Draining fuel filter stalls engine
 

When trying to drain the fuel filter in my 94 GMC, K2500, 6.5TD, I open the fuel cap, start the engine and then open the T-handle. An ounce+ of fuel comes out and the engine stalls. Also, I get no fuel flow out of the filter air bleed and opening it also stalls the engine. The lift pump is working since it clacks when starting and when the ig. key is turned off. What goes?

ok you have 1 or thing going on bad OPS or LP just because you hear the lift pump don't mean it working in side the can fall apart in still run the best way see if the pump working right is to put 12v right to the pump and open the T-valve at T-Stat and see if fuel come ut if it don't most likey you have bad OPS it runs the LP

Thanks Crazy--I'll check the LP tomorrow and get back. Where is the OP switch and how do I check it?

well if you put 12V power right the lift pump and open T-Valve and fuel come out it and OPS is bad OPS is on back of the left head you have to remove the bolts the hole fuel filter housing so can move it to the side to get at OPS and going need 12pt 1 1/16 socket

here are parts #ers but i woud go with the ACDelco one or you be replacing it about 6 months

Oil Pressure Sensor:

* OEM: 12555492
* ACDelco: D1808A
* Car Quest: PS262

Thanks again Crazy--I have some tim in the AM and then into the hospital Tuesday. I'll get back after that.

I checked the voltage to the lift pump--got 14.4V, the charging voltage but wanted to know for sure that the pump was running when the engine was off. I used some old test leads from an expired voltmeter to plug into the pump connector and then connected the battery to them. The pump ran normally and I got fuel flow when I opened the T-handle and fuel filter, which I didn't get when the engine was running. So the pump ran off the battery but not when the engine was running. So, I conclude that the OPS is capable of providing the voltage but not enough current to run the pump. The pump needs about 7 amps to run full speed (I tested that too). If the OPS has points in it they could be weak or corroded. Any other ideas??

change the OPS bet you be up and running if you got fuel running 12V power to pump it pump fuel then pump good OPS runs it just because you see oil psi doesn't it good

Thanks Crazy--I'll have the OPS in the morning and put it in by 10 AM. Also FYI, the pins I put into the lift pump connector measured .080 dia.and were a little loose. About .090-.095 would work better. Polarity is critical--don't want to run the pump backwards when testing.

I'll be posting a new thread about my PMD (works like PMS). Look for it.

make sure you get ACDelco any other brand won't last long

Absolutely got AcDelco at O'Reilly but they had to order it. Thanks