2003 4.6 v8 start problems
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Post Fiend
Joined: Jan 2009
Posts: 6,521
Likes: 11
From: Greenwood, SC
2003 4.6 v8 start problems
I tried searching, no luck so I am asking for help/suggestions.
My friend has an '03 with the 4.6 v8 motor. It runs good and generally is in excellent condition. Has 112,000 miles on it.
Problem, the starter turns the motor for about 10 seconds before the engine will fire. It's a very long time to be turning the engine with the starter.
Fuel filter been replaced, air filter new, not an issue with bad gas, battery is new, vehicle gets driven daily so it's not an issue of sitting.
Are there any common things that go wrong with this engine?
I told him we need to replace spark plugs, could have a fuel pump problem.
I told him that it could be the oxygen sensors, fuel pump, spark plugs and coils (this motor have a coil on each plug?).
Does this EFI system have a specific "start" strategy with a sensor or switch somewhere that could be failing?
Once it starts there are no other driveability concerns.
Thanks for your thoughts......
My friend has an '03 with the 4.6 v8 motor. It runs good and generally is in excellent condition. Has 112,000 miles on it.
Problem, the starter turns the motor for about 10 seconds before the engine will fire. It's a very long time to be turning the engine with the starter.
Fuel filter been replaced, air filter new, not an issue with bad gas, battery is new, vehicle gets driven daily so it's not an issue of sitting.
Are there any common things that go wrong with this engine?
I told him we need to replace spark plugs, could have a fuel pump problem.
I told him that it could be the oxygen sensors, fuel pump, spark plugs and coils (this motor have a coil on each plug?).
Does this EFI system have a specific "start" strategy with a sensor or switch somewhere that could be failing?
Once it starts there are no other driveability concerns.
Thanks for your thoughts......
Cargo Master
Joined: Aug 2003
Posts: 3,263
Likes: 92
From: BC Canada
Although some of these test may seem redundant, Pay particular attention to bold test (for your issue)
time to connect a LIVE DATA SCANNER.
COLD engine, (KOEO)
AIT (air temp)and ECT(coolant temp) must be with in 2% of ambient temperature (confirm with IR gun)
TPS, 0% at stop and rise smooth and steady as throttle is advanced
MAF, 0% with no air flow
Battery, 12.6vdc, fully charged.
Start engine.
ECT, must start to rise and attain and hold 180* at idle and 2000rpm
CL (ECU) must maintain at idle and 2000rpm
MAF, small reading at idle and rise steadily as throttle advances.
O2, (B1S1, precat), must start actively switching with no lean/rich bias...
LTFT, (long term fuel trim), close to 0%, +/-2 is allowable, if more, time to investigate fuel delivery/illegal air
Battery, >13.8vdc (14.5vdc optimum), when charging
Vacuum, at unregulated manifold port, 19-21”hg..with a dead steady needle, investigate jitter or bounce.
.. Philip
time to connect a LIVE DATA SCANNER.
COLD engine, (KOEO)
AIT (air temp)and ECT(coolant temp) must be with in 2% of ambient temperature (confirm with IR gun)
TPS, 0% at stop and rise smooth and steady as throttle is advanced
MAF, 0% with no air flow
Battery, 12.6vdc, fully charged.
Start engine.
ECT, must start to rise and attain and hold 180* at idle and 2000rpm
CL (ECU) must maintain at idle and 2000rpm
MAF, small reading at idle and rise steadily as throttle advances.
O2, (B1S1, precat), must start actively switching with no lean/rich bias...
LTFT, (long term fuel trim), close to 0%, +/-2 is allowable, if more, time to investigate fuel delivery/illegal air
Battery, >13.8vdc (14.5vdc optimum), when charging
Vacuum, at unregulated manifold port, 19-21”hg..with a dead steady needle, investigate jitter or bounce.
.. Philip
Logistics Pro
Joined: Jun 2009
Posts: 4,814
Likes: 83
From: Cedar Rapids, IA
Assuming your friend doesn't have access to a fuel pressure tester, suggest they try the following after the car has sat awhile, in similar to conditions to when it would struggle to start:
1) Turn the key to the Run position (not the start position). Leave the key there for 2 seconds.
2) Turn the key to the Off position. Leave the key there for 10 seconds.
3) Repeat step 1).
4) Repeat step 2).
5) Turn the key to the Start position and see if the engine starts quickly.
If so, that would suggest there is something preventing the system from building proper fuel pressure. Cycling the key as above causes the fuel pump to repeatedly prime the fuel rail and build fuel pressure. If the pump is weak or there are restrictions in the line, the rail may not be properly pressurized from a single "priming" event.
-Rod
1) Turn the key to the Run position (not the start position). Leave the key there for 2 seconds.
2) Turn the key to the Off position. Leave the key there for 10 seconds.
3) Repeat step 1).
4) Repeat step 2).
5) Turn the key to the Start position and see if the engine starts quickly.
If so, that would suggest there is something preventing the system from building proper fuel pressure. Cycling the key as above causes the fuel pump to repeatedly prime the fuel rail and build fuel pressure. If the pump is weak or there are restrictions in the line, the rail may not be properly pressurized from a single "priming" event.
-Rod
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