Help! New 408 will crank and backfire but not start
10-10-2007, 07:11 PM
#1
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Help! New 408 will crank and backfire but not start I am trying to fire up my HPE 408. The car has a nitro dave's victor jr converted to fuel injection and has a baseline tune by Rapid Motorsports. The car has full bolt ons and all supporting mods. It also has a th400. i double checked the wiring and everything is good. The starter is getting 12 volts the fuel pump primes. Everything works as normal and the car turns over normally. However, the car will not start up. I am getting about 150 cranking rpms. The car has a new starter as I thought the old one was bad but the car still has the same problem. I hooked up the data logger and all of the sensors are reading correctly (TPS,rpm, O2's). The car is getting spark and plenty of fuel. I changed the plugs as the old ones were soaked with fuel but still have the same problem. Any idea of what other areas to check or what the problem could be? 
Thanks in advance,
T.C.
Thanks in advance,
T.C.
10-10-2007, 07:19 PM
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I am trying to fire up my HPE 408. The car has a nitro dave's victor jr converted to fuel injection and has a baseline tune by Rapid Motorsports. The car has full bolt ons and all supporting mods. It also has a th400. i double checked the wiring and everything is good. The starter is getting 12 volts the fuel pump primes. Everything works as normal and the car turns over normally. However, the car will not start up. I am getting about 150 cranking rpms. The car has a new starter as I thought the old one was bad but the car still has the same problem. I hooked up the data logger and all of the sensors are reading correctly (TPS,rpm, O2's). The car is getting spark and plenty of fuel. I changed the plugs as the old ones were soaked with fuel but still have the same problem. Any idea of what other areas to check or what the problem could be?
Thanks in advance,
T.C.
Thanks in advance,
T.C.
10-15-2007, 06:57 PM
#10
I have been helping Nozr1 install the engine in his car and went over tonight to check it out.
It was not the coil packs. We are getting plenty of spark and I confirmed all of the coild packs are wired up correctly by using another car as the template.
Could it possibly be the tune? I wouldn't think it would be that far off for it not to start but it is still a possibility.
I would think the cam sensor and crank sensor are correct as the car has plenty of spark at what seems to be the "correct timing" and I would think those sensors would stop the spark entirely. I am an old school lt1 guy but I would think the same stuff would apply. You can smell fuel and the spark plugs get plenty wet (we changed these out).
The car will studder a little when first started and backfire a little. If you hold the throttle at WOT and let it close while cranking it will backfire again.
I am going to try some starting fluid and check the fuel psi but if that is not the case the only other thing it could be is cam timing. Is there any easy way to check cam timing on an LS1 without pulling the front cover? (i.e.-is there a mark on the balancer that indicates the timing at TDC in correlation with the No 1 cylinder?)
Thanks for all the help and suggestions...we appreciate it.
Regards,
Matt
It was not the coil packs. We are getting plenty of spark and I confirmed all of the coild packs are wired up correctly by using another car as the template.
Could it possibly be the tune? I wouldn't think it would be that far off for it not to start but it is still a possibility.
I would think the cam sensor and crank sensor are correct as the car has plenty of spark at what seems to be the "correct timing" and I would think those sensors would stop the spark entirely. I am an old school lt1 guy but I would think the same stuff would apply. You can smell fuel and the spark plugs get plenty wet (we changed these out).
The car will studder a little when first started and backfire a little. If you hold the throttle at WOT and let it close while cranking it will backfire again.
I am going to try some starting fluid and check the fuel psi but if that is not the case the only other thing it could be is cam timing. Is there any easy way to check cam timing on an LS1 without pulling the front cover? (i.e.-is there a mark on the balancer that indicates the timing at TDC in correlation with the No 1 cylinder?)
Thanks for all the help and suggestions...we appreciate it.
Regards,
Matt
10-15-2007, 08:00 PM
#14
The engine was assembled by frans96ss and he assured us that the correct 7.35" pushrods were installed as I had thought the same thing you had posted. I will also be bringing a compression tester just to get an idea if the engine is generating enough compression--this would also be a good way to check and see if the cam is off and/or the pushrods are incorrect.
Thanks for the suggestion.
Matt
10-15-2007, 08:08 PM
#15
I would think the engine would still be able to start although it would run like *** but maybe I am wrong. As I said before, I am more of an LT1 guy and the LS1 is a learning experience for me but I love to trouble shoot so it is killing me to not find the issue.
If the compression test comes up terrible than I will have to assume it is either the pushrod length is incorrect or cam timing. I am still assuming the engine is not the problem but everything we try keeps pointing to it. I need to eliminate any other easier variables before I go into the engine. I just want to try everything before having to tear into an engine that was supposed to be built correctly.
I would like to know if there is anything electrical that would cause this (i-e.-could the cam sensor/crank sensor be installed wrong?) (Any other sensors that could cause a no start condition?)
Fran---was the intake gaskets installed on the engine (the ones that gasket the intake to the heads?)
Thanks again for all of the suggestions...keep them coming.
Matt
If the compression test comes up terrible than I will have to assume it is either the pushrod length is incorrect or cam timing. I am still assuming the engine is not the problem but everything we try keeps pointing to it. I need to eliminate any other easier variables before I go into the engine. I just want to try everything before having to tear into an engine that was supposed to be built correctly.
I would like to know if there is anything electrical that would cause this (i-e.-could the cam sensor/crank sensor be installed wrong?) (Any other sensors that could cause a no start condition?)
Fran---was the intake gaskets installed on the engine (the ones that gasket the intake to the heads?)
Thanks again for all of the suggestions...keep them coming.
Matt
