Injection Pump Question

[kentuckycucv]

My truck has surging and air in the return line. It stalls (gets air in system) while driving. Bypassed fuel filter. installed electric pump.
I had a trail of fuel to my truck across a parking lot. THE TRUCK WAS NORMAL HOT, BEEN DRIVING... The next morning it started but no fuel leak.

Question 1. Does the Throttle shaft seals allow air to be sucked into the pump?
2. will they leak when HOT/ or IP leak when hot?
3. Can I replace the O rings with my harbor freight O ring set?

 

[cucvrus]

At the risk of being a wise guy. I do not see how the injection pump throttle shaft seals could leak so badly that it would leave a fuel trail in the parking lot. And with the new improved electric fuel pump pushing pressure to the pump it would not be sucking air at the injection pump. It would possibly be forcing fuel out thru the throttle shaft seals when the key was turned on. That I doubt. I have seen metal fuel lines that are rust free and have a chaff hole worn thru them. The best bet is to remove the fuel line at the rear of the electric pump and try to vacuum or pressurize the fuel feed line and the fuel return line. And then go from there. This is a simple case of a broken line/ loose clamp be it rubber or steel. Air is getting in somewhere as you already know. If it is coming out and leaving fuel trail on the ground it should be easy to find. Do not plan on attending any social functions for the next day or 2 as you search for the fuel leak. Replace the rubber hoses that are in the entire fuel system. Unless Old spice diesel fuel is what you use for after shave you will need to scrub yourself real well when finished with this job. Old clothes that you can throw away are my recommendation for this task.

 

[richingalveston]

I have read post here that a leak on the fuel line at the IP and the IP itself can leak which will puddle on you intake manifold and only run to the ground when the truck is at the right angle so a small leak looks like a large one for a short period of time and also seams intermittent. I believe if you are leaking at the IP and it is not the fuel line then a rebuild is in order.

Your signature says you are running WVO so I would think your fuel may only run down the engine when hot and puddle heavily when cold thus your leak shows up more when it is hot.

clean the Intake manifold under the air cleaner. Put a rag in there and run the motor to see if fuel is building up at that location. If it is in the fuel line, start at the top and work down. It is cleaner at the top and you may find it before you get real dirty.

 

[Chaski]

1) Yes, where fuel leaks out, air can leak in.
2) Yes, but I think it is more normal for them to leak when cold.
3) No, they are viton, and complete rebuild kits can be found for less than $30.00.

Also keep it in mind if you pull the throttle shaft to replace the seal it is critical to make a jig to clock the advance cam to the exact same position it was originally in. The cheap way to do it is with some kneadable epoxy. Just mix up a ball and press it against the flat part of the advance cam and push it onto the cross pin that is in the throttle shaft. Don't encapsulate anything, you want to be able to easily remove it when it is hard. The point of the epoxy casting is to make a tool to align the cam with the crosspin. There is a tool made for this, but it isn't worth buying for one use. Make the epoxy allignment tool before you loosten or touch the advance cam.

 

[kentuckycucv]

another question. There is a fuel port by the passanger rear tire. I think it is for an arctic heater. Can I run a new fuel line from there so I don't have to drop my tank and replace the rubber fuel hose on top? does that line have a sock?

 

[cucvrus]

That will not draw to the bottom of the tank. I believe it will only draw till a 1/4 of the tank and run out. It does not have a sock on the end. Just remove the tank. It is simple. And then you can replace the 30 year old rubber hoses and clean up under the tank and refinish the tank and skid plate. Do not reuse the bolts. Put new 3/8" bolts on the skid plate and 7/16" nuts on the tank straps. You can even buy new tank straps at Auto zone if you need them. Do the job right the first time it pays in the long run.