743 smoking on start up

[Gbannish]

Hi, After not fixing my existing 743 bobcat with a wheel bearing problem, I instead bought a second 743 for what I thought was a good price, and came with 2 buckets and pallet forks. The seller said it was hard to start, there was a lot of smoke on start up, and whenever the throttle was changed. He also said was air in the lines, could not get out, and suspected a bad injector (although said he didn't know much about diesels). He had replaced the glow plugs, starter, hydraulic pump (he said). Once I got it home, I found a missing nut on the glow plug wire (I think on cylinder #3, the second closest to the front of the machine). After putting a new nut on it, the machine started much easier cold, but still stumbled, stalled once, then upon restart ran fine. The smoke however, was impressively large in quantity (just about smoked myself out of the barn!), I thought was mostly black, smoked about 5 minutes, then stopped mostly, and did not come back, even when changing the throttle.
I usually misdiagnose everything, so am looking for some advice. First off, I replaced the engine oil (did not tilt the bobcat back and made a bit of a mess), added coolant (took about 1/2 gallon), checked the hydraulic oil (no sight glass, instead was a plastic "bolt"). I plan to replace the air filters (cost me a "mere" $60 at the dealer!). I'm also planning to replace all the fuel lines, primer bulb, fuel filter, remove fuel tank and replace the pickup tube/screen), because I have the parts and think I can do without screwing up too badly. Also bought a replaced bleed screw (that screws into the injector assembly and used to bleed the fuel line).
I suspect that 1 or more fuel injectors may be bad? Perhaps leaking, which is causing the huge amount of smoke on startup. Thoughts?
Oh yeah, just had to mention, the previous owner must have removed the piston for the boom, and replaced it upside down. I found that out when trying to grease it up! Incredible!

 

[farmshop]

I would guess injectors. Could be seeping causing fuel to drain out causing hard starting. To test crack open lines one at a time with it running and listen for change in how it runs. A temp gun on exhaust manifold works also a bad injector or cylinder will show up cooler than the rest.

 

[Gbannish]

I would guess injectors. Could be seeping causing fuel to drain out causing hard starting. To test crack open lines one at a time with it running and listen for change in how it runs. A temp gun on exhaust manifold works also a bad injector or cylinder will show up cooler than the rest.

I worked on it today. It smoked bad on startup as usual, got it into the driveway, checked the temp of the exhaust pipes at each cylinder as you suggested, found the back three were at about 195F, and the front one was at 160F. Cool! I then removed the injector, disassembled it, sprayed with wd40, reassembled, reinstalled. I also replaced the injector bleeder screw thingy. Then I removed the fuel tank, took me a long time due to some old bolts, checked the dip tube (was fine), then replaced the fuel lines, all except one from the fuel filter to the engine (will do next time, along with a fuel filter), also replaced the fuel bulb thing, and a new cutoff switch(taken from a scag mower). During this process, I found loose wires at the fuel tank and corroded ground(?) wires at the top of the cab near the fuel tank, and fixed all of these.
I went to try to start, heard the starter start to crank for a split second, then died. Then no power to anything, no engine lights, etc. I removed the instrument panel, probed around a bit, in my novice way, and then the engine lights came on, then out, then on. So must be a loose connection, or ground?
How frustrating! I can't test my fuel line work because I can't crank the engine!! Not sure the best path forward, guess will start cleaning the battery terminals. And then every other electrical connection I can find! Forgot to mention the previous owner had a lot of loose wires, cut wires, etc... fun times!

