IP - screwy main shaft

[greg lousy]

I noticed a while ago that my injection pump sprocket wasn't lined up correctly, sending the belt to one side and forcing the rim on the intermediate shaft pulley to pull it back, resulting in visible wear on the belt. I went to replace the belt and deal with the problem and realized that the problem is that the main shaft on the IP has a little play to it, maybe a millimeter or so but the effect is increased on the sprocket itself (kind of like the belt is always pulling the outer edge of the sprocket out a bit). I bought the remanned pump recently, maybe 1000 miles on it, and I think it came this way, as the misalignment was immediately visible.

So now I've got things back together with a new belt and I've made adjustments on the mounting so the belt runs straight. The belt and sprockets look and work fine but I keep thinking about the play on the pump's mainshaft.

I'm wondering if anyone here has had this experience or has any insights

[Quantum-man]

There are 2 causes of the play.
#1 over-tightening of the tensioner, which results in premature wearing of all the bearings, but primarily the pump bearing as it's the smallest, and

#2 merely old age with long service.

Over-tightening is a common issue due to the paranoia of those due to all the horror stories of belts jumping. Truth is, a belt can be relatively loose without jumping. Pulleys can slip sometimes because of a sudden increase in torque on the belt, due to something internal failing. My belt is such that I can rock it up and down about a 1/2" with a fingertip.
Being able to twist 45 degrees between the cam and pump with thumb and forefinger is another test.

Not saying that belts cannot jump, but it would have to be extremely loose, or its happened after the cam has wedged on something, or belt cover is off and a stone has climbed in under belt.

Only sure thing is as I've already stated; over-tightening will wear the pump bearing. Air ingress can then make starting hard as well as your belt tracking off. Once you are sorted; don't repeat the error. Bearing probably not serviced in the rebuild, if your issue was happening from the start, and your previous pump had not been suffering from the same issue.

[greg lousy]

thanks - the bearing makes sense

I started out as a paranoid belt overtightener but have gotten looser the more I've worked and read.
- (did you mean 90 degrees?) I can turn it 90 degrees with a few fingers, but not easily - may go looser still with this situation.

you'd think (or hope) that the bearing/ shaft union would be a high wear area and a priority for remanufacturers

it was starting and running fine before I got into this and expect it to again, as the condition of the pump seems the same as before. I guess I'll just check for air now and then and hope for the best. Would I see fuel leakage too?

[82vdub]

You could see fuel leakage out of the front input shaft seal, but it's unlikely. That is the suction side of the IP (injection pump) and when the engine is shut off, it could allow air to seep in, allowing the fuel to siphon back to the tank making for hard cold starts. Or, while it's running, it sucks in air that causes running issues with the engine as the fuel is injected with air bubbles. Those are the typical issues with the front main seal.

It may have passed a wear test during the remanufacturing process, or depending on the rebuilder, missed or simply a cheaply rebuilt unit.

[greg lousy]

I'll test for air upon start up to check it out. Hoping the seal can flex to adjust for this variance - its probably only a fraction of a millimeter where the shaft goes through it.

all I know about the remanufacturer is that they are bosch certified

[greg lousy]

I've had a clear line on the outbolt for a few weeks - a lot of air after sitting overnight, which works out after about a minute of idle, less with any throttle, after which no air at all. no smoke at all after a minute and it sounds/ feels great, which makes me think the pressure builds up fine. AIUI, the pump is well sealed when running, not while sitting, unless there's some other place air getting in, but I don't think so.
Starting a little rough, probably while air is worked out/ pump pressure builds, but started at 7 degrees this winter with the pump in this condition, so I guess I'll just ride it out.

still frustrating after the work and money getting everything to where it is


sound about right?

[TylerDurden]

If the overnight air clears in about a minute, I'd say the injector return lines are the prime suspect. Copper washers on the OUT fittings, maybe.

A mainshaft seal leak sucks in air when running.
Small shaft seal leaks are pressurized when running and drip fuel, same with the lid.

[ctange]

Is there a replaceable mainshaft bearing?

[TylerDurden]

Is there a replaceable mainshaft bearing?

There is a bushing that needs to be reamed to tight tolerance - need special tools. I would disassemble the IP and take the body and mainshaft to a shop and have them do it for ~$50.

[ctange]

Ok, it would have been easyer with at replaceble bearing.

[Fatmobile]

I'm not sure how easy it is to make a replaceable bearing with 1thou tolerance.

[greg lousy]

I would disassemble the IP and take the body and mainshaft to a shop and have them do it for ~$50

I might do the same if I had either another vehicle or less places to go

I've been working on the veggie oil system and in doing so have been messing with the return line. I still have clear hose in there and now it seems that the air may have been due to the configuration of my return line, and the way an air pocket was playing. Today I was running diesel from the WVO line (cleaning out the system). This line has the return looped into the fuel line and no air has been visible while running or sitting. I just checked after sitting for 6 hours - zero air. It just seemed like my IP losing pressure while sitting, then taking a minute to build pressure when first starting perfectly explained the small amount of white smoke when starting and the sporadic misfire (non-fire) the first minute after starting. Maybe that's not it though. Maybe its just be due to the compression, which is decent but inconsistent.
(360 310 400 420 .... with crap harbor freight tester). Maybe my slightly off IP mainshaft isn't so much of a problem.

I guess the only way to find out would be to put a pressure gauge on the IP like I've read about here. Maybe soon... I dunno, what do you guys think? Is it just that damn number two cylinder, waking up all crotchety, taking a little time to warm up?