the voltage at the MAP pins A & C? If you were checking for voltage across A & C try checking for voltage from C, which is the 5V supply pin and the center of the battery Negative post. Just in case you have lost your sensor ground circuit which is pin A from the ECU.
 
Note from DJ
In your post #12 you stated QUOTE: “Checked the A & C pins on MAP for 5volts on key to Run = no volts”.
My question to you is what you were using as ground source for your meatier when checking for the voltage at the MAP pins A & C? If you were checking for voltage across A & C try checking for voltage from C, which is the 5V supply pin and the center of the battery Negative post. Just in case you have lost your sensor ground circuit which is pin A from the ECU.

Excellent idea DJ.
Cruiser’s Renix Sensor Ground Test
Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.
You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well.
Revised 05/03/2012
 
Note from DJ
In your post #12 you stated QUOTE: “Checked the A & C pins on MAP for 5volts on key to Run = no volts”.
My question to you is what you were using as ground source for your meatier when checking for the voltage at the MAP pins A & C? If you were checking for voltage across A & C try checking for voltage from C, which is the 5V supply pin and the center of the battery Negative post. Just in case you have lost your sensor ground circuit which is pin A from the ECU.

Good advise and just to be clear, I would disconnect the MAP and test the ECU side of the harness to MAP connector for the 5 volts.
 
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