Trailblazer 302 acting up

[thegary]

I have a fuel injected 302 that has about 350 hrs on it. I had not used it for a couple months and figured I better go out and run it through its paces to make sure it is ok. It starts right up and idles down fine. It will run fine for about 5 minutes then it starts acting like it is getting too much fuel and starts with some black smoke and missing. It gets worse if I switch to full power . If I shut it off and restart it it runs fine for 5 minutes again then does the same thing. I thought it might just be because of the cold( it was 10 dregs when I started it). I have since run it 3 or 4 times on different days and the same thing. Today it is 33 degrees and it seems to take a little longer for it to act up but it still does it.

I thought maybe I over filled the fuel tank and it let fuel get into the engine but I have checked the oil and it is fine . Up until now it has never missed beat. I am wondering about the fuel injection system now.

[duaneb55]

Sounds like the throttle body may be icing up. It's my understanding that Kohler has a "warm air" duct setup that is supposed to alleviate icing in cold weather - if that's the issue.

[thegary]

Thanks Duane I will have to look into that kit . I have run it last winter and do not ever remember having any trouble. I think I have even run it on some sub zero days.

[Mark_D]

Humidity level plays into it.

[duaneb55]

Thanks Duane I will have to look into that kit . I have run it last winter and do not ever remember having any trouble. I think I have even run it on some sub zero days.

An EFI Trailblazer owner over on the Millerwelds forum had a similar issue with theirs a year or so ago but I don't recall what the solution/outcome was for them.

[snoeproe]

My carb bobcat was acting up this winter as well. The cure was adding some isopropyl alcohol in the fuel to prevent icing of the carb.

[thegary]

My carb bobcat was acting up this winter as well. The cure was adding some isopropyl alcohol in the fuel to prevent icing of the carb.

That was the first thing I did . Did not make any difference.

[snoeproe]

My carb icing was happening at -20 temps. You were no where near those temps.
Another issue I’ve had with my carb bobcat was throttle surging and rough running because of the engine oil level being too high. The machine came this way new from the LWs. Brand new machine and not running worth a darn. The oil level was much higher than the full line on the dip stick.
After reading through the manual, I found out it can cause irradiated fuel pump operation with the pulse operated fuel pump.
After draining some oil from the engine, the engine surging and rough running went away.
Pretty poor quality control on Millers part and I reported that back to the LWS who sold me the machine.

Not sure if this same situation can have the same effect with an EFI machine or not?

[thegary]

My carb icing was happening at -20 temps. You were no where near those temps.
Another issue I’ve had with my carb bobcat was throttle surging and rough running because of the engine oil level being too high. The machine came this way new from the LWs. Brand new machine and not running worth a darn. The oil level was much higher than the full line on the dip stick.
After reading through the manual, I found out it can cause irradiated fuel pump operation with the pulse operated fuel pump.
After draining some oil from the engine, the engine surging and rough running went away.
Pretty poor quality control on Millers part and I reported that back to the LWS who sold me the machine.

Not sure if this same situation can have the same effect with an EFI machine or not?

The oil level is touchy but in this case its not the problem. On mine if the oil level gets low but not as low as the low level mark it starts getting a tick in it when its running.The oil level is slightly below the full mark when I checked it thursday. Its supposed to be 40 tomorrow and I will have some time to mess with it. I am going to remove the air filter and check out the opertion after inspecting the throttle body.

[thegary]

OK I had time to play with it little bit today. It is not crb icing. It is 45 degrees today. I removed the air filter and waited for it to act up. When it happens the throttle plate opens too much and it starts missing, then the slower the rpm get as its missing the more the throttle plate opens and the worse it gets. If I grab the governor linkage anf force the throttle closed it straightens out and I can slowly let it open bsck up until the machine is running at its high speed and it stays running good. I did this at least a half dozen times and each time I could correct it manually with the governor manipulation by hand.

[duaneb55]

Low fuel pressure? Clogged fuel filter?

Sounds like it's starving for fuel and running lean.

