Injection Pump Throttle angle switch setting

[DMS]

So I had to chase an IP pump leak yesterday. Turned out to be a seal on the bottom of the IP, but I tore apart the top to find it and in the process removed the TP switch. So I dont believe it has affected anything, but its completely adjustable and getting the height setting correct and position setting correct is a royal pain. Add to this that both the FSM's I have just say its sealed from the factory and should not be adjusted ever... so I have no way of properly setting it now. In the mean time Im going to set it like I would on a gasser and hope for the best.

Any input would be helpful as I have to pull the PS pump in order to get to it and set it each time. I believe this only controls the EGR, but there is an advancing solenoid that I have no clue as to its function... Im worried it comes on at higher RPM's, but it may all just be egr related. Im ok with the EGR not functioning and gunking up the intake and valves to be honest, but if its gonna affect performance I want to keep it intact and functioning properly.

Thanks folks

Ray

[asavage]

That throttle position switch interacts with the EGR controller on the left kick panel to both operate the EGR valve, the vacuum-actuated throttle valve at the air filter, and the IP timing advancer. From memory, 1982 used a two-position throttle valve (open and closed) and 1983 has three positions.

The IP advance under EGR system control is two position for all years.

I don't know how to calibrate the TP potentiometer. The EGR system is active at hot idle, that I figured out -- the opposite of what you'd expect, working with gassers.

IIRC, the EGR-controller IP advancer solenoid modifies the timing when the EGR valve is open (but, perhaps, not at idle?).

In any event, it isn't a huge amount of difference. Unless you have a new or rebuilt IP installed, I doubt if the LD28 is getting anywhere near its factory timing advance in any condition. The internal hydraulically-operated timing advance mechanism just can't build enough pressure after some number of miles. These VE-type IPs seem to lose their advance fairly fast in normal use. At least, that's what I've been seeing.

So, even if the EGR timing advancer valve gets power from the EGR controller at certain times, all it does is block (or unblock?) an orifice and since I doubt there's enough internal housing pressure for that orifice to effect much difference, it doesn't matter whether it works or not (or, by extension, works at the correct time).

The EGR operation will continue to work independently of the IP timing being modified, of course. Whether it may now operate at too low or too high RPM is an open question. The system does have a tach pickup in the lower of the IP sprocket area, and I've seen a couple bad ones (the one in the '82 Wagon I sold you was bad) and that prevents the EGR system from activating at all, IIRC. I had an NOS one but sold it a couple years back. Pics of it and its location are in this post. Note the 1310 ohms -- you can check to see if yours is somewhere near that range without removing it.