FSS Wiring Refresher

[apt403]

Hey everyone,

Just need a refresher on the wiring for the FSS on the DB2 - There's three wires coming off the IP - One is yellow, closest to the cab. The other two are red and red with a green stripe, wired together, and closest to the radiator. The two red are for the FSS, and the yellow one is to the idle advance, yeah?

I'm chasing down a gnarly case of air intrusion in my fuel system* Started the truck up this afternoon after getting it primed again the day before, surged and died. Been cranking through 2 battery charges now, still can't get 'er primed.

* It's a total mystery. While the truck is running stationary, I can't find the leak. Nothing from the injectors, the fuel filter, feed to the fuel filter, input or output on the electric fuel pump I've had installed for ~3 years. When I drive, I can see a line of fuel dripping on the ground, the engine bay from the belts to the bellhousing gets soaked in diesel. Leaks when it's parked. Can't figure out where it's coming from, it's dripping from somewhere I don't have visual access to.. Went from 15-16 mpg to 12.

 

[G. Mann]

Check the olive at the back of the engine on the return fuel line.. check for any dampness at any of the return caps or return fuel lines. Check for and dampness at the injector line connections.. either end..

If you have a stream of fuel when driving, you should get a stream of fuel when parked and running at higher RPM .. I think..

If you are losing prime to the IP.. I'm betting you have a cracked injector line that is losing fuel while running, and leaking down prime when parked. Time to get some Gunk Foamy Engine Brite cleaner.. spray down the engine [seal up the intake] and wash the hell out of it.. let it dry .. then look for the fuel wet spot..

 

[apt403]

I'll check out the olive tomorrow morning - Return caps are bone dry, I didn't think about the injectors where they come off the pump.. I'll add that to the check list, thanks.

I know, right? Truck off, electric fuel pump off - Leaks, can't find it. Pump on, truck off - doesn't leak. Truck running (rpm independent), stationary - doesn't leak. Truck moving - leaks.

 

[G. Mann]

Have a good look at the hard line that runs from driver side under the engine across to the passenger side.. to the fuel pump... you could have a crack or a rust hole in that line..

Where is your electric pump mounted? Is it mounted on the frame before that line? Or , is it mounted in the engine bay somewhere? Did you remove the mechanical pump completely and bypass it?

Which side of the truck is the stream of fuel coming out? Drivers or Pax?

 

[OLDBULL8]

Looked at all 8 posts of your's and didn't see what truck you have except that it's possible an 85. By putting your truck info in your signature, it gives us folks an idea of how to answer your questions. Thru the ~10 yrs these IDI's where built a few changes where made.

When I drive, I can see a line of fuel dripping on the ground, the engine bay from the belts to the bellhousing gets soaked in diesel.]

That would be an indication that there is a leak somewhere around the lift pump. How and where did you plumb the electric fuel pump in? Is the original lift pump still there?

 

[apt403]

Added truck to sig.

The electric pump is plumbed below the passenger side battery, maybe 8 inches above the frame - Roughly level with the vacuum pump. The stock lift pump has been removed as per:

http://www.oilburners.net/forums/sh...pump-with-a-Facet-Duralift-electric-fuel-pump

Except I used a Facet Posi-Flow.

So far I've got the following on my list to check out today at lunch:

- Metal return line
- Injector lines coming out the DB2
- Rubber hose leading to the input side of the fuel pump, where it's plumbed into the stock fuel line from the tank
- Metal fuel lines from front and rear tanks.

Still need to figure out what's going on with the DB2, as well. The Red/Red Green stripe combo connector is power to the FSS, right?

I'm thinking it's something before the injection pump - The fuel filter drains, that's why the truck died - The filter was probably half empty. I replaced the stock fuel filter housing that features the notorious fuel heater/water separator that weeps around the o-rings with an older version that lacks that feature, so I doubt the fuel filter assembly is the issue.

Thanks for the replies so far, guys.

 

[sjwelds]

Except I used a Facet Posi-Flow.

Side note: (copied and pasted from Facet's website, on the "posi-flow" page)

"For best results, mount the pump close to the fluid or fuel tank and below the liquid level."

From what it sounds like, the pump and the location it is mounted may not agree with each other....

JM2CW

Not sure if it would affect your current issue, but maybe something to keep in mind

 

[apt403]

I was a little concerned with the pump location when I was planning things out, but it's far enough below the fuel tank that there's a decent amount of gravity feed going on - Not to thrilled to admit that I probably dumped 3/4 gallon of diesel on myself before getting the line pinched off.. Kinda did that one bassakwards.

If and when this pump dumps on me, I'd like to move over to a Duralift and plumb a big filter before it - My adventures in WMO and WVO tell me that even with centrifugal filtering, it's not a bad idea to have a couple more in-line, assuming I can keep the fuel pressure and flow up.

 

[OLDBULL8]

Electric fuel pumps are made to push, not suck fuel for the most part. Duralift pumps used on ****** trucks/trailers by law have to be up at the engine that drives the refrig unit.
When you said the belts and so forth are covered with fuel, I'll bet where you have the pump mounted is the place your fuel is leaking.

Your IP won't be the problem, pic below for connections. Why are you concerned about the wiring?

 

[apt403]

Your IP won't be the problem, pic below for connections. Why are you concerned about the wiring?

Thanks for the pic. I'm having trouble getting fuel to the IP - Whenever I've lost prime before, I bleed the air out of the fuel filter, crank the starter for about 15 seconds, let it cool, crank again for 15 seconds, let it cool, hit the glow plugs and I'm off and running. I've killed the batteries twice now trying to get fuel back to the injectors. My first thought was the FSS, needed a sanity check on whether I was getting power to the right terminal.