Jeep Cherokee / Liberty 2004 3.7 Crank but no Start

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Chris French

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Hello from a Newbie. I just bought my first Jeep and looking forward to experiencing the 4wd on our UK off road courses and green lanes. But first I have to get it started!

I bought the car 3 weeks ago as a project. I like a challenge and don't often get beaten, but this one has me at the moment. I’m thinking ECU / PCM but before spending proper money I thought I’d reach out for some advice.

The car is a 3.7 Liberty, we call them Cherokees in the UK as we are not educated in the ways of Jeeps. It is a smart looking car with a big engine in a small car, leather, and most of the extras you could want. I might even keep it and get rid of my X3 if I can get it going. It has 112,000 miles and looks like it has been well looked after (e.g. 5 matching tyres).

The story goes.. The car was sold as 'with an unknown engine issue'. The previous owner said ‘it just wouldn't start one morning’. He said he replaced the battery and still no fix so gave up. Make of this what you will, my approach has been to judge based on what I find. The seller is also local so if he is hiding something he knows I will see hime again.

After I got the car home I did some basic checks. Engine oil looked very good (i.e. clean and full) but the expansion tank was empty, short by about 4 litres. I put water in but plan to replace the coolant later. Suspecting head gasket I looked at the underside of filler cap and there was no oil/water gunk, but I am still suspicious that the car may have this problem.

Previous owner said he put new battery on but looks on the small side at 520cca.

No codes available on my basic OBD2 reader.

Once the battery was charged I tried to start the car but the starter cranked real slow. I pulled the starter motor and the solenoid switch was faulty so I replaced the starter. Now it cranked well, but didn't start, so the investigation could begin.

Testing on cylinder 2 I have spark and compression. I haven’t tested the rest as (I think) there are 6 cylinders and if one is ok I’ll bet at least a few more are so I should get a bit of firing action, but nothing. It is the six coil version of the engine.

50 PSI fuel pressure and the injectors fire fuel. I know this as I pumped up the pressure then pulled the fuel pump relay, cranked the engine and watched the pressure drop in a few seconds. It is also petrol not diesel as I extracted some fuel from the fuel rail and set light to it, it burned like petrol. I guess I could also confirm this in my lawn mower.

So I have fuel, compression and spark. What about air? I pulled the IACV and it appears to work (old 9 volt battery across the terminal made it move), I also tried starting with a bit of throttle, still no joy.

So whats left? Timing. I spent some time on youtube looking at videos on timing issues, looked like it might be a possibility. So without too much robust testing, I bought new cam and crank sensors and replaced them (after fighting the crank sensor for several hours).

Still no joy.

I pulled the TPS and tested as if it were a potentiometer. Couldn't understand the reading so I ordered a new one and took the old one apart, of course no potentiometer found inside. I’m learning!

During this process I also checked the ASD relay, not that it indicated an issue as I was getting a spark, but it tested good. I've also done some random fuse testing in interior fuse box and PDC but found no issues.

I’m running out of things to test. So looking for your advice.

Possible ideas:

- What sensors stop the engine running? Oil pressure? MAP?

- Which sensors change the timing? Knock?

- Which fuses, if blown, would stop the engine starting?

- At what point do I call someone with an oscilloscope or get my ECU/PCM tested?

- Anything else…

Setting fire to it is an option but I'm not there yet!

For the record I'm about £500 in and the car would be worth at least £1500 running, if not more if it was snowing.

Any advice or direction will be gratefully received. And I promise to report back when I get it going.

Thanks
Chris
 

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Billwill

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Welcome to the site...I also have a "Cherokee"...2002 Export 2.5 CRD!:)

The early KJs such as mine there is no chance of finding a Reader to pull codes...early KJs use PCI Bus which Readers cannot handle! The 2004s though should be able to find a Reader!

In the meantime use the "key" method to pull codes.

