Slow cranking engine after rebuild
- Thread starter FuNkYMoNk85
- Start date
I don’t have a noid light but looks like my AZ does, I’ll go grab that and test the injectors.
With it have an ignition coil instead of wires I don’t know a good way to check for spark.
Baffles me because it was running really well for the 20ish miles that I put on it after the break in period.
Think I’m also gonna pull my valve cover and crank it through, hope to god I didn’t wipe my cam out or something.
With it have an ignition coil instead of wires I don’t know a good way to check for spark.
Baffles me because it was running really well for the 20ish miles that I put on it after the break in period.
Think I’m also gonna pull my valve cover and crank it through, hope to god I didn’t wipe my cam out or something.
Just got back with the noid light and every injector is lighting up when I crank it. Also all have about 12.8 ohms across each pin.
Pulling my valve cover, I’ll report that finding soon.
Pulling my valve cover, I’ll report that finding soon.
Thanks for the link, gonna have to grab one asap. I assume I just pull the whole rail and hook up one at a time?
Pulled my valve cover and had my wife and daughter checking valve movement, all seems good there thankfully.
Any chance the pump could have enough power to prime but not enough to sustain it running? I removed the “Do Not Remove” valve on the rail and replaced its o-ring. Maybe clogged filter of some sort in the pump?
HF will have to wait until likely tomorrow so at least I know my cam is still ok.
Pulled my valve cover and had my wife and daughter checking valve movement, all seems good there thankfully.
Any chance the pump could have enough power to prime but not enough to sustain it running? I removed the “Do Not Remove” valve on the rail and replaced its o-ring. Maybe clogged filter of some sort in the pump?
HF will have to wait until likely tomorrow so at least I know my cam is still ok.
Could spray some brake cleaner or starting fluid in the throttle body and see if it barks off.
At this point it's spark, fuel, compression and timing. Knock one down and check the next.
-Mac
At this point it's spark, fuel, compression and timing. Knock one down and check the next.
-Mac
I’ll give that a shot. It’s driving me insane, we got just a small taste of driving it again after the rebuild just to be back down.
Thanks for all the responses, very much appreciated.
Thanks for all the responses, very much appreciated.
Unfortunately I haven’t had any shop time this week, I did grab an inline spark tester and some starter fluid as well. So hoping I get some time this weekend to dig some more into it.
One thing I can’t find a definitive answer on is my crank sensor operation. With it removed and inducing my own 5v to it I can get the 5v signal to come on when I place a screwdriver in front of it and the is steady. When I hook it up to the harness and back probe it, I can get the 5v signal when placing it next to something metal. However in the car I hear the relays kick on as I’m standing right over the PDC, but the 5v signal coming out shows up for a second and then shuts off almost immediately. Is that normal operation since the engine isn’t cranking and the PCM is shutting it down via the ASD relay?
One thing I can’t find a definitive answer on is my crank sensor operation. With it removed and inducing my own 5v to it I can get the 5v signal to come on when I place a screwdriver in front of it and the is steady. When I hook it up to the harness and back probe it, I can get the 5v signal when placing it next to something metal. However in the car I hear the relays kick on as I’m standing right over the PDC, but the 5v signal coming out shows up for a second and then shuts off almost immediately. Is that normal operation since the engine isn’t cranking and the PCM is shutting it down via the ASD relay?
I have reread this post,I’m still not getting what you did?you say it runs great but now it won’t start?
Pretty much. I rebuilt the motor after finding a broken skirt on #5 piston.
Got it installed and running. Went through a 20 minute run at around 2k rpm per the machine shop that did all the machining. Ran great but slow crank every time. Ended up getting about 30 miles on the rebuild over a couple very short trips through the country, each time it took longer and longer to start after cranking. Now it will crank but not start.
I think I was too scattered with my trouble shooting after reading all the responses here, so I’m starting over. This morning I took the air inlet tube off (it’s an after market “cold air” intake from AEM, already on it when I got it) and sprayed some starter fluid in while my wife cranked and didn’t even act like it wanted to start.
Assuming that means no spark, so now I’ll hook up the inline tester I picked up to start checking for spark starting at the head.
I used a meter to check my relays and fuses in the PDC under the hood. Per service manual all relays check out ok.
Starter fluid didn’t do anything for it. Had spark on at least one plug (I will check the rest shortly). Took ASD relay out checking the receptacle for power. I get constant 12v on one pin, key in ON position I get 12v on another (don’t know pin numbers without the manual in front of me). When I tried to check the ground I get nothing, if I’m checking it right. I placed one lead in the ground pin, and one on battery terminal. Continuity on meter is showing open, am I doing that wrong?
Back probed crank sensor again since that’s the only piece that isn’t new. I get my 5v signal that fluctuates when I crank it by hand. But here’s the kicker, it’s always 5v, as I crank it’ll drop to 0 and I’ll stop there. Within about a second it reverts back to 5v without me doing anything. I’ll post it to YouTube and then post a link here.
Back probed crank sensor again since that’s the only piece that isn’t new. I get my 5v signal that fluctuates when I crank it by hand. But here’s the kicker, it’s always 5v, as I crank it’ll drop to 0 and I’ll stop there. Within about a second it reverts back to 5v without me doing anything. I’ll post it to YouTube and then post a link here.
Do you get rpm on the gauge when cranking? If you see around 500-700 rpm the CPS is working.
If you have spark, and starting fluid (fuel), isn't working then it's compression or timing.
-Mac
If you have spark, and starting fluid (fuel), isn't working then it's compression or timing.
-Mac
Just started checking the rest for spark, #6 is first to check and it lights up but barely. Going to keep checking the rest, not sure how bright this light is supposed to be when checking spark but it was really faint. It’s a Harbor Freight light.
Checked while cranking and I get no rpm on the gauge, can’t believe I never thought to check that
Does that point to a faulty crank sensor then?
Checked while cranking and I get no rpm on the gauge, can’t believe I never thought to check that
Does that point to a faulty crank sensor then?
Just started checking the rest for spark, #6 is first to check and it lights up but barely. Going to keep checking the rest, not sure how bright this light is supposed to be when checking spark but it was really faint. It’s a Harbor Freight light.
Checked while cranking and I get no rpm on the gauge, can’t believe I never thought to check that
Does that point to a faulty crank sensor then?
Yes.
Or wiring.
Really easy to screw up both working on transmissions.
-Mac
I believe it! I keep going back to that because I found in the trans install portion of the manual to take it out as damage can occur during installation. However it doesn’t say anything about it in the engine install section.
I rebuilt the motor but left the trans installed in the jeep, was a PITA to get the input shaft lined up enough to get it seated so next time the trans comes out too.
Checked all of my leads and they all have spark, but the light is very faint when it lights up.
No rpm shows up during cranking at all, stays at 0
Put a crank sensor on it,make sure you use the cardboard spacer
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