[1978 T/A]

Is is possible to not correctly install a cam eccentric? I tried to fire my car for the first time in almost a year on Friday, and it was dertermined that the arm on the RobbMb pump was not making contact with the eccentric. The eccentric is spinning correctly in the motor. And when I installed it, I had the engine builder look over everthing, and confirm it was right. I kept the stock eccentric, and the only thing that changed as a new pump.

So I am wondering if is is somehow installed improperly. I don't want to pull apart the front of the motor for something that might not even be wrong.



This is the only picture I can find of the eccentric during the motor assembly, and it looks to be correct.

[grivera]

Is it possible the locating tab on the eccentric broke and is allowing it to freewheel when it meets the resistance of the fuel pump arm?

[BVR421]

Pretty hard to do it wrong, 4 pieces, eccentric, rotator ring and a bolt and special washer.
As Rivera said, screwing up the tab is only a remote possibility, thats pretty obvious even if you never saw one before.
As far a stabbing the pump in I am completely unaware of any way to get the pump all the way on without having the arm correctly placed UNDER the eccentric ring. 1978TA, you do remember installing the eccentric in two pieces?, the eccentric and a close fitting slip cover that rotates freely?
Sorry Im as lost as you on this deal.

[Kenth]

Also different styles of eccentric.....

[1978 T/A]

I remember installing the eccentric and thinking there is no other way it can go on. The eccentric seems to sping as it should in the motor. I cranked it without the pump in and had my mechanic watch it and he said its spinning right. And I remember the sleeve going on the outside. If you look closely at the picture you can see the wear patter from the old pump arm.

Is it more likely that my RobbMc fuel pump arm is out of wack or they possibly sent me the wrong pump? I had it shipped to them that day. I'm just trying to make sense of this in the mean time.

[1978 T/A]

The pump also goes in with minimum effort if that makes a difference. I remember reinstalling a eccentric on a cutlass I replaced the timing chain and it was kind of a PITA to put the pump in.

[screamingchief]

I've seen them installed wrong so many times now,it's not even funny,so ask me if it can be installed wrong,and I'll tell you most certainly yes,they can be installed incorrectly.

And IMHO,that is probably one of the single most common pontiac "mistakes" folks make with these engines,especially if they are put together by a non-pontiac person.

The eccentric has to fit around the snout of the cam to allow the cam to be completely pulled into the cam gear and set the cam endplay by setting the clearance between the cam gear and the first cam journal relative to the thrust plate.

When done correctly,the cam snout will protrude past the face of the cam gear.

When done incorrectly,the cam usually only gets pulled "flush" to the face of the cam gear.

This is checked during assembly by measuring the cam endplay after it's all assembled.

There should be .003" to .007" or so endplay @ most,so almost no endplay to speak of,and anymore than that and it was assembled incorrectly and it's back to square one.

When assembled incorrectly there is often like 1/8" to 1/4" of endplay depending largely on just how much movement the chain & distributor gear allows.

And when assembled incorrectly,it's not @ all uncommon for the cam bolt work it's way loose and eventually fall out,have seen that happen a couple times too.

Other than not torqing the balancer bolt to it's full 160 lb/ft of torque,this is a very common pontiac mistake.

So unless your 100% certain you did all that,I'd be pulling it apart to check it.

As that can affect more than just the fuel pump operation,too much endplay is'nt good for the cam & lifters either,or the timing chain.

There are numerous threads about this on this forum,so a search should pull up a bunch more info,with specifics like how far the cam snout should be pulled past the face of the cam gear & such.

I seriously doubt there is anything wrong with that Robb Mc. fuel pump.

FWIW

Bret P.

[1978 T/A]

I know we didn't check clearances on those things. So if the eccentric is not installed properly, what exactly am I having to take apart again?

[1978 T/A]

I was looking through more pictures, and found one where the cam is being degreed and the snout of the cam is protruding from the cam gear.

My builder does not specialize in Pontiac motors, but he has been doing this for 20+ years and is extremely meticulous. He has done several Pontiac motors before with none coming back to him as well.

[East]

It would be nice if it worked out like the other post where the arm of the pump was accidently installed with the top of the arm not positioned correctly when the pump was bolted to the timing chain cover. He was told to check to make sure that the top of the arm met against the eccentric so that he could feel the spring tensionon the arm as he was drawing the pump up against the timing cover.

[1978 T/A]

Honestly that is what I am really hoping on. I am dreading the possibility of having to pull apart the motor again.


This is the picture I was speaking of.

[Brent Flynn]

try a stock pump of you have access to one, then you will know if its the pump or not... kinda looked like eccentric was off center of the timing gear in your first pic(as it should), but anything is possible... try stock pump... if that dont work, it doesnt take too long to get cover off, unless you have a radical serpantine system

[1978 T/A]

I don't have a stock pump, so I would have to buy one. I have been working on my car at a buddies shop, so I wouldn't even be able to mess with it till Monday. I should be hearing back from RobbMc on Wednesday when they recieve my old pump too.

[johnta1]

Take the pump out and re-install, making sure the arm goes under the eccentric.

If it still doesn't work right, then tear it down.

[BVR421]

Originally Posted by Brent Flynn

try a stock pump of you have access to one, then you will know if its the pump or not... kinda looked like eccentric was off center of the timing gear in your first pic(as it should), but anything is possible... try stock pump... if that dont work, it doesnt take too long to get cover off, unless you have a radical serpantine system

definition of eccentric
1.(of an axis, axle, etc.) not situated in the center.

[1978 T/A]

I took the pump out and reinstalled it twice. So I am thinking it is an error with the way the arm was mounted on the pump or an error on my part.

Hopefully it is just a part issue..

[johnta1]

Do you have a pic of the pump off?
Showing the arm?

[1978 T/A]

No, I wish I did snap one real quick though. I was so concerned about getting the pump out the day I didn't take a picture of it, or compare it with an original.

[6ragtop8]

The first thing I would do is match your pump arm with a stock Pontiac fuel pump arm. If you can find a local parts store that has a Pontiac V8 fuel pump on hand, I can't see why they would'nt let you look at the two side by side. If the arms are the same length, and shape, it is not your problem. Then you will have to tear it down. Just what I would do.

[1978 T/A]

I went ahead and ordered a factory fuel pump. I am going to try and install it tomorrow and see if it works. I am hoping on everthing that the fuel pump is the problem.

If I have to tear the front end apart again, what will I have to take apart to move the cam into the correct position. I know I will have to remove the water pump and timing cover. But will I have to remove the timing set or possibily more?