I have a 1995 4X4 6.5 Ltr diesel 3/4 ton. I've owned the truck for 9 years and have put about 70K miles on it for a total mileage of 144K. I replaced the fuel filter about 2 years ago with no problems. The new filter was easy to change and bleed. On a trip to Savannah, GA, this week, I kept getting an intermittent "Check Engine Soon" light, even though I noticed no difference in the performance of the truck. I assumed it could be the fuel filter needing another replacement because the annunciation only came on during highway speeds and acceleration. Basically, I figured it was sensing a difference in fuel pressures from the filter inlet and outlet. Sure enough, after buying another filter, I removed the old filter to find the old filter full of junk. When I began the process to install the new filter, I opened the gas cap and the fuel filter bleed nipple but after cranking, no fuel would come out of the top of the filter. I got the engine started by pulling the filter, filling the filter housing with diesel and reinstalling the filter and starting the engine. Then, wanting to bleed the filter, I unscrewed the bleed nipple while the engine was running, and nothing came out of the bleed nipple. With the engine running and the the fuel bleed nipple open, the level simply lowered in the housing and the engine would quit. I can prime the filter housing and replace the filter and it will run well enough that I got all the way back to the Knoxville TN area, from Savannah GA; but, if I shut the engine off, it takes priming again (which I did in a parking lot in downtown Atlanta while my wife and 4 kids watched.) So, the question is: what do I look at as being my culprit? All fuses are good and the engine runs fine, once started, except for higher RPMs where I can tell the filter needs a good bleeding. After replacing the fuel filter, the "Check Engine Soon" light never reappeared. Any information or experience is appreciated. Scott

No fuel in filter >probably oil pressure switch. Next choice supply pump.

SES light on highway is probably boost pressure to high.

Welcome aboard.. Do the signature thing so we can see what you got.

a quick answer would be to do the checklist in the stickies. and please fill out your signature so we know what truck we are dealing with.

no pressure at the top of the fuel filter is one of 5 things in decreasing order of likelyness.

1 bad ops not driving fuel pump. jumper the outer 2 wires on the ops connector fuel pump should pump fuel if not pump most likely is bad.

2 bad fuel pump do above test

3 low pump flow could be a bad pump or snot in the sock (sock on fuel intake in the tank)

4 if you are getting air in the filter you have (most likely at the fuel tank sender unit) a hole in the fuel line before the fuel pump.

5 a bad fuel cap. when you open the fuel cap a LARGE woosh of air goes into the tank.

a paperclip works real well for the ops wiring test. if you have a voltmeter measure the voltage at the fuel pump with the pump running it should be at least 12 volts.

i think you will find that you have a bad ops. an ac delco holds up better than most but even those are weak. our vendors has an ops bypass type unit that is well worth its weight in gold it is available either from heath or kennedy i dont remember at the moment.

good luck getting it fixed.
wes pierce
houston, tx

Thanks. With the junk I found in my old filter and the possibility of having pumped contaminated fuel into my tank from a bad station I'm thinking about dropping the 42 gallon fuel tank from under the Suburban and checking the condition of the inlet sock and in-tank pump. Is this something that's easily done? I've dropped the tank on a mid-80s Ford truck (gas burner)once and it wasn't too difficult......a motorcycle jack makes for a great fuel tank lift jack....thoughts?

There is no in-tank pump in this truck unless you installed it yourself. The sock is a possibility assuming your LP and OPS are both good.

As mentioned above, your LP (Lift Pump) and/or OPS (Oil Pressure Sender) are bad.

Wes have told you on how to do the test.

i just dawn'd on me if you had a bunch of junk in the filter (i'm not talking about the very small stuff) your sock is nonexistant or has a hole in it. the particles at the filter should be no larger than 1/64 of an inch in size that is about the size of the screens on the sock.
wes

I've taken a test light and am getting good power to the Lift Pump (LP) when the engine is cranking. I feel no vibration of the LP while it is being powered and believe I should be able to feel a slight vibration (after all, everything else on this truck vibrates!) I guess the question is: "Should I feel a vibration from the LP when it's being powered?) If so, I will replace that part and go from there. In cranking the engine again this AM, it started, initially, then quit when the filter housing cavitated again. Thoughts on replacing the LP? Thanks in advance.....Scott

Thanks to all three of you who made this a much easier task. In my last post, I had checked the Lift Pump (LP) for voltage and pump operation. My wife cranked the starter to activate the Lift Pump but there was no apparent operation. I bought a new LP from Advance Auto Parts ($90w/tax) and installed in 20 minutes. I primed the filter housing with fuel and cracked the bleed valve on the filter housing to bleed the system...lo and behold, the engine fired up and a small geyser of fuel was shooting from the bleed valve. (Prior to the new LP it would suck all the fuel from the filter housing). Thanks again, y'all, and I hope that this posting will help another in the same situation. Scott