802 running on one cylinder

[fa35jsf]

Help me! My 802 is only running on one cylinder. This all started after I pulled the head off and cleaned the valves, their seats and the top of the pistons. The injectors are brand new Onan brand injectors. I keep getting white smoke from one cylinder.

For testing I swapped the injectors around. The white smoke carried over to the other cylinder, however, the unit would not run at that point. So my thinking is I may have two issues. One being an injector which is not quite in spec and the other being an issue with the valves in one of the cylinders.

Additionally I took all of the rockers off and re-torque them to spec. I check to make sure all the pushrod spin freely. They all appear straight.

I used a new head gasket. The smoke is definitely fuel and not water. As you can see in one of the videos the spray pattern on both injectors look good to me. Maybe the left injector is not putting out as much fuel or for as long? That happens to be the injector that doesn’t want to work on any cylinder.


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[WWRD99]

I am not sure about 2 problems until you get the one injector that isn't working right...since you swapped it left to right and the smoke traveled with it that injector would be a issue....any chance they sent you a wrong one but boxed right? I think they are marked to show lbs or injector size. Sticking valves are usually very obvious with a loud tapping noise from a rocker arm...unless you tightened them down with the valve open a smidge...is installed spring height ok, if it is a valve that's how you'd know about being open...a compression check would tell you a bunch too if you have one of those testers...but I'd bet you have the wrong injector or bad new one.

 

[fa35jsf]

I am not sure about 2 problems until you get the one injector that isn't working right...since you swapped it left to right and the smoke traveled with it that injector would be a issue....any chance they sent you a wrong one but boxed right? I think they are marked to show lbs or injector size. Sticking valves are usually very obvious with a loud tapping noise from a rocker arm...unless you tightened them down with the valve open a smidge...is installed spring height ok, if it is a valve that's how you'd know about being open...a compression check would tell you a bunch too if you have one of those testers...but I'd bet you have the wrong injector or bad new one.

Idk if it was the wrong one. I’ll have to pull them and cross check numbers. One injector came in a nice new, clear plastic bag. The other injector, the bag was all faded yellow like it had been sitting on a shelf for several years. I also need to check valve height like you said.

My fear is that I damaged the exhaust valve on that one cylinder in the area of the seat. Don’t want to lay out all the details because I know it was an idiot move. Let’s just say, one should not use wood clamps in place of actual valve spring compression tools, just because they want to get the job done.


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[WWRD99]

Ok you just wrote your answer...the one in the yellowed bag was used or a return...probably had a deisel smell too...I've seen that a bunch...someone gets a new one and returns the old one saying it was wrong...company sells old part not knowing it...plastic bags don't turn yellow unless out in the sun...or has fuel on it...I can imagine the fun stuff that can be done to get valve keepers out...most issues are getting them back in...not getting them in the grooves thinking they are is common...they'll hold for a bit until they get revved up good...drops a valve most of the time.

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[Ray70]

You should either check the smoking cylinder's compression or check the valves for leaks. Neither is easily accomplished without the correct tools.
Easiest thing to do is loosen both rocker arms to ensure both valves are closed, then with the injector out find a way to pressurize the cylinder with air, even 20 PSI is plenty. Be warned that that piston will be forced to the bottom of it's stroke so stay clear of the fan / belt etc.
With the air pressure on, listen or feel the intake and exhaust ports for air leaks. Any air leaking indicates a problem with that valve.
NOTE: you will hear a small amount of air leaking past the rings into the crankcase, this is normal.

Also, after you tightened the rocker arms, did you let the motor sit a 1/2 hour or so before cranking it over? If not there is a possibility the lifters dis not bleed down yet and valves can hit the pistons. Luckily they just barely touch and the hit flat, so usually the pushrod will bend rather than bend the valve, but I can't say 100% of the time.

 

[fa35jsf]

You should either check the smoking cylinder's compression or check the valves for leaks. Neither is easily accomplished without the correct tools.
Easiest thing to do is loosen both rocker arms to ensure both valves are closed, then with the injector out find a way to pressurize the cylinder with air, even 20 PSI is plenty. Be warned that that piston will be forced to the bottom of it's stroke so stay clear of the fan / belt etc.
With the air pressure on, listen or feel the intake and exhaust ports for air leaks. Any air leaking indicates a problem with that valve.
NOTE: you will hear a small amount of air leaking past the rings into the crankcase, this is normal.

