At a loss with this crank / no start

freedom_in_4low

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At this point I feel like I'm just guessing and throwing parts at it. "Fixing it with my wallet" so to speak. I feel so much less confident diagnosing an engine and modern EFI system than I do brakes or suspension. And I find modding to be much more enjoyable and rewarding than diagnosis and repair.

ASD relay is good
no codes
fuel pressure (and therefore fuel pump relay) is good
No sign of ever having had an immobilizer installed
gauges all operate correctly
Gassy smell coming out of exhaust and plugs smelled strongly of fuel when I took them out, so it seems injectors are firing
New battery (it was 7 years old and not holding voltage up under load)
new Champion 3034 plugs (old ones were super worn and gapped at about .065)
new AC Delco plug wires (because they were halfway off to change the plugs anyway)

I have 120psi of compression on 4 cylinders, but only 60 on cylinder 4 and 90 on cylinder 5...which kinda sucks but I would think it should still at least try to start, and the fact that the condition started literally 5 minutes after it had been running and idling just fine tells me that this probably isn't the problem. All 6 plugs looked normal (maybe a little darker brown, but no significant deposits) and were really consistent in color and wear.

I have spark, though I'm not sure how to tell whether it's strong enough. I used a spark tester and it's sparking but it's pretty dark orange. Not sure if it's supposed to be bright blue, especially when it's jumping like half an inch. So I've got a new Delphi coil coming from Amazon and figure why not grab a cap and rotor while I'm at it, even though I don't see how they could have spontaneously gone from running just fine to no start in 5 minutes.

So it seems like I have everything needed to run, but it's just...not.
 

Daryl

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May be a head gasket problem with the low compression on two adjacent cylinders. Get a can of starting fluid. Remove air intake tube at throttle body. Spray a small amount of starting fluid into the throttle body while a second person cranks the engine over. If it starts you have a fuel delivery issue. If it doesn’t start you have an ignition issue.
 
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Chris

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Well, the compression issue isn't a good sign. That may be a head gasket issue, but it could also be something more serious such as a cracked head or worse.

I agree with trying what @Daryl suggested above. That will at least give you some insight.
 
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CharlesHS

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IF you are not seeing any oil in the water or water in the oil; then with the symptoms your are describing... I would check the rocker arms and push rods.
Remove the valve cover, pull the Automatic Shutdown relay (no fuel sent to the cylinders) and then crank over the engine to make sure the rocker arms and push rods are moving correctly. There may be a problem with the rockers or push rods for the low compression cylinders.
 
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freedom_in_4low

freedom_in_4low

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Yeah, I might grab a leak down tester and some starting fluid tomorrow. It's always felt a little short on power compared to my 2005 but there was 5 years between owning them and I owned the 05 at 600' and my 99 at 6000'.

Buuuut...that still doesn't seem like it would happen in 5 minutes after running fine and not even getting to operating temp or cause a total no start so I don't want to focus on that yet. If I get it to start and run exactly how it did a week ago, I'll probably do exactly nothing about the compression until next winter. But I guess a head gasket would be a great opportunity to change my noisy lifters. Maybe even put a cam in it.
 
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freedom_in_4low

freedom_in_4low

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IF you are not seeing any oil in the water or water in the oil; then with the symptoms your are describing... I would check the rocker arms and push rods.
Remove the valve cover, pull the Automatic Shutdown relay (no fuel sent to the cylinders) and then crank over the engine to make sure the rocker arms and push rods are moving correctly. There may be a problem with the rockers or push rods for the low compression cylinders.
No mixing water with oil.

The leakdown test should tell me whether it's going through a valve or between cylinders. Something like stuck pushrods or rocker arms would be an easy fix though.
 
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freedom_in_4low

freedom_in_4low

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found another thread on here where somebody had the same issue and it turned out to be a bad ground. That's an interesting idea because I swear there have been a couple times where it's sat overnight and almost sounded like it fired once but didn't keep going. I can see how a weak coil or a bad ground could do that.
 
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freedom_in_4low

freedom_in_4low

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Tried starting fluid, still wouldn't start. So that seems to indicate a spark issue. I have a new coil, cap and rotor being delivered today that I'll try to get on tonight if the weather doesn't turn to crap before I get to it. Probably gonna have to charge my brand new battery, too, cause I've drained it a bit with all the cranking.
 

