Why can't I adjust my timing while my engine is running?

Tried searching, but even using my best google-fu doesn't help me when my only words are "IDI timing not running". LOTS of old threads. Some fun, it's cool to see how far we've come since 1999.

But no one ever says why, just that you shouldn't do it. How come?!

You shouldn't adjust the timing while running because the shaft spinning in the pump will cause the entire pump to move and slam against the mounting studs. This can cause the driveshaft in the pump to snap, making the pump not usable as a core at most pump shops....

@Thewespaul may have more insight, but that is what I have always heard.

Cuz when the bolts are loose the pump will slam over to the end of the adjustment slots, plus possibly break other stuff

Great to know! That makes sense, because the one guy I saw do it, had it turnbuckled over to the passenger side so he could adjust it while it was running. Don't know that I trust that enough to do it myself. Thanks for the explanation guys!

while I've got you guys here, have you ever seen timing marks like this? I know they are just a starting point and and should be adjusted from there, but the top one looks like barely a scribe Mark comma there's a much more heavily indented mark off to the driver's side, about 9:00 position looking towards the front of the truck. Does that side line mean anything?

Pump has been replaced no doubt. Mine has different marks because I replaced a couple of pumps but I know which marks are correct.

Another reason to not adjust the IP while it's running is because the gearhousing cover is very brittle. If you put too much strain or impact on that housing, it's very easy to crack it. They aren't easy to find for replacement.



I've seen a few that had hairline cracks up along the corners, and also some that have chips like this in the base. I can only imagine the stress on those rear studs if the IP had been quickly rotated to the maximum of the IP mounting slots.

The pump is that hard to turn when it's running? What sort of setup does the tester/setup machine use? It's must be a pretty large electric motor of some sort?

I know a guy who was never told this, and would always leave the nuts loose on the initial start after pump replacement. He would let it idle until warm and then set timing with a meter. Only made adjustments with the engine off, and then tightening upper nut until timing was correct, then tightening all three. On the initial start up and warm up, the nuts were loose.....saw it with my own eyes, and the pump really didnt move around at all.

I wouldnt do this, but he did it many, many times.....

On some timing belt driven engines like the old vw idi's and such, the pump can move with the engine running but the rubber belt also takes up a lot of the jarring/clash/zero tolerance for looseness, that a gear drive setup has.

Lot of torque at those gears.

One more reason to not try to adjust the timing when the engine's running. If the pump happens to lock up, you won't be able to hold whatever you are using to adjust the timing with. It will slam over to the side along with the pump. If you happen to have your head in the wrong place, it can put you in the hospital or maybe even kill you. I used to not be completely sold on that reason until I saw a pump lock up while the engine was running. All three nuts were tight and they didn't seem to slow down the movement of the pump at all as it slammed into the studs on the IP housing. This engine was running at an idle too.

IDIBRONCO said:

One more reason to not try to adjust the timing when the engine's running. If the pump happens to lock up, you won't be able to hold whatever you are using to adjust the timing with. It will slam over to the side along with the pump. If you happen to have your head in the wrong place, it can put you in the hospital or maybe even kill you. I used to not be completely sold on that reason until I saw a pump lock up while the engine was running. All three nuts were tight and they didn't seem to slow down the movement of the pump at all as it slammed into the studs on the IP housing. This engine was running at an idle too.

Click to expand...

Whoa. Not a good day.

franklin2 said:

The pump is that hard to turn when it's running? What sort of setup does the tester/setup machine use? It's must be a pretty large electric motor of some sort?

Click to expand...

So before I ever knew you weren't supposed to adjust with the engine running, I figured it was like a distributor and did my timing like that all the time. But in my case I would leave one nut tight and as the engine ran, hold the wrench in place, loosen nut with one hand then adjust with the other, tighten one nut, check timing, etc. It never tried to pull me over more than the injector lines already did, so I agree it doesn't seem to move all that much on it's own.

Not saying to do it...but I have been wondering the same thing myself quite a bit. Especially if you just barely loosen the nuts and used a turnbuckle or something. This hit-and-miss timing really ****** me off, as silly as it sounds. I'd much rather be able to get the timing I want the first time, every time, instead of taking 4 tries and 30 minutes while running the not-quiet IDI in my neighborhood at 2,000 rpm the whole time.

That said I haven't timed it loose since that original pump, over 10 years ago.

The_Josh_Bear said:

Whoa. Not a good day.

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That customer bought a reman engine from us, but he'd paid a lot of money and bought a lifetime guaranteed pump and injectors from Ford. It was his pump. That pump never did act right after the engine was running and it only lasted maybe 10 minutes. It suddenly gave out a loud squeal and then stopped, slamming to the side. I believe that the driveshaft broke since we could turn the input on the pump by hand and couldn't feel and clicking. He wasn't very happy to have to buy a pump from us to get home to have his replaced. I believe that his was from the local dealership instead of an actual offering from FoMoCo. We were in Salina, KS (about in the middle of the state) and he was from somewhere in Wyoming (IIRC) so there wasn't any running over to the dealership to get another pump.

I would think if you are going to "time it by ear" that having the pump barely loose would be they way to do it. Goosing the throttle and watching the tailpipe smoke while you are moving it a little bit.

There must be some other reason why it's said not to do it. I haven't seen a good reason listed yet. The pump locking up would be a very rare occurrence I would think, not caused by the pump being loose.