 

[farmshop]

I worked on it today. It smoked bad on startup as usual, got it into the driveway, checked the temp of the exhaust pipes at each cylinder as you suggested, found the back three were at about 195F, and the front one was at 160F. Cool! I then removed the injector, disassembled it, sprayed with wd40, reassembled, reinstalled. I also replaced the injector bleeder screw thingy. Then I removed the fuel tank, took me a long time due to some old bolts, checked the dip tube (was fine), then replaced the fuel lines, all except one from the fuel filter to the engine (will do next time, along with a fuel filter), also replaced the fuel bulb thing, and a new cutoff switch(taken from a scag mower). During this process, I found loose wires at the fuel tank and corroded ground(?) wires at the top of the cab near the fuel tank, and fixed all of these.
I went to try to start, heard the starter start to crank for a split second, then died. Then no power to anything, no engine lights, etc. I removed the instrument panel, probed around a bit, in my novice way, and then the engine lights came on, then out, then on. So must be a loose connection, or ground?
How frustrating! I can't test my fuel line work because I can't crank the engine!! Not sure the best path forward, guess will start cleaning the battery terminals. And then every other electrical connection I can find! Forgot to mention the previous owner had a lot of loose wires, cut wires, etc... fun times!

Nothing worse than patching somebody else's patched up or hacked up wiring. I would start with the main ground and the positive connection at the starter

 

[Tazza]

Nothing worse than patching somebody else's patched up or hacked up wiring. I would start with the main ground and the positive connection at the starter

The 743 has fuses in the panel, it could be a bad fuse ir corroded connections behind the panel or even the connector that you will see if you flip the cab up.
If you need to jump it for a test, jump the small wire on the starter to the +ve terminal on the starter.
I didn't think an injector could cause smoke like that, but the temperature readings do show there was no or little ignition in that cylinder.
The first thing i'd have done was to change the air filter, black smoke is unburnt fuel, it can be due to a bad spray pattern or not enough air.

 

[Gbannish]

The 743 has fuses in the panel, it could be a bad fuse ir corroded connections behind the panel or even the connector that you will see if you flip the cab up.
If you need to jump it for a test, jump the small wire on the starter to the +ve terminal on the starter.
I didn't think an injector could cause smoke like that, but the temperature readings do show there was no or little ignition in that cylinder.
The first thing i'd have done was to change the air filter, black smoke is unburnt fuel, it can be due to a bad spray pattern or not enough air.

Thank you Farmshop and Tazza! I found the problem this evening while cleaning the battery terminals. The thick red positive cable had a small red wire (ie 12 gauge) coming out of it right near the cable end. it had been crimped a few inches away and came apart. I reattached it. That small red wire traveled alongside the fuel lines, not sure where it ended. But once I reattached that wire, the electrics seemed to work. I heated the glow plugs for 30 seconds, then hit the starter. At first it did like before, started to turn for a split second and then stopped. But once holding the key in start, it started turning. I had a heck of a time getting the thing started, but eventually she fired. I then tested the temperature of the exhaust pipes at each cylinder, and the first (front) cylinder was still about 20F cooler than the rest.
I'm calling this a win and frankly am elated, as I was able to get the thing started, and moved into the barn before a storm tomorrow. I'm pretty sure it will smoke as bad or nearly so as it had before. Next steps? Unless advised otherwise (and please advise!), I think I'll a) finish replacing the last fuel line and filter, b) switch injectors and check to see if the cooler temp moves with the injector, and c) try to do a compression test, and d) replace the air filter. My fear is that the head may be cracked, and I'd like to find out if something serious is wrong before going much further. Depending on the results, maybe I'll also order some injectors off the internet, they're pretty cheap...

 

[farmshop]

