Thread: No first start?
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Old 07-25-2002, 02:20 AM   #4
PKRWUD
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Join Date: Mar 1999
Location: Ventura, California
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Allow me to elaborate.

In order for a fuel injected engine to fire, the fuel has to be injected, rather than "drawn" in by vacuum and gravity. In order for the fuel to be injected, there has to be sufficient pressure behind it. This is not a problem once the car is running, because the fuel pump is on, but what about when you try to start it? I'll tell you. When you first turn the key on, the ECM sends a signal to the fuel pump relay telling it to power up the fuel pump. If after two seconds, the ECM doesn't receive a signal from the igntion system, telling it that spark plugs are trying to fire, which means that you are trying to start it, it kills the power to the relay, and the fuel pump stops pumping. In a perfect world, drivers would understand this, and would wait for 2 seconds to pass between the time they turned the key ON to the time they turned the key to START, allowing sufficient time for the pump to build up enough pressure to start the engine.

The engineers, however, knew that this was not a perfect world, and that most drivers would just jump in and go straight from OFF to START, and expect it to start right away. To solve this dilemma, they made sure that a healthy fuel system would retain the pressure, even after the key was turned off, and the pump was powered down. In fact, it should retain at least half of the normal idle pressure over night, easing start-up the following day.

Your system is not doing this any longer, which means one of two things is happening. Either there is a leak in the system at the engine end of things, or a failure in the tank end of things. At the engine end, the most likely source for such a leak would be leaky injectors. A bad FPR is also a possibility. At the tank end, there could be a bad or weak check valve, which allows the fuel to bleed back into the tank. Most in tank fuel pumps have the check valve built in, so if that is what was failing, your pump would be at fault, even though it still performs sufficiently to run the engine. Another sign that the pump is getting weak is the amount of time it takes for it to build up sufficient pressure to fire the engine. It should be able to do this in two seconds, tops. If it takes longer, that means the pump is getting weak. It takes a lot more work for the pump to build up the pressure than it does to maintain it while the engine is running, so even if it took longer than 2 seconds to prime the pump so it would start, it would still be able to maintain the required pressure to keep the engine running.

Remember that if the ECM doesn't receive a signal from the ignition system telling it that you are trintg to start the engine, it will shut the pump off, and you will start to lose pressure again. This is why you may have to cycle the key from OFF to ON to OFF to ON a few times before adequate pressure has built up to start it.

SO, if it starts the first time you try to start it, AFTER cycling the key a few times, this verifies it's a fuel system problem, and I will teach you how to determine which part of the fuel system it is that's going bad after you try what I suggested.

Hope that helped.

Take care,
~Chris
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