With the ignition OFF rapidly turn the ignition ON/OFF 4 times without turning over the engine. After the 4th ON action leave the ignition ON....the Odometer Readout on the Cluster should start displaying Codes in sequence from the latest to the oldest. Write these down.

USA models seem to need only 3 ON/OFF actions.

Any code is only shown once so you will not see a code repeated. You cannot erase codes but old codes do seem to fade away over time. Start with the first code displayed.

Then download the Jeep KJ Service Manuals here...2004 not listed but 2003 probably should be close enough.

Also do a Cluster Check to see if all warning lamps are working:

While depressing the Odometer Reset Button, turn ignition ON. The gauges should move around and all lamps should light up in turn. This is not a diagnostic but an excercise.

The early KJs have an amber "key" icon for the SKEES anti-theft system. Newer KJs use a red LED at the left of the cluster. Either way you need to know that this warning lamp is working.

If there is a problem with the chipped key not being recognised..the SKEES Lamp will either Flash or Stay ON.

Also watch out when you replace the cooling fluid...clean water with the Mopar Hoat or Zenex...Orange in color...do not use Green anti-freeze!

www.colorado4wheel.com/manuals/Jeep/KJ/
 
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Chris French

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Welcome to the site...I also have a "Cherokee"...2002 Export 2.5 CRD!:)

The early KJs such as mine there is no chance of finding a Reader to pull codes...early KJs use PCI Bus which Readers cannot handle! The 2004s though should be able to find a Reader!

In the meantime use the "key" method to pull codes.

With the ignition OFF rapidly turn the ignition ON/OFF 4 times without turning over the engine. After the 4th ON action leave the ignition ON....the Odometer Readout on the Cluster should start displaying Codes in sequence from the oldest to the newest. Write these down.

USA models seem to need only 3 ON/OFF actions.

Any code is only shown once so you will not see a code repeated. You cannot erase codes but old codes do seem to fade away over time. Start with the last code displayed.

Then download the Jeep KJ Service Manuals here...2004 not listed but 2003 probably should be close enough.

Also do a Cluster Check to see if all warning lamps are working:

While depressing the Odometer Reset Button, turn ignition ON. The gauges should move around and all lamps should light up in turn. This is not a diagnostic but an excercise.

The early KJs have an amber "key" icon for the SKEES anti-theft system. Newer KJs use a red LED at the left of the cluster. Either way you need to know that this warning lamp is working.

If there is a problem with the chipped key not being recognised..the SKEES Lamp will either Flash or Stay ON.

Also watch out when you replace the cooling fluid...clean water with the Mopar Hoat or Zenex...Orange in color...do not use Green anti-freeze!

www.colorado4wheel.com/manuals/Jeep/KJ/

Hi BillWill, thanks for your reply. I really appreciate you spending the time.

Lucky fo me, the key method of code retrieval matches my OBD2 reader exactly. I know this as in testing I have created a load of codes (but there were no codes when I picked it up). And all the codes I have had relate to me removing sensor cables and relays. Unless you are telling me something else I am pretty sure this fault is not throwing a code. I did a ECU reset so currently have no codes.

I love the cluster check, very clever, everything works fine. The anti theft / key light is amber and goes out.

One other thing while doing this I noticed, when I turn the ignition on the MIL flashes several time before going solid, is that what it should do?

Also thanks for the tip on coolant. The car isn't getting any 'presents' until it runs, so its just water for now!

Any clues on where I go next. Bearing in mind I have spark, fuel, air and compression, what other simple checks are there before getting into oscilloscope / ECU checking.

Thanks for anything anyone can contribute!
 

LibertyTC

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It would be best to get the psi compression readings on all 6 cylinders.. What are the readings?
What spark plugs are in there? Use NGK ZFR6F-11G only- gapped at .040 inch.
The Jeep only likes Mopar sensors. Best to stay away from any aftermarket sensors.
 

