Intermittent Knocking with Loss of Power.

[the-486]

I got a second 720 KC. Rusty as all, but running nice.
It had sat for a number of years, with a full tank of petro diesel.
I've only driven 25 miles so far, and have yet to pump out the bad fuel. I added a Cetane booster (stp diesel injector cleaner) but that has not seemed to help

The truck will start after you glow the plugs 3-5 times and wide open the throttle. Glow system must be ill. I hate starting this little guy up for the first time on a cold day.. it's really rough! Runs like it's on 2 cylinders for the first 30 seconds, Tramendeous amounts of black/blue smoke pour from the tail pipe.

Once it's warmed up, it still smokes @ idle. The truck runs really well! And I am super suprised at just how well it feels. Purring. However, Under any load durring acceleration the smoke cloud is thick and black. Power leaves alot to be desired. 30mph up almost any grade. There is an occasional Sharp pinging / poping / krackling / knocking that seems to be somewhat inermittent. It can be caused when accelerating.. but at times if I just let it Idel at 1500 - 2000 rpm's it will hickup like this every so often.

Is this water in the fuel? Bad Fuel? Dirty Injectors? Improper Timing?

What is the most probable cause of this nasty sound?

I'm going to check the glow system and remove all the old fuel and filters.

I am tempted to fuel with a full tank of ASTM b100 (as I use in my other 720 and mercedes 300d) But still unsure if this is the best Idea. I thought it may be good to clean things out.

Anybody have feedback for me on this one?

[asavage]

There is an occasional Sharp pinging / poping / krackling / knocking that seems to be somewhat inermittent. It can be caused when accelerating.. but at times if I just let it Idel at 1500 - 2000 rpm's it will hickup like this every so often.

Almost certainly, this is an injector that is not operating correctly.

Running some B100 through it may or may not help. But it won't hurt (in the short term).

This kind of injector failure is very hard on the piston.

[philip]

I got a second 720 KC. Rusty as all, but running nice.
-SNIP-
Anybody have feedback for me on this one?

From all you described, the engine runs badly at times and it's a wonder there isn't a broken piston by now.

DRAIN all the fuel tank (plug on the bottom), refill with fresh.
SKIP the B100 until you get the tune situation ironed out.
CHANGE the filters.
Pull out the fuel injectors and get them bench tested as it appears you've got at least one that is popping off early and/or leaking.

[asavage]

With the smoke situation, I'm betting leaking. While B100 might help, it would be a long shot that a chemical solution will fix this.

A holed piston will be the result of letting it go like this.

[the-486]

From all you described, the engine runs badly at times and it's a wonder there isn't a broken piston by now.
-SNIP-
Pull out the fuel injectors and get them bench tested as it appears you've got at least one that is popping off early and/or leaking.

"Runs badly at times" is not how I would describe this engine. It runs really smooth. Only under a load does is occasionally Pop/Ping and only for several revolutions. However, the smoking is very craptastic, and maybe that is what you mean

I've bypassed the fuel tank (it's full of rusty expired PD) and used a fresh can of b20 to start/run the truck. New fuel filters too. Installed a CAT block heater/coolant circulator to ease starting (it's been hovering around -0C in Portland, OR) The smoke is less, starting was easier. I did all this in order to move the truck to a place where it can sit while the injectors are being tested.

I was SOOOO carefull moving this little guy. I don't want to loose it's SD22 to bad fate. It was pinging a bit still, but I was very carefull and never drove over 30 on the short drive (22 km)

I'm wondering if anyone knows of an Injector Shop in the Portland area? Seems like alot of you are in the North West.

My hope is the $300-ish that I will invest in injector repair will render this little engine a happy runner. I'm loving the construction of these power plants.. I want to stick it out.. and get this lil guy in top shape. It's just the $$$ that could stand in my way. I just got a nice '82 gasser KC body to transplant.. and a flatbed will be in the works. Prolly suited for a new topic, but I'm wondering about a dualy rear end for this?

