David Brown 990 Injection Pump??

I put a message out there awhile ago about my DB 990. If you search, "David Brown 990 don't run good" you can read more in depth about it. Basically, the thing lacks power and has a lot of white smoke. It happened suddenly last fall.

Someone suggested testing the injectors at idle by loosening each one individually. I did that, and two caused a big change in idle and two did not change the idle at all. My wife's brother was just hear and knows a lot more than I do. He says I am lacking fuel with the white smoke. We did the injector test again today and when I loosened one of the two that had an effect on the idle the engine stalled.

He thinks my pump is the problem. I have a Cav pump on this tractor. Could anyone provide information on what kind of problem this pump can have such that two injectors are lacking fuel all of a sudden?

Thanks.

White smoke means engine is getting fuel, but not burning it. Take loose the two lines to the injectors that don't change the engine speed, if the smoke clears some, then returns with the lines tight those cylinders don't have enough compression heat to burn the fuel. Which two cylinders are they? Are they next to each other, may be a head gasket blown between those two. If you have the CAV DPA rotary pump it won't cause what you describe. Again, white smoke means pump/injectors are working, but fuel is not burning..

Thanks for the reply sir. It looks like you completely nailed it! The cylinders are next to each other, the furthest two from the seat. I rebuilt this engine 8 years ago, and the head gasket was shot. I still have it and looked at it, and it has a thicker piece of gasket in the middle and two much thinner pieces between the first two and last two cylinders. The thin piece was what was broke last time, but I can't tell which side of the gasket goes up or down so I don't know if it broke between the first two or last two cylinders last time.

I tried to loosen those two lines individually, could not tell much with the smoke. I loosened both of them together and it made a big difference in smoke. There is a hole at the bottom of the exhaust manifold where a tube was screwed into in the past. The threads are shot and I never fixed it. When the tractor idles, white smoke puffs out of that hole pretty hard, and also comes out between the bottom of the exhaust pipe and the exhaust manifold. When I loosened those two lines, the smoke from those two places disappeared. Then reappeared when I tightened the lines to the injectors.

I guess I will pull the head and see what I got there. All my manual says about the pump is that the make is a C.A.V.

Thanks a whole bunch. I feel like I should send you $50 or something.

I really appreciate it.

Hi I believe the pump is like Dieseltech said it is a CAV/DPA rotary similar to the one used on Perkins Diesels and the UK build IH Diesel engines.
CAV/DPA Pump

Just keep us posted on what you find will help someone else in the future. Been repairing injection pumps forty years, and have gone through a lot of pumps for the trouble you have when the problem is elsewhere. If you have access to a diesel compression tester will help confirm your trouble too before pulling the head..

That is the one without a doubt.

Thanks.

Well thanks again. This may sound stupid, but does the fact that two injectors don't affect idle vs. one tell you that the head gasket is bad and not an injector? I had posted a week or two ago looking for a reason why two injectors would have problems at the same time. I figured it could not be the injectors.

I would like to check compression. Maybe I should get a tester for the number of times people have told me to "check compression" over the last 10 years.

I will post again as I get it fixed.

Sure appreciate this site and people like you.

The hole in the manifold is just a drain, so that when water runs into the muffler, there is a way out and it doesn't freeze and crack the manifold. What ever comes out the hole is the same thing that is coming out the stack.

Hello RGMartin, thanks for the reply. If I remember right, you have parts for DB 990's? Is that right? The oil bath container on my air filter has a small leak in it and someday I would like to replace that if possible. If you have that part or can lead me to it that would be great.

Thanks.

Any time a head gasket blows between cylinders then compression is lost on both cylinders. Since the pump and injectors keep delivering fuel, and cylinder is too cold to burn it that's why there's white smoke. Taking the fuel away from cylinders with the line nut loose will clear the smoke. If the fuel stop rod is left in the off position, and engine is cranked with the starter you will hear a change in cranking sound and speed too. It will sound faster on the weak cylinders and slow to normal on the good compression cylinders. A good engine will sound the same as each comes up against compression.

(quoted from post at 16:28:16 06/11/16) Thanks for the reply sir. It looks like you completely nailed it! The cylinders are next to each other, the furthest two from the seat. I rebuilt this engine 8 years ago, and the head gasket was shot. I still have it and looked at it, and it has a thicker piece of gasket in the middle and two much thinner pieces between the first two and last two cylinders. The thin piece was what was broke last time, but I can't tell which side of the gasket goes up or down so I don't know if it broke between the first two or last two cylinders last time.

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Did you have the head checked for flatness when you did the rebuild or did you just put in a new head gasket and go? If the head gasket keeps giving problems then something isn't right.

Thanks for the reply. I don't remember what was done with the head, but I did have that sent out to the pros, along with the crankshaft and the engine block. I'm not sure if the head gasket broke in the same place or not, if that is the problem. I guess I will find out this week.