[thegary]

Well I had some time to work on it today. I checked a possible grounding issue but that was not it. I changed both fuel filters and after starting it it did the same thing once. Then I started it back up and ran it for about 15 minutes switching from idle to welding speed several times and it seems to be running as it should. I figure the first hiccup on the first start up to being air in the fuel system from opening it upto install the filters.
There is still one concern I have but it might be unfounded. The fuel filter is clear plastic and I can see the fuel level in it. The most fuel I have seen in it is about 1/3 full. When I run it at welding speed the fuel in the filter drains down to where there is no fuel level in it. I can see a trickle of fuel going into it from the line but it seems to be just enough to keep the engine running with none extra to raise the fuel level in the filter. I have not had it under any load where it would demand more fuel so I am hesitant to say it is fixed but it will stay running good now with no load. I am wondering if the vacuum operated lift pump is going bad. I know the high pressure fuel pump to the injectors is working because it will run for a few seconds before I start the engine.

[duaneb55]

A "near empty" filter when new is not that unusual seeing as there is little to no resistance for the fuel to run thru it.

[lars66]

An EFI Trailblazer owner over on the Millerwelds forum had a similar issue with theirs a year or so ago but I don't recall what the solution/outcome was for them.

was that the vent hole plugged in the fuel cap? with frost?

[thegary]

was that the vent hole plugged in the fuel cap?

That is not what happened with mine. I removed the fuel cap and it still did the same thing. I am ordering a new vaccum operated lift pump tomorrow because I still think there is something wrong even though it is running ok now with no load. I believe that lift pump is barely working . Before I changed the filters I could still see into the old filter and I could watch the fuel level go down as it was running and once the filter was empty the engine started acting up about 30 seconds later. The filter still drains but evidently not enough to make the high pressure pump to start sucking air but it has to be very close . I can not see that it would work with a load on it. If it still acts the same after I install a new pump then I will conceed that it was fixed just by changing the filters. If so I will not be out that much money for the pump. If it improves the fuel flow to the filter I will have saved me destroying the high pressure pump from it trying to suck fuel instead of having fuel fead to it. The reason I believe it still is not fixed is that this happened suddenly and if it was the filter clogging it would have been a gradual thing. Either way I will sleep better knowing I am not starving the high pressure pump.

[thegary]

Well just for my own curiosity I went out and started it today. The problem is back. Today I can see fuel in the filter and it stays steady as far as fuel level. The engine runs for a few minutes and operats normally then it starts leaning out and missing just like before. If I turn it off and flip the switch back to on after it stops the high pressure pump runs for about 5 seconds and stops . I believe it stops when it reaches full pressure just like they do in a car with EFI. Once the pump stops and I start the engine it runs fine again for another few minutes and then starves out again. I can do that all day if I wanted to. That is telling me that it is not getting fuel to keep up with the high pressure pump. I am still ging to change the lift pump to see if that cures the problem but I am beginning to think their might be a problem with the High pressure pump too. When the engine is running it is too loud for me to hear if the high pressure pump kicks back on but for now I am going to assume it does.

[Mark_D]

My Lincoln Ranger 305, also with a Kohler, has an electric fuel pump instead of a vacuum pump. The vacuum pumps are known to fail frequently. You might consider buying a universal electric low pressure pump. They are available at most parts stores. Then you could bypass the crappy vacuum pump all together.

[leightrepairs]

You could try running it out of bucket of fuel, set the bucket a couple of feet above the carb and just gravity feed it. This would prove or dis-prove you thinking that the problem is the vacuum pump.

[thegary]

Well I put the new vaccum operated lift pump in today. Visually there does not seem to be any difference in fuel flow. The machine is still doing the same thing . I did get it to run for another 15 minute stretch then shut it off. I went back out about an hr later and it started acting up again. Just like before it will run fine for a few minutes but then starts into a lean mis condition. If I shut it down and flip it back to run I hear the High pressure pump run for 3-4 seconds then I restart it and it will run good for a few minutes again. I know the High pressure pump works because if I unplug it it dies immediately . There is nothing else in the fuel feed system before the HP pump that it could be. I can see fuel flow through the filter at all times though sometimes the amount of fuel in the filter does go down but there is still fuel flowing into the filter from the vacuum pump. I have tried it with the fuel cap loose and there is no change.

I am not sure what the next step is. I down loaded the engine manual and I will have to study it some to see what I am missing.

[thegary]

Well I put the new vaccum operated lift pump in today. Visually there does not seem to be any difference in fuel flow. The machine is still doing the same thing . