84 6.9 wacky throttle issues./ Electric diesel fuel pump mod

[84diesel6.9nonturbo]

I recently bought a 1984 2wd f250 xlt 6.9 non turbo.

1. My mechanical fuel pump is deleted but still attached to the block with the old fuel hoses cut and capped as of this week. Is that ok?

2. My truck surges sputters and lunges forward at stop lights and at about 60-70 mph feels like is has a big boost of power sometimes? Air leak in fuel from my old pump bypass? Do i need the fuel warmer hooked up? I live in the sunny state of california... also, how do i drain the water from the fuel?

Thanks in advance for all your help. I like this truck so far its not a lot of work to make her happy once you know her spots. Like a woman

 

[IDIoit]

about 2 hours or so east of me.
leaving the lift pump on, with the fuel lines disconnected wont cause you an issue.
unless of course the arm of the pump breaks and falls into your timing gears......
i use block off plates.

the issue youre seeing is inadequate fuel pressure from the electric pump.
what pump are you using? and where is it located?
this also could be a couple of other things.
broken pieces of the fuel pick up clogging the line.
fuel switch valve acting up,
or clogged vents in the tank.

i suggest you go through the entire fuel system starting from the sending units/pick ups

lots of issues with the fuel switch valve, and they are not cheap.

on your 84, there should be a water separator on the driverside firewall.
inbetween the drivers side fender and brake booster/master.

once you pull the plunger to try to evac the water, i can pretty much grantee you will start having air intrusion issues.

the best thing to do is to get a later style water fuel separator off of the 90+ trucks, and delete the stock fuel sep.

REPLACE ALL RUBBER LINES!!!!!!

 

[bobs_idi]

where in auburn are you?

 

[84diesel6.9nonturbo]

Ok cool. Very helpful thanks! I pulled that water separator thingy recently to see if it was full, to drain it or whatever??? Nothing happend. Can i bypass it, (the water sep) for... say 100 to 200 miles without issue to see if that corrects it? Can i run two separate fuel lines? I have no switch.... my pump draws from both right now i guess? I was using the 2 big @$$ pumps the previous owner put on next to each tank (pushing the fuel) the return line was filling up tank A while drawing too much from tank B. To further complicate things... the fuel guage isnt working nor could i switch to check them if it did cuz like i said i dont have a tank A tank B switch. So, i keep her full. I put in the electric pump and she stoped ******* diesel fuel all over the street via the overflow lines and fuel caps. I was thinking i would pull off the bed, check the tanks and run two elect pumps and two switches? The switch pannel is already installed for the two oversized pumps. I left them inline for backup pumps/priming, i dont know if thats an issue or not

 

[84diesel6.9nonturbo]

Auburn is fairly close to me. Im a few miles up the road from "Cool CA"

 

[Shawn MacAnanny]

I just pulled the filter and separator, lines and and bracket from my 93 turbo if you're looking for one. $30 plus shipping if you want it.

I'd also check and make sure the pre filter for your electric pump isn't clogged, or the pump itself isn't clogged if there's no filter.

Whee does the fuel return for your IP run? It has to run back to a single tank, teeing it and running back to both will never send an even amount back

 

[jhenegh]

I just pulled the filter and separator, lines and and bracket from my 93 turbo if you're looking for one. $30 plus shipping if you want it.

I'd also check and make sure the pre filter for your electric pump isn't clogged, or the pump itself isn't clogged if there's no filter.

Whee does the fuel return for your IP run? It has to run back to a single tank, teeing it and running back to both will never send an even amount back

^^^Thats a good deal BTW

 

[OLDBULL8]

Can i run two separate fuel lines? I have no switch.... my pump draws from both right now i guess? I was using the 2 big @$$ pumps the previous owner put on next to each tank (pushing the fuel) the return line was filling up tank A while drawing too much from tank B.

You cannot use two fuel pumps without having a three way solenoid valve in the return to tank line. The solenoid has to have a minimum of 1/4" flow thru ports. A three way solenoid has one input port and two outlet ports, energized it will direct the fuel to A outlet port to A tank, de-energized, it will direct B outlet port to B tank.

With one fuel pump, you would have to have two of the three way solenoids. The fuel suction lines from each tank and to the filter has to be a minimum of 5/16" ID. The fuel suction solenoid has to have 5/16" flow thru ports.

The alternative having two tanks is to have manual valves. Search on here for the information.

The next alternative is to have the OEM fuel selector valve (FSV), that would be mounted on the frame rail by number one {forward) tank. The OEM FSV is a six way valve. They are expensive from a dealer ($260). A substitute is a FSV from an auto parts store, they mount a little different and have barbed inlet/outlet in place of the OEM snap on line fittings.

Without one of the three alternatives, the return fuel has no way of returning to the tank that is being drawn from, hence, one or the other will overflow.

http://www.clippard.com/products/el...p549-1rjjji4&gclid=CNqHmojN2csCFQcLaQodkw8E6g

 

[madpogue]

Another previous owner hack job; people who do stuff like that should be issued a lifetime bus pass. +1 to Bill; if you intend to run both tanks, you'll need the FSV or manual-valve it. For the time being, you could find a way to re-plumb it so you're feeding from, AND returning to, just one tank. Who knows, that may just make your issues go away. That'll buy you time to decide what to do more permanently to employ both tanks.

 

[hesutton]

Sounds like several issues going on at once.

Do you have a Fuel tank Selector Valve (FSV) on the driver's frame rail and it just isn't hooked up or is it gone? If it is gone, you need to get one (from Ford or otherwise). Is the plug for the FSV still on the chassis harness on the driver's side frame rail? Hope so. The fuel sending units from your tanks use the FSV to switch and send the fuel level signal to your gauge in the dash. No FSV, no functional fuel gauge (unless the PO did something else crazy to try and rig the senders to the gauge).

Like stated above, doing what was done to try and get fuel from the tanks, to the engine, then back to the tanks isn't going to work. It must be fixed.

What electric fuel pump is on the truck now? What are the spec's on it?

Do you have a fuel pressure gauge? Need to know what your fuel pressure to the IP is doing. The surging and sputtering at highway speeds is fuel starvation until proven otherwise. My guess is you have zero fuel pressure at higher RPM, the IP runs low or out of fuel, and it surges/sputters.

There is a high likelihood (with all the "mods" the PO did to the fuel system) that you have air intrusion/fuel leak in the system. Probably in several places. Like stated above, you need to check the entire system for wet spots (leaking). Ditch the stock water separator (notorious for leaking) and get a 7.3 IDI fuel filter head.

Heath

 

[84diesel6.9nonturbo]

Thanks Heath, i think youre 100% correct. Im going to try to hook it up or check the wires because its there i just dont know how to (check it) but maybe itll be something obvious. Thank you!

 

[84diesel6.9nonturbo]

Ya i may end up using just one tank for a week or two- if i cant fix the stock- fuel valve thing mounted on the frame.

 

[Shawn MacAnanny]

You could always just install a 38 gallon rear fuel tank and not need the front one

http://www.ebay.com/itm/New-Fuel-Ta...ash=item35c9e91a73:g:QpAAAOSwAuNW4uVJ&vxp=mtr

http://www.thedieselstop.com/forums/f30/f26e-38-gallon-rear-fuel-tank-install-540154/

 

[Shawn MacAnanny]

I installed a cat filter/pump setup, it's 5 micron, could probably get away with that but i put a 10 micron on before it just to make sure i dont clog the filter faster than i should.

 

[84diesel6.9nonturbo]

Nice cat set up. How much would those parts run me new?