engine and drivetrain Recipe For Sorting Out Fuel Delivery Problems in a Tii

[thehackmechanic]

I posted this as a comment in the For Sale section on someone's newly-bought $3500 tii that ran for a while, then acted like it was running out of gas. I thought I'd enshrine it here in the main forum.

 

Having recently sorted out three tiis that had sat for varying lengths of time, this is now the recipe I would advise for either sorting out a fuel delivery problem or resurrecting a long-dormant tii. I just did it with Old Blue, the '73tii I just bought that had been sitting for ten years.

 

--Pull the pickup tube from the gas tank.

--If, as soon as you open the tank up, it smells like varnish, you already know that you're going to need to systematically clean everything -- at a bare minimum, you'll need to drain the old gas and blow out all the lines.

--Inspect the screen at the base of the pickup tube.

--Verify that both the outflow and return lines on the pickup tube aren't clogged (I've just seen three tiis with this problem). Ream then out with a coathanger and compressed air.

--Shine a flashlight in the gas tank and make sure it's not full of rust or sediment. I've seen them look like pot roast. If it's bad, pull the gas tank and clean it. At a minimum, pressure wash it, dry it,  put it back in, and refill it with five gallons of clean gas.

--Pull the fuel pump and inspect the conical screen at the inlet. It may be clogged or completely missing. 

--If the fuel filter inlet screen is missing, tap the inlet side out onto a paper towel. If rust and sediment come out, I'd recommend you replace the fuel pump.

--Disconnect the fuel filter to the left side of the radiator.

--With the fuel pump and fuel filter disconnected, blow the main fuel line out with compressed air into a bottle to catch what comes out. Inspect it. If there's massive amount of rust, blow brake cleaner into it and repeat until the rust is no longer visible when blown into a clean rag.

--Undo the return line from the back of the Kugelfisher pump.

--Do the same blowing out of the return line.

--Remove the pressure valve from the back of the Kugelfisher pump and visually inspect it, looking through it against a bright light. There should be a pinhole of light visible. If there's not, clean it with brake cleaner until there is.

--Pull the banjo bolt out of the front of the Kugelfisher pump and inspect the barrel-shaped screen inside it. I've spent hours removing and cleaning them.

--As said above, if the fuel smells like varnish, you really should blow out the plastic injection lines with compressed air, and pull the injectors and have them cleaned and tested.

--Reassemble everything, preferably replacing every fuel hose -- or at least every fuel hose that is too soft or rock-hard -- with OEM.

--Put a fuel pressure gauge just before the Kugelfisher pump. Turn on the ignition to run the fuel pump. It should read 29psi. 

--Inspect every part of the fuel delivery system for leaks.

--Try to start the car. Look in the throttle body at the cold start injector. If no fuel is being squirted, you'll have to troubleshoot the thermo time switch, or simply wire the cold start injector temporarily to the battery, or semi-permanently via a switch.

--Start the car. Inspect the plastic injection lines carefully for leaks, both at the base of the lines at the Kugelfisher pump as well as in the lines themselves (they do crack with age). 

--Look in the throttle body at the cold start injector to make sure it's not leaking.

 

If the car still doesn't run right, follow the procedure in the "BMW 2002 Tii Injection Manual" to the letter to isolate the problem to the delivery valves, the suction valves, or the injectors. Add to that the information in my article about pulling the head off the Kugelfisher pump. Don't pull the head if you don't need do, but that article (and other posts) tell about removing the delivery and suction valves and verifying, using a small wooden dowel, that the plungers ("pistons") inside the Kugelfisher pump's head aren't stuck and are free to move up and down. But worry about the injectors first. Old varnished fuel MAY sit in the Kfish pump head, but it DEFINITELY will sit in the injectors.

 

--Rob

This post has been promoted to an article Edited October 7, 2015 by thehackmechanic

[PaulTWinterton]

Thanks for the post Rob.   One thing I learned -

 

  "Remove the pressure valve from the back of the Kugelfisher pump and visually inspect it, looking through it against a bright light. There should be a pinhole of light visible. If there's not, clean it with brake cleaner until there is."

 

Although my engine runs well, I've always wondered if that valve is working properly, as I never had a test or instructions to verify.    Visual test is good enough for me.     Thanks.

Edited October 5, 2015 by PaulTWinterton

[ray_]

Rob, I think you should add that in the Tutorial section.

 

Cheers,

[thehackmechanic]

That's other Rob, not me Rob, right? :^)

[Redtail]

Rob, I think you should add that in the Tutorial section.

 

Cheers,

I agree, great info and worth saving!

[thehackmechanic]

Sorry, couldn't resist

[jgerock]

Sorry, couldn't resist

Unless it has been bastardized and converted to a carb..Wonder who ended up getting this early 72tii.