Hot Start Issues
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2nd Gear
Joined: Jan 2018
Posts: 6
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From: New Zealand
Hot Start Issues
Hi Team
Im in desperate need of some advice, I have recently completed the build on my street bob and it will start fine when cold but as soon as I try to start it once warm it will backfire, puff black smoke as if it is running too rich. I have had it in at the local dealership and also in at the local "expert" but no one seems to be able to diagnose the problem.
mods include:
-se 113 barrels and pistons
-ported and polished se 110ci heads
-se 260 cams
-se pro super tuner
-se 50mm throttle body
I have changed on the recommendation of the local expert:
-new o2 sensors
-new throttle body seals and flanges
-new map sensor + swapped all electronics off original throttle body
the dealership has swapped out the temperature sensor and also reccomend I take off the FP3 tuner which I have and still wont run.
it is not throwing any codes
surely there is someone who can help me please im running out of parts to swap out!!!
Im in desperate need of some advice, I have recently completed the build on my street bob and it will start fine when cold but as soon as I try to start it once warm it will backfire, puff black smoke as if it is running too rich. I have had it in at the local dealership and also in at the local "expert" but no one seems to be able to diagnose the problem.
mods include:
-se 113 barrels and pistons
-ported and polished se 110ci heads
-se 260 cams
-se pro super tuner
-se 50mm throttle body
I have changed on the recommendation of the local expert:
-new o2 sensors
-new throttle body seals and flanges
-new map sensor + swapped all electronics off original throttle body
the dealership has swapped out the temperature sensor and also reccomend I take off the FP3 tuner which I have and still wont run.
it is not throwing any codes
surely there is someone who can help me please im running out of parts to swap out!!!
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,064
Likes: 1,003
usually hard starts on efi are fuel related.
i ride gravity, it never fails, but in the auto world, fuel pressure is key.
on a cold engine (at least the temp sensor is calling it) the ecu adds more fuel buy increasing injector on time to help starting. in the start mode, the ecu ignores sensor input and uses a base map programmed into it.
on a warm engine, the ecu does not see a cold start so it will not increase on time and couple this with LOW FUEL PRESSURE, you will have start issues like increase crank time, lean out and back-fire.
this is just one avenue you can look at.
i ride gravity, it never fails, but in the auto world, fuel pressure is key.
on a cold engine (at least the temp sensor is calling it) the ecu adds more fuel buy increasing injector on time to help starting. in the start mode, the ecu ignores sensor input and uses a base map programmed into it.
on a warm engine, the ecu does not see a cold start so it will not increase on time and couple this with LOW FUEL PRESSURE, you will have start issues like increase crank time, lean out and back-fire.
this is just one avenue you can look at.
Last edited by bustert; Feb 7, 2018 at 09:19 AM.
Carl,
First, stop throwing parts at it. To me this is indicative of needing to lower the cranking fuel in the warm temp areas. I don't understand why he had you change O2 sensors for a hot start but it's moot at this point. I can't speak to whatever map you have in the FP3, but 260 cams have extremely poor airflow/velocity and low rpm and if your map is for something more efficient, that will be an issue.
First, stop throwing parts at it. To me this is indicative of needing to lower the cranking fuel in the warm temp areas. I don't understand why he had you change O2 sensors for a hot start but it's moot at this point. I can't speak to whatever map you have in the FP3, but 260 cams have extremely poor airflow/velocity and low rpm and if your map is for something more efficient, that will be an issue.
Last edited by Ed Ramberger; Feb 7, 2018 at 02:52 PM.
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