12 valve Cummins fuel line replacement. (Long post, go get a beer)
John Jacob
This weekend I took on the task of replacing the 5/16 return line as
described in TSB 18-06-98.
I wanted to describe the procedure to anyone that may be experiencing
this problem and is considering repairing it themselves. I replaced both
the supply 3/8" and return 5/16" fuel lines.
The symptom: Hard to start. Long cranking time.
There are 2 rubber sections of fuel line that connect steel lines from
the engine, to steel lines that run along the frame. These lines are
almost completely hidden. The rubber lines crack, allowing air to enter
the system. This displaces the fuel, allowing it to flow back into the
tank when the engine is not running.
Tools needed:
Small screwdriver.
Long screwdriver.
Long needle nose pliers.
Side cutters.
1/4 socket on a 1/4" drive ratchet.
9mm socket.
About 3 feet of 5/16 rubber fuel line.
About 2 feet 3/8 fuel line.
4 mini-clamps.
About 6 PVC cable ties.
Drain bucket.
Fuel filter.
Procedure:
Leave yourself about 5 hours for the job.
The fuel tank should be almost empty to avoid fuel running out of the
lines while disconnected.
To gain access to the fuel lines, you need to remove several things that
are in the way.
Drain and remove fuel filter. Save the water indicator/drain valve.
Remove the gasket along the edge of the firewall that seals to the hood.
Open the wire looming clips above the fuel relay.
Remove the 2 ganged together relays located above the fuel filter on the
firewall. These are secured with a single bolt.
Unplug the 2 relays by pressing in the release lever, then pulling off
the plug.
Open the vacuum line at the "T".
The vacuum line, along with the relay plugs may be tucked out of the way
behind the master cylinder.
Locate the 5/16" return fuel line. Reach under the intake manifold
behind the injector pump, just above the pre-filter. You should feel a
rubber line with a hose clamp. Loosed the clamp and slide it back from
the end. With a sharp knife, cut along the rubber lines about 2 inches.
The line should easily come off of the steel line. Do not try to pull
off the line without first cutting it, as you may damage the steel
injector line. This line passes through a support ring at the rear of
the engine.
Locate the 3/8" fuel supply line. Reach behind, near the top of the fuel
filter. Loosen the clamp, slide it down the line. Cut along the line
about 2", then remove it from the steel line.
Now comes the hard part.
The other ends of these rubber fuel lines are connected to rigid steel
lines that are clamped to the bell housing of the transmission. I could
not see the connections at all. I could not even feel them. From under
the truck, I could see the steel line holding clamps. The rigid steel
lines change to steel braided lines as they leave the mounting clamps,
and run to the frame.
There are several plastic clamps that must be removed that attach the
fuel gauge wires to the fuel lines.
While working under the truck, with a real long screwdriver, push the
rigid steel lines from under the spring steel hold down clamp. Be
careful not to damage the clamps. There are a total of 4 spring clamps.
You may need to push from the top also.
Once the lines are unclamped, they may be pulled down under the truck.
At this point, the lower clamps holding the rubber hose to the steel
lines may accessed and removed.
Using the old lines as a measure, cut 2 new lengths of rubber line.
While under the truck, install the new rubber lines and clamps. Route
the lines back up in place, carefully pressing the rigid steel lines
back under the spring steel clamps. Long needle nose pliers work well
squeezing the lines under the clamps. Replace the plastic wire looming
clamps holding the fuel gauge wires. I added several PVC cable ties here
to hold the entire bundle together.
Working under the hood, slide the 5/16" line through the holding ring at
the rear of the engine. Slide the hose clamp on the end of the 5/16"
hose, push the hose on the steel tube. Tighten.
Slide the hose clamp on the end of the 3/8" supply hose. Push the hose
on the steel line. Tighten. Now go back and check to see that the rigid
steel lines are completely under the spring clamp.
Install a new fuel filter with water drain valve in place. Connect water
sensor wires. Replace relays, insert plugs. Reconnect vacuum lines.
Replace hood gasket.
Open air bleed screw located on top of the fuel filter's forward line.
Crank engine for 30 seconds. Check for fuel exiting air bleed. Press
primer pump located under the fuel filter until all air is removed from
system. Tighten air bleed screw. The engine should start now.
Check for leaks. Check all clamps.
Carry back in all the tools you have been bringing out for the past 5
hours.
I hope this helps anyone contemplating this frustrating job.
John