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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

92 spins Over but Won't Start

Old 02-24-2019, 04:18 PM
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john89gt
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Default 92 spins Over but Won't Start

92 LX Convertible 5.0- It was running but started surging while idling, then died and hasn't started since. I checked the fuel pressure and it was 40 psi. I pulled the spark plug and it seems to be firing( meaning I could see blue). It seems to start at the initial turn of the key but then spits or sputters and never starts. The only other thing I noticed is the fuel pump runs steady when you turn the key on. On my 89GT, ithe fuel pump seems to run until it builds pressure and stops until you start the car. On the 92 with the key just on, I hear the pump running constantly. Any thoughts would be great. TIA.
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Old 02-24-2019, 08:01 PM
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TrimDrip
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there is a checklist you can follow for this issue. google Joel5.0 and checklist.

before that though, try unplugging the maf and starting it.
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Old 02-24-2019, 08:38 PM
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john89gt
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Thanks for the advice. What does unplugging the MAF do for it?
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Old 02-25-2019, 05:52 PM
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the computer has a table stored to follow for when the maf fails. Unplugging it should default it to that table and allow the car to idle if the maf is bad. OR MAYBE allow it to idle if a capacitor is bad in the computer.

The capacitors in the computer are prone to go bad over the years. They can even go bad while the computer is sitting on a shelf. You could just pull the computer out and look at them, but that is a lot of work without doing any prior testing.

Have you tried pulling codes on the car?
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Old 02-25-2019, 06:13 PM
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john89gt
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So I did get enough ether in the throttle body today that it ran for a second or two. Which leads me to believe it's fuel related. I checked the fuel pump this weekend and it seemed to pump fine. Today with the car key switched on I could hear the fuel pump running constantly and heard some hissing around the injectors. That's as far as I got with it today. Any thoughts?
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Old 02-25-2019, 07:04 PM
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TrimDrip
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the pump running all the time is strange. Here is a link to a schematic. Lots of info on this site. http://www.veryuseful.com/mustang/tech/engine/#Diagrams
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Old 02-25-2019, 07:29 PM
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john89gt
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Thanks. Yes, the fuel pump running constantly is very strange. I thought maybe the contacts on the relay may be stuck.
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Old 02-25-2019, 07:54 PM
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maybe someone else will chime in. If memory serves me correct, it seems like a distributor may cause that issue.
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Old 02-26-2019, 06:08 PM
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john89gt
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Good evening. I got in a little early, so I thought that I would run a KOEO test. I got nothing. No flash at all. I checked the TFI on the coil with a test light and it flashed while turning over the engine. Looks like next move is just running down the fuel.
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Old 02-26-2019, 07:39 PM
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The ecu could be the issue,if the pump is running constantly and the code test wont run.If you used a scanner to run the test,try this instead.Run a jumper wire from the STI terminal to the SIGNAL RETURN terminal, turn the koeo,see if the cel is flashing the codes out.If no,run the jumper wire from the STI terminal to the neg battery terminal then turn the koeo & see if the cel is flashing the codes.If it is,thats a verification the ecu is damaged.A burnt signal return trace usually causes the issue above and bad capacitors usually cause the constantly running fuel pump issue.
If the ecu is ok,a stuck open injector or leaking fuel pressure regulator could also be the cause for the constantly running pump,no start & the hissing noise.With the koeo,remove the fpr vacuum hose and see if fuel is seeping out of its port and check the vacuum hose for fuel also.Fuel out of either= defective fpr.If a injector is stuck open,the spark plug for that cylinder will be wet with fuel.You can also remove the fuel pump relay to see if it makes the pump stop running constantly.If it does,the fuel pump relay is bad.If the pump continues running with the relay out,the caps in the ecu are likely the issue.

The following link details capacitor and signal return trace inspection & repair.
http://sbftech.com/index.php/topic,37389.0.html




Last edited by wbrockstar; 02-26-2019 at 07:48 PM.
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