Ls1 with cams --- starting problem
09-22-2019, 01:19 AM
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Ls1 with cams --- starting problem Hello there everyone...need some help or ideas if possible...
I have an ls1 with btr cam...I've had quite a few problems that I've sorted out...now I'm stumped...
Its WAS a good running motor. It was in my 300zx. It sat for a long time and I never finished the car. I pull the motor to put in my son's car.
We tore the motor down to the short block. Cleaned up the face of the piston. Cyclinders walls looks good. I didnt take apart the rods or the end caps to inspect because it was turning with no resistance and it was running with no problems when it was in my car. Verified torque specs of the bottom end, all is well. New head gasket, new arp head bolts, btr cam and springs, ls2 chain and tensioner, ls7 lifters, new push rods, lapped the valves and tested the heads with no leak. Assembled everything back, no big deal.
I'm able to turn everything by hand no problems without spark plugs. We drop the motor onto the car. Discovered some stuck open injectors and some stuck closed...got some used OEM ls1 injectors and bench test no problem....discovered rust on oem fuel rail...pulled my fuel pump on my 300zx and found everything rusted to hell...bought new Holley fuel rail...also found my push rods were slightly too long...kept valves open and wont build compression....starter spun motor freely...no weird noises....put stock push rods in...without the spark plugs starter can turn the motor over with a little more resistance now...still no weird noises...I make everything normal...verified theres spark and fuel...I go to start motor and it struggles to turn over...it turns quarter turn at a time...I'd be lucky if it turn 1 full revolution with starter engaged for about 30 sec...I even added a 200A battery jumper/charger on it to assist, still same result...
Any idea where I could have went wrong during reassembly or something I'm missing??? Thanks in advance for any assistance....
I have an ls1 with btr cam...I've had quite a few problems that I've sorted out...now I'm stumped...
Its WAS a good running motor. It was in my 300zx. It sat for a long time and I never finished the car. I pull the motor to put in my son's car.
We tore the motor down to the short block. Cleaned up the face of the piston. Cyclinders walls looks good. I didnt take apart the rods or the end caps to inspect because it was turning with no resistance and it was running with no problems when it was in my car. Verified torque specs of the bottom end, all is well. New head gasket, new arp head bolts, btr cam and springs, ls2 chain and tensioner, ls7 lifters, new push rods, lapped the valves and tested the heads with no leak. Assembled everything back, no big deal.
I'm able to turn everything by hand no problems without spark plugs. We drop the motor onto the car. Discovered some stuck open injectors and some stuck closed...got some used OEM ls1 injectors and bench test no problem....discovered rust on oem fuel rail...pulled my fuel pump on my 300zx and found everything rusted to hell...bought new Holley fuel rail...also found my push rods were slightly too long...kept valves open and wont build compression....starter spun motor freely...no weird noises....put stock push rods in...without the spark plugs starter can turn the motor over with a little more resistance now...still no weird noises...I make everything normal...verified theres spark and fuel...I go to start motor and it struggles to turn over...it turns quarter turn at a time...I'd be lucky if it turn 1 full revolution with starter engaged for about 30 sec...I even added a 200A battery jumper/charger on it to assist, still same result...
Any idea where I could have went wrong during reassembly or something I'm missing??? Thanks in advance for any assistance....
09-22-2019, 06:42 AM
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Bad starter be my guess
09-22-2019, 08:47 AM
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I would take out the plugs and do a compression test to see what sort of cylinder pressure you're dealing with. If it's excessive it could only be a valvetrain problem. Either cam timing or pushrod/lifters, ie: valves not opening enough or at the wrong time.
If cylinder pressure seems reasonable I would look harder at the starter and wiring, specifically the grounds and feed to starter motor.
If cylinder pressure seems reasonable I would look harder at the starter and wiring, specifically the grounds and feed to starter motor.
09-22-2019, 09:56 AM
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I would take out the plugs and do a compression test to see what sort of cylinder pressure you're dealing with. If it's excessive it could only be a valvetrain problem. Either cam timing or pushrod/lifters, ie: valves not opening enough or at the wrong time.