Chris French

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It would be best to get the psi compression readings on all 6 cylinders.. What are the readings?
What spark plugs are in there? Use NGK ZFR6F-11G only- gapped at .040 inch.
The Jeep only likes Mopar sensors. Best to stay away from any aftermarket sensors.

Thanks so much for your response. I guessed I might have to do this at some stage. I'll test PSI out this week and have a look at the plugs as well. The plug I pulled had a large looking gap but I didn't measure it.

Hmmm on the sensors. I need to back probe them to reassure myself that they are ok as they are certainly aftermarket.
 

Billwill

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Yeah when it comes to any of the Sensors it is not worth trying non-Mopar products!:(

I know on my CRD that some fuel related issues do not post a CEL....a blocked fuel filter for instance!o_O

The Electronic Modules such as the PCM and BCM are generally pretty robust but they can fail sometimes.

Definitely check all fuses...under the Hood and inside the Cabin....they may look OK but could be making bad contact so need pulling out...measure with Multi-meter and re-fit.

Swap identical Relays around to see if something changes.

Try remove the ASD Relay and jumper female pins 30 and 87 inside the empty socket together..something may change.

Definitely only use correct NGK plugs gapped properly.

So unless you pick up a valid CEL code the psi readings may suggest something.o_O
 

LibertyTC

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Here are the specs regarding compression.
'02-'04 3.7 has 9.1:1 compression ratio, cylinder pressure should be between 170psi-225psi with no more then 25% difference. This is from the '02,'03,and '04 FSM.
 

Chris French

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OK, spark plugs are close, NGK R ZFR5F 11. Gapped at 1mm to 1.2mm.

Compression reading are 1 - 210, 2 - 170, 3 - 170, 4 - 175, 5 - 160 and 6 - 177 psi. This could indicate a blown head gasket or a few leaky valves but it should at least run even if be a bit lumpy.

Bizarely I was hoping for a disaster with the compression check so I'm slightly disappointed! I'll have to find something else to take apart while we're in lockdown in the UK.

So, to recap, there is a clear spark indicated on my spark tester, fuel is going in and it burns like petrol, the iac valve is working and now we know we have compression. Surely it is only spark and fuel timing thats left? Does that mean ECU?

Comments gratefully received!
 

Chris French

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I don't spend much time on forums so not sure whether this sort of thing is relevant, but the condition of the spark plugs is fascinating! See pic. The clean one looks like its been washed by coolant, compared to the sooty ones. I think I'll be in for a HG replacement at some stage.

Also got a damaged 'tang' on one of the plugs, look like electrical erosion, but can't imagine how it would happen, maybe overheating?

I wish I had kept track of which one came from which cylinder so I could compare the two. Still learning.
 

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LibertyTC

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One thing is for sure, they are all fouled, possible cold condition. I believe the 5F may be a colder plug= wrong plugs anyways.
Install as mentioned NGK ZFR6F-11G & see if it will fire up with the new/correct plugs.
Your Gap conversion sounds about right.
Electrode damaged hmm, sorta see something cracked off there, too bad you did not note its location/cylinder.
 

Big Al

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Any chance that you have bad fuel, maybe the last time the previous owner filled up, he picked a station that had old or water in the fuel.
 

Chris French

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Thanks Liberty TC and BigAl.

Next steps new plugs and change the fuel, not expensive and easy to do so I might as well before spending any more.

I will report back. Thanks again.
 

LibertyTC

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I wonder how long that fuel has been in there? Open gas cap & have a sniff, does it smell bad like old gas?
I would consider using a high octane fuel initially.
There is an amazing product that cures old gas called Starbrite Star Tron, best stabilizer period, worth investigating, Avail in UK.
 

Chris French

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Thanks LibertyTC, this answers my question about what I do with the 20 litres I will be removing. I guess I could put some Starbrite in the tank with a bit more fuel to mix it up, but then I might need to remove 30 litres.

