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!

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