Need help.. stranded
12-10-2010, 10:23 AM
#11
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Re: Need help.. stranded
Summary... my engine bay grounds are all good, main relay ground is good, still only getting 2.8 volts to the fuel pump fuse and not sure why.. 0 volts to fuel pump itself.
What I cant figure out is how the ecu plays into this. All the wiring diagrams I can find say that the fuel pump wiring goes battery - fuse - relay - pump. Where does the ecu come in?
What I cant figure out is how the ecu plays into this. All the wiring diagrams I can find say that the fuel pump wiring goes battery - fuse - relay - pump. Where does the ecu come in?
Last edited by aksnowbrder; 12-10-2010 at 12:29 PM.
12-11-2010, 03:04 AM
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Re: Need help.. stranded
If you're getting 2V at the fuse, find out why. I suspect this is directly related to why you're also cranking slowly. You probably have a broken battery cable clamp, corroded ground, or something along those lines. Basically if you're getting 2V at that fuse, keep tracing back to the battery until you're getting proper battery voltage. If I'm correct, this is going to be something that affects more than just the fuel pump circuit.
If it's cranking a lot faster when jumped to another car, that would tend to say that you're bypassing the factory power and ground and using power from the other car, which would make the starter motor circuit work fine. The other circuits could easily still be affected by whatever is causing the actual problem though, such as a bad ground.
If it's cranking a lot faster when jumped to another car, that would tend to say that you're bypassing the factory power and ground and using power from the other car, which would make the starter motor circuit work fine. The other circuits could easily still be affected by whatever is causing the actual problem though, such as a bad ground.
12-11-2010, 09:26 AM
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Re: Need help.. stranded
Im in agreement here. I just had to replace my GFs moms battery because the cold weather killed the cells in it after she let it sit for almost a week. It had barely enough juice for accessories MUCH LESS cold cranking starting, and would have to be jumped to get anywhere.
12-11-2010, 09:40 AM
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Re: Need help.. stranded
Summary... my engine bay grounds are all good, main relay ground is good, still only getting 2.8 volts to the fuel pump fuse and not sure why.. 0 volts to fuel pump itself.
What I cant figure out is how the ecu plays into this. All the wiring diagrams I can find say that the fuel pump wiring goes battery - fuse - relay - pump. Where does the ecu come in?
What I cant figure out is how the ecu plays into this. All the wiring diagrams I can find say that the fuel pump wiring goes battery - fuse - relay - pump. Where does the ecu come in?
You should check voltage at the inputs and outputs of all the relevant fuses in the fusebox under the hood. It still doesn't sound like you've started at the fuel pump fuse and traced backwards toward the battery. Also, just replacing the main relay doesn't mean that the relay is actually working properly.
If you have 12V on the input to the fuel pump relay, you can probably assume that the relay is bad or that the relay isn't getting turned on by the ECU. If you have 2V on the input to the fuel pump relay, go upstream (toward the battery) and find the next point to check for voltage.
A vehicle electrical system is a like a tree. The battery is the tree trunk, and everything branches out from there into multiple circuits and then subcircuits, etc.. So if you don't get power at the tips of the branches, start tracing back toward the trunk.
So let's explore this a little more..
How did you check if the grounds are all good? Are you just assuming that they're good because they're bolted down properly, and you haven't checked if they're restricting power flow? I don't want to second guess everything you're doing; I want to make sure that everyone is communicating properly.
Stop crossing your fingers and randomly replacing stuff until you actually see if things are working or not.
I'm not trying to go on a rant here but it gets really frustrating when people replace things instead of diagnosing them. That's the most expensive, time wasting thing you can possibly do when trying to fix a car. So far you've unnecessarily replaced a fuel pump and a main relay without checking if they're working or not.
Last edited by Fabrik8; 12-11-2010 at 09:53 AM.
12-11-2010, 09:57 AM
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12-11-2010, 11:55 AM
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Re: Need help.. stranded
The ECU controls the fuel pump relay usually.
You should check voltage at the inputs and outputs of all the relevant fuses in the fusebox under the hood. It still doesn't sound like you've started at the fuel pump fuse and traced backwards toward the battery. Also, just replacing the main relay doesn't mean that the relay is actually working properly.
If you have 12V on the input to the fuel pump relay, you can probably assume that the relay is bad or that the relay isn't getting turned on by the ECU. If you have 2V on the input to the fuel pump relay, go upstream (toward the battery) and find the next point to check for voltage.
A vehicle electrical system is a like a tree. The battery is the tree trunk, and everything branches out from there into multiple circuits and then subcircuits, etc.. So if you don't get power at the tips of the branches, start tracing back toward the trunk.
So let's explore this a little more..
How did you check if the grounds are all good? Are you just assuming that they're good because they're bolted down properly, and you haven't checked if they're restricting power flow? I don't want to second guess everything you're doing; I want to make sure that everyone is communicating properly.
Stop crossing your fingers and randomly replacing stuff until you actually see if things are working or not.
I'm not trying to go on a rant here but it gets really frustrating when people replace things instead of diagnosing them. That's the most expensive, time wasting thing you can possibly do when trying to fix a car. So far you've unnecessarily replaced a fuel pump and a main relay without checking if they're working or not.
You should check voltage at the inputs and outputs of all the relevant fuses in the fusebox under the hood. It still doesn't sound like you've started at the fuel pump fuse and traced backwards toward the battery. Also, just replacing the main relay doesn't mean that the relay is actually working properly.
If you have 12V on the input to the fuel pump relay, you can probably assume that the relay is bad or that the relay isn't getting turned on by the ECU. If you have 2V on the input to the fuel pump relay, go upstream (toward the battery) and find the next point to check for voltage.
A vehicle electrical system is a like a tree. The battery is the tree trunk, and everything branches out from there into multiple circuits and then subcircuits, etc.. So if you don't get power at the tips of the branches, start tracing back toward the trunk.
So let's explore this a little more..
How did you check if the grounds are all good? Are you just assuming that they're good because they're bolted down properly, and you haven't checked if they're restricting power flow? I don't want to second guess everything you're doing; I want to make sure that everyone is communicating properly.
Stop crossing your fingers and randomly replacing stuff until you actually see if things are working or not.
I'm not trying to go on a rant here but it gets really frustrating when people replace things instead of diagnosing them. That's the most expensive, time wasting thing you can possibly do when trying to fix a car. So far you've unnecessarily replaced a fuel pump and a main relay without checking if they're working or not.
12-11-2010, 02:24 PM
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Re: Need help.. stranded
It will also trigger a CEL, which there is none. Most crank position sensor problems aren't detected until the engine starts rotating unless the sensor is missing or there is a major fault on the sensor input. A CPS problem doesn't explain the 2V at the fuse either, because a functional fuel pump circuit with a functional relay will show 0V at the output of the relay, not 2V. A properly functioning relay is either on or off, it's not sitting at 2V on the output.
12-11-2010, 02:27 PM
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Re: Need help.. stranded
I understand your point. I checked my grounds with a multimeter, checked to make sure I got 12v when holding the multimeter to both the positive terminal and both sides of each ground. I did trace power back from the fuel pump, I get 0v at the pump, 2.8v at the relay, and 2.8v at the fuse itself. All underhood fuses have proper voltage.