Jeep Cherokee / Liberty 2004 3.7 Crank but no Start

Chris French

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Hi BigAl, first apologies for the wrong nationality, I should have paid more attention to your 'location Vancouver'.

Thanks for suggesting immobiliser, crank and camshaft sensors. There are a few reasons why I've ruled these out, maybe wrongly. First, the immobiliser light goes out when I put the key in. I have replaced both crank and cam sensors for new, although they may be faulty. But the acid test is do I get a spark and a fuel pulse on the injectors? If any of these were causing the car not to start surely either spark or fuel would be cut. And I get spark and fuel when I crank it.

If I can get hold of the wiring diagram for the ECU pins and an oscilloscope I could back probe to make sure all the signals into the ECU are operating, I could also check timing of spark and injector pulse. But getting hold of this kit is expensive. I could get an auto electrician to do it, but again expensive. Cheap would be to use a timing gun if the crank has convenient timing marks.

Or I could get the ECU tested to be 100% sure that is working, testing is not too expensive.

Why do I suspect ECU? A few reasons. I have played with removing sensors and cranking the engine, removing relays and cranking, fuses etc. I only get codes out for the ECU when removing relays and fuses, not for removing sensors. I am sure the TPS was faulty, again no codes. This is a 'classic' ECU fault indication according to the internet. The car also 'just didn't start one morning', again a classic ECU fault indication. I'm going to talk to some of these companies on Monday morning and see what I can learn. Will post anything interesting.

Thanks again!
 

Billwill

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Have you tried spraying some Ether into the Air Intake to see if it fires?

Have you removed the ASD Relay as I suggested and jumpered female pins 30 and 87 together inside the empty socket to see what happens?

A new PCM would have to be programmed with your VIN and SKEES code.

It would be nice if you could get some form of timing gun to check the timing or read the 2003 Service Manual and remove covers to check the timing is correct.o_O
 
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Chris French

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Thanks BillWIll, this is great advice.

I put petrol down the throttle body, about 50ml, and nothing, I don't think you can get ether in the UK.

Checked and double checked the ASD relay and jumped it. It energises for a moment when the ignition goes on and is full on when cranking the engine.

I've resisted taking the covers off the engine to look at timing, I've never come across this as a cause on this engine (on the internet) and I would have thought a chain is unlikely to skip a tooth without breaking, and the timing marks are set on the cam. I believe the previous owner when he says it just wouldn't start one morning so haven't pursued this. The only mechanical thing I have checked in compression, the rest have been electrical. I may come back to this.

Timing gun involved spending a bit of money and is still on the agenda, but for now I have decided to post the ECU off to get it checked. I am committing to about £50 to get the reassurance that it works, or the answer to why it doesn't. And if it is faulty its around £300 for a full rebuild. That would mean a working car for £900, so I would still be ahead.

Finger crossed!
 

LibertyTC

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The timing light don't bother..
It can be read by OBD2 but will be all over the place, it's electronically controlled.
Camshaft position sensor (CMP) is a hall effect sensor & there is a tone wheel etc.
That being said, start reading the factory service manual & with the valve covers off, check for the correct timing marks.

Engine base timing can be verified by the following procedure:
(1) Remove the cylinder head covers. Refer to the procedure in this section. (section 9-140 Valve timing)
(2) Using a mirror, locate the TDC arrow on the front cover (Fig. 102). Rotate the crankshaft until the mark on the crankshaft damper is aligned with theTDC arrow on the front cover.
The engine is now at TDC.
(3) +++ etc..
 

Chris French

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Thanks Liberty TC, if my next step doesn't work I will check the base timing.

So, I sent the ECU for checking, it was sent straight back with a 'we can't check or fix this type of ECU', and I got the same response on the phone from 3 other UK companies. So I have ordered a plug and play ECU from Flagship One in the US for £165 delivered, cheaper than a fix of my old unit but it feels risky, I hope it works out.

I also tested the MAP sensor and IAT sensors and found the MAP to be unresponsive, so I've ordered a new one. So thats Cam, crank, throttle and MAP sensors replaced, £100, all the 5 volt sensors as best as I can tell. When I unplugged the MAP and cranked the engine, it sounded different, more hopeful, as if it were trying to start. But didn't!

