The Summer (Autumn, Winter, Whatever) of Ven: Fuel Return Line and Glow Plug Surgery on an IDI Turbo Diesel

This is the last of a three part series about retrofitting an electric fuel pump and frame-mounted fuel filter onto my 1985 6.9 liter IDI turbodiesel spool bus. Last post, I got everything wrapped up and operational from the fuel system end, but discovered that the steady 10PSI feed pressure was now causing a whole bunch of the injector return fittings to leak!

Go figure, as part of the problem is the o-rings that seal them become crispy. I actually drove for a while like this to make sure everything was operational when it came to the fuel system. However, by the late November into December timeframe, the leaking was getting steadily worse, and I really had to address it.

What it did show is that the electric fuel pump will help extend the time horizon of having to deal with all your fuel line fittings on one of these things. I could leave the key in the “on” position after it sits a few days and hear the bubbling and gurgling coming from the lines for the first few seconds. What the e-pump does is keep the inlet end of the injection pump primed, so it can at least light off quickly. Then you can usually inertia through any further problems.

But that’s no way to live, so before it got cold, I was out to correct the problems and also repair the glow plug circuit – up to this point, I was still monkey-starting it with a little shot of ether.

The downside to all this? I have to go back in there. UGH.

Off the cover comes! By now I’m well used to digging around under here, so the crankcase vent value, intake hose, and some other hoses actually went away quickly. I made sure to leave the hose clamp screws in accessible positions last time since I knew this would be inevitable.

A 5/8″ regular wrench (I guess you could use a 5/8 flare nut wrench if you wanted) releases the injector line fittings. They pull up slightly, and then the plastic return caps come off, leaving O-rings behind.

So here’s the story on these “return lines” and why they’re nightmares besides being hidden in a cave. The only thing sealing the fuel being returned to the tank are those O-rings. They’ll get old and crispy, and with the fuel system under vacuum due to the engine and filter being higher than the banks, they’ll start letting air in to drain out the fuel system slowly. Then you have a bad time.

Dunno why anyone thought a series of handmade rubber hoses with plastic caps was a good decision here (seriously, they definitely had to build each of these by hand on a stand). Maybe a single molded plastic or cast metal “rail” was considered but ended up being too costly. Maybe secondary compression/flare fittings were considered too underserviceable.

Whatever the case, just grab a return line kit from Accurate Diesel and use the existing line lengths as a guide. I’m being a little dishonest with these photos – I did the same operation for Murdervan a few months prior, but haven’t written anything else about it because it ended up being just quite functional and as you recall, I ended up selling it in early September.

I learned from that time to cut the hoses very slightly short, like 1/16″ short. It’s easy to pull them a little outwards from the fittings to get the line of them to sit straight. The spring clamps grab a fair bit of width, so I wasn’t concerned about having enough seated over the push fittings to seal.

Otherwise, if the hose is curved between them, looking like an S or snake shape installed, it’s exerting a pressure towards one side which could cause premature hardening/deformation of the O-ring over (let’s face it, a long) time.

Because Spool Bus has the aftermarket turbo system, the return lines are set up differently than OEM with the crossover line occurring at the front of the engine and the “master drain” at the very back of the driver’s side. I needed more of the 180 degree straight-through fittings than provided, so I ended up recycling in some of the old ones.

There’s nothing wrong with them, mind you. I cleaned them up and inspected them for cracks or chipping. The only thing that causes pressure sealing loss is the O-rings, which disintegrated as I was picking them off the injectors.

After crafting the two sides and the “reacharound hose” to connect the two, the installation involves lubing up the O-rings (I used some plain lithium grease; any petroleum grease will dissolve in the fuel bath to come), shoving them on, then seating the return line caps over them.

I used a remote hose clamp grabberator to maneuver the clamp into position on the Reacharound Hose, which is at the very front of this arrangement behind the A/C compressor – not super tight here, just awkward and out of sight. Remember what I’ve said about working on vans being Nightmare Mode Wrenching – you need to be comfortable with wrenching by feel and estimating positions.

I was expecting the turbo side to be impossible to access, but actually it wasn’t at all. I did undo the mounting bracket of the turbo itself to let it shift an inch or so to get better wrench clearance.

The injector train and Reacharound Hose connection on this side is actually easier reached from the front side behind the alternator, with an approach from the centerline (i.e. right in front of the grille). If the turbo wasn’t there, it would be an easy reach from the interior.

All return lines now installed and fully seated. I let the system fully prime and sit for a while with the fuel pump running to make sure nothing was coming out.