Thanks again for the input, ya'll are great!

keep ya'll posted on my findings.

[moose60]

Hi there,
You could probably ship your injectors to the folks who rebuilt mine. They are near Tacoma WA. Their contact info is in the thread titled "SD22 Injector Experience". Mine were about $200 to re-nozzle.

Actually, I'll just copy and paste from there. It was actually $230, and took 2-3 days. They will give you the wrong washers, so ask for the flat ones. They should be replaced, and can be tough to get out. Use antiseize on the threads, and be careful with the fuel return piping.


Fuel Injector Rebuilder I Used.

H&H Diesel
407 Porter Way
Milton, WA 98354
(253) 838 3030

Milton is about 5-6 miles east of Tacoma.

Or try the Yellow Pages, which is how I found these guys.

Good Luck

[the-486]

Finally managed to pull my injectors.

The were progressively worse from no. 1 looking a bit coked, to no. 4. looking totally clogged. I'm on my way to Diesel Fuel Injection Services in Portland, OR.

I'll post before and after pics.

Bad news is. I broke the fuel return piping, coming out of injector no. 1

I was holding the injector body with an adjustable wrench, my hands slippery with fuel oil, lost my grip while torquing down on the fuel return nut.. broke that sucker clean off right @ the fitting on the injector body. damn. I'm trying to scheme up a way to hack it.. in other words.. a way to repair my stupid mistake.

Anyone know if the fuel return line assembly is avail. from Nissan or other parts supply? Any one have a spare they would like to send me for a nominal fee

[asavage]

Anyone know if the fuel return line assembly is avail. from Nissan or other parts supply? Any one have a spare they would like to send me for a nominal fee

I'm certain you can buy it new. If not from Nissan, then from a forklift supplier.

Looking at it, as long as the "donut" is undamaged, I'd think you could silver solder any old tubing on it. Do a hose barb, then use some flexible line to connect to the next one. That would certainly work until you could find a permanent replacement, or it could be the permanent solution. Not prettiest, but effective.

Some of the replacement parts prices from Nissan are quite reasonable. Others . . . well, see the "Oil Cooler tale of woe" post, where I found a replacement oil cooler, brand-new.

I don't think any of us have a spare engine for parts. My blown-up one I'm planning on looking hard at turning into an SD11, so I'm not parting the engine out yet.

[the-486]

Anyone know if the fuel return line assembly is avail. from Nissan or other parts supply? Any one have a spare they would like to send me for a nominal fee

I'm certain you can buy it new. If not from Nissan, then from a forklift supplier.

Looking at it, as long as the "donut" is undamaged, I'd think you could silver solder any old tubing on it. Do a hose barb, then use some flexible line to connect to the next one. That would certainly work until you could find a permanent replacement, or it could be the permanent solution. Not prettiest, but effective.

I got the injectors back, from Diesel Fuel Injection Services in Portland, OR! They are great. Did the job in ONE DAY, and only charged me $150 even. Such a solid experience with them.

I told the guys there how I accidentally broke the return line off the "donut fuel return" They pulled out this neat brass fitting, that fit perfectly in place of the old donut. The fitting has a port off the side, with a 1/16 FPT port. I got a hose barb and a short length of hose from a place down the road from the injector shop, I was back in business!

I had wanted to take pictures of the injectors, before and after. Alas, my crummy digi camera is on the fritz, but it was like this. the injector closest to the firewall was by far the worst. and they got better moving towards the front of the block. They were all pretty crummy, and I saw the spray pattern on the test bench @ Diesel Fuel Injection Services.. pretty sorry.

The injectors now, look brand new. Amazing. I got the right crush washers from them. Issues arose with the washer extraction, I was unable to remove the old washer from the injector port closest to the firewall. I asked the guys at the shop about it, they suggested I put the new crush washer on top of the old untill I have the tooling needed to extract them both and put in a fresh washer. So reluctantly, that Is what I did.

