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Replaced intake manifold and it won't start

Tiny
KIRKTENIKA
  • MEMBER
  • 2000 FORD MUSTANG
  • 193,000 MILES
Replaced intake manifold on 2000 Mustang 4.6L GT with a PI manifold. Placed all wiring and lines back correctly and tried to start it but failed. It started briefly with starting fluid but after a while it didn't start at all; rough misfires. I saw antifreeze in the # 5 and #8 plug. I haven't cleaned it yet i.E. Dried them out. The car has been parked for months and the gas hasn't been replaced even longer. What do you think the problem(s) are? Is it gas? I had an additive, Marvel Mystery Oil in the gas. The car started before but with starter but it misfired due to a crack in the thermostat housing which leaked antifreeze into those plugs I mentioned earlier. Any assistance would be greatly appreciated.
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Wednesday, September 19th, 2012 AT 3:36 AM

11 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Before replacing theintake manifold, were you able to start?

If starting fluid works, it means a fuel problem so you should be checking for fuel pump operations, its pressure and injectors.
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Wednesday, September 19th, 2012 AT 9:09 AM
Tiny
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Before I changed out the intake, I was able to briefly start the car only with starter fluid and it idle for a short time before it cut off. I researched this problem and a forum read that it could perhaps be the IAC valve. I'm not sure actually. How would I check the fuel pump's pressure? Should I disconnect the fuel line and try to start it to see if gas is being pumped through the line?
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Wednesday, September 19th, 2012 AT 2:55 PM
Tiny
KHLOW2008
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You need a fuel pressure gauge to check the pressure.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

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Wednesday, September 19th, 2012 AT 2:58 PM
Tiny
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OK I'll try to rent one and see what happens. So you don't believe it's the aged fuel? Just the fuel system i.E. Pump, injectors, relay, and etc? Thanks again. If it doesn't work out, I'll post again. In the mean time, thank you.
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Wednesday, September 19th, 2012 AT 3:10 PM
Tiny
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Sorry I missed that out. Aged fuel can cause a lot of problem and it is possible to be the cause.
Btw the presence of coolant at the spark plugs are something to be concerned about and if possible, have the engine compression and cooling system leakdown tested as well.
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Wednesday, September 19th, 2012 AT 9:23 PM
Tiny
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Thanks again. I think I'm going with the least expensive option i.E. Aged gas, first. Then check the relay, regulator, and fuel pump. I cleaned the IAC valve with brake fluid and let it thoroughly dry along with the EGR valve-throttle body cleaner. I say again, before I changed out the intake which was cracked at the thermostat housing which was causing the leak; I had no real problems starting the car albeit with starting fluid on occasion. The car was parked for a very long time with the same gas.
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Thursday, September 20th, 2012 AT 3:20 PM
Tiny
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IAC is for idling concerns and if you slightly depress the gas pedal, it would override that which means you should be able to start even if the IAC is bad.

Fuel pressure problem would cause non starting. If it is the injectors, that can mean a bad engine computer. You would need to use a noid light to test the pusling.
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Thursday, September 20th, 2012 AT 7:47 PM
Tiny
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Thanks again. I'll work my way starting with siphoning off the old gas first and then work my way through steps. I'll keep you posted on my progress. Thanks again.
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Thursday, September 20th, 2012 AT 8:00 PM
Tiny
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Hello. I'm trying to get the old gas out of the tank. I tried to siphon but the siphon won't go down into the tank; I think it's the anti-siphoning device in the filler neck. Is there any other way to get the gas out beside dropping the tank? I don't have to tools, i.E. Floor jacks, safe place to work, and etc; to perform this step(s). Is there a 'drain cock' on the gas tank of this car? Any assistance, as usual, is greatly appreciated. Thanks in advance.
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Friday, September 21st, 2012 AT 6:24 PM
Tiny
KHLOW2008
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Check under the tank for a drain plug.

One other way is to use the fuel pump to drain. Disconnect the hose at fuel rail and remotely work the fuel pump.
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Friday, September 21st, 2012 AT 8:40 PM
Tiny
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Thanks again. I'll keep you posted on my progress.
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Saturday, September 22nd, 2012 AT 2:25 PM

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