The next weekend, I was out to change the glow plugs, so I can continue building this thing up to turnkey operation (instead of, you know, Pop-the-hood-puff-the-ether-close-hood-open-door-get-in-then-turnkey operation). Another order from Accurate Diesel for their IDI 6.9 glow plug kit was on the way so that means….

Taking the fucking thing apart again.

I had ascertained from testing the circuit that at most one of these were still working. They’re positive temperature coefficient resistive heaters, so they start out drawing a burst of high current and very quickly settle down. I got the entire glow plug harness to draw only about 20 amps, when it should be 200 to 300 amps.

Before I started, I used alternating blasts of shop air and brake cleaner to really clean out the wells they sit in. Spool Bus had accumulated a lot of wildlife in its years of sitting wherever, and I did not want any grunge getting into the open glow plug holes once I removed them.

These dudes are one of the “middle difficulty setting” service items in an Econoline IDI engine setup. They stick out and can be grabbed with a 3/8″ deep-well socket on a swivel. But you do need to wiggle it through the injection lines and rely some on proprioception to land the socket. Loosening the clamps for the injection lines helps them be able to wiggle a bit to get you some more space. Notice in the photo I also swiveled the Diesel Delivery Dongle out of the way to get at the front two on the driver’s side.

For some reason, the passenger side is actually easier again, probably because they are displaced towards you instead of away. I used one longer extension to get around the turbo outlet pipe.

Now, installing them again is definitely a “By Feel” exercise. I started with putting some copper antiseize grease on the threads (In case I had to do this again…. or someone else) and started the thread manually. If everything’s clean, you can thread all the way up to when it stops by hand, then tighten with the socket handle.

I decided to connect them up one at a time and measure the increase in current draw. Each plug will add about 20 to 30 amps at the start and taper down to ~7-9 amps each, after which they should be cut off from power to prevent damage. I suspect a failed glow plug controller, apparently a known defect in this generation of the engine, caused them to burn out.

A shot after all 8 were hooked up. The current momentarily bursts up to 280A and falls rapidly to about 100 over the course of 10 or so seconds. Obviously, taking a picture of this was hard.

With this complete, I know that the glow plug contactor was working fine – since I’ve been throwing it with an alligator clip touched to the battery – and all the heavy wiring leading to it. What was not working was the glow plug controller. I obviously couldn’t tell exactly why not, because….

Yeah, uh, this is going to be a problem for another day. My upcoming mission was to tear out this Wiring Teratoma as I called it and just start from scratch after reaching the OEM layer.

For now, I just rigged up a switch as usual so I could activate the glow plug contactor by hand, count to 10, and let go. Spool Bus then starts with a single key bump, so all is good up to whatever has happened to the control wiring for the OEM glow plug control module!

The Summer of Ven: Reassembling the IDI Electric Fuel Pump System

Last time I ripped most of the OEM fuel system out of the engine cave on Spool Bus, and received the parts needed to fabricate the new fuel system. So here’s where I get to put it all back together!

First things first, the new Facet e-pump itself has to be mounted. I chose to put it on the frame, right next to the filter head that some previous owner added. If you wanted something comprehensive, it seems like the R&D frame-mounted filter and pump kit is the go-to. But I already had the hard part done for me, so might as well use it!

And here it is all mounted up. At this point the fittings were just threaded in for visual effect – after I installed everything I realized some of them had to change.

So here’s what’s going on now with the plumbing. The long arc at the top is the inlet coming from the fuel tank selector valve. The fuel gathers at the clear strainer (so I can see how much poo is in it) and is sent to the filter head, then from there, to the rest of the fuel system.

This is what it looks like on the inside. It passes through the frame at two pre-existing holes – I suspect the filter head location was chosen by a P/O for this convenience. For completion’s sake it needs a plastic grommet here at the holes, which I ordered but wasn’t here yet (BURNOUTS NOW, GOOD IDEAS LATER)

With the system plumbed up to the filter outlet, time to test everything and give it its first powered break-in!

The magic van juice flows. The Facet pump makes a pretty loud clicking sound as it’s operating, possibly indicative of it being a vane type pump instead of a small centrifugal or axial flow turbine like most in-tank pumps that make a more whirring or buzzing sound.

I had this setup hilariously looping back on itself (hose back into the fuel tank) for about 5 minutes or so to break the pump in.

The remaining plumbing steps were all engine-side. I needed to cut the existing injection pump feeder line that went to the OEM filter housing and turn it into a fitting I could attach to the fuel hose, then add a return system.

Getting to the injection pump inlet fitting was, how should we say, unpleasant. Again, no overhead view, so this was done with a phone camera inspection video and then by feel. First, I had to remove the intake plenum thing to get access to the injection pump’s backside, which was an easy enough operation (though I had to loose and shift, but not remove, the turbo). There’s only space to turn the wrench 1 hexagon side at a time.