I'll try plugs when they arrive and if that doesn't work I'll drain the tank. I'll let you know how it goes.

Thanks again or your support.
 

Chris French

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I wish it were good news!

So my fuel can, TPS and plugs arrived. I drained the tank using the fuel pump and fuel rail valve. Fuel pump working well, nice a quiet and pumping well. With the fuel out I put in a splash of star brite and 10 litres of shell v-power bought 2 days ago.

I think the fuel gauge is stuck on about 1/4 full. I wish I had noticed when the tank was empty. I took out about 10-15 litres (I guessed it was empty as it started pumping bubbles) and put 10 litres in and its measuring 1/4 tank? I would have expected a lower reading. Does this mean anything to anyone?

New plugs went in, gapped to 1mm. TPS went on.

A quick one on the TPS, I tested this with my multi meter before fitting. It behaved exactly as I would expect a potentiometer to behave unlike the old one, so maybe the old one was faulty? Again no code. Question, is there a reset for the TPS or, bearing in mind I have the battery off the car and back on charge, should I just expect it to work?

Still no start, although when I first cranked it it did fire. Then nothing.

I have cranked it for 5 seconds a time about 20 times to allow any air to get through the fuel and still nothing. So I took the battery off the car and put it on charge while I have a think.

I'm highly encouraged by it firing, maybe there was some fuel in one of the cylinders from a leaky injector or my messy workmanship. Causes me to wonder if the injectors are actually working. The only test I have done on this is to prime the fuel with a meter on the fuel rail, then remove the pump relay, crank the engine and watch the pressure drop from 50psi to 0. Does anyone have a more definitive injector test? I will google it but any help appreciated.

So, in summary, its still not working and I'm losing hair where I'm scratching my head.
3 Questions:
- does stuck fuel sender mean anything apart from the obvious?
- is there a TPS reset procedure?
- how do I test that the injectors are working?

Thanks for anything you can give me.
 

LibertyTC

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Geez what fun o_O...
re tps..You do have to turn the TPS slightly clockwise, to align the interior throttle tab, holding it inwards, then swing it back counter clockwise 1/4 inch aprox, to screw it back in.
As far as a re-set it should work, and if & when it starts/drives, all should be well.
Battery connected, Fuel pressure with ignition on, what is the reading 50 psi? & then 15 min later what does it read while key has been off?
1/4 tank may be about right as the jeep has a reserve and add the 10l it may be within spec..IDK.
If the injectors are plugged eek. The best move will be to remove the fuel rail & injectors.
Next would be a shop to inspect the spay pattern & clean them. or replace with OEM's.
 

Chris French

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What fun indeed!

Thanks for the reassurance on the TPS.

In answer to your question, 55psi and it holds it above 50 for 15 minutes with the ignition off.

I've done some injector testing this morning and can find nothing wrong. The injectors have a voltage, they get a pulse, the spark still happens. I even put a slug of fuel in the throttle body, usually works on lawnmowers! But nothing.

I can only imagine the spark is happening at the wrong time. I remember seeing a number on my OBD2 reader of 60 degree ****** on the freeze data, but haven't been able to replicate it. A neighbour suggested getting a timing gun and strobing 'old school'. Might give that a try tomorrow if my old timing gun works and I can find timing marks.

I think the next realistic step is to get the ECU tested. Shouldn't be too much ££ to get it tested and it can be done by courier while we're in lock down.

So thanks again, I'll keep the thread updated as I have found these conversations invaluable, hopefully it will be useful to someone else.

And you guys got a new President today!
 

Big Al

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Did a bit of surfing wondering why it's so hard to start new cars.
First one that I came across is maybe your immobilizer key is preventing your jeep from starting.
Then there is a crank case sensor and a camshaft sensor that may be preventing it from starting.
I'm no expert on newer cars, just throwing this out there trying to get you on the road again.
Nope, no new president for us, we're both from CANADA.
 

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