daverd4

Member
I have a 850 Diesel 172 cu that lobes real bad at low rpm's. Had pump and injectors rebuilt at a cost of $1400 and tractor has sat for 7 years with occasional starting only has about an hour on motor. A good friend with over 40 years tractor mechanic experience rebuilt the motor not sparing an expense it was the last thing he finished before cancer got him that's why it has sat. Now wanting to finish it but can't get it to run without lobbing and blowing white smoke. Pump shop says it went bad from sitting NOT buying that. Checked compression timing and valves all cylinders where 295 on compression which is low but can't spin it @ 1000 rpm's with the starter. There was a guy I think named Denny on here that had the same problem but never came back to tell what he found.
 
White smoke says coolant/water in the cylinders. Head gasket could be bad from sitting and if it was not started and run then the head bolts re-torque could well have a blown head gasket
 

I'm guessing you have an 851. Ford did not produce an 850 diesel.

First thing you need to do, since it's been setting that long, is drain and flush the fuel system. Fill it with fresh fuel. Next, verify that you are getting a good steady fuel supply at the injection pump by removing the supply line and observing the flow. If not, correct that next. If you are still in a no start condition, I'd concur with your friend. A Roosa Master (now Stanadyne) pump that has set that long tends to seize metering valve and timing pistons.
 
Yes it is an 851, yes we have good fuel to the pump, I didn't say it would not start I said it lobes after starting runs good at higher rpm's. It is not burning antifreeze you could smell that it is unburnt fuel that is making the whitest smoke like it is over fueling. It sound like it is bouncing off the governor @ 1000 rpm's. Tested all the injectors and they are all good pop off @ 2800 and good sray
 
To much fuel in a diesel is black smoke and in a diesel not likely to smell antifreeze
 
To much unburnt fuel under no load is white to much fuel under load is black. I have owned a trucking business for 33 years I know what over fueling looks like. I didn't come here to argue over facts I came here to see if someone has had the same problem. It seems no one read my post the tractor starts and runs just runs rough at idle up to 1000 rpm's
 
Have you checked timing? Not an expert but I have seen others fire a tad late and not burn fuel well.
 
Thanks yes the timing was at 18 and put it at 23 and no change. was hoping that was it. Anyone run a compression test on a 172 Diesel I know its a new not broke in motor and it should be at 554 @ 1000 rpm's but 295 @150 to 200 rpm's seems about right?????
 
I don't know about compression ,try taking fuel filters off emptying fuel and refill with New engine oil ( when oil won't go in easily top off with fuel ) I have had people say no don't do it but I have had good luck cleaning and lubing pump and injectors like this.
 
You are correct on your diesel smoke analysis. The pump shop could be correct also as things tend to stick after sitting too long. I have had the diesel shop send back an injector on a Detroit with the wrong parts inside that did this.(for a different series)

Can you loosen the lines one at a time and see which cylinder is missing at low speed?

Since it is running good at high speed I would verify the injector numbers are all the same, re check the valve lash, and put it to work long and hard to seat the rings. That may solve the problem.
 

Yes, I did miss the fact that it runs! I'm not sure what lobes or lobbing is. I'm guessing you meant lopes or loping from other comments you made. [b:71b0ab0e4d]Now![/b:71b0ab0e4d] You need to read what some of us wrote rather than being overwrought that we didn't read what you wrote! You more than likely have advance pistons hanging in that pump!!!! Your pump shop is likely correct!!!!
 
I had the same problem with my 861, loping at idle. I had set the timing per manual, still had the same problem. I ended up moving the pump slightly while idling tell loping stopped, runs fine now. I should also mention it did lope at pto speed while running my haybine, timing reset cured that too.
 
Surging is the new word lobbing is a 60's word. Have done everything everyone said pulled the top off the pump while running and can stop the surging with the tip off my finger on the governor so I have a load against the governor from something in the drive train our the governor has a problem.
 

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