And here it is, the original filter to injection pump line.

I used a tube flaring tool from Harbor Freight to cut, then form, then put a gentle flare onto the end of the rigid line. It’s supposed to stick up just a little out of the center valley so I can slide the rubber fuel hose over it.

If taking the fitting off was a lengthy video game side quest, then re-mounting it was some kind of next level miniboss that didn’t even drop goodies. I had to do most of the initial mating and threading by hand.

The updated feeder line terminates in this photo just under the rubber vacuum hose to the right.

Here’s a new front-towards-back view of the now much more spacious engine cave.

The original fuel feeder line coming from the selector valve was wrapped around under the front of the engine, rising upwards on its forward passenger side face. I gently bent the rigid line where it began on the frame to point towards the back of the engine. Again, slightly badly lit photo, but you can see the “Nipple to Nowhere” pointing downwards in the center, which is where I’ll attach the new fuel line.

While doing this, even more parts had been arriving. A new expandable intake hose, for one, but more importantly, I received the electric solenoid valve and fittings for making a device I nicknamed the Dongle of Diesel Distribution:

So here’s what’s going on. The DDD takes in fuel from the pump/filter on the bottom left fitting. The electric solenoid is connected vertically above it, in order to give a high point for air to collect. It then does a U-turn while touching a pressure sensor, and the injector pump hooks in on the rightmost fitting. The top “exhaust” fitting will be routed into the fuel return lines.

I decided it’ll mount right here, at the studs where the former OEM filter housing was located.

I decided to get silly and design up a snail-shaped mount to be 3D printed. Bent piece of sheet metal? Sure, why not. But that wasn’t extra.

Whatever, it’s a snail if you squint hard enough.

It’ll be made on one of my Markforged machines from their carbon fiber nylon composite material, Onyx. My favorite vegetable for making dishes as diverse as entire beetleweights to welding fixtures to …. stuff like this.

I actually modeled this up and had it running on the printer while I was doing the plumbing work that night, so it was ready by the morning!

The finished snail bracket assembly! The only place to “mount” this so to speak was using the solenoid valve’s mounting holes.

I grab one of the studs of the former OEM filter mount to locate this thing, and also function as a ground point for the solenoid valve.

Am I confident that the print will survive underhood temperatures? Absolutely. Hell, just about everything in a new car is made of fiber-filled Nylon of some sort… to my chagrin.

Time to do some final plumbing. I’ve linked up the injection pump (hose labeled -> IP ->) and the feeder line, and the free hanging one will be the return vent line.

For fuel pump power, I fished up a long 16 gauge wire following existing brake lines to meet the repurposed fuel heater power drop.

Here’s what’s going on underneath. The orange and black bundle going off to the right is the fuel pump power.

The DDD purge solenoid is grounded on the OEM filter mount stud and I ran a purple wire up and over the engine cave (note the orange and purple wires in the wiring tray at the top) to meet the solenoid wire.

I connected the solenoid wire to a 12V access point at the Centurion-supplied fuse block. Then I pulled the doubled-up wire into the cabin via the same terrible, un-insulated, un-grommeted hole everyone else has been using (“Not the better redneck, just the most recent”) and the cut the doubled up loop. Now I just need to connect the ends to a switch to enable the solenoid.

A photo of the Wiring Teratoma now with my own additions (blue overdrive connection, purple purge solenoid….)

I found a button switch in one of my Collections and decided to just position it above the fuel selector switch. It’s a momentary button, so if I ever do some kind of service on the fuel system that empties it out, I’d just key ON (not start) and hold the button a few seconds to let the system quickly prime.

To be fair, once you have an e-pump, it will eventually shove all the air out of the system anyway, save for any air that might be trapped in the injection lines themselves which will need to be individually bled at the injector (no thanks) or cycled out through brute force.

On the reassembly path some more! Here’s the back side of the intake reassembled with the new extend-o-hose, now free to run diagonally across the engine cave without tripping on ANYTHING.

The “Cold” “Air” “Intake” is now back in place as well. That’s really all there is to it for this install.

And now we’re ready to fire back up. Verdict? Well, it works the way it’s supposed to. If I push the purge button, fuel begins blasting out of the return tee junction instead (oops, forgot to tighten that clamp). However, now that the system is being consistently pressurized to 10 PSI, I’m watching ALL of the injector return fittings spew diesel fuel every time the pump is running.

Welp. That’s what the next post in this series will cover: all the collateral damage, including repair of the return lines and fittings. While I waited on these parts, I also decided to get new glow plugs and repair that circuit.