No fuel to fuel filter

[N9Phil]

Here is my story (problem). My 95 half ton 6.5 suburban started a while back acting like the oil pressure switch was bad so I replaced it. I also installed a new fuel filter and it seemed to work better for a few days. It was however a little harder to start in the mornings but after it had been run and the engine warmed up it would start great until the next morning. Since I had a new FSD in the glove box, I replaced it with no improvement. I found that my lift pump was not working right so I replaced it and everything was fine again for a few days. This time I found the new lift pump to be bad so I replaced it again ( part was under warranty) . Since I now had fuel to the filter I figured that the injector pump must have gone bad ( 170,000 miles on the pump). I therefore ordered a new injector pump and installed it on labor day. By the end of the day I could hardly move. ( I am getting to old to get in the positions needed to do this kind of work). It took a while to get the truck running but once I did I found a fuel leak in the line from the filter to the pump. After fixing this line I was able to get the truck started again and I set the timing. When I shut the engine off after it warmed up it would start right up. If I let it sit for a few minutes it wouldn't start again unless I used a shot of eather. I found another bad hose on the fuel filter so I replace it. I put in another new fuel filter and tried to prime the filter and I don't get any fuel to the filter. I talked to a neighbor that has an auto body shop and he suggested that the fuel pump in the fuel tank is bad. I didn't know that there is one in the fuel tank on a 6.5 diesel. I have run out of ideas and am open for suggestions. I have never dropped a fuel tank before to replace a pump in one and of course I have a full tank of fuel. Does this look like the problem or am I barking up the wrong tree?

Thanks in advance

Pihil

[Yukon6.2]

Hi N9Phil
No pump in tank.Sounds like you should get a pressure gauge on the fuel line to see if you are always getting pressure to the injection pump.
Thats where i would start at this time.
Thomas

[Robyn]

There is a very real chance that you have an air leak between the tank and the lift pump, and or a plugged sock in the tank.

Running the lift pump should bring fuel right up to the filter.

There is also a possibility that the hose from the lift pump to the filter is going bad inside and the hose lining has started to "shed" and has a "flap" that intermittently plugs the line.

Check the lines from the tank to the lift pump, if OK, then be sure the hose that connects to the tank does not have a crack or ???

If all well there, remove the hose from the lift pump to the filter and make sure its OK .

Good luck

Missy

[N9Phil]

Thanks for the tips. I filled the filter with fuel this morning before going out on calls and was able to get the engine to fire up and run until the fuel ran out so I now have to get the front wheels back on so I can get under it and figure out where the real problem is. I might not be able to get back to it for a few days but I will make a post and let you know what I find.

Phil

[arveetek]

Definitely check the fuel "Sock" in the tank. The only fuel lift pump found on the 6.5L diesel is on the frame rail. In the tank there is a pre-filter called a "sock" that strains out large debris in the fuel before being sucked up and into the fuel system.

I chased a similar problem for months on my '95 before finally discovering that the sock on the pickup tube in the tank would collapse and prevent fuel from flowing. Letting it sit for a while would let the fuel start flowing, but driving for a few miles I would run out of fuel again. It about drove me nuts. After several lift pumps, fuel lines, and dropping the tank several times, I finally figured it out.

Casey

[Dennydiesel]

My 93 6.5 did the same thing. It turned out to be a lot of debris in the tank and it would lose suction to the IP then stall on me. I cleaned the tank, replaced the sock and it was better. I also found the fuel line from the tank to the lift pump has an o-ring where it goes into the lift pump, the land that the o-ring fit over was damaged and letting air get sucked in the line. No external fuel leak so it was really hard to find. But if you pressurized the tank via the fuel cap by installing a valve stem then pressurizing the tank to 5-10 psi you cold see fuel leaking at the lift pump. Just running it you will never find it. I've now put almost 1,000 miles on the truck and would not hesitate to drive it across the country.
I would start by dropping the tank and taking a look or pressurize the tank to look for a leak. Good luck.

[Dennydiesel]

If you replace the sock in the tank, buy it from a Chevrolet dealership because the aftermarket ones can collapse and prevent fuel flow. GM has a newer design that will work just like the OEM one. Keeps you from having to drop the tank a second time.

[N9Phil]

sorry for the delay getting back to reply. I haven't had a chance to get back to the truck for a while. I need to get to it before the cold weather starts. I will post what I find. Thanks for the tips.

Phil

[racer55]

Also check the fuel cap-it must be a diesel ONLY vented cap-sometimes a gasser cap gets put on by mistake and it can prevent fuel flow when vacuum in the tank overcomes the lift pumps ability to pull fuel.

AC Delco ONLY for OPS and google OPS relay mod and install for long term reliability.

How did you set timing-tech 1,techII with OBD 1 expansion pack or GMTD ScanTech are the only scan tools capable of iniating the TDCO relearn on 94/95 trucks.

If you ran a timeset command with ascan tool you have not yet set the electronic timing.