Thank you Farmshop and Tazza! I found the problem this evening while cleaning the battery terminals. The thick red positive cable had a small red wire (ie 12 gauge) coming out of it right near the cable end. it had been crimped a few inches away and came apart. I reattached it. That small red wire traveled alongside the fuel lines, not sure where it ended. But once I reattached that wire, the electrics seemed to work. I heated the glow plugs for 30 seconds, then hit the starter. At first it did like before, started to turn for a split second and then stopped. But once holding the key in start, it started turning. I had a heck of a time getting the thing started, but eventually she fired. I then tested the temperature of the exhaust pipes at each cylinder, and the first (front) cylinder was still about 20F cooler than the rest.
I'm calling this a win and frankly am elated, as I was able to get the thing started, and moved into the barn before a storm tomorrow. I'm pretty sure it will smoke as bad or nearly so as it had before. Next steps? Unless advised otherwise (and please advise!), I think I'll a) finish replacing the last fuel line and filter, b) switch injectors and check to see if the cooler temp moves with the injector, and c) try to do a compression test, and d) replace the air filter. My fear is that the head may be cracked, and I'd like to find out if something serious is wrong before going much further. Depending on the results, maybe I'll also order some injectors off the internet, they're pretty cheap...

That small wire you repaired is most likely the main feed for the key or fuse panel. Little victories are what keep us turning wrenches

 

[Gbannish]

That small wire you repaired is most likely the main feed for the key or fuse panel. Little victories are what keep us turning wrenches

Thanks farmshop. I had a good day today, for me. I removed the exhaust pipe to gain better access to the fuel lines and injectors. The nuts on the exhaust studs were impressively rusty, I heated them with a map torch (don't have acetylene), then added PB blaster, then the nuts came off. I took off the fuel lines, but unfortunately also removed the diversion valves. I also removed the glow plugs, tested them (all had about 1 ohm resistance). I cleaned all of the injectors, found that the first one was stuck, but was able to free it up. Oh yeah, I bought a compression tester and tested in the glow plugs, and all cylinders were 420 +/- 10. I put it all back together, thinking I solved it, but no. After starting, the first cylinder was still way cooler by about 30-40f. So at this point, should I switch injectors and see if the cooler cylinder goes with the injector? Not really sure what else to do...

 

[farmshop]

Thanks farmshop. I had a good day today, for me. I removed the exhaust pipe to gain better access to the fuel lines and injectors. The nuts on the exhaust studs were impressively rusty, I heated them with a map torch (don't have acetylene), then added PB blaster, then the nuts came off. I took off the fuel lines, but unfortunately also removed the diversion valves. I also removed the glow plugs, tested them (all had about 1 ohm resistance). I cleaned all of the injectors, found that the first one was stuck, but was able to free it up. Oh yeah, I bought a compression tester and tested in the glow plugs, and all cylinders were 420 +/- 10. I put it all back together, thinking I solved it, but no. After starting, the first cylinder was still way cooler by about 30-40f. So at this point, should I switch injectors and see if the cooler cylinder goes with the injector? Not really sure what else to do...

Wouldn't hurt to switch injectors around. Other thought would be valve clearances in the head. Otherwise fuel pump would be suspect

 

[Gbannish]

Wouldn't hurt to switch injectors around. Other thought would be valve clearances in the head. Otherwise fuel pump would be suspect

Thanks much for the replies! I switched the injectors (bad one was in the first cylinder, switched to the second). After warming up the engine, I tested the temp of the exhaust pipes from each cylinder again, and the cool exhaust pipe remained on the first cylinder even after switching injectors (the temps were 160-165 for the back 3 cylinders and 140 for the front one).

So what does this mean? I'm guessing the injector is not to blame, and had thought this test would definitively point to a bad injection pump. I guess I don't understand how valve clearances could still be an issue if the compression test was good? Sorry, just not too averse in engine troubleshooting! (In fact, I'm pretty impressed I didn't break something by now!). Would you recommend I try a new injector pump now, or pull the head and look at valve clearances, rockers, and or anything else that might be amiss. I don't know how to find TDC, will have to research that, in order to look at valve clearances. And if I do pull the head, do I need a new gasket or any other parts to get it back together?

I didn't mention, but I also changed out the air filter as Tazza had suggested, and the old one was horribly dirty, I don't see how that could not have been a problem! Also, I might be imagining this, but the machine does seem to be running a bit better, less black smoke, now see some white smoke, also something is coming out of the blow by tube, I'll need to monitor how much. Perhaps I'll go run it for 1/2 hour and see what happens...

