Backfiring on start up - Engine Conversion
04-20-2016, 02:04 PM
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Backfiring on start up - Engine Conversion Hi yall, im new to the site. I currently have an ls1 with a t56 box in my 2003 toyota hilux.
What ive got - Engine was out of a hsv 2001 clubsport with a mafless tune. With a bosch 044 inline fuel pump and a regulator currently sitting on 58 psi on idle. Running it on 98 octane.
My problem - There is a 50% chance that when i start it up, that i will backfire for about 6 seconds before she roars into life. Sometimes it will start with no problem. Once running she runs fine with no missing. Had a power run on the dyno, mixture seems fine all the way through. Made 220kw atw without an intake setup or tune since before transplant. Also fuel pressure drops off almost instantly once turned off. Have clamped both before and after reg and fuel pump to iliminate leakage though one way valves. Also took her into a mates workshop and he check all my coil packs and injectors with a electronic stethiscope, everything is normal. Thoughts on what it could be??
Have a feeling it could be leaky injectors? But no blue cloud on start up or fuel smell. However things like my coolant temp sensor doesn't wire back to my ecu and only to a tacho gauge. Would this also affect my engine start up?
Cheers for anyhelp
Rohan
What ive got - Engine was out of a hsv 2001 clubsport with a mafless tune. With a bosch 044 inline fuel pump and a regulator currently sitting on 58 psi on idle. Running it on 98 octane.
My problem - There is a 50% chance that when i start it up, that i will backfire for about 6 seconds before she roars into life. Sometimes it will start with no problem. Once running she runs fine with no missing. Had a power run on the dyno, mixture seems fine all the way through. Made 220kw atw without an intake setup or tune since before transplant. Also fuel pressure drops off almost instantly once turned off. Have clamped both before and after reg and fuel pump to iliminate leakage though one way valves. Also took her into a mates workshop and he check all my coil packs and injectors with a electronic stethiscope, everything is normal. Thoughts on what it could be??
Have a feeling it could be leaky injectors? But no blue cloud on start up or fuel smell. However things like my coolant temp sensor doesn't wire back to my ecu and only to a tacho gauge. Would this also affect my engine start up?
Cheers for anyhelp
Rohan
Last edited by ChevyLux; 04-20-2016 at 02:39 PM.
04-20-2016, 03:08 PM
#2
When the engine is cold, fuel entering the exhaust system does not explode violently, if at all. That means if your injector is leaking, and fuel is spilling into the exhaust system, it would not be burning (no backfires).
a cold engine backfire, usually comes from the spark. So you are having a spark, ignite fuel, while the exhaust valve is open (ka-pow!). This could be due to a sync problem (ecu -> camshaft position) or wastespark (ignition of fuel on the exhaust stroke due to leaking injector) but if it were a wastespark + leaking injector problem, it would not just go away on its own, unless the leak was very tiny (leaks a puddle while sitting to cause backfires on next start)
I would say, obviously first check the injectors. You should be able to pressurize the fuel system with the injectors out somehow. Most engines have some kind of retainer ring to hold the injectors in the rail, does yours? If so pull the rails off, turn on the fuel pump, and check for fuel SMELL. The best way to diagnose a fuel injector leak is via SMELLING the fuel, because if the leak is very tiny, the fuel will evaporate before you see it.
If you cannot do that (some engines hold the injectors in via fitment) then your next best option is to pressurize the fuel system for some period of time (1~minute) then check your plugs for fuel/fuel smell. You can do it two or three times to see if the smell gradually gets worse, or plugs gradually get wetter.
You can also examine the plugs, all of them tan except one which is very black should be an obvious sign for example.
from there, No leaky injector, I would start looking into the tune, and maybe my camshaft/crank position sensor. Timing, both valve and spark, could be related to this issue. The coolant temp sensor is usually an essential thing for the ECU so I would certainly look into that asap as well. Coolant temp sensors (CTS) regulate fuel, a global % depending on the temperature.
a cold engine backfire, usually comes from the spark. So you are having a spark, ignite fuel, while the exhaust valve is open (ka-pow!). This could be due to a sync problem (ecu -> camshaft position) or wastespark (ignition of fuel on the exhaust stroke due to leaking injector) but if it were a wastespark + leaking injector problem, it would not just go away on its own, unless the leak was very tiny (leaks a puddle while sitting to cause backfires on next start)
I would say, obviously first check the injectors. You should be able to pressurize the fuel system with the injectors out somehow. Most engines have some kind of retainer ring to hold the injectors in the rail, does yours? If so pull the rails off, turn on the fuel pump, and check for fuel SMELL. The best way to diagnose a fuel injector leak is via SMELLING the fuel, because if the leak is very tiny, the fuel will evaporate before you see it.
If you cannot do that (some engines hold the injectors in via fitment) then your next best option is to pressurize the fuel system for some period of time (1~minute) then check your plugs for fuel/fuel smell. You can do it two or three times to see if the smell gradually gets worse, or plugs gradually get wetter.
You can also examine the plugs, all of them tan except one which is very black should be an obvious sign for example.
from there, No leaky injector, I would start looking into the tune, and maybe my camshaft/crank position sensor. Timing, both valve and spark, could be related to this issue. The coolant temp sensor is usually an essential thing for the ECU so I would certainly look into that asap as well. Coolant temp sensors (CTS) regulate fuel, a global % depending on the temperature.
04-20-2016, 03:52 PM
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Sweet! Cheers for the help.
No retainer clip for my injectors to my rails.. But ill have a go at making some sort of ziptie baskets to hold them in haha. The backfires also happen on hot starts. Ill try attempt this after work.
Also fuel pump is wired to my ignition key not to my ecu. If this affects anything? Will try get that coolant wired up asap. Cheers
No retainer clip for my injectors to my rails.. But ill have a go at making some sort of ziptie baskets to hold them in haha. The backfires also happen on hot starts. Ill try attempt this after work.
Also fuel pump is wired to my ignition key not to my ecu. If this affects anything? Will try get that coolant wired up asap. Cheers
04-24-2016, 03:05 PM
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I tested the right side rail out, by it out and ziptieing the injectors into the fuel rail and placing some clean white paper underneath the injectors. Pressurised it and no leaks haha. How ever, for some reason my fuel reg seemed to hold pressure for a lot longer. When i installed the fuel rail back i manged to nip one of the orings putting it back in.... Bugger..
Anyone know where i can buy an oring kit for my injectors? Thought i may aswell replace them all. See if thus helps my reg pressure drop atleast.
Should have coolant temp hooked up this week. Will let you guys know the result. Cheers
Anyone know where i can buy an oring kit for my injectors? Thought i may aswell replace them all. See if thus helps my reg pressure drop atleast.
Should have coolant temp hooked up this week. Will let you guys know the result. Cheers