I will try again when the MAP sensor arrives. Then wait until the ECU get here. I'll report back when I know something else.
 

Chris French

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MAP sensor arrived, still no start as expected.

To recap, I have crank but no start. Got compression, spark and fuel, so it must be timing - right? Having now checked or replaced the important sensors I have presumed it is the ECU so waiting for a replacement to arrive.

While I'm waiting I'm taking LibertyTC's advice to pull the rocker covers off and check the engine timing. Only half way through the job as I need to fabricate a tool to get the fan off. But so far I have found:
- horrible sludgy oil in rh bank, clearly a problem with water in the oil and likely breather hose from oil filler clogged up
- no.6 exhaust valve rocker has fallen off (overheat, sticky valve, carbon build up, valve seat??)

On the plus side, the rh cam and chain look good, no wear on cam lobes and no slack in the chain. I can't imagine the timing will be wrong.

So the heads are coming off, when I get access to them, and I will sort out the head gaskets. Any advice on doing a head gasket? Is it worth taking the covers off (and checking the tensioners), or can I just do it all from the top? Anything else worth doing at 112,000 miles?

None of this explains why the car won't start so I am hopeful I didn't waste money on an ECU, unless anyone knows different. Don't forget I got 160PSI on cylinder 6.

Next step is to get the fan off, get the LH rocker cover off and check the timing.

I'll keep you posted.
 

LibertyTC

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Your determination deserves an award.
Is it possible you could post a few photos, I'd like to see how bad the gunk is on both sides, and what the remaining rocker actually looks like.
Dropped rocker might be able to be cleaned up & placed back on, there is an online video showing how to do that.
You are on the right track, and considerable amount of work ahead.
Take your time & follow the all factory service manual instructions, re base timing /heads, & tensioners etc.
You are going to need to have a good torque wrench for installation and note all of the required torque specs.
 

DadOSix

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Stupid idea - but - did you try a shot of ether or brake clean down the throttle body to see if it would indeed run? A little ether goes a l-o-n-g way
 

Big Al

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Why am I always leaning toward the imobizer system. You have all the right numbers for spark, pressure and fuel, but no go.
I would call a locksmith and see if he can be of any assistance.
Do you have a couple of keys to try in the ignition.
 

Chris French

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Excellent suggestions DadoSix and BigAl.

I hope Dad o' six, thats Jeeps and not kids!

Had a bit of a revelation today pulling the LH rocker cover off. 2 more rockers lying comfortably in the oil. So that'll be 3 pistons with valves stuck shut. I'm guessing thats the problem!

I need a few minutes to think it through so will post some thoughts later, but for now here's some pictures!

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DadOSix

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lol -

nope not jeeps! Definitely kids - all boys to be precise. ages 11 up to 22.

Looks like you now have a handle on this mess. Why they jumped is another story. I seem to recall one plug had a buggered electrode? Dropped a valve seat? 3.7, 4.7, 5.7 all seemed prone to this accourding to my you-tube mechanics.

I bought a cheap-ish bore scope at Harbor Freight and used it to diagnose my #3 sons cobalt - bad cyl #3 knock. piston top is torn up. but it still runs!
 

Chris French

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I think the next step is to get the heads off, probably do that tomorrow and hopefully that'll be as deep as I need to go.

I'll post some pictures when its done. Then put it together replacing only bits that need replacing. I might still be able to get it running for under a £1000.
 

JeepJeepster

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Shew wee, that is one nasty 3.7. This is what happens when you dont keep up with oil changes.

Looks like there is some coolant in the oil too.
 

LibertyTC

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Are you taking those heads into a machine shop?
They should be magnafluxed, fully re-built & decked.
 

LibertyTC

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Ya Good Glad to hear a machine shop is involved.
Yes with aluminum heads I thought that magnaflux made a dye, anyways the shop will know what they are doing.
 

LibertyTC

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Just looked at your pics again..
You must have a late model 04 as they updated to the higher pressure rockers in 2005 for better oil lubrication.
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Ensure they are using the correct part, which from the 05 fiche is 53021913AB.
There could even be a newer rocker part # consult dealer.
 
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