Sd22 detonation knock

[Wilsunsd22]

Hi all i am a newbee here. Wondering if my problem could be my diaphram. My sd22 sat for i have no idea. Did some barter work to get it and its history is a mystery. I believe it is from an 82 720. She ounce and awhile has an engine rap but it only seems to happen when i bring the rpms up and it doesn't do it all the time. If i keep the rpms down and drive easy it is fine. This motor is in a home made buggy we call Wilsun it has the axles and transmission from a 1953 Willys with a jack shaft from the Datuns 5spd. Any help would be greatly appreciated TY

[racerx]

Check your timing, too advance can make engine ping. Cheap gas also.

[datzenmike]

Um.... it's a diesel. The injection pulse is the timing. It explodes from the heat of compression. Wayno will know more about the SD but it sounds normal to me. Diesels make a distinctive loud rappy sound.

[wayno]

OK, I do not know everything about these small diesel engines, but I will try to tell you what I believe I know.

The diaphragm has a spring that tries to floor the injection pump rack(rich), the venturi in the throttle body(carb looking thing) is what pulls the rack back to the idle position, when you let off the pedal that cuts off the air creating a lot of vacuum in the venturi which pulls the rack to the idle position, when you give it pedal, that creates less vacuum which lets the injection pump rack move to a richer position.

If that venturi is blocked, or if that vacuum line going to the rack/IP from the throttle body has a crack(air leak) in it, it causes issues like a lot of black smoke out the tailpipe, if the diaphragm has a crack in it you will have the same issue(black smoke coming out of the tailpipe), you will also have an elevated idle as the engine is getting lots of fuel but no air.

If it sat a long time the diaphragm could have dried out, if that has happened and the injection pump diaphragm may not move like it should, that could also cause a rich or lean issue, lean usually means no power, rich creates black smoke out the tailpipe, it depends on what position the rack was in when it sat, this depends on if the rack is controlled by a choke cable or if it still has the stock electrical system with a IP controller and a DPC module, does the engine quit when the key is turned off or do you use a choke cable to start/stop the engine?

If you have white smoke coming out the tailpipe you likely have low compression, bad glow plugs, a wore out injection pump, or a combination of all of the mentioned plus other stuff I know nothing about.

Keep in mind that diesel engines do not sound like gas engines, they have there own special sounds, the injection pump advanced or retarded too much can make them knock or make them hard to start, but it also can give them more power and that makes them way louder which sounds like rod noise.

I have found that if they run good and don't smoke you have a winner, it they have issues then they are a headache, they tend to get parked when they have issues, this likely means you are the proud owner of some ones else's headache.

[racerx]

Um.... it's a diesel. The injection pulse is the timing. It explodes from the heat of compression. Wayno will know more about the SD but it sounds normal to me. Diesels make a distinctive loud rappy sound.

...duh, gee Tennessee.

[Wilsunsd22]

Thanx for the input ?

[Wilsunsd22]

Ok tank you guys so much. I will try and run a vacuum line from tbi to inj. Pump.

Does the diaphram have a gasket and if it is torn where oh where would i find one.

[wayno]

Keep in mind that someone may have fiddled with the IP timing, you mentioned it sat for a long time, who knows what has been done to it.

I mentioned that vacuum line because if the stock line has a crack it will create issues, mostly an idle issue, does your engine idle smoothly at around 800rpms, does it blow black smoke out the tailpipe when you rev it?

A cracked diaphragm will have the same issues as a cracked vacuum line going from the throttle body to the IP(injection pump), it would likely run rich(blow black smoke out the tailpipe), if your not blowing a lot of black smoke out the tailpipe then your vacuum line and diaphragm are likely OK.

I have 2 SD series engines, they are timed differently, one has this sort of knocking sound, I believe that when the former owner put the home made turbocharger on it he fiddled with the injection pump timing, I removed the turbocharger as the waste gate was wired shut which is not a good sign, I ran the engine without the turbo for years with it timed that way, it had alright power but was hard to start when the block is cold, nearly impossible to start under 40 degrees, about a year ago I installed a smaller turbocharger on that engine than it had when I bought it, it is still hard to start but has lots of power on the freeway.

My other SD engine which has had a turbocharger on it since I bought it starts easy even when cold out, it has never made that knocking sound, that engine is a different animal, the turbo and injection pump have been modified, it is set up for low end torque, it really isn't set up for freeway driving.

Does your engine idle smoothly, it would help if you went into more detail, does it start hard or easy(how long does it turn over before hitting), does it blow a lot of white smoke out the tailpipe when first started, how long does it blow white smoke, does that smoke smell funny?

Have you ever used ether to start the engine?

Another thing I just thought of is the gear that is connected to the IP has a set of springs on it, it changes the timing of the IP according to RPMs, if that mechanism is rusted solid, the timing of the IP will not be correct at higher RPMs, is the knock load related, meaning do you hear the knock more when speeding up fast rather than slowly getting up to speed?

[Wilsunsd22]

Hello again

I tried replying from my email. However now i see it doesn't show up. So yes you are correct i have no idea what went on with this sd before last year when i found it. It does not blow black smoke i do get white smoke until it warms up i dont believe it is excessive. I have disconected the lingage arm from the electric controler and i have run a choke cable to a handle i made from an old window crank. With this i can put the ip in the start position. The glow plugs i run manually and they work fine starts right up on cold 40 degree mornings. I have run a jack shaft from the rear of the sds 5speed into a t90 jeep 3spd giving me 8 speeds forward and 5 speeds in reverse. The 3spd is hooked to a dana 18 transfer case which drives the front and rear axles. They are geared to 538 the sd seems to operate this setup perfectly. Now back to my issue. The sound is similarto a piston slap that you would hear on a bad gas engine. However it doesn't do it all the time. I notice if i operate it like a tractor and hold the rpms instead of operating the throttle like a car,it seems to like it. I did happen to notice as its warming up and I'm trying to keep the rpms up a little. I get a little flutter when it makes the noise. I am wondering if a may have a slight air leak in my fuel line. I have a steel linrun from the tank to the water seperator filter the n rubber from there to my ip. All lines are new including the return. I will say it took a lot of research viewing pics and reading threads to figure out how the plumbing needed to be run. I will try and check my lines over the weekend and see what happens. I am really grTeful for your interest in my project. My son, nephew and i have had alot of fun building it. I am trying to figure out how i can post some pics of the beast. I love the little sd and Wilsun just wouldnt be the same without it. Thanks again all.

[Wilsunsd22]

Oh just a couple of other things. I have never used the bad stuff to start it didn't need to. Fires right up once you get the fuel lines right. I do need to replace my primer bit weeps a little. It appears to be threaded into the pump assy. And i have an idea i have seen them online. We rebuilt the Buggy we named Wilsun. It used to be run by a 95 Subaru but it was really beat and the subaru wheels are odd to find a replacement for. We addaed 2 inch wheel spacers to the jeep axles which gives it a much better stance. The lt 245 75 16 tires now clear all the gagged edges.lol