Also, after you tightened the rocker arms, did you let the motor sit a 1/2 hour or so before cranking it over? If not there is a possibility the lifters dis not bleed down yet and valves can hit the pistons. Luckily they just barely touch and the hit flat, so usually the pushrod will bend rather than bend the valve, but I can't say 100% of the time.

Thanks for the info. I already did the poor mans compression test that you mentioned with an air compressor and 100psi. No noticeable leaks from either cylinder. Some, but very little air down into the crankcase. That was at TDC and rockers still attached (valves closed).

And yes I waited for the hydraulic tappets to bleed down before cranking the motor over. Luckily I read that far through the TM.


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[Ray70]

Ok, so it sounds like your valves are good. So this motor was running fine before you opened it up to de-carbon it?
And all you did is remove the head, clean it up and replaced the injectors?
Do you still have the old injectors and was there an issue with them other than being dirty? Sticking open.... clogged etc.?
I assume if you start it, that white exhaust feels cold to the touch? if you let it run for 30 seconds does that cylinder start popping and eventually run clean or do it smoke and feel cold forever?

 

[fa35jsf]

Ok, so it sounds like your valves are good. So this motor was running fine before you opened it up to de-carbon it?
And all you did is remove the head, clean it up and replaced the injectors?
Do you still have the old injectors and was there an issue with them other than being dirty? Sticking open.... clogged etc.?
I assume if you start it, that white exhaust feels cold to the touch? if you let it run for 30 seconds does that cylinder start popping and eventually run clean or do it smoke and feel cold forever?

Yup. That’s all correct. It started with me addressing dry rotted fuel lines, then digging in to clean it up and see why I thought I had some blowby (I thought it was bad so wanted to check and make sure I didn’t have a cracked piston. Long story).

Took the injectors which looked awful to a place that tests diesel injectors. They called me up a few days later and said the spray pattern was awful and one of the injectors was sticking open. Quoted me way to much to rebuild them because they were Delphi brand and obsolete. So I bought two supposedly new Onan injectors. I’ve yet to go pick up my old injectors from the shop. Hope they still work.

Yes the white smoke is cold. I’ve let it run up to 5 minutes and nothing changed. The fuel is now washing out all the carbon from the exhaust side.


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[Ray70]

Wow that is strange. The cold smoke is definitely a lack of compression in my experience. However, a slight lack of compression will usually start to fire after 30 seconds of running due to increased heat and the excess fuel increasing compression in that cylinder. You aren't getting combustion at all but you have enough compression to make the fuel smoke.
I think you definitely need to do a compression test. If it was running fine before I would suspect either a leaky valve or head gasket, but your air test proved that not to be the case.
I have seen slightly bent ( barely noticeable ) connecting rods and worn ( severely worn ) rod bearings cause low compression just from the slight increase in piston to head clearance lowering the compression. BUT, that should not be the case with you.
The head gasket could be an issue if by chance it was way too thick, but I have used both Onan and China made head gaskets and never had a problem.
And that SHOULD affect both cylinders.
Best bet is a compression test. You would need a special adapter to test it.
I made my own adapters for 002/003 and 802/803. If you have access to a lathe or a machinist friend I can send you a sketch of what to make..
I pretty much made a dummy injector with a 1/4" NPT to thread my gage into it and an inset o-ring in the tip to seal to the head rather than the copper washer used with the injector. You will also need a 500 Psi gage. A standard 300PSI automotive gage is not high enough.

 

[fa35jsf]

Update. I had two problems. Got a bad injector sent to me and I bent an exhaust valve.

I lapped a new valve in and got a replacement injector and now this thing runs stronger than I imagined.

New fluids and stress tested it and I was able to pull 7,400 watts of resistive load before the motor bogged down. What’s even better, I only had to remove load down below 75% for it to recover. Before the rebuild, I had to reduce lid to 40-50% to get it to recover.


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[fa35jsf]

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