Kibbles and bits

[anders]

Well here is a very bad ending for d24T that I thought I was going to install in my 240. I bought a rebuilt D24T complete with around 40,000 miles on it. I got it home, primed the injection pump with fresh fuel, and changed the oil. On Sunday I put it on the running stand, rolled it over till it had oil pressure. I preheated the glow plugs and fired it up, Started great. A few seconds went and the engine revved up to the sky and before I could shut it off, BANG!!! Smoke all over. Engine stopped faster then it started. So I was done for that day, thinking well I need a piston and a new head now, I wish! Pulled it apart last night, I pulled the valve cover off, #1 and #2 exhaust valves gone, valve stem From #2 popping back up in a new location. Pulled the head off, and holy crap, there was no piston in #1 cylinder, well there wasn't much of a #1 cylinder also. Connecting rod looks like a egg noodle. I pulled some piston pieces out of the engine block and some cylinder wall. I will try to post some pictures this week. And by the way, Timing belt(s) was intact in great shape and still on time when pulled apart!

[ian2000t]

Guy at the local diesel shop had a 740 D24 in when I was down there - apparently it had sat for years. When they started it up, it revved up fine, but would not fall - apparently there was something in the pump that had siezed so would not reduce the fuel supply on letting the accelerator off. Luckily it only hung around 3,500rpm.

Did you take your pump apart in any way? I've heard if the governer doesn't go back together correctly it can do the same when there is no load on the engine.

Would be interested to see the pics - don't imagine they are too pretty though!

[anders]

I Didn't do anything to the pump, It was rebuilt along with the engine. This is not the first time a VE pump has done this to me. I bought two Cummins 6AT engines that sat in storage for years and both the engines did the same, but they held together. I believe when the VE pump have been sitting for to long the governor will get stuck in the start position and not let the engine idle down. I was hoping letting the pump sit for a week with some fresh diesel in it I would not come across this problem again. After a few days the VE pumps on the Cummins broke lose and operated just fine.

[anders]

Pictures of the carnage.

[IceV_760]

Oh mine.. Totally blown up..

[ian2000t]

Wow, that is incredible carnage! Don't think I'll bother messing with the governer on my pump after seeing that....

[ngoma]

What a shame!

There is a failure mode that causes a runaway, stoppable only by blocking the intake.

Ball actuator at the bottom of the fulcrum lever breaks off, leaving the fuel collar uncontrollable. If the fuel collar slides into WOT or near-WOT position the engine will rev uncontrollably.

Member v8volvo had this happen; his main theory is that running w/ clogged fuel filter caused the internal vane pump to self-destruct somewhat, sending shavings into the rest of the IP, some of which lodged between the fuel collar and shaft, causing the fuel collar to seize on the shaft, breaking the ball actuator off the end of the fulcrum lever, the weak point.

De-energizing the fuel shutoff solenoid may not be able to overcome this. Actuating the manual fuel shutoff (auto trans IP) has no effect (linkage is effectively disconnected at the fuel collar in this scenario). Dumping the clutch (manual trans car) may not slow engine in time to avoid damage.

Now that this failure mode has been identified, for future bench testing, we should all make sure to have a suitably-sized wood (or similar) plate positioned ready to slap over the intake.

What are you going to do with it now?

[anders]

From the time it started to the time it exploded was only approx 20 seconds. I had a piece of plywood handy, but there just wasn't the time. I'm not sure what I'm going to do with it, I will strip it down to nothing to save the usable parts and I might just scrap the block.

[ngoma]

Don't beat yourself up over it. You would almost have to have the board ready to go in one hand, while starting the engine with the other. The good thing is that you were not hurt by any parts grenading out of the engine, which is a real possibility.

Which leads us to an exploded:o view of the IP, to show the parts I was talking about in my earlier post:

http://postimage.org/image/rmdi5o9w/

What I referred to as fuel collar they call Control sleeve

The fulcrum lever they call Governor lever

Shaft they call plunger.

[anders]

Well it was close to having parts on the outside of the block. There is a crack in the block. If that was a 6.5 GM diesel I might not be here... ( I'm working on a 929 cast 6.5 with 78,000 miles that has six main web cracks) They will blow up just running normal...

[v8volvo]

What a bummer. Looks like there's not much there that can be saved.

Yep, I had something like this happen to one of mine while I was driving it. I was able to stall it -- barely! -- by dumping the clutch in high gear. Even then, it slipped the clutch for a good few seconds before it finally killed. These motors can certainly produce a huge amount of power when they are getting major fuel and boost... I was glad it didn't break the transmission.

In the case of my incident, turning off the key did nothing. Evidently when the pump is turning at high RPM, fuel is able to be pushed past the plunger of the shutoff solenoid. Not a happy situation. My motor seems to have survived and still runs OK with a new pump on it, but I wonder whether the rotating assembly may have been damaged by high stresses from the over-rev and could fail later on... Haven't yet decided whether or not to tear it down preemptively.

On a different car in a separate incident, I also had a pump that had sat for years do something similar, though not nearly as extreme. It would start and immediately speed up to 2500 rpm, and would not move from that speed no matter where the throttle lever was set. Then eventually it would stall. Needed a full rebuild.

Glad you have an extra replacement motor to get your project back on track. It would have been a tough pill if that had been your only unit.

Anders, you have quite the collection of interesting cars. Will be interested to see your 244 TD when it is finished. Maybe those of us in the Puget Sound area will have to have a get-together sometime. There are several of us out here.

[v8volvo]

Don't beat yourself up over it. You would almost have to have the board ready to go in one hand, while starting the engine with the other. The good thing is that you were not hurt by any parts grenading out of the engine, which is a real possibility.

Which leads us to an exploded:o view of the IP, to show the parts I was talking about in my earlier post:

http://postimage.org/image/rmdi5o9w/

What I referred to as fuel collar they call Control sleeve

The fulcrum lever they call Governor lever

Shaft they call plunger.

Does the Datsun motor use a Bosch pump too? I would have thought it would have a Zexel or Nippon Denso unit. All the Japanese diesels I have seen before have used Zexel or ND pumps, but I have never gotten close to an LD28. Worked on an SD33 in a Scout one time, but I don't remember what kind of pump it had on it. I think it was an inline pump but I can't recall whose.

[ngoma]

The LD28 had a Zexel IP, a Bosch-licensed VE knockoff made in Japan, identical for all intents and purposes to a Bosch VE, except for the nameplate, and of course the outer accelerator lever and cold start device are different. The CSD works in the same manner as the D24 but the thermostatic actuator itself is fatter and shorter. It also has an additional electrically-actuated solenoid mounted on the rear of the top cover (looks like another fuel cutoff solenoid) to advance timing, controlled via RPM sensor and a potentiometer that reported throttle position. The LD28 was a beefed-up L24 (240Z engine), well-made, smooth and reliable. Iron block and head, timing chain, etc.