I got it primed and started. It started ALOT easier. Was rough only for 2-5 seconds (I assume from small amounts of air in the lines still) and then it was smooth @ high idle. No smoke show this time!

So, I took it for a drive around the 'hood. Still smoking like a beast, but a little less. Lots more power too. I was concerned about the Smoking.. ???

But sadly, The problem that started this whole effort, has not subsided!
It suddenly appeared during my test drive.



After 5 minutes of driving.. I got that sickening Ch-rat-ta-ta-ta-ta-tat. It's only ever that long.. lasting only one 2 seconds or less. I produced the nasty sound several times while driving in 2nd and 3rd gear, at low rpms, on flat ground, with no serious load on the engine.



I pulled back into my garage and popped the hood. I saw a minor leak on the pressure line nut, going to the injector closest to the firewall. I fixed that and then idled the engine up from under the hood by hand, to about 2200 rpm. I held it there for 30 seconds, to hear another startling Rat-tat-tat-tat-tat.... followed by smooth idling again. I ended my testing.

I'm going nuts trying to figure out the cause of this. Not sure what to do next.

Fuel, filters, and all seem good.
Looking to the injection pump or my injectors again for possible solutions?

[philip]

[SNIP- I held it there for 30 seconds, to hear another startling Rat-tat-tat-tat-tat.... followed by smooth idling again. I ended my testing.
SNIP

You're describing random injector knock ... perhaps.

For $150, did you actually get NEW nozzel/pintle assemblies as shown in the fuel injector thread? Just cleaning isn't worth the money.

When you had the high pressure lines off, did you pull the delivery valve holders and inspect for valve wear, a piece of dirt, etc?

[the-486]

You're describing random injector knock ... perhaps.

It certainly is random, and knocking..

For $150, did you actually get NEW nozzel/pintle assemblies as shown in the fuel injector thread? Just cleaning isn't worth the money.

Yeah, or as far as I was told? I didn't get the old Pintle assemblies.. I asked if they were new and was told yes.

When you had the high pressure lines off, did you pull the delivery valve holders and inspect for valve wear, a piece of dirt, etc?

Nope, I guess I should go there tomorrow eh?

What about the smoke clouds that I leave for 1/4 mile behind this little guy? What is that all about?

thanks Philip!

[asavage]

I don't know about this one . . . but let me throw out some ideas.

If you have a bad enough cylinder back there on No. 4, or a cracked piston, you could be getting enough oil up into the combustion chamber for it to run on the oil in addition to the fuel, which will give you that noise, and will also explain the massive smoke you're seeing.

I'd like to see the results of a compression test. See this thread for details. I can loan you the test setup, if you can come up with a deposit on the equipment -- I want it back!

[the-486]

If you have a bad enough cylinder back there on No. 4, or a cracked piston, you could be getting enough oil up into the combustion chamber for it to run on the oil in addition to the fuel, which will give you that noise, and will also explain the massive smoke you're seeing.

Hmmm... I sure hope it's not this dire, but certainly is a new direction to take towards a working truck.

Not sure how I would be able to offer you collateral for the tester, but thanks Al!

I'll figure out how to get / do a compression test and get back on this one.

[philip]

What about the smoke clouds that I leave for 1/4 mile behind this little guy? What is that all about? Thanks Philip!

Take a logical approach

Oil can escape with the exhaust by way of faulty intake guide seals, faulty oil rings, damaged pistons/cylinder walls, and by intake injestion if you have a closed crankcase venting system as found on the SD25. When severe combustion knocking occurs, a perfectly good piston will be shocked violently which will result in oil passage between the ring and piston. Then there is the -possibility- that your muffler has a lot of residual fuel/carbon/oil in it.

Fuel smoke is a lighter color and can be fairly continuous depending on why the fuel is not being ignited reliably. Insufficient heat is the usual culprit. Low compression means less heat than optimal. These little critters (in spite of their incredibly late intake valve closure) generate close to 450 psi cranking pressure.