 

[Gbannish]

Thanks much for the replies! I switched the injectors (bad one was in the first cylinder, switched to the second). After warming up the engine, I tested the temp of the exhaust pipes from each cylinder again, and the cool exhaust pipe remained on the first cylinder even after switching injectors (the temps were 160-165 for the back 3 cylinders and 140 for the front one).

So what does this mean? I'm guessing the injector is not to blame, and had thought this test would definitively point to a bad injection pump. I guess I don't understand how valve clearances could still be an issue if the compression test was good? Sorry, just not too averse in engine troubleshooting! (In fact, I'm pretty impressed I didn't break something by now!). Would you recommend I try a new injector pump now, or pull the head and look at valve clearances, rockers, and or anything else that might be amiss. I don't know how to find TDC, will have to research that, in order to look at valve clearances. And if I do pull the head, do I need a new gasket or any other parts to get it back together?

I didn't mention, but I also changed out the air filter as Tazza had suggested, and the old one was horribly dirty, I don't see how that could not have been a problem! Also, I might be imagining this, but the machine does seem to be running a bit better, less black smoke, now see some white smoke, also something is coming out of the blow by tube, I'll need to monitor how much. Perhaps I'll go run it for 1/2 hour and see what happens...

Ok, to clarify, today the machine is running better now at start up, idle, and up to medium throttle. I'm not getting the black smoke issues. I'll bet if I start it cold tomorrow, there will be white and black smoke at start up, but will resolve pretty quick. However, at 3/4 throttle the engine seems to struggle to rev any faster, and at full throttle, the engine sounds bad and starts smoking black. If I lower the throttle, the smoking stops and it sounds fine. After I ran it for 1/2 hour, the cylinder temps were 260-265F for the last 3 cylinders, and 225F for the front cylinder. So I guess it's running on 3 cylinders?

For my homeowner purposes, perhaps running at 1/2 throttle will work fine for a while. But I don't want to damage it further and would like to know what's wrong with this machine!

 

[farmshop]

Ok, to clarify, today the machine is running better now at start up, idle, and up to medium throttle. I'm not getting the black smoke issues. I'll bet if I start it cold tomorrow, there will be white and black smoke at start up, but will resolve pretty quick. However, at 3/4 throttle the engine seems to struggle to rev any faster, and at full throttle, the engine sounds bad and starts smoking black. If I lower the throttle, the smoking stops and it sounds fine. After I ran it for 1/2 hour, the cylinder temps were 260-265F for the last 3 cylinders, and 225F for the front cylinder. So I guess it's running on 3 cylinders?

For my homeowner purposes, perhaps running at 1/2 throttle will work fine for a while. But I don't want to damage it further and would like to know what's wrong with this machine!

With consistent compression numbers one would think it's still a fuel problem. When you speed it all the way up. Look at your fuel line and primer bulb is it sucking flat indicating a restriction some place. Make sure the primer bulb arrow is the right way. Did you get rid of your first machine? If not you could try flip floping parts

 

[Gbannish]

With consistent compression numbers one would think it's still a fuel problem. When you speed it all the way up. Look at your fuel line and primer bulb is it sucking flat indicating a restriction some place. Make sure the primer bulb arrow is the right way. Did you get rid of your first machine? If not you could try flip floping parts

Thanks Farmshop, I'll recheck the fuel bulb direction and see if its compressed at full throttle. I do have my other machine, lucky for me, and can try flipping parts if it gets to that. If I were to swop fuel injector pumps, would I transfer the shims too?

Today I adjusted my valves. First, I took off the fan shroud to visualize the crankshaft pulley with TDC marks on it, and one of the bolts also holds on the thermostat housing. It turns out that bolt was buggered, silicon was on the thermostat housing gasket, and there was no thermostat inside! So I cleaned up the threads with a tap and die, but will need a thermostat before running the machine (I don't have a gasket and not in that much hurry to use silicon). Next, I removed the fuel lines to access the glow plugs, and removed those to relieve compression.

The valve clearances were horrifyingly loose! Like 1/8 to 1/4 inch loose! I couldn't believe it. I noticed that at about the TDC mark for 1-4, either cylinder 1 or 4 would have a little bleb of fuel come out the top of the fuel injection pump on that corresponding cylinder (the bleb seemed closer to the TDC mark than the FI mark). I believe Tazza mentioned this in a post in 2005. At that point for cylinder #1, I then adjusted both valves to 0.008 (took about 3 full turns!). Then I did the same for the other cylinders.

Did I adjust the valves correctly? How could they have been so loose? I don't suspect I've solved any problems, as there was nothing specific to cylinder #1.

 

[farmshop]

Thanks Farmshop, I'll recheck the fuel bulb direction and see if its compressed at full throttle. I do have my other machine, lucky for me, and can try flipping parts if it gets to that. If I were to swop fuel injector pumps, would I transfer the shims too?

Today I adjusted my valves. First, I took off the fan shroud to visualize the crankshaft pulley with TDC marks on it, and one of the bolts also holds on the thermostat housing. It turns out that bolt was buggered, silicon was on the thermostat housing gasket, and there was no thermostat inside! So I cleaned up the threads with a tap and die, but will need a thermostat before running the machine (I don't have a gasket and not in that much hurry to use silicon). Next, I removed the fuel lines to access the glow plugs, and removed those to relieve compression.

The valve clearances were horrifyingly loose! Like 1/8 to 1/4 inch loose! I couldn't believe it. I noticed that at about the TDC mark for 1-4, either cylinder 1 or 4 would have a little bleb of fuel come out the top of the fuel injection pump on that corresponding cylinder (the bleb seemed closer to the TDC mark than the FI mark). I believe Tazza mentioned this in a post in 2005. At that point for cylinder #1, I then adjusted both valves to 0.008 (took about 3 full turns!). Then I did the same for the other cylinders.

Did I adjust the valves correctly? How could they have been so loose? I don't suspect I've solved any problems, as there was nothing specific to cylinder #1.

Not sure on the valve adjustment procedure but sounds right. Anytime I adjust valves if anything seems way off I double check to make sure I am on the right cylinder. Not sure on swapping the pump maybe tazza will check in

 

[Tazza]

Not sure on the valve adjustment procedure but sounds right. Anytime I adjust valves if anything seems way off I double check to make sure I am on the right cylinder. Not sure on swapping the pump maybe tazza will check in

Changing the pump is pretty simple, but i'd like to think that is a very last resort.
I'd start with getting compression readings, see if it could be a compression issue.
A little smoke out the breather tube is normal, if there is a lot of air/oil coming out of it, you have worn cylinders/rings.
A compression test will tell you a lot about the condition of the cylidners.

 

[Gbannish]

Changing the pump is pretty simple, but i'd like to think that is a very last resort.
I'd start with getting compression readings, see if it could be a compression issue.
A little smoke out the breather tube is normal, if there is a lot of air/oil coming out of it, you have worn cylinders/rings.
A compression test will tell you a lot about the condition of the cylidners.

Yep, I checked the compression with a cheap harbor fright tester, and came up with 420 for all cylinders. Had never done before, let the engine crank for 2or 3 seconds until the pressure stopped increasing. I think one of the cylinders took a little longer to build pressure.

My thermostat arrives Friday, I might recheck the compression and or my valve lash, then give her a go. The valves on all cylinders were so far off that that has me concerned (but I'm a novice at this stuff...). But there was nothing specific to cylinder 1, so I'm still stumped...

 

[Tazza]

Yep, I checked the compression with a cheap harbor fright tester, and came up with 420 for all cylinders. Had never done before, let the engine crank for 2or 3 seconds until the pressure stopped increasing. I think one of the cylinders took a little longer to build pressure.

