More MFI maintenance notes: pump, belt and oil feed

[304065]

I recently had my MFI pump rebuilt by Gus Pfister at Pacific Fuel Injection. I thought I would transcribe a few mental notes.

Disclaimer: be careful working with gasoline, it is highly toxic and can kill you. Work outside in a well-ventilated area.

Removing the old pump is straightforward. Remove the paper thermostat hose, then remove the injection lines at both ends. Don't try to jam the pump in there with the injection lines connected at the injectors, you wil just frustrate yourself. Remove the feed and return lines noting which goes where. Also remove the pump oil feed, this is a 14mm ATF fitting, and loosen the hose clamps for the return hose. Slide the return hose down the pipe on the breather about two inches to the right.

Remove the port-side stack.

Remove the pump. It holds about a quart of oil so be careful where it drips.

A note for Shaun: I don't recommend the RSR red top breather modification for any but the most die-hard race cars. The reason is, you must REMOVE THE MFI PUMP in order to change the oil, which you should do after every race (when you change the engine oil). Removing the pump is a VERY time-consuming activity. Having to do this every few thousand miles when an MFI car's oil should be changed due to fuel contamination is asking for torture. If you insist, send the pump to Gus or Henry.

Next, the trick is to get the new pump on and the belt aligned. If you have changed the drive gear, note that it bolts to the pump drive shaft only one way, because there is a woodruff key. Three allen bolts allow the pump gears to be loosened to rotate relative to the center. Approximate a centered setting and tighten them down.

Start with the line on the drive gear lined up with the line on the pump. You should fill both lines with white-out so you can see them. You WILL need an inspection mirror for this operation, it can't be done without one.

You must set the engine at #1 TDC in OVERLAP. The best way to do this is with a whistle hooked to the compression tester hose. Turn the engine clockwise until you hear the whistle loudly, then fade away, and watch the distributor rotor point to the notch in the body: this is #1 TDC on the compression stroke. THEN rotate the engine another 360 degrees until the TDC mark comes up again. THEN go another 40 degrees until you see the FE mark, "Fuel-Einspritzung" or whatever. Don't move the crankshaft.

The trick is to slip the belt on without disturbing the alignment of the MFI pump drive pulley. Do NOT let the belt slip off the cam drive pulley, either. The FWM procedure calls for "remove left heat exhanger" as a first step to changing the belt. The prospect of breaking exhaust studs should deter you from changing the belt until it actually breaks, or unless the engine is out of the car. In any case, after a couple hours of wrestling with the pump, I found that the best solution was to place the pump on all four mounting studs and slip the drive belt over the pulley. Not easy to do, but certainly easier than trying to slip the belt on and then put the pump on the studs. Before you even think of putting the nuts on, check the alignment with the mirror.

If you don't have the crank set to FE 40 degrees after overlap TDC, the engine won't run. I know this because I had to remove the pump to reset the belt. I was doing some alternator work and couldn't turn the engine over by the crank pulley, so I put the car in gear and gently bumped it into position, wrong! (and not good for the engine, either, I know)

With the belt on, push the pump to the starboard side to tension the belt and tighten down the four 13mm ATF nuts. Reconnect the supply and return lines and the injection lines, these use a 17mm flare wrench.

Somebody suggested this could be done without removing the port-side stack. Impossible. However, the stack comes off in about five minutes. You need a 10mm socket with a universal and a long extension to reach the nuts. Do NOT drop them down inside the throttle body when the stack comes off. Don't forget to connect the oil supply and return hoses. The supply hose with the banjo fitting is prone to cracks, check it before you finish. I had to replace my (original) hose, a new one from Cohline is about $30. Don't forget the correct aluminum crush washers too. Finally, reconnect the paper thermostat hose.

That's all I can remember that was really important. Now that the new pump is installed I can get back to chasing CMA gremlins. . .

[Shaun @ Tru6]

Thank you for posting this John. If I tackle this job this summer, I'll post digitals as well. I just found out that I don't need to pull my exchangers (chasing an exhaust leak), so if I ever want to drive the car again, need to focus on getting it back together for the drive out the West Coast. Will check the condition of my current belt, which has been exposed to oil. We'll see. thanks again!

[Grady Clay]

John,

I just had to laugh through your post. Ben there, done that.

I recall my first attempt was on my (then new) engine dyno in about late ‘69. Much easier.

We should post images. Installing a new belt is something every MFI owner should be able to do in the “field”. Only once have I had to do this on a friend’s 911 alongside the road. A real PIA even when I knew what I was doing.

The key is to have these parts like NEW all the time.

Best,
Grady