New motor backfires and wont run!?! HELP
06-21-2009, 10:39 PM
#1
10 Second Club
Thread Starter
iTrader: (26)
Join Date: Feb 2006
Location: Ohio
Posts: 410
Likes: 0
Received 0 Likes
on
0 Posts
New motor backfires and wont run!?! HELP Just put in my new lt4 motor, le3 lt4 heads, custom le4 cam, le welded intake, caddy racing lifters, 42lb injectors.. Go to start it and it just backfires out the exhaust? Wires are right on the optispark and with the lifters pumped up and zero lash gave the wrench 1/4 turn to set the rockers.. Is that a problem? I also did not download my new tune from Bryan herter yet? old one is for a 355, 30lb injectors and 306 cam, so trying to start it on that tune? Not sure where to look? Any help?? Thanks
Last edited by Meen95z; 06-21-2009 at 11:26 PM.
06-22-2009, 01:21 AM
#2
Just put in my new lt4 motor, le3 lt4 heads, custom le4 cam, le welded intake, caddy racing lifters, 42lb injectors.. Go to start it and it just backfires out the exhaust? Wires are right on the optispark and with the lifters pumped up and zero lash gave the wrench 1/4 turn to set the rockers.. Is that a problem? I also did not download my new tune from Bryan herter yet? old one is for a 355, 30lb injectors and 306 cam, so trying to start it on that tune? Not sure where to look? Any help?? Thanks
Are you sure the opti is on correctly?
06-22-2009, 10:39 PM
#3
10 Second Club
Thread Starter
iTrader: (26)
Join Date: Feb 2006
Location: Ohio
Posts: 410
Likes: 0
Received 0 Likes
on
0 Posts
Took opti off and reset dowel pin, check rockers and not over tightened, plug wires are correct, plugs smell like gas and still backfires out the exhaust and will not run.. Now what? Just tuned it for the motor with the correct tune, but did not try and fire it yet..
06-23-2009, 01:28 PM
#7
10 Second Club
Thread Starter
iTrader: (26)
Join Date: Feb 2006
Location: Ohio
Posts: 410
Likes: 0
Received 0 Likes
on
0 Posts
its a 95' so opti is in the right hole, checked last night, rockers are not to tight checked that, plugs smell like fuel and never been fired, wires are correct, cam is in time. Just got the new tune in it last night, but havent tried to fire it yet.
Trending Topics
06-23-2009, 01:40 PM
#8
TECH Apprentice
iTrader: (3)
Join Date: Dec 2002
Location: Houston, TX
Posts: 391
Likes: 0
Received 0 Likes
on
0 Posts
That sounds like a timing issue to me. Double check and triple check your cam timing marks and opti. That happened to my first motor, found the cam timing two teeth off.
06-23-2009, 02:08 PM
#10
I'd check for spark like Merv said. Also you want to be sure you are getting spark at the right time. It does sound like you have a timing issue. Either your cam is off, or you could possibly have a bad opti.
Sounds like the same thing that happened to me when my rotor detached. Car would crank strong and back fire out the exhaust and diesel a little, but not fire up. Got spark at the plugs but it was intermittent. Took off the cap and the rotor fell out, lol.
Sounds like the same thing that happened to me when my rotor detached. Car would crank strong and back fire out the exhaust and diesel a little, but not fire up. Got spark at the plugs but it was intermittent. Took off the cap and the rotor fell out, lol.
06-23-2009, 02:58 PM
#11
10 Second Club
Thread Starter
iTrader: (26)
Join Date: Feb 2006
Location: Ohio
Posts: 410
Likes: 0
Received 0 Likes
on
0 Posts
if its backfiring doesnt that mean it has spark? But I'll take the opti apart and look at it.. Also the machine shop said the timing is on, no doubt. They put the short block together (cam, timing chain, ect..) So I rule that kind of out. But anything is possible.. I'll pull the plug and see if it has spark also..
06-23-2009, 03:33 PM
#12
if its backfiring doesnt that mean it has spark? But I'll take the opti apart and look at it.. Also the machine shop said the timing is on, no doubt. They put the short block together (cam, timing chain, ect..) So I rule that kind of out. But anything is possible.. I'll pull the plug and see if it has spark also..
06-23-2009, 03:44 PM
#14
Remove the coil wire from the opti and test for spark, then plug it back in and test for spark at the plugs.
06-23-2009, 06:58 PM
#16
TECH Resident
Join Date: Oct 2008
Location: Redondo Beach, CA
Posts: 968
Likes: 0
Received 0 Likes
on
0 Posts
06-23-2009, 09:47 PM
#17
10 Second Club
Thread Starter
iTrader: (26)
Join Date: Feb 2006
Location: Ohio
Posts: 410
Likes: 0
Received 0 Likes
on
0 Posts
Well it dont backfire anymore. Changed the BR7 plugs out that was reaking of fuel for the some older tr7s I ran, acted like it was gonna run then it just doesnt do anything besides turn over and reak those plugs of fuel.. It has spark, checked a plug. It has a pcm4less tune from Bryan Herter tuned for the motor and 42lb injectors.. Is it possible its just flooding the **** out of it? Or whats some suggestions?
06-25-2009, 04:14 PM
#20
10 Second Club
Thread Starter
iTrader: (26)
Join Date: Feb 2006
Location: Ohio
Posts: 410
Likes: 0
Received 0 Likes
on
0 Posts
Ahh F my life.. found the problem I think.. I have a LE custom grind cam and the pin is too short.. The pin doesnt even go into the optispark, u can grab the rotor and spin it while its on the cam pin and scuffs across where the 3 holes for the dowels are. Just alittle too short. So guessing thats the problem.. Now what do I do?