Hi Squad!

I joined this forum last year as I started to work on an F150, 1987 4.9L 300 i6 and I'm SO close to getting it fired up.
I've replaced pretty much the entire EFI but confess.. I'm a noob and didn't document enough on the inline fuel pump.

As of now, the fuel lines from the tank to the fuel pump have gas in them.. the line going from the fuel pump to the fuel filter (and therefore the engine) is bone dry.
Thus something is up with the fuel pump I think.
It's one of these..

Now.. some things to note...

- I can DEFINITELY hear and feel the fuel pump getting power.
- I have the red wire from the power pigtail connector on the negative (smaller tab), and the black on the positive (bigger tab).. the shovel connectors fit as per their size
(** I went with this because the fuel pump also has a dab of red paint on the negative smaller terminal... which I still deemed odd but, the shovel connector fit as the positive one is 6mm, the negative (black in this case), is 8mm)

- This seems odd to me because 'red' is typically indicative of positive. (This is an old truck so maybe someone messed with the wiring.. not sure)
- The end of the pump with the tabs (pictured above) is the end pointing towards the fuel filter (the engine block), the other end is 'receiving' gas from the gas tank (rear of truck)

1) Is it possible that I have the CORRECT polarity (power connectors are correct) and that the fuel pump is pointed in the wrong direction? (I double checked with the manual and saw vids on Youtube that seem to indicate the pump is installed correctly)??
2) Is it possible that I have the WRONG polarity, and the fuel pump (has power) is pumping the wrong way?

It def seems like the pump seeing how fuel is making it TO the pump, but not from then onwards. I'm not sure if the pump can RUN on a switched polarity?

I know this is seemingly silly but this truck was given to my Dad, so who knows what has been 'finagled' on it

My next steps...
I was going to disconnect the fuel protector plate, disconnect the fuel line from the pump to the filter so I can see if the pump is spitting out anything after I
1) reverse the polarity
2) if that doesn't work, reverse the pump
3) if that doesn't work, reverse the pump AND the polarity
4) I have a 2nd new pump.. maybe this one (brand new) is broken?

Would appreciate any thoughts!
Sorry for the long description!

 

Your signature essentially says 87 4.9L. That's barely any info. And it contradicts the thread title, which says 86. You should put ALL your truck's details & history (as much as you know) into your signature so it shows with each post, as this page explains:

(click this text)


Upload an avatar of the truck. The more pics you post (NOT in your sig) of the truck, engine, wiring, labels, & undercarriage, the more likely we can help you. Not all its details are relevant to these issues, but you don't necessarily know which ones are relevant, so just put everything in now. Pics of your actual fuel pump would be much more-useful, including any markings on it. Clean it after taking several pics (in case cleaning removes some markings or labels), and then take several more (in case cleaning reveals more markings or labels). The '87 fuel system is deceptively complicated, and there are several configurations based on exactly how the truck was built (which is why ALL its details need to be in your signature). Study this page & follow the relevant links on it:

(click this text)


The presence of gas in the lines or filter is nearly meaningless. What matters is PRESSURE at the fuel rail. Does yours have a pressure test port (looks like a tire valve)? It's hidden at the right rear top of the engine.

(click this text)


In this pic, it's barely visible behind the woven cover on the EGR tube near the left middle of the pic:

(click this text)

 

Hey Steve,
thanks for the info and all the help! Big time.

Judging by the flow of fuel chart that you added, I've got it right except for the potential reverse polarity, or pump in the wrong direction.
The fuel rail pressure valve simply CAN'T have enough pressure because gas isn't making it that far.
I'm going to try the reverse polarity situation because it seems to make sense.
There is no fuel making it from the fuel inline pump to the fuel filter (therefore, it can't make it to the fuel rail either). Thanks dude!

 

Here's a picture showing the large terminal as positive. Some manufacturers mold the signs in to the pump. It's a DC pump so it will run backward.

In your picture the bottom is the inlet and the top is the outlet. There's a check valve in the top.

https://www.rockauto.com/en/moreinfo...t=6256&jsn=617

 

Yessir, that's the one and would seem I have the outlets arranged and connected correctly. The only thing I can think is perhaps the electrical on this truck is wired up incorrectly and thus the pump is turning the wrong direction. It's brand new and the fuel line from the outlet is dry.

I got some gator clips so tonight will probably run the positive/negative from the pigtail electrical connector from the wire harness, to the negative/positive terminals on the pump. Otherwise, either it's defective (I'll try my second one), or I'm right... I think.
Not sure?

 

You should click that second link in Steve83's post and read it, like he said.

There's another pump in the tank. Two pumps.