Questions re: MFI pump timing

[lopena]

My MFI pump timing is out by just a smidgen…with the crankshaft at F-E mark, the timing notch on the pump pulley is about 1/8” ahead of the notch on the pump housing.

Adjusting the drive belt by one cog is way too much so I’ll have to loosen the three allen screws on the pulley and make a very small adjustment. My questions:

1) is 1/8” close enough? Should I just leave it alone?

2) if I should fine-tune the pump timing and line up the timing marks perfectly, can I do this with the pump in situ? Removing the MFI pump is doable but a complete PITA, as you know.

Thanks for your help!
Alan
N.J.

[Richy]

It is definitely possible to adjust the pulley with the pump in place . Is 1/8 inch ok ? probably , but you may notice a difference if you change it .

[Jeff Higgins]

It might be easier to re-clock the drive pulley on the camshaft. There are four mounting holes, but only two are used. You will notice that the two sets of holes are not clocked at 90 degrees to one another. If you take that pulley off and re-mount it with the other two holes, it moves the pulley about half a belt tooth's worth. That might get you close enough, or at least closer, and it's a whole lot less work.

[Richy]

I don't think removing and reinstalling the left front eng. tin for pulley access is a whole lot less work . You need a 5mm Allen wrench or socket and a 19 mm combination wrench to adjust the pump pulley .

[Jeff Higgins]

Access is the issue. It's much, much easier to get to that lower pulley and to see what you are doing.

Remove the left rear wheel, the throttle rod from the tranny bellcrank to the pump (it goes through a slot in the piece of tin that needs to be removed), and the piece of tin that covers the belt. There are only two screws that hold that piece of tin in place on its outboard end, the inboard end is held in place with a little tab that engages the right hand tin. I've done this many times to both replace drive belts and to replace leaky seals on the end of the camshaft. I even installed a Speedi-Sleeve on one, right there in the car. It takes less than five minutes to jack up the car, remove the wheel, then the throttle rod and tin. Easy peasy.

[gled49]

I’ve adjusted a lot of MFI systems, and never found a tooth one way or the other out of adjustment made a performance difference. Not apples and apples comparisons, but race pumps are advanced some 50* to 14* BTDCO, from 40*’s after. I’ve also worked on cars that were 180* out, but still ran and not horribly.

[lopena]

Thanks, guys, for all of the helpful suggestions…it’s much appreciated.

Turns out, I had to remove the MFI pump anyway to address another issue with the oil input line (the threads are stripped on the magnesium pump body). After I fix the thread problem I’ll goose the pulley back 1/8” and should be spot-on (even if it doesn’t make a significant difference).

I’ll keep you posted.

Thanks,
Alan
N.J.

[Bridgeguy]

Maybe useful for later readers since the OP is in disassembly:

Got a timing light? Using a mirror, see what it is at idle with lead clamped to cylinder 4. Roland Kunz, a long passed (RIP) German tech from the 60-70s claimed they always double checked them in this way. Perhaps your would be closer to the mark when running.

[lopena]

Many thanks, Bridgeguy!

I’ll give the timing light protocol a try once I have everything buttoned up.

Alan
N.J.