Chevy 93' 3500

This happens randomly. Sometimes everyday for a week, sometimes it won't happen for a month. Hot or cold. There is no rhyme or reason to it that I have found out thus far.

When it does die, it is always 1-3 minutes after it has been started, and only within that time frame. Usually this time frame is when it is warming up in the driveway or taking off from the parking lot, has never died after that time frame.

Sometimes, if I take off right after starting and I'm on a downhill slope or have enough speed for gravity to keep it going long enough, it will catch back up when it wants to die (about 5 seconds). Runs really rough when it does want to die, until it comes to a stop.

After it dies. I have to crank the engine for a while until it slowly starts to get going, and then it will take off. It's never happened twice in a row...

Been doing this for about 2 years now. It's a work truck, so it only gets driven on vacations and when I need to haul things.

Any ideas what is causing this?

 

when you turn the key to the on position (not start) do you hear the lift pump running? it is located on the frame rail .

 

when you turn the key to the run position you should hear the supply pump aka lift pump running

 

fire it up and crack the filter air bleed. if no fuel comes out you need to investigate the lift pump circuit.

 

Next time it happens I'll try to see if I can hear it. Hard to diagnose since it happens at random.

So your saying crack the air bleed on the fuel filter next to the intake?

 

Yes or power up the lp using the G terminal on the aldl socket under the dash with the bleeder open if fuel comes out lp is good.
And added a old thread with pictures to help.https://www.dieselbombers.com/chevy-...el-system.html

 

it doesnt have to be acting up to do this test. start it up and ontop of the filter is a air bleed. open it. it either makes a mess and your lift pump system is good or the truck dies and you need to diagnose your lift pump system.

 

Okay, so keep the truck running when I crack the bleeder? If fuel comes out everything is okay, if not I'll be back on here.

 

Thanks Mayhem for supplying my old write up. I forgot all about that! And on terms of the original post, it sounds like the injection pump is not getting enough fuel, which, like many others have already said, a faulty lift pump. The lift pump is the canister on the frame rail below the drivers foor. It kind of looks like a fuel filter for a gas truck. Anyways, you can start by laying underneath the truck, with the engine off. Have someone else turn the key to the one position. You should hear the lift pump 'hum' and push fuel for about 3 or 4 seconds. If you don't hear it, then try jumping the G relay with a hot power wire like Mayhem said.

 

Finally got around to all of this. I did the test where you crack the brass tee valve. Sure enough no fuel came out of the bleed tube and the engine died after 15 seconds.

So here is what I have done thus far:
Replaced the lift pump with a new delfi (or something to that name)
Replaced the fuel filter
Bench tested the OLD lift pump and when hooked up to 12v it runs
Tested the new delfi lift pump by pulling the fuse and applying 12v directly to where the fuse was. During this test I bled the fuel filter, and the tee valve and had a healthy stream of diesel come out.
Now here is the weird thing, I tested for 12v at the lift pump connector and it reads 12v

After all of this the engine is still dying and the lift pump does not turn on at the glow plug stage, I cannot here it run or feel the buzz with my hand when the truck is running. AND, when I crack the brass tee valve with the new lift pump there is no diesel fuel coming out and it dies in 15 seconds.....

So why is it not working still?