86 F150 302-Need help understanding code scanner
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Junior User
Joined: Jan 2005
Posts: 52
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From: Moreno Valley, CA
sorry mdstud, i forgot to answer the question about clearing my codes. two ways...one, by disconnecting the negative from my battery for a while . and the second way was with my code scanner, you can clear the memory with it by switching it on then off then on again , something like that.
O.K. the fuel filter was replaced this afternoon and i still have the same results. from what i understand theres a one way valve inside the HP pump that should hold the pressure? So if that valve was stuck open the fuel would just return back to the tank through the same line it came thru to get there? Which makes sense. But what would cause my injectors to not work at all? If the low pressure in-tank pump wasn't working would the high pressure pump still be able to suck fuel from the tank at all? Cause it still has a steady flow of fuel but not at the specified pressure.
O.K. the fuel filter was replaced this afternoon and i still have the same results. from what i understand theres a one way valve inside the HP pump that should hold the pressure? So if that valve was stuck open the fuel would just return back to the tank through the same line it came thru to get there? Which makes sense. But what would cause my injectors to not work at all? If the low pressure in-tank pump wasn't working would the high pressure pump still be able to suck fuel from the tank at all? Cause it still has a steady flow of fuel but not at the specified pressure.
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Joined: Feb 2005
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So I'm guessing the injectors aren't firing? put a noid light on the injectors if they aren't being told to fire from the computer then you need to address that problem first before proceding with the fuel system. If the computer isn't sensing a proper signal from the tfi module on the distributor, you will get an error code 18 and the injectors won't fire. But make you really need to test and see if they are being fired. If they are being fired then the problem is just the fuel pressure. The computer has no input for fuel pressure so it doesn't care if the fuel pump aren't working it will still open and close the injectors. To isolate the fuel problem, disconnect the high pressure pump and have an assistant turn the key on while you listen for the low pressure pump operation, try both the front and rear tanks if you don't hear either then it's possible they're both bad. If they are working then replace the high pressure pump.
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Junior User
Joined: Jan 2005
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From: Moreno Valley, CA
your probably right. but thanks alot for trying, i really appreciate it mdstud. Although i have a volt/ohmmeter with a needle so maybe if i tried it with that i would be able to see the needle jump. I guess its worth a shot, im running out of options. I will post with results.
Post Fiend
Joined: Jan 2004
Posts: 5,377
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From: Elkhart IN
yes the hp will pull gas out of the tank its just hard on it as pumps are ment to push not pull. my 88 will run and drive just fine on just the hp until you really get on it the it kind of stutters. runs fine with both
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Thread Starter
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Junior User
Joined: Jan 2005
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From: Moreno Valley, CA
Well, I made a mistake on the fuel pressure. Apparently the fuel pressure guage isn't ready to use right out of the package. i guess you have to tighten the fittings more before using it, in the daylight today i noticed some bubbles around the fittings and after tightening them and testing all over i had nearly 40 pounds. I should have known better.
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Junior User
Joined: Jan 2005
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From: Moreno Valley, CA
The bad news is that it still wont start. I found a guy thats a certified ford mechanic with the dealers version of my cheap code scanner who says he'll be over tonight to hook it up and see what it says. With any luck he'll be able to pinpoint the problem better than i could with my cheapy scanner.
MDSTUD.......I havent tried to test the injectors with my meter yet but i will by the end of the day. I'll let you know what happens.
MDSTUD.......I havent tried to test the injectors with my meter yet but i will by the end of the day. I'll let you know what happens.
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Junior User
Joined: Jan 2005
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From: Moreno Valley, CA
ok.... heres the problem....low compression!!! All this time i thought my compression test guage was no good. If im lucky it'll just be the timing chain that jumped. ill check in later, i gotta go.
