something strange is afoot

[flatlander]

So after blowing snow last night I was heading up to pick up the Sunday night pizza when the '85 died. No warning, acted like it was out of fuel. Fortunately I came to rest at the top of an incline and I could push it into a gas station. Also fortunate, I had my tools in the front seat with me.

I checked to see if I had power at the pump, which I did, pressed the schraeder valve on the filter, got a little air, so I cracked #2 and jumped the starter solenoid to see if I was getting fuel, and she fired right up.

I'm assuming that my 12V connection at the pump was not made and jiggerin' with it remade it, but here's the strange part: When I cracked #2 and it was running, it didn't stumble a bit. In fact nothing changed. Prior to and now it runs fine. If I had a bad injector, it'd run bad, right?

Oh and now that line leaks a little bit.

Barney

 

[yARIC008]

Perhaps you just didn't have the line cracked enough to make a difference. There is alot of fuel in the line that the injector doesn't use and it gets sent through the return lines, so maybe you had it cracked just enough to act like a return line. Loosen it more and it'll probably start stumbling then. If you have a bad injector you'll know, the engine will bouncing around like it seen much better days. Once when i did the injectors somehow i left one of the lines off one of the injector. And man, it was shaking something fierce running only on 7 cylinders.

To get it to stop leaking, i'd pull the injector line loose again, and then reseat the screw on coupler. Like... loosen it, a little, then, pull up on the metal line until it hits the top of the nut dealie, then retighten it. Sometimes the line just doesn't seat properly in the nut coupler there.

 

[ericboutin]

Hey Barney - Like the other Eric said!! I know when I had just a crack in one of my injector lines it shook the whole truck like crazy!! I thought my 4 year old in the back seat was gonna come popping out of her car seat!!

 

[L.Wilkinson]

The comment "there is a lot of fuel in the line that the injection doesn't use and it gets sent throught the return lines" - not on this fuel system. All of the metered fuel being delivered to any individual high pressure fuel line is destined to be injected with the pintle style tips, but depending on stem wear, a small amount might leak back upward, and this is what is returned through the leak off caps and return lines. Its not like a common rail, just a relief valve of sorts. Otherwise yah, it might not have been loosened enough to allow a miss, or perhaps that cylinder doesn't act as aggressively when shorted to others.

 

[argve]

The dead in the water thing has me concerned a little. Did it stumble before giving up the ghost? If so you might want to check out your fuel heater or quality of fuel. I know is was bone chilling cold out and it might have started to gell up - my overhead last night on the way into work was only reading 4°F. Are you running an anti-gel additive like a good little diesel head?

*tapping foot awaiting answer

 

[flatlander]

Geez Trav give me a break. Of course I've forgotten to add anything to my fuel.

Oh, and I don't know if it stumbled or not 'cuz I had Fox Sports AM cranked on my factory 1 speaker in the dash boomin system.

Barney

 

[Agnem]

Barney, I've seen injector nuts that needed a whole half to 3/4 turn before it would start stumbling. I think you just didn't have it loose enough.

 

[yARIC008]

Originally posted by L.Wilkinson
The comment "there is a lot of fuel in the line that the injection doesn't use and it gets sent throught the return lines" - not on this fuel system. All of the metered fuel being delivered to any individual high pressure fuel line is destined to be injected with the pintle style tips, but depending on stem wear, a small amount might leak back upward, and this is what is returned through the leak off caps and return lines. Its not like a common rail, just a relief valve of sorts. Otherwise yah, it might not have been loosened enough to allow a miss, or perhaps that cylinder doesn't act as aggressively when shorted to others.

Seems like even on a "new" system there is quite a bit of leak off. Even with return caps not quite sealed up good, you get a good puddle of fuel in no time. But i suppose you're right, i'm just going off observations here.

 

[L.Wilkinson]

Well to be fair, yes and no. There is a significant fuel return rate through the leak off line circuit, from the fuel the pump doesn't use at lower load conditions, as our mechanical (or electric) transfer pumps seek to keep a certain flow and psi of fuel available in the pump. What ever isn't used is returned to tank, and if there's a leak on the return caps'n lines then out it comes. But the injector pintle stem leakage rate is low by spec. When injectors are rebuilt this is one of the criteria for failure. If you pop one plumbed to a test fixture, after a few strokes it may start to soak out the cap orifices of the injector body, which is OK.
Worn out pencil injectors as used by the 3208 Cat's for instance can get quite aggressive in return cap leakage rate, where they actually spray hard upwards (worked at a fuel lab way back when - my boss used to get choked when I worked too fast)
Lorne

 

[Fred Hemer]

Yup ya need to slow down Lorne!

 

[L.Wilkinson]

Fred, have you ever seen the old Robby Bosch training film where the apprentice was trying to take a delivery valve or something off a fuel pump, using the wrong tool and the "Master" mechanic boxed him in the ears and set him straight on his procedures?
Now adays you just have to encourage and be correct like politicians would.
Hard thing to slow down, seems to go faster everytime I turn around. That must be good, right?