Distributor knocking?

In the quest to run 87 octane in my '96 without pinging (and yes, I saw the flash ECU thread), I replaced my fuel injectors today with some from an LS1. They've been sitting on my shelf for this purpose for at least 2 or 3 years, so I don't remember the details ... however I am certain at the time that I did extensive calculations and arrived at the conclusion that these injectors would be suitable (5-10% richer) replacements.

After replacing the injectors I fired up the jeep, and it started right away. Idle seemed maybe a little rough so I revved it a couple times and all seemed well. I was kind of expecting massive backfiring or an engine fire given my luck, so this is pretty cool.

I go to close the hood and head to the gas station to fill the tank so I can get an idea of mpg with the new injectors - when I hear a light knocking noise. Uh oh. I start picturing my valvetrain disintegrating or worse ...

but when I trace the sound to the passenger side of the engine block, I feel nothing when touching the block. I look carefully (using my flashlight as it's night now), and the distributor cap appears to be vibrating. I touch the side of the cap, and it is very clearly vibrating in time with the knocking noise.

Is it time to replace the distributor, or do I need to do further investigation to make sure it isn't something else?

I also changed the oil today (and only got 4.5 quarts back out of the engine), and have been getting belt squeal on startup (ran out of daylight before I could change the belt).

Not that either of those things or the new injectors should affect the distributor, but thought I would throw that all out there in case someone sees a connection that I don't.

Pisser that NAPA isn't open on Sunday. Anyone know how autozone's distributors stack up?

New injectors will not help with 87 octaine either, only flashing your ECM will help because it's a timing issue and the ECU controls the timing.

Well, I'll find out firsthand and let you know, as long as the whole thing doesn't crap out on me first

It's probably worth mentioning, with regard to various internals going bad, that about two weeks ago I held the engine at 5k rpm for about 2-3 minutes with the tranny in neutral while I was blowing out some seafoam.

At the time I really didn't think it would cause any problems ...

lilredwagn said:

At the time I really didn't think it would cause any problems ...

Click to expand...

Famous last words!

Sounds like one of the ears on the oil pump may have snapped off, causing the bottom of the dizzy to run out of true. Pluck the distributor and check for problems, sounds like an oil pan R&R is in your near future...

Two things,1 the dist has play in the shaft and the rotor is hitting the contacts in the cap.
2-The cap is loose,
Have replaced distributors in a 96 and 98 because of this problem(shaft).Have a Autozone rebuilt to put in a 87 because the internals disentergrated in the original unit. I hope they are a good unit.
Wayne

Get a factory distributor!!

The rebuilt one I checked out from Napa had lots of obvious wear, and a used sensor.

Pick one up from the dealer, you get a brand new distributor, brand new sensor, and even a new cap and rotor.

Thanks for the help so far.

I have determined:
-It is not a loose cap or rotor

-The oil pump fitting appears to have both ears intact. I wiggled it a couple times with a screwdriver and it turned freely with no obvious separation.

-The distributor has minor play in the shaft. Unfortunately I don't have a mic, but I would estimate vertical play <1/64" and horizontal play less than that (maybe 1/100 travel at the end of the rotor). The play may decrease more when it is installed.

-There is wear on the pump end of the shaft. I have no idea if it is all recent, or if it is cumulative over 100k miles. While the wear may be indicative of a problem elsewhere, I don't *think* that this sort of wear would cause the knocking.

So what do you guys think?

pics of the wear(click for larger image):

What do the contacts look like in the cap.If they have been hit then there is too much play in the shaft.
Wayne

Wayne Sihler said:

What do the contacts look like in the cap.If they have been hit then there is too much play in the shaft.
Wayne

Click to expand...

Definitely not too much play then. The only silver showing inside the cap is on the center button. A fair amount of crust on the contacts, but no strikes.

Here's the fine how do you do: I put the distributor back in and was reinstalling the electric fan when I noticed the idler pulley bolt was almost walked completely out of it's threads. Tightened that back up...
Fired it up, went to listen .. the only knocking is the ticking of the injectors. They are noisier than stock - clearly audible ...

I'll feel like a total dummy if that's what I was hearing last night (and I remember it being louder), but for the sake of my engine I hope that's what it was.

I am unable to feel the knock in the distributor cap now, so I will also hope that was a result of the pulley (though that seems ridiculous).

For anyone wondering, the part number on the LS1 injectors is 12555894

They have 4 flow holes in the pintle as opposed to the Jeep's 1, and the spray pattern is taller (closer to the Jeep cylinder dimensions) than the typical Ford Mustang injectors that everyone likes. Once you do the calculations adjusting for the flow ratings at specced pressure, they come out closer to stock jeep than the fomoco's too.

I picked up a set of 8 on ebay that were pulled from an engine with less than 10k miles for $80 - from lingenfelter, actually. Everything was in great shape and clean, but I picked up some new o-rings (jeep ones worked fine) just to be safe.

The stock injectors with 100k miles on them had some gunk around the pintle, but the actual head was as clean as my new ones, so any improvements will probably be from spray pattern or flow, rather than because they are newer/cleaner




Thanks for the help... I'll post back results of the injectors. And of course if anything else goes wrong