Injection Pump, Degree of Throttle Movement

[Val]

I am in the process of tuning my 280sl which shows signs of having had most parts of the injection pump and linkage having been played with  

Because the linkage was a mess, I have replaced all the ball joints and made a pair of protractors to ensure the relationship between the throttle body and IP are correct. However, I think I have a problem. The BBB has a table of the various angles, the last of which is 80-82 degrees on the throttle body and 79-82 degrees on the IP. My problem is that I hit the full throttle stop on the IP at 75 degrees.

This indicates to me that the idle speed stop may have been moved?? I had already suspected this before I found this problem.

The question is, how many degrees of movement should I get on the IP?

Also, is there a recognised method of adjusting the idle stop? (accepting that you 'should' do it on a test stand).

Many thanks

[Benz Dr.]

NEVER thouch the idle stop on the injection pump. If you get 75 degrees then that's all it has. I once tried to do what you're trying do and gave up after a while. There are ways to set it up using a base measurment from the IP lever to the cross shaft lever. All other adjustments are made from that setting.

[glennard]

The IP idle stop could have been adjusted, also.  JA and others say never adjust this.  But, some POs and ? mechanics ? have been ignorant of this sage advice.  Furthermore, other adjustments and modifications have probably compromised the system.  Therefore, everything in the fuel system is suspect.

[jameshoward]

Val,

Notwithstanding that the BBB has photos with all manner of contraptions showing how to carry out linkage adjustments, it's probably worth noting that you don't NEED to worry about angles. Instead, you can use a ruler to get the measurements as accurately. If you haven't already done so, read, re-read and re-re-read the linage tour by JA17. It's at the top of the page about engines and is superb. Note that it could take a few goes to get the linkage correct. I had to do it 3 times before I was happy. It's very much an art.

Let us know how you get on.

JH

[Val]

Thanks for the replies Dan, Glen and James. But what I really need to know is should I have more movement?

I'm between a rock and a hard place on this. Just about everything has been messed with. The cast lever on the throttle cross linkage that links to the IP looks to have been changed and the hole in it has been re-drilled so I have no confidence in its geometery, hence the need to use the protractor method for setting the linkage. However, as it now looks like the idle stop on the ip may have been moved, I am really struggling to find a point that I can adjust from.

Also, all the adjustment screws on the IP have been moved (I know this because both the Black Lower Partial and the White Upper Partial screws were out of sync with each other).

I am attempting to recover the fuelling setup with the aid of a wideband o2 sensor and a datalogging kit, an amazing bit of kit that I will detail the use of in another post when I have managed to solve my issues. It looks to me, from the fuel maps, that I am getting far too much fuel in the 1500-3500rpm range. So much so, that I can not adjust it out satisfactorly with the available adjustments. My first thought was that the IP lever must be moving too fast in relation to the throttle, but it does not. This is what is also leading me to believe that the idle stop may have been moved.

Time to ponder some more.......

[psmith]

You probably know about the idle fuel mixture screw on the back of the injection pump, but there are also mid and upper range screws under the cover on the back of the pump.  It is strongly recommended that only an expert in these pumps ever adjust these screws.  Given what you are seeing on the O2 readings, it doesn't sound like your PO read any of these warnings.  If it were me I'd send it to an expert.  H&R on the east coast or Pacific Fuel Injection on the west coast here in the states.  Don't know sources in the UK.