Too much fuel
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Too much fuel
I'm having trouble with my EFI 302, 1986 F150 fuel to the engine. It is running extremely rich. It runs very rough at idle. Fuel pressure is good. I have replaced the fuel pressure regulator, the MAP sensor, and the TFI. Nothing has changed. It's been to four different mechanics and they can't find anything wrong. All the EFI sensors and components check okay. Can't find any vacuum leaks. The computer thinks it is getting too much air so it's dumping more fuel. Next step is to remove the the throttle body to see if it is getting air from somewhere but don't really know what I'm looking for.
Help!
Help!
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Joined: Jan 2001
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From: S. Mississippi
Check your throttle body gasket...it might be leaking there... Also check your injectors to make sure you aren't dumping fuel that way.
Also check your Temp sensor....there are two of them, one goes to the computer, one goes to the instrument cluster, if the one going to the computer is out of range, it will cause the engine to run very rich.
O2 sensors might be suspect too...i'd replace them if they were over 80k anyway, just as a precautionary measure.
Good Luck!
Also check your Temp sensor....there are two of them, one goes to the computer, one goes to the instrument cluster, if the one going to the computer is out of range, it will cause the engine to run very rich.
O2 sensors might be suspect too...i'd replace them if they were over 80k anyway, just as a precautionary measure.
Good Luck!
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Thanks for the tip. I'm going to check the throttle body first. What would cause the injectors to dump fuel? That will be my next move if the throttle body and intake manifold don't appear to be leaking air.
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I found a huge hole in the EVR solenoid bracket. Now the truck runs enough to drive it but it is still getting loaded down with fuel. It has little power but runs good at higher speeds.
The codes had come up for the oxygen sensor but that had been replaced.
Is there a way to check for the air plenum leaking without removing it?
If the o-rings on the injectors are bad will it leak internally or externally? There are no external fuel leaks.
Could the throttle body have some kind of internal failure or have some restriction. It appears to be okay.
Is it normal for the engine to have a lot of internal pressure?
A lot of questions but all the EFI components have been replaced or checked okay. It seems like it has either an air leak or a mechanical problem.
The codes had come up for the oxygen sensor but that had been replaced.
Is there a way to check for the air plenum leaking without removing it?
If the o-rings on the injectors are bad will it leak internally or externally? There are no external fuel leaks.
Could the throttle body have some kind of internal failure or have some restriction. It appears to be okay.
Is it normal for the engine to have a lot of internal pressure?
A lot of questions but all the EFI components have been replaced or checked okay. It seems like it has either an air leak or a mechanical problem.
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Posting Guru
Joined: Jan 2001
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From: S. Mississippi
You have to remove the upper intake plenum to get to the gasket between it and the lower intake... its starting to sound more & more likely that this is what is leaking...
An easier way to check i'd think is by covering up the throttle body at idle and see if the engine revs up...if it does, you indeed do have a vacuum leak.
An easier way to check i'd think is by covering up the throttle body at idle and see if the engine revs up...if it does, you indeed do have a vacuum leak.
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I covered up the throttle body completely and it made little difference in the RPM. Wouldn't this mean there is an airleak somewhere from the throttle body to the intake manifold and as you said most likely the plenum. The butterlfy valves are closed at idle and when I opened them just a little the RPM increases alot. I think this has narrowed down the problem.
I have switch to cut off the high pressure fuel pump. When it is idling it loads up with fuel. When I turn off the electric pump it continues to run, the RPM increases and it runs smooth. With all the fuel in the system it will run for a while unless I load it down.
I'm going back offshore tomorrow but when I get home next week I'm going to pull off the throttle body and the plenum and check for the air leak. Any tips on doing that? It looks simple enough
I have switch to cut off the high pressure fuel pump. When it is idling it loads up with fuel. When I turn off the electric pump it continues to run, the RPM increases and it runs smooth. With all the fuel in the system it will run for a while unless I load it down.
I'm going back offshore tomorrow but when I get home next week I'm going to pull off the throttle body and the plenum and check for the air leak. Any tips on doing that? It looks simple enough