Goatman

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How old are the plug wires? Especially the wire from coil to distributor. Be sure to get a multimeter on the ground straps. I have seen a battery have enough juice to crank over the motor just fine, but still come up short to fire the spark plugs. A good fresh battery and away it went. If you are getting weak spark with the plug pulled, then under compression it will be an even weaker spark.
Knowing its electrical is a big step to getting it fixed. Coils can be wired up backwards and still work until they don't.
 

Daryl

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Tried starting fluid, still wouldn't start. So that seems to indicate a spark issue. I have a new coil, cap and rotor being delivered today that I'll try to get on tonight if the weather doesn't turn to crap before I get to it. Probably gonna have to charge my brand new battery, too, cause I've drained it a bit with all the cranking.
Post a picture of your coil. They’re known to crack.
 
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freedom_in_4low

freedom_in_4low

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How old are the plug wires? Especially the wire from coil to distributor. Be sure to get a multimeter on the ground straps. I have seen a battery have enough juice to crank over the motor just fine, but still come up short to fire the spark plugs. A good fresh battery and away it went. If you are getting weak spark with the plug pulled, then under compression it will be an even weaker spark.
Knowing its electrical is a big step to getting it fixed. Coils can be wired up backwards and still work until they don't.
They're brand new since 2 days ago 🤪 , as are the plugs.

As for what was in there before this all started, no idea but I'm guessing pretty old based on how stuck the boots were to the plugs, and how the plug gaps had worn to the point that eyeballing the gap compared to my .045 feeler gauge I'm thinking it had to be .065+.

20200325_164402.jpg


Post a picture of your coil. They’re known to crack.
When I pull the cap and the coil I'll make sure to look for carbon traces as well as cracking.
 
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freedom_in_4low

freedom_in_4low

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Post a picture of your coil. They’re known to crack.
In the excitement of getting it started I didn't take a photo of the coil but it showed no signs of cracking. It has what looks like a Mopar part number and a stamp that it's from Japan. Guessing it's original.


I do feel a little better knowing the compression wasn't keeping it from running, but thanks to this issue I now know that it feels underpowered because a third of the engine is probably at half power. But I've been living with it for 3 years...so it almost doesn't even seem worth the risk of breaking a fastener off in the block and having that to deal with.
 
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freedom_in_4low

freedom_in_4low

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Have you tried putting a good known CKP in there? I'm surprised no one suggested that, unless I am missing something.
no one suggested it, but I got it started so it seems the crank position sensor is good.

The PCM shuts down the FI system if it doesn't get a CKP signal within 3 seconds, and mine wasn't shutting down so I took that to mean the CKP was good.
 

Whitetrash

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no one suggested it, but I got it started so it seems the crank position sensor is good.

The PCM shuts down the FI system if it doesn't get a CKP signal within 3 seconds, and mine wasn't shutting down so I took that to mean the CKP was good.
The CKP can cause a few more symptoms than that, unless I'm missing something. On mine, it caused erratic idle at times when the sensor got hot, complete crank no start, and the tachometer to randomly bounce when the idle wasn't jumpy at all. This was with 2 Vatozone sensors, went with OEM Mopar and it all went away. If you think yours is good though, ignore this. Just some food for thought if you ever have any other issues. :)
 
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freedom_in_4low

freedom_in_4low

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The CKP can cause a few more symptoms than that, unless I'm missing something. On mine, it caused erratic idle at times when the sensor got hot, complete crank no start, and the tachometer to randomly bounce when the idle wasn't jumpy at all. This was with 2 Vatozone sensors, went with OEM Mopar and it all went away. If you think yours is good though, ignore this. Just some food for thought if you ever have any other issues. :)
interesting, very good info. I've never had one go bad before so not familiar with the failure modes.

Did you get codes with yours?
 

Whitetrash

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interesting, very good info. I've never had one go bad before so not familiar with the failure modes.

Did you get codes with yours?
I did, i believe it was P1391, CMP or CKP intermittent signal loss, which only came on twice. The rest of the time it just had the symptoms I described, with no light.