[N9Phil]

I am getting closer to getting the truck back on the road. Last week I dragged the Suburbn to a freinds Body shop. They found the fuel line bent and leaking from the fuel filter input. They relocated the fuel filter on the firewall and had the truck running. I went over with my Tech-1 and hooked it up. Not knowing what I am doing I managed to get the timing screwed up. We got it running real well so I drove it home. It ran crappie all the way home. I shut it off and my friend drove me back to get my other Suburban. That night I spent a few hours on the computer seeing if I could find any info on setting the timing with the Tech-1. I knew that there was info out there on the Diesel Page because I had used it years back when I replaced the water pump and put in the timing gears. I found an old post that GMCTD started 11-21-2004. I printed the whole thing. (I can't sit in front of a computer for that long to read something) After going through it all I realized my mistakes so this morning I went out and tried to fire up the truck to set the timing. I have had it plugged in for a day so it should have started up but it wouldn't. Next I tried swapping out the FSD and I put in the DTech one that I had in there when this problem first started. It started and I was able to get the timing set. I could only get it to set to -144 instead of the old -194 that I had in the past. I tried moving the pump a couple of times to get this and when I got this close I decided to stay there. Now I need to go check my glow plugs and see how many of those I have screwed up while working on this problem because if I restart it right after shutting it off, it starts immediately. If I wait a while it will crank a while before starting back up.

[racer55]

Long cranking could be glow plugs but can also be air in the fuel or an aftermarket CPS.

[N9Phil]

Well, it looks like it will be a few months before I will get back to the truck. I managed to really screw it up this time. I know that it has been mentioned many times about using either to start these engines but even tho I have done it so many times in the colder weather, my luck ran out. I think that I managed to shear the pin on my timing gear. Since the weather has gotten colder and I work on the truck outside it looks like I will be waiting for the warm weather to return.

Phil

[N9Phil]

The saga continues. Well after I told the neighbor with the body shop that I was going to wait until spring to work on the truck he said that if I brought it over to his shop he would let me let me use a spot in the shop and he would give me a helping hand. After replacing the batteries and starter (the new starter had a bad spot and replaced under warranty) the problem was determined to be prior to the fuel pump. Since I had almost a full tank of fuel, I suggested that they cut a panel above the fuel tank to get at the sending unit. This is my work truck so I am not concerned about going in from the top. They did a great job and now I have easy access if I need it in the future. It was determined that there was a leak in the line to the fuel pump so it was replaced. I also replaced the sending unit while we were at it. After getting everything put back together I still had a problem starting. Yesterday I replaced the line from the fuel pump to the fuel filter with a new line and it starts much better but with the pressure gauge connected to the filter I get 3 # of pressure and when the engine is shut off this pressure drops to zero within a few minutes. My thoughts at this time are maybe my fuel filter housing has a pinhole leak. I have another filter housing off my parts car so I will try swapping that out. When I do I will hook up the pressure gauge to the output of the fuel pump and see if it holds pressure prior to the filter. I have also noticed that when I open the fuel tank cap I do not hear any pressure or vacuum noise that used to be there. Do these fuel pumps have any kind of check valve in them? I have also been told by some that there is a pressure regulator in these cars.

Any comments and help are greatly appreciated.

Phil

[racer55]

I wouldn't expect the line to hold pressure when the pump is not running.

There is a pressure regulator that tries to prevent over pressure in the IP fuel return.

Hard starting after repairing an air leak is expected,but once going hard starting should not re occur if tehrest of teh system is good,like glow plugs and no more air trobles exist.

Replace the IP fuel return line with clear diesel rated line and with the truck safely parked and idling-watch that line for bubbles,bubbles indicate air is still getting in pre LP.

[JTodd]

Siphon as much fuel out of the tank as you can and drop the tank. That should be easier than cutting a hole. I found my air leak just to the side of the fuel tank where the lines turn to go to the front. I ended up cutting the metal tubes at the sender unit and up stream of the leak and putting rubber hose there with hose clamps. It has worked like a champ since.

[Warren96]

Whenever I have a fuel problem, the one thing I do first is re- read "Air in the fuel system ,A TUTORIAL". It's in the forums on the first page under " 6.2 Diesel", the 3rd from the top. It can save a lot of time and MONEY.

[N9Phil]

Since my last post I replaced the filter housing and I put my old oil pressure switch back in a few days ago. The truck has been working but it still had a time starting. The batteries were dead the other day so I now had another problem. I had ordered new glow plugs and a new glow plug harness from John Kennedy the other day so when I went out to change the harness and plugs I herd something running. It ended up being the fuel pump. That oil pressure switch that I put in the other day was bad allowing the fuel pump to run continuous. I now have 6 new glow plugs and the truck pops off great. My #8 glow plug has been broken off for several years. The #7 glow plug is swelled and would not come out so I retightened it and left it unconnected until I get time to remove it. I am so glad to get the truck starting good again. Thanks to all that have helped with advise. Thanks to John Kennedy for having the parts I have needed over the years.