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  #1  
Old May 15th, 2019, 17:15
MechanicalType MechanicalType is offline
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Crank no start..

First time poster, first time XJ owner. Jeep won't start. Cranks all day, shows only code 12 and 33. Fuel pump kicks on for about 1/2 second when ignition is keyed on, Schrader valve releases decent fuel pressure. Unplugged MAP sensor, checked ASD relay, checked fuel pump relay. I understand the ASD is switched to ground.

Fuel pump relay has power to all 3 prongs, 4th prong (green/white) gets battery voltage when cranking. You can unplug the crank sensor and plug it back in w/ key on engine off and hear the pressure build in the fuel feed line. Crank the key and it's pumping fuel, distributor is getting spark.

I can get the engine running with a very small spritz of ether and it will sit and run until I shut it off. I've cranked it with the fuel line in a jug and it pumps plenty of fuel. I tried swapping out the crank sensor (compared resistance of old and new and barely any difference) installed it anyways, still no luck. spritzed a bit of ether, pedal to the floor, fired up and has been idling and revving to 3500rpm w/out any sputter or misfire.

Anyone have an idea? At first I thought it was sucking air, but it seems to have plenty of fuel w/out aeration when cranking. Possibly a MAF or tps sensor? Anyone have any idea how to test them?

Note: Ether is bad, mmkay..

Note: yes, I know ether bad, but it's was just a one time thing.. Guess I've been a diesel mechanic too long.


Thanks in advance,
Mechanicaltype
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  #2  
Old May 16th, 2019, 05:48
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Re: Crank no start..

Specs on the vehicle would be good. Year, engine and transmission at least. There are some differences which matter.

Could this be an ignition problem? I have not played around with ether, but could it be that ether ignites more easily and gets things running where a weak spark is unable to ignite the gasoline?
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  #3  
Old May 16th, 2019, 06:22
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4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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Re: Crank no start..

Any chance you have a leaking injector and your starting flooded?

You say you have pressure, has it been measured after this ether start, while running, then checked for bleed down?
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Old May 16th, 2019, 09:12
MechanicalType MechanicalType is offline
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Crank no start..

My apologies. 94 Cherokee 4.0L. Haven稚 ran a fuel pressure test on the engine. Just verified fuel delivery. Occasionally it will randomly start on its own with no ether assist. But then you run it a while (not driving, just idling in driveway) and then as soon as you shut it off, won稚 start next time without ether.


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  #5  
Old May 16th, 2019, 09:27
MechanicalType MechanicalType is offline
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Crank no start..

Ether (starting fluid) ignites more easily than gasoline. I seem to be getting consistent spark from the coil and distributor.

Also, 4.0L auto trans 4wd.


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  #6  
Old May 16th, 2019, 09:49
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Re: Crank no start..

It sounds like your fuel isn't atomizing well enough. I would first be looking to ensure fuel pressure is at the correct pressure. Low pressure could be caused by:


1) dirty fuel filter
2) failing fuel pump
3) failing fuel regulator valve


If the pressure checks out I would start looking at the injectors.
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  #7  
Old May 16th, 2019, 09:58
MechanicalType MechanicalType is offline
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Crank no start..

Not arguing your advice, but I am curious as to why it would run perfectly after it finally gets started if the pressure was low?


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  #8  
Old May 16th, 2019, 11:13
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Re: Crank no start..

I am wondering if it could not be voltage related somehow, and the operation of the alternator is the key to its ability to run.
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  #9  
Old May 16th, 2019, 11:16
MechanicalType MechanicalType is offline
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Crank no start..

I thought the same about voltage. I charged my battery and even tried boosting it with a commercial booster (up to 250A , 6/12/24v) with no change.


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Old May 16th, 2019, 11:17
MechanicalType MechanicalType is offline
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Crank no start..

I値l run with 4x4jeepmanthing痴 injector comment and try to unplug an injector at a time to see if I get any change.


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  #11  
Old May 16th, 2019, 15:11
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Re: Crank no start..

Quote:
Originally Posted by MechanicalType View Post
Not arguing your advice, but I am curious as to why it would run perfectly after it finally gets started if the pressure was low?


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It may sound ok but may not be running perfectly. If the fuel isn't atomizing properly it may still be able to shoot a stream of fuel into the cylinder. When cold, the engine would simply flood but once that cylinder is heated up by the ether blast, it may be hot enough to keep running but perhaps not as efficiently. I have seen this kind of thing with a bad relief valve. The valve was holding some pressure but not enough so it was a bear to start but would seem to be ok after you got it going. Problem was that once I took it out on the road, it lacked power.



The challenge I have is that if it starts after an ether blast it doesn't make sense that it is a power issue plus you said that you have good spark. An engine needs only 3 things to start: Spark, Fuel and Compression. It wouldn't hurt to do a quick compression test to see if you have a blown head gasket but a pressure test on the fuel system is also a good idea.


FWIW, I am in the process of rebuilding a high performance engine that blew a head bolt and lost all compression on cylinder 1. Went to start it a couple of weeks ago and it was uncharacteristically tough to start but once started it "sounded normal". I crawled under the car and found the top of my head bolt.


You have spark so strike that off the list. The next step needs to be to confirm fuel and compression.


HTH
Todd
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  #12  
Old May 17th, 2019, 05:06
MechanicalType MechanicalType is offline
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Crank no start..

I値l run a compression test. I just replaced the head gasket with a severe duty fel pro one. Followed torque spec and sequence, etc. I値l be working on it a bit over the weekend. I値l update you guys if I make any progress.


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  #13  
Old May 17th, 2019, 09:49
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Rob Mayercik Rob Mayercik is offline
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Re: Crank no start..

Maybe a bad fuel pump ballast resistor? You can bypass it (it's only there to lower voltage to the pump because owners were complaining about fuel pump noise), and see if the no start issue returns.

I had one in my '92 until it started breaking apart due to age, at which point I inline-spliced the two wires together and threw the remains of the resistor away.
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  #14  
Old May 17th, 2019, 11:29
MechanicalType MechanicalType is offline
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Crank no start..

I致e got to check fuel pump voltage. Got 6 or 7 other jobs going on right now ontop of the day job, I forgot to do that. Ack. I know I知 getting battery voltage on the out side of the pump relay. I値l check for voltage drop. The pump has a super short burst upon key on engine off. Usually pumps prime for 1-2 seconds, this one primes for a half a second at most.

Thanks for the ideas guys, got a trans to tear down and I値l hop back on the Jeep.


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  #15  
Old May 17th, 2019, 12:04
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Re: Crank no start..

Quote:
Originally Posted by MechanicalType View Post
I値l run a compression test. I just replaced the head gasket with a severe duty fel pro one. Followed torque spec and sequence, etc. I値l be working on it a bit over the weekend. I値l update you guys if I make any progress.


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When you installed the new head gasket did you put thread sealer on that one bolt that extends into the water jacket?
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