My thermostat arrives Friday, I might recheck the compression and or my valve lash, then give her a go. The valves on all cylinders were so far off that that has me concerned (but I'm a novice at this stuff...). But there was nothing specific to cylinder 1, so I'm still stumped...

I wouldn't bother checking the compression again, if it was low, then yes, but 420 is pretty damn good.
I was told that 350 was about the lowest limit for a dieselto start.
The figures you gave on the valve lash was quite a lot out. You mentioned where you found TDC was closer to the fuel injection time. the injection is only a few degrees before TDC
A bit of smoke at startup is normal, but it should clear up within a few seconds.

 

[farmshop]

I wouldn't bother checking the compression again, if it was low, then yes, but 420 is pretty damn good.
I was told that 350 was about the lowest limit for a dieselto start.
The figures you gave on the valve lash was quite a lot out. You mentioned where you found TDC was closer to the fuel injection time. the injection is only a few degrees before TDC
A bit of smoke at startup is normal, but it should clear up within a few seconds.

With white smoke I would keep an eye on coolant levels if you have a small leak leaking into a cylinder that could cause white smoke. A leak down test on the cooling system would rule it out. Everything you are finding would make you think somebody tore into it and couldn't make it right

 

[Gbannish]

With white smoke I would keep an eye on coolant levels if you have a small leak leaking into a cylinder that could cause white smoke. A leak down test on the cooling system would rule it out. Everything you are finding would make you think somebody tore into it and couldn't make it right

Thanks Tazza and Farmshop! Well some good news today, I received the thermostat and so was able to put it in and test her out. I was lazy and did not repeat the compression test or check for valve clearances. Well, after priming she fired right up. There was some white smoke but not a huge amount. There seems to be some blow by but not a huge amount (although I don't know what is a lot). The first cylinder temp is still low, but not as low (maybe about 185 when the other cylinders are 200). Upon revving up, there is now no hesitation, no knocking and black smoke, just a bit of white smoke after hitting the throttle, then goes away (mostly, there are still some fumes). In contrast, when I got the machine 2 weeks ago, it was very, very hard to start, then poured black smoke (probably masked the white smoke), then white smoke, and would knock and pour black smoke when going past 1/2 throttle. So in summary, although the engine doesn't seem new and has some signs of wear, I'm thinking it might be ok to run it like it is (the engine at least!). Well, I didn't mention the rockers with uneven wear, but will save for another day. I did bugger up two of the injectors (a brass washer on the injector for cylinder 1, and the thing that has the return hoses for the injector on cylinder 2), and will need to address.

During replacement of the thermostat (or more accurately, adding the previously non-existent thermostat!), I flushed the coolant, and upon removing the coolant hose to the overflow tank, discovered that the copper nipple where that hose attaches to the radiator (just below the radiator cap) had broken off! So once the coolant heats up, it pushes against the cap and instead of going down the overflow hose in to the overflow reservoir, pours down into the engine compartment and on top of the battery! Just another sign of the lack of attention from the previous owner, or a pessimist might even think deception from the previous seller (and my lack of careful evaluation before purchasing). I attempted a repair, using a propane torch, flux and solder, and it seemed to work, we'll see if it holds up (it seems to be holding after 10 minutes of driving).

Tazza, my compression gauge is so cheap, I can't be sure that the 420 reading was accurate. But will hope it is!

Farmshop, thanks, I'll keep an eye on the coolant levels, and if they drop, will start stressing about how to do a leak down test...!

I'll try her out tomorrow, and if good, will just focus on fixing the injector seals, and then call the engine fixed enough for me, for now. I would like to express my sincere thanks to Farmshop, Tazza, and this forum for the help on this problem in particular, and general helpful suggestions in this forum over the years. It's really helpful for unknowledgeable guys like me...!