Need help diagnosing no-start

Tob

Tob

Paint-Matched Bezels Club
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Jan 15, 2020
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Lake Charles, Louisiana
Here's what I know. The Jeep has been sitting since December 24th, when it was parked due to a water pump failure. After replacing the water pump, belt, and fan clutch, I tried to start it but the battery was weak and almost dead. I tried to jump start it from another vehicle but it wouldn't start. I charged my battery and it still wouldn't start. The engine starter cranks and the engine spins but won't start. The fuel pump turns on and builds fuel pressure when the key is turned on. I pulled the air intake off the throttle body to spray some starting fluid and it smelled like gas. The starting fluid did not help it start. I pulled the spark plugs today to check them out and I see no red flags. They have a heavy gas smell.

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I'm not sure where to go from here. Any help is appreciated!
 
Well, I tried replacing the spark plugs with some spares while I had them out, but still no luck. I tried starting it with the throttle wide open (for no more than a second) and it ran until I let off the throttle. I don't know what to make of that or what the problem could be.
 
Tob said:
Well, I tried replacing the spark plugs with some spares while I had them out, but still no luck. I tried starting it with the throttle wide open (for no more than a second) and it ran until I let off the throttle. I don't know what to make of that or what the problem could be.
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I might check the IAC & throttle body too. There’s a cleaning procedure posted here but even just wiping it down can help.

You have fuel, and since you did manage to get it to fire you have spark as well. Seems like air is what’s missing in the equation.
 
hear said:
I might check the IAC & throttle body too. There’s a cleaning procedure posted here but even just wiping it down can help.

You have fuel, and since you did manage to get it to fire you have spark as well. Seems like air is what’s missing in the equation.
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Yeah, I've read Jerry's method and I do have some throttle body cleaner. Might as well try that.

Edit: I can't use Jerry's method since it's not running... I'll just take it apart and clean it instead.

krgawe said:
Check your crank position sensor
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How do I know if it's the culprit when inspecting it? Visual signs of failure? Electrical test?
 
Do you have a check engine light on? Some things won’t always trigger a CEL but if it is, it would help to pin point the issue. I agree with @hear it sounds like something fishy with the throttle body sensors.
 
TJ4Jim said:
How did you confirm the fuel system builds pressure.
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Well, it's a '04, so I don't have a Schrader valve to actually test it, but I am pretty sure there's fuel pressure based on how it sounds when it cranks. I've had a fuel pressure leakdown issue on and off for a while, so I'm accustomed to cycling the key a few times to build pressure before starting.
 
Throttle body look dirty? Give it a good cleaning especially the IAC. Used TB cleaner and a tooth brush gently to clean it. If you do replace any sensors, highly recommend using Mopar sensors. Have had bad luck with part store sensors.
 
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Tob said:
Well, it's a '04, so I don't have a Schrader valve to actually test it, but I am pretty sure there's fuel pressure based on how it sounds when it cranks. I've had a fuel pressure leakdown issue on and off for a while, so I'm accustomed to cycling the key a few times to build pressure before starting.
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Exactly how did it respond to starting fluid.
 
WolfMan said:
Throttle body look dirty? Give it a good cleaning especially the IAC. Used TB cleaner and a tooth brush gently to clean it. If you do replace any sensors, highly recommend using Mopar sensors. Have had bad luck with part store sensors.
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Not really dirty. I cleaned it a while back, but I'll clean it again.

TJ4Jim said:
Exactly how did it respond to starting fluid.
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No noticeable change. I pulled the intake tube off, sprayed a good 2-second blast into the throttle body, then tried starting.
 
and it m
Tob said:
Not really dirty. I cleaned it a while back, but I'll clean it again.


No noticeable change. I pulled the intake tube off, sprayed a good 2-second blast into the throttle body, then tried starting.
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It made no attempt to start with the fluid ?
 
You need three things for an engine to run, fuel,spark,compression. I would assume you have compression as it ran before,correct? Fuel you said pump runs and you sprayed starting fluid and no attempt to start? IAC and dirty throttle body won’t stop it from running. So you are down to spark check for spark coil rail off install a plug run a ground wire from the plug threads to the engine and crank it over. If you have no spark things to check is power to coil pack, crank and cam sensor. You put a water pump and belt on it. I would take a good look at the crank sensor as you were in that area when you replaced the belt. Maybe the connector or harness got damaged or loosened.
 
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I just had a similar issue on my 98. A buddy suggested I start with the Crank Position Sensor. Replaced, but still couldn't get it to start. I started checking fuses. Blown fuse in F21, under the hood. Replaced and the jeep started right up.
 
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