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Fuel issue
1991 Ford F-150

Fuel issue

(1991 Ford F-150)
Fuel not making it to the injectors, pumps seem to sound like they're working. What are the odds of sensor/electrical problem compared to something mechanical such as the fuel filter or pressure regulator? Engine barely runs on its own. When helped with ether or gas directly in the manifold it winds up normally. This is the same regardless of which tank is selected. What type of regulation module/computer is used for this engine?
1 answer & 7 comments
Popular Answer
on January 30, 2011
The thing you need to do to rule in or out a problem with the fuel system is to have a base fuel pressure test for each pump, and test each pump for bleed down. If it passes both of these tests, then start looking at an air intake leak. Remember that if you richen the fuel at the intake manifold, it will smooth out not only for a lack of fuel, but also for an overabundance of air.
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code 417 (idle control not switching/ snap throttle) pumps 55lbs. Bleed down? No intake leaks (sprayed ether all around) could this be a map sensor problem? Another thing I noticed just after or while the problem was occuring suggests a lean mixture and that was a glowing red catalytic converter....hmmm? Still stumped and coming down with a case of the head scratchin's...

Thanks for the guidance!
on January 31, 2011
Glowing red cats means that the fuel is being dumped due to the engine computer telling the fuel control that there is never enough. This is what I was meaning about the potential air intake leak - or actually the baro in the MAP sensor on this vehicle too. The MAP sensor can indeed cause an issue.

Code 417 could be occuring if you did not do a WOT (wide open throttle kick) during the test when required.

I think the key here is that when you richen the air around the intake you have better running. You almost certainly have a leak somewhere - intake gaskets, PCV hose, something...
Hello-
This fuel problem is still not resolved. Now I have replaced the fuel pressure regulator and map sensor. Fuel pressure and bleed down were fine. I have checked for impulses to the injectors and there is nothing. The vehicle runs rough, like on 2 cylinders. I have unplugged the connectors on the injectors and it runs exactly the same (rough). Could this point to the engine control module? Are the injectors timed and what controls their accentuation?
on February 04, 2011
So, I am frustrated (from my computer) that I can't really be of more assistance. On one hand, I'm hearing from you that the cats are glowing red, then on the other hand, you're saying there is no injector pulse.

There is probably something invalid in the test method, but it's too hard to determine from where I sit. I think you've done everything you can to narrow down the problem. You have to remember that you're dealing with a primitive system for an electronically controlled engine, and you're dealing with aged components. Anything goes. I think getting down to injector issues or a PCM issue is off the track.

Did you clear the memory of the processor when you replaced the MAP? If not, it will still be thinking it is where the old one was reading.

Also, how is the engine vacuum? The MAP sensor relys on it. Goes back to the whole "vacuum leak" theory on why it may be getting too much fuel.

In any case, you may need to get a local opinion near you...just for further perspective. Good luck!
Thanks Dave for everything! You know I only disconnected the battery thinking that would reset the memory after the map replacement. How do I reset it? Yes it is an old system where it's either freshen up or forget it, no vehicles run forever for nothin'.

Thanks again for you guidence--you're one heluva guy!
Resetting it...you have to basically allow the battery to sit disconnected for a little bit...like...10 minutes.

Even so, I'm betting it's not the problem you are having.

I'm all about fixing stuff like this, but I just think you might need some fresh perspective locally that can really look and see what you have going on there.
on February 05, 2011
That was from me...just didn't log in. Cheers.
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on January 30, 2011
The thing you need to do to rule in or out a problem with the fuel system is to have a base fuel pressure test for each pump, and test each pump for bleed down. If it passes both of these tests, then start looking at an air intake leak. Remember that if you richen the fuel at the intake manifold, it will smooth out not only for a lack of fuel, but also for an overabundance of air.
Sign in to reply
code 417 (idle control not switching/ snap throttle) pumps 55lbs. Bleed down? No intake leaks (sprayed ether all around) could this be a map sensor problem? Another thing I noticed just after or while the problem was occuring suggests a lean mixture and that was a glowing red catalytic converter....hmmm? Still stumped and coming down with a case of the head scratchin's...

Thanks for the guidance!
on January 31, 2011
Glowing red cats means that the fuel is being dumped due to the engine computer telling the fuel control that there is never enough. This is what I was meaning about the potential air intake leak - or actually the baro in the MAP sensor on this vehicle too. The MAP sensor can indeed cause an issue.

Code 417 could be occuring if you did not do a WOT (wide open throttle kick) during the test when required.

I think the key here is that when you richen the air around the intake you have better running. You almost certainly have a leak somewhere - intake gaskets, PCV hose, something...
Hello-
This fuel problem is still not resolved. Now I have replaced the fuel pressure regulator and map sensor. Fuel pressure and bleed down were fine. I have checked for impulses to the injectors and there is nothing. The vehicle runs rough, like on 2 cylinders. I have unplugged the connectors on the injectors and it runs exactly the same (rough). Could this point to the engine control module? Are the injectors timed and what controls their accentuation?
on February 04, 2011
So, I am frustrated (from my computer) that I can't really be of more assistance. On one hand, I'm hearing from you that the cats are glowing red, then on the other hand, you're saying there is no injector pulse.

There is probably something invalid in the test method, but it's too hard to determine from where I sit. I think you've done everything you can to narrow down the problem. You have to remember that you're dealing with a primitive system for an electronically controlled engine, and you're dealing with aged components. Anything goes. I think getting down to injector issues or a PCM issue is off the track.

Did you clear the memory of the processor when you replaced the MAP? If not, it will still be thinking it is where the old one was reading.

Also, how is the engine vacuum? The MAP sensor relys on it. Goes back to the whole "vacuum leak" theory on why it may be getting too much fuel.

In any case, you may need to get a local opinion near you...just for further perspective. Good luck!
Thanks Dave for everything! You know I only disconnected the battery thinking that would reset the memory after the map replacement. How do I reset it? Yes it is an old system where it's either freshen up or forget it, no vehicles run forever for nothin'.

Thanks again for you guidence--you're one heluva guy!
Resetting it...you have to basically allow the battery to sit disconnected for a little bit...like...10 minutes.

Even so, I'm betting it's not the problem you are having.

I'm all about fixing stuff like this, but I just think you might need some fresh perspective locally that can really look and see what you have going on there.
on February 05, 2011
That was from me...just didn't log in. Cheers.

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