Cranking speed

[N9Phil]

I have finally got the 6.5 working fairly good. It starts good when cold but when it is hot it cranks for quite a while before starting. I called to place where I bought the injector pump from last August to let them know that I might have a bad pump. ( I should have used a Diesel Page sponsor but I went to E-Bay instead)I was told that I should check my crank speed and it should be 200 rpm. I asked about pouring some water on the pump to cool it when I have a long hot start and was told that this masks the problem ( slow crank speed). When I checked my crank speed I only got 150 rpm when cold or hot. This is a new starter that was installed a few months back. I decided it make better battery cables so I made new cables out of 1 awg welding cable. After completing this project I now have a cranking speed of 169. Is there really a problem if the cranking speed is not 200 rpm?

[DmaxMaverick]

A cranking speed above 100 RPMs (GM's spec) will mask other problems, such as a failing IP. 200 RPMs is optimistic. I've never seen one spin that fast, in a running condition. If you are getting 150 or 169 RPMs, you are well into the "excellent" range. Of course, faster is better, but a healthy engine should have no problem starting at 100 RPMs or better. Pouring water on a hot pump won't mask other issues. It will show that your IP is probably worn out (or a poor reman), if it improves starting (this closes the tolerance at the rotor-head, by "shrinking" the housing). You can also disconnect the ECT sender for a test. This will enable the longest glow cycle, and maximum advance (reconnect after a start).

It certainly could be something other than the pump, but it's an Ebay purchase, which is suspect to begin with. They aren't all bad, but there are enough of them to be suspicious, early. I buy a LOT of things from Ebay, but I'd never buy a new/reman IP there. I've picked up core pumps there, but that's a different story.

[16gaSxS]

I just had a thunk that your lift pump maybe weak or inop. The injection pump will pull fuel to run on it's own but takes cranking to start.