1986 GMC Astro rebuild...questions

I thought that was Cummins motors that pinching the return line would give more feed pressure.

 

Like I said, my memory is like Swiss cheese now, lol. I do recall working on more than a few 2-strokers where drivers had turned the governor up around 26-2700 rpm.

I recall one driver for a linen service in Grand Rapids, came back raising holy hell at the shop where I worked because his truck wouldn’t go as fast as it used to. I had replaced the blower on the 8V-71 and after setting the rack, etc., turned the rpm back down to 2100 and safety wired the cap over the governor adjustment.

 

In the 70's, my 1st trucking job had Macks and IH 4300's ( guess who got the Mack) The IH's had BC Cummins, and the mechanic said it was part of the PM to check the return line for vise-grip marks.

 

May want to check inside the return line , just may be a dime with a hole drilled in it .

 

If you have to try and restrict the return on a PT fuel system to make power you should probably give up working on them.

 

The Detroit 2 Strokes have a gear-driven low pressure pump that that puts the fuel to the Head and the injectors and circulates back through the return line.

I think if you want to prime it you would have to bypass that gear pump and prime the engine and when you have the engine fueled that the return line is pushing out no bubbles then you can hook your lines back up to the Gear pump. Make sure you are primed up through the filters right up to the gear pump and that should start you.

Make sure you have no leaks no way for air to get in etcetera. You'll know you have it right because that engine should Fire Within maybe one turn of the starter. A properly Primed 2-stroke starts almost instantly.

You can use whatever pump to circulate it through the engine but I use another one of those gear pumps from a Detroit
using a drill to spin it.