Starting problem when hot
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Junior User
Joined: Jul 2003
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Starting problem when hot
Hi all. I posted this over in the Bronco forum as well. Hoping for a solution to my weird problem.
First let me give a summary of my problem. When my Bronco has been sitting for 6-8 hours, it starts right up with no problems. However, if the truck has been sitting for an hour or so after being driven for a while, it takes 5-6 seconds of cranking to get it to start. When it does start, the smell of gas coming from the exhaust is quite strong. Once the engine is running, it runs very well and has yet to ever miss a beat.
I think the problem is caused by a leaky injector flooding out the cylinder, making it hard to start. Here's my theory.....it starts right up when it's been sitting for a long time because the residual pressure left in the line has leaked out completely and the gas in the cylinder has evaporated. When the truck sits for an hour or so, the gas is still leaking into the cylinder which floods it out making it difficult to start. To reinforce this theory, there is a strong smell of gas coming from the air inlet.
I've done the various fuel system tests(engine off pressure test, engine running pressure test, static pressure leakage check, overpressure test, underpressure test, etc.) per the shop manual and everything checks out, including the system pressure holding steady at around 38 psi for over a minute. The shop manual says everthing in the fuel system is ok, but the smell of gas and the starting problem makes me think otherwise.
I just changed the plugs, cap, rotor, and wires. I checked the coil primary and secondary resistance, primary circuit continuity check, and the voltage going to the coil and it passed all tests.
One thing I did check that wasn't quite right was the fact that I'm getting around 3.5 mV of stray voltage at module harness connector pin 2 but the shop manual says there should be absolutely no voltage. The corrective measure is to "service short to power in harness and perform general ignition checks."
What do you guys think? Could the leak in one of the injectors be small enough to allow gas into the cylinder while still passing the static pressure leakage test? Or is it the stray voltage at the module? How do I perform the corrective measure the shop manual recommends for the stray voltage?
I've heard the TFI module is the weak point of the Ford system and that it can cause weird ignition problems when they heat up, so I've already ordered a new one from Ford. My unit is remotely mounted on the drivers side inner fender to minimize heat but it still gets pretty hot to the touch. What else could it be?
Sorry for all the questions but I'm at a loss. Thanks!
First let me give a summary of my problem. When my Bronco has been sitting for 6-8 hours, it starts right up with no problems. However, if the truck has been sitting for an hour or so after being driven for a while, it takes 5-6 seconds of cranking to get it to start. When it does start, the smell of gas coming from the exhaust is quite strong. Once the engine is running, it runs very well and has yet to ever miss a beat.
I think the problem is caused by a leaky injector flooding out the cylinder, making it hard to start. Here's my theory.....it starts right up when it's been sitting for a long time because the residual pressure left in the line has leaked out completely and the gas in the cylinder has evaporated. When the truck sits for an hour or so, the gas is still leaking into the cylinder which floods it out making it difficult to start. To reinforce this theory, there is a strong smell of gas coming from the air inlet.
I've done the various fuel system tests(engine off pressure test, engine running pressure test, static pressure leakage check, overpressure test, underpressure test, etc.) per the shop manual and everything checks out, including the system pressure holding steady at around 38 psi for over a minute. The shop manual says everthing in the fuel system is ok, but the smell of gas and the starting problem makes me think otherwise.
I just changed the plugs, cap, rotor, and wires. I checked the coil primary and secondary resistance, primary circuit continuity check, and the voltage going to the coil and it passed all tests.
One thing I did check that wasn't quite right was the fact that I'm getting around 3.5 mV of stray voltage at module harness connector pin 2 but the shop manual says there should be absolutely no voltage. The corrective measure is to "service short to power in harness and perform general ignition checks."
What do you guys think? Could the leak in one of the injectors be small enough to allow gas into the cylinder while still passing the static pressure leakage test? Or is it the stray voltage at the module? How do I perform the corrective measure the shop manual recommends for the stray voltage?
I've heard the TFI module is the weak point of the Ford system and that it can cause weird ignition problems when they heat up, so I've already ordered a new one from Ford. My unit is remotely mounted on the drivers side inner fender to minimize heat but it still gets pretty hot to the touch. What else could it be?
Sorry for all the questions but I'm at a loss. Thanks!
Thread Starter
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Junior User
Joined: Jul 2003
Posts: 67
Likes: 0
Starting problem when hot
Alright, just an update and a couple of quick questions for those in the know. I decided to leave the fuel pressure gauge on the fuel rail for awhile to see how fast the pressure would leak down even though the system passed the static leakage test.
I got 38 psi when I shut the engine off. After about 1/2 an hour, the fuel pressure had dropped 20 psi and the smell of gas was quite strong from the air inlet tube.
This seems like excessive leakage to me. Isn't that more than enough leakage to flood out a cylinder and cause the hard start condition I'm having? Is it time for new injectors?
I got 38 psi when I shut the engine off. After about 1/2 an hour, the fuel pressure had dropped 20 psi and the smell of gas was quite strong from the air inlet tube.
This seems like excessive leakage to me. Isn't that more than enough leakage to flood out a cylinder and cause the hard start condition I'm having? Is it time for new injectors?
