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  #1  
Old 01-12-2002, 08:11 PM
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280SEL4.5 intermittent hot start problem

On occassion, if I shut down the hot engine then wait about a half hour the engine is very difficult to start. If it is cold or just shut down it starts instantly. The problem occurs about one time in 5 roughly. It has been happening for months. It may be flooding because I have to hold the accelerator pedal down and let the engine chug for a couple of minutes before it gets going. Could be something sticking. Any ideas?
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  #2  
Old 01-12-2002, 09:09 PM
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You shouldn't need to hold down the pedal on a 4.5 'cause it's fuel injected (pedal only adds air, not gas at start). But if you are flooded, holding down the pedal sure helps.

Do TWO things...

1. Get a fuel pressure guage and plumb it into the system instead of the cold start injector. It should hit 32psi the moment you start the car and it should stay there for a while after you turn the car off. If it doesn't, then either the pump is defective or an injector is leaking. If the problem goes away, it was your cold start valve leaking. If the pressure isn't 32psi during operation, adjust the pressure control (can at the back with 3 fuel leads) until it is.

2. Pull one plug from each side of the engine (and not directly opposite each other) just to see if they are wet (and becareful, 'cause they sure will be hot) prior to the restart.

-CTH
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  #3  
Old 01-12-2002, 11:20 PM
ShadeTreeSteve
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Me too

My 4.5 does the same thing. Maybe an injector leaking down after shutoff. Injectors about the only thing I haven't addressed with this problem. I'm sure they are getting tired.

STS


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Old 01-13-2002, 02:33 AM
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Thanks guys. I'll pull a plug on each side the next time it happens to see if they are wet. BTW, what causes an injector to leak? Do they get gummed up and stuck open? If so would a fuel injection cleaner added to the gas help or solve the problem completely? Would the same apply to the cold start valve?
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Old 01-13-2002, 07:19 AM
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Yup.

The injector is but a precision ground spring loaded pin pressed up against an equally precision ground seat. Some injectors (like yours) have a solinoid. Mechanical injection systems just rely on fuel pressure.

If you ever get to the point of pulling the injectors, there are two rubber bits on each one that have to be replaced. One is at the tip, the other is a ring that you can see at the point where the injector hits the head.

-CTH
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Old 01-13-2002, 04:58 PM
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My injectors had no o-rings on my 72 280SE 4.5, unless they stayed down in the hole when I removed it, just covered in a green rubber. I examined it, lubed it, and reinstalled it.
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Old 01-13-2002, 05:10 PM
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Does the 4.5 have an overvolt protection relay (OVP)? I have read elsewhere that it can also be the cause of hot start problems.
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Old 01-13-2002, 05:22 PM
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The injector at the tip stays in the head after a while. If you don't replace it when it gets stiff, you get a bad air mixture and things don't go so well.

the big rings are held onto the injectors by a C clip.

-CTH
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