If cylinder pressure seems reasonable I would look harder at the starter and wiring, specifically the grounds and feed to starter motor.
If cylinder pressure seems reasonable I would look harder at the starter and wiring, specifically the grounds and feed to starter motor.
09-22-2019, 10:05 AM
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Sounds like a grounding issue to me. Verify grounds are battery to rails to engine block, not necessarily in that order, and tight. I had this issue on a show truck I built once, and didn’t want wires showing. Added a ground and fixed it.
Which BTR camshaft did you buy, and did you check ptv?
Which BTR camshaft did you buy, and did you check ptv?
Last edited by Che70velle; 09-22-2019 at 10:11 AM. Reason: I’m retarded...
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09-22-2019, 10:36 AM
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Sounds like a grounding issue to me. Verify grounds are battery to rails to engine block, not necessarily in that order, and tight. I had this issue on a show truck I built once, and didn’t want wires showing. Added a ground and fixed it.
Which BTR camshaft did you buy, and did you check ptv?
Which BTR camshaft did you buy, and did you check ptv?
Stage 2 n/a btr cam...I did not check ptv..while assembling, I just turned the motor by hand and didnt get any uneven resistance...
09-22-2019, 11:00 AM
#10
Originally Posted by Yellowbrother
The starter wont spin the motor fast enough to get a compression reading...as it sits now, it spins maybe quarter turn at a time and maybe a full revolution in 30 seconds....
09-22-2019, 11:29 AM
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At the very beginning....when I had longer push rods (apparently too long, even after following instructions on how to measure push rod length) it was keeping both intake and exhaust open at all time...with spark plugs in coil connected and all...motor would spin freely with starter...no abnormal noise of things hitting...it just spins....
After swapping out the push rods to the stock one, I can tell that now compression is building...but it still dont turn the motor fast enough....I just assumes I was draining the battery...I went out to oreily and bought a big battery charger/battery jumper and added that too while starting....it still dont turn the motor any faster...
In summary
- too long push rods...motor fully dressed....starter just free spin motor with no resistance....no compression...
- stock push rods...passenger side spark plugs out...injectors out on all 8....starter turns the motor maybe 1 rev every 10 sec....thought maybe battery draining, sound like compression is building but doesnt register on compression tester....
- put everything back...bought new battery charger/jumper to work in tandem with battery...even after charging...turn maybe quarter turn at a time and make maybe 1 full turn every 30 sec....
I'll check the ground and stuff later...I'll run a wire straight to the block to battery....
09-22-2019, 12:34 PM
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Originally Posted by Deguila
What head gaskets, are the heads milled? Were valve springs changed? Perhaps lifter preload too high, holding valves closed. PTV clearances?
Battery output could be weak too but he said a 200 amp starter pack didn't help.
Pretty much points to starter or grounds.
09-22-2019, 01:34 PM
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How much torque is the starter suppose to put out and how is one to truly test a starter other than grounding the case and positive 12v to the starter and solenoid??? I heard the truck starter has more torque and i had one from my 5.3 motor but no difference....
Any other guesses??? I've been charging battery all night to make sure it's all juiced up...I'll ground it at multiple points just to make sure...I'll report back later when I get around to if after football...
09-22-2019, 07:43 PM
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Thanks guys...just wanted to report it was a grounding issue...I got it to fire up with whatever fuel was left in the fuel rail as I didnt turn on the fuel pump....
I put jumper cable from battery positive to thick positive wire going to starter...I put black lead from negative to the head....I took my black lead on the 200a charger/jumper to the chassis ground wire on the car....the red lead to the big starter cable also...it struggled the first 3 seconds to pick up momentum but once it did, the engine fired up and burnt off all the fuel in a 3 second run....
Thanks everyone for their input....
I put jumper cable from battery positive to thick positive wire going to starter...I put black lead from negative to the head....I took my black lead on the 200a charger/jumper to the chassis ground wire on the car....the red lead to the big starter cable also...it struggled the first 3 seconds to pick up momentum but once it did, the engine fired up and burnt off all the fuel in a 3 second run....
Thanks everyone for their input....
09-22-2019, 09:00 PM
#15
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Awesome!