Hello,

My name is Mark and I've been coming here for a year or so reading the forums and have found them very useful. This is the first time I've posted.

I recently rebuilt my 7.3 in a '90 F-250 due to a lifter problem. I spent a whole lot of time and money to which I could never recoop should I decide to sell, but never plan to.

During the rebuild I opted to install a new injection pump and injectors which I found a very good deal on ebay. Rather than buying it through ebay I contacted the company directly. The person said that the numbers on the new pump may very slightly from the original numbers, but that this want be a problem. The injectors I received were not to my satisfaction so I purchased new stanadyne injectors from a local injection service shop.

The problem is, now that I've assembled and installed the motor There is a slight Knocking sound (similar to a spark knock in a gas motor) when I'm cruising at around 2000 rpm. I've pretty much ruled out a timing issue, as I set the timing with a snap-on diesel pulse meter and a snap-on digital timing light to 8 degrees before TDC. I've also played whith the timing advancing and retarding it to no success.

My question is does anyone know the difference if any between a Stanadyne L9-DB2831-4821 (Original Injection Pump) and a Stanadyne DB2831-4817 (New Injection Pump).

Any ideas or comments on this issue would be greatly appreciated.

 

Can you narrow down the noise to one particular cylinder by "shorting" the injector. This is done by loosening the nut on top of the injector fuel line and allowing the fuel to leak by the injector. The one that makes no difference is the culprit. Try moving that injector to another hole and see if it does the same thing. Did you install the crush washers when you installed the injectors? Also, was the injection pump rebuilt? for sure? Are all the lines on tight at the pump? I would imagine that by now you have all the air out of the fuel system. Hope this helps you out. Get back to us.

 

I do not know where you got the IP but that # is not recognized ........sure it's not a 4812 which would be for an 88-89.........

cut and paste

http://www.usdieselparts.com/pages.cfm?id=100&application=Ford&product=Injectio n%20Pumps&code=60

 

I double checked those injection pump #'s and there correct, the old pump is a 4821 and the new pump is a 4817.

The sound don't seem to be coming from one particular injector more like the sound a gas motor makes with low octane fuel.

 

what is the code letter stamped on the nut flat of the injectors.........

 

The code letter on the injectors is D

From the link above it appears that the correct injection pump is the 4821. I'm considering putting the old pump back on to see if it will correct the problem.

 

injector(s) "slobbering" will make a sound similar to low octane gas. Do you have the timing correct?

 

I replaced the injectors with brand new stanadyne injectors during rebuild. I set the timing with a diesel pulse adapter and digital timing light to 8 degrees before TDC. I've also played with it retarding and advancing it. Playing with the timing doesn't make any changes. So I'm leading to a fuel problem rather than a timing problem.

 

When you say "slobbering" your refering to the injectors leaking past the nozzle and not leaking by the return O-rings right?

I am having trouble with the # 2 injector leaking by the return O-rings. I've replaced the O-rings and it still has a very small seep.

 

No the slobbering is when the injector has a weak spring and lets fuel drip into the cylinder before enough pressure is developed to make a spray pattern. You might be hearing a lifter noise too. Or the noise is coming from the flex plate area of the trans and carrying thru the truck. The injector o ring is sometimes tuff to fix but should be able to get it done. I used to lube my plastic caps with stp or something like it before pushing them over the o rings. The noise, I dont know what to tell ya, can you get hold of a stethoscope and try to narrow it down. Perhaps the noise is still in the cylinder that caused the problem in the first place.

 

sounds like your getting air in your suction side,mine is doing the same thing,it started a few days ago.waynebo

 

I would fill both tanks full,see if thats not your problem.If that fixes it then your tank selector valve is bad and letting it suck air through the empty or low tank,waynebo