Replacing Fuel Pump on '87 F-150

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#16

12-22-2006, 06:03 PM

Tdvjensen

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The only problem with that would be that he says he can hear the pump in the front tank working, and the pumps are tied together on one relay, so if the relay or the connection at the relay was the problem then niether pump would work. Still, that is a good place to check if no pumps were working. Nice fix too by the way.

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#17

12-22-2006, 08:06 PM

FreeFall

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Hey guys, thanks again for all the replies and great advice!

subford, in response to your post, I am in fact only seeing 12 volts at the in-line pump for the second or so that the relay is engaged (sorry for the confusion). The 12 volts drops as soon as I hear the relay click off. The low pressure pump in the front tank shuts off as well when the relay disengages. I think you're right, though, that if there was a constant voltage, something would be wrong with the computer. Any other thoughts?

Ogriv, thanks for the awesome tip! I think Tdvjensen makes a good point, though. The voltage I measured was pretty consistent, and the front tank pump never fails to run. I didn't realize they were on the same circuit, but it makes sense. BUT, I'm willing to bet I'll be facing that same thing you did at some point.

I'm still thinking it's that pump, but I'm going to post-pone ordering the replacement for a day or so in case ya'll have other thoughts. I do have one newbie question, what redirects fuel from the main line to all the injectors? I mean, if it's an EFI, something up there has to be controlling it. Does the computer control the injectors directly? If so, what actually redistributes the fuel to all the cylinders? Can that thing get clogged or break down?

By the way, I was having trouble figuring out how to get the in-line pump out of the metal, cylindrical housing before. Ya'll may already know this, but the entire thing just unbolts from the frame. I'm only mentioning it in case someone else reads this and needs the advice. Also, to test for spark, I ended up getting this nice little tester from the O`Riley that you just plug into the cable and clamp to the block. It was a couple bucks, but at least I got stand away from it.

Last edited by FreeFall; 12-22-2006 at 08:09 PM.

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