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Bleeding air out of a P7100 pump.

The Griff

The Griff

High drag, low speed
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This has become big enough of a headache to justify me starting a new thread for it.

94 12 Valve, P7100, 157,000 miles, 5 speed.

Truck sat since 2007, last August I got it started just by cracking the fuel lines and cranked until I got fuel. Once I got it running it did seem to idle a bit lower than it was supposed to, but it had no problem running around town.

I had to give the batteries back to their rightful owner, so then it sat for another month or so while I got all the stuff it needed together. I just put new batteries in it, and changed the fuel filter, and now I can't get fuel out of the injector lines to save my life.

#6 has fuel, but I can't get fuel to any of the others, and I've been trying to get it going for a week now.

It does need a new fuel shutoff relay, but I can lift it up and will stay until I shut the key off.
 
Start with the basics. Prime the lift pump, bleed the fuel filter, and there is an additional bleeder screw on the fuel distribution block ( where the 6 fuel injection lines break off ). I am basing everything off a 97 6bt, just so we're clear.
 
What I've been doing is pumping the primer button the lift pump until I hear pressure squeaking out of the overflow valve on the P7100, then I break one injector line loose and start cranking hoping to find fuel coming out.
 
Nothing?

I've tried pressurizing the tank, it didn't seem to help any.
I a couple of buddies who are actual diesel mechanics by trade, they both basically said the same thing, if its getting fuel to the injection pump, start it on ether and keep it running until it pulls on its own.

I know these guys well and they make good money doing this stuff, but I'm still hesitant to put ether into it.
 
I don't know what to tell you. This is my first diesel as well. I ran it out of fuel tonight, had to go get 5 gallons of diesel and force it to run. Blew white smoke for 3 minutes, after that, smooth as silk again.
Have you been able to get the motor to run at all? It took some massaging to get mine to run tonight, lots of feathering the pedal for about 2 minutes.
 
Yeah it did run, just idled a bit lower than it should.

I last had it running in September, Parked it because I had to give the batteries back to their owner.
Bought new batteries last month, changed the fuel filter, and as soon as I can move it off of the gravel I'll change the oil.


Today I messed with it some more, I bled the filter again, bled the supply line into the P7100, and broke loose the return line from the pump, and turned the engine over, and still got nothing.
 
Mine wouldn't even idle, had to keep feathering the pedal. Looked like a forest fire at my tailpipe. Crank it till it runs?
 
I've pretty well killed the brand new batteries hoping to "crank it till it runs"

I went and "borrowed" my buddy's battery charger, had that on it all day today, and the batteries still aren't really enjoying life very much.
 
I'm a diesel mechanic and they are sometimes a real pain in the ass. I had a 24 valve one time that took forever. Like the others said. Get fuel to the filter then to the injection pump and just keep moving through the system. I like to do like you did and pressurize the tank a little then crack the line feeding the injection pump. Sometime the lift pump can be in a position to not allow fuel though so if you need to crank it a little while the tank is pressured and the feed line is open. Once you get fuel to the pump crank the engine and crack one line at a time(while cranking) until fuel starts to spurt out and then close it and move to the next till all six are good. Make sure your fuel solenoid/shut off valve is on too which it should be while cranking.
 
Well, I did get somewhere today.

My sister's boyfriend helped me by watching which lines were getting pressure and which ones weren't. I got fuel and pressure to #1, #2, #4 and #6 I've got bubbles coming out of #3, and nothing at all from #5.
 
My guess would be an air leak on the filter. Probably the o-ring, especially as you said the fuel filter is one of the things that has changed since it did work previously.
 
I know almost all the rubber goods were replaced only about a year before it was parked.

It could be the O-Ring on the filter, as when I stuck the new one on the threaded piece, it immediately fell off and landed in the tall grass under the truck. I had no luck finding it, so I used the old one, I cleaned it as well as I could, but was a long was from perfect.
 
I used to work on diesels when I was a mechanic in the army. Some of those old mechanical diesels are down right cantankerous if they run out of fuel, especially larger trucks and the older 2 stroke Detroits. We actually modified a gas cap with an air fitting, and keeping a constant pressure (less than 10 psi) was helpful in pushing air out of the system, and for detecting leaks. The old 12 valves are pretty simple, there's only so much that can go wrong. Check everything that has been listed here, and you'll find your culprit. If you've got fuel to 4-5 injectors, a shot of ether can probably get you going.
 
It's alive!

Roped in the neighbors help to be my ether sprayer, but just a little shot and VROOM!

I think it's still got low pressure though, as it wants to idle around 300 RPM, and has some white haze.

But she made a lap of town without issue, now to change the oil and start getting it roadworthy.
 
Ok, just changed the oil in it, (Hadn't been changed since 2007) And whoa. Its perfectly fine. Started on the first crank, idled right where it was supposed to, (750) still has a little grey smoke, but not nearly like it did.


The old oil was black as hell and thin as water.
 
Never can understand why people are so scared of starting fluid. I never even bother trying to bleed anything, just fog it and let it pick up fuel it's self.
 
Ok, Now its starting on a regular basis, But, its awful hard to get going. Lots of cranking. And when it does it's not always on all six. And its quite smokey.

If I pump the primer button I get hisses from somewhere around the IP. And, then it'll start on the first crank, on all cylinders, and smoke-free.

I know air's getting in somewhere, but would the hissing mean anything?
 
Anything between the lift pump and the injectors should show fuel leaks while running
Any leak prior to the lift pump would suck air and possibly show fuel residue when not running all the way to the fuel pickup in the tank (depending on fuel level)
 
Is it possible that the low fuel pressure could be caused by a clogged fuel heater/strainer?

Look at this thing and tell what me what you all think.
iSGLaTz.jpg


I can't get the strainer out, I'm afraid it's going to come out in pieces.

QopAYiV.jpg
 
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