Recently swapped a '93 12V into an 84 Chevy K30 and it ran great for a couple months. All of a sudden it died while pushing in the clutch at highway RPM, started right back up.

After driving it more, it seems more consistent, if you don't push the clutch in until the RPM's are closer to idle it's fine. If you push it in at ~2300 it dies or almost dies and then jumps back to life.

On a possibly related note, it seems to have recently developed what seems like a drainback issue (if you let it sit it acts like it has air in the system for a bit, then works it out). I may have fixed that but I'll have to give it a little time. The air in fuel issue, assuming that's what it is, is more recent and I believe is fixed after tightening a fuel line.

Not sure if the two are related and it's a pretty recent swap so it could be different things. Seems like I read that the stumble off of higher RPM could be injectors, I keep wondering if it could be the lift pump. There is no fuel in the oil and no apparent sign that the lift pump is bad, I haven't checked it's pressure.

Any help is appreciated, I'm new to this diesel stuff

 

Check your fuel shutoff solenoid wiring, just to be sure its tight and has good contact.

How is your clutch switch wired?

 

I tend to think it's all related. Check your supply lines for any dampness, a leak on the suction side usually does not show up as drips because there's no pressure. Throwing a fuel pressure gauge on will point you in the right direction, if you have no leaks and the truck is dropping fuel pressure at road speed - then unless your fuel filter is plugged (should have been your first reaction to change it, you did that, right?) then the lift pump is shot.

 

While driving the truck seems fine, will the IP draw fuel without the injection pump working? I thought that it could, and if the lift pump isn't doing much it may cause what I'm seeing.

I can't find any spot that anything is leaking, and the dying at speed issues seems unrelated to that to me. I just changed the filter.

Fuel shutoff switch connection seems fine, I don't think my problems indicate anything bad with the switch but let me know if I'm wrong about that.

As for the clutch switch, didn't know it had one so if it does it's safe to say I didn't wire it up


Basically the truck drives fine. If it's been sitting over night it will be rough on start up (or not want to start), really feels like air is getting in the system. When it hasn't wanted to start, cracking the injectors fixed it.

 

The VE pump will draw fuel through a dead lift pump. Many VE applications have no lift pump.

It sounds to me like you are either getting air in the suction side, or the lift pump is dead.

 

Replaced the lift pump with no apparent change.

There was a VERY good siphon coming from the tank to the pump, the truck had sat for 24 hours before that. I'm starting to think it's not drain back or the lift pump, maybe injectors or injection pump.

At this point the truck starts and runs rough for 10-20 seconds then runs perfect. This is a new swap, only a few months old, but it ran/started perfectly for the first two months, if there's anything I could've missed when wiring everything up? The only thing that's really wired on the motor is the fuel shutoff, no grid heater yet, starts the same whether it's 30 or 90 out so I don't think the heater matters yet.

Any ideas?

 

You're getting air in it. How's the fuel heater gasket?

 

Replaced it today, no change.

It almost seems like it's getting worse, is it possible I'm not getting the system bled enough? I guess I've assumed that when the truck idles smooth and drives fine that the air is gone, is that a bad assumption? At this point you can run/drive it, it idles smooth and drives fine. Then you can shut it off and start it 5 seconds later and it will sputter a little then return to a regular idle (which it never did before).

The puzzling thing is that it started and ran perfectly for a couple months then started acting up, so it seems like everything was hooked up and working right not long ago.

Is there an easy test for injectors? Seems like I've read something along the lines of cracking them while the motor is running to test them, maybe not. I'm far from new to fixing cars but the diesel stuff is new to me so bear with me

 

I recently replaced broken return springs in my IP. Very similar symptoms.
you can plumb sections of clear line on the suction and return lines to check for air.
Check the FSS for metal, the plunger stays slightly magnetized, catching steel shavings (spring, cam plate)

 

I would like to install a fuel pin and governor spring in the near future so if there's anything else to look for when inside the pump let me know!

 

Washed the motor real well yesterday to find leaks easier, drove the truck a little and it looks like three injectors are leaking! I've checked them before and while they looked a little suspect, they weren't really wet like they were leaking, hence why I cleaned everything real good to make it more obvious.

One had a small pool under it and bubbles were coming from it, pretty easy to blame the injectors for all of this I suppose (there was more diesel on them after driving, some of it evaporated or drained back in which I wouldn't have expected, it was definitely clean before and the leak is repeatable):







Seems like I would have found this sooner, I've checked the injectors many times with no obvious signs that they were really leaking, I think they just recently started leaking bad which is why my problem was getting worse.

So my next question is what injectors should go in it? I've driven a '99 24V that had all kinds of aftermarket goodies and made stupid amounts of power and only made lots of smoke when you got on it, when he switched to bigger injectors it puked smoke all the time which I REALLY don't want. More power is always good but I don't want it to smoke like crazy when I'm not on it.

We have an account with a company that I can get the BD diesel injectors through (so 15% off or so), any better recommendations?

 

Also this is my tow rig, not a truck that will ever see the track. More power is good but it's worthless if the EGT's hit the roof in short order, mileage is of concern as well.

If it matters, it's a '93 12V with an '02 intercooler and 3" intercooler plumbing (fits easy in the Chevy core support), plans for a fuel pin, 3200 RPM spring, 4" exhaust and to turn the pump up and that's it.

 

New washers under the injectors will fix that for less than $10.

Unless you are just looking for an excuse to buy injectors...

 

Well I had certainly though about it

Where can I get the washers (or a part #) and what do I have to do to change them?

Thanks so much, all of you are so helpful!

 

You can try torquing the nuts down, 44 ft-lbs. It's easier to work on the injectors with the lines removed, but I have seen people remove the holders of the lines and "flex" them out of the way, but the last thing you want to do is bend an injector line.
If the stuff is coming from around the big lower nut only, that is just a minor compression leak. (bubbles) The copper washers are at the tip of the injectors, and seal the injector to the combustion chamber.
While any problem is worth fixing, I don't see this solving your main issues. But it is pretty easy to pull the injectors, have them tested, or upgrade This tool comes in handy, https://www.dieseltruckresource.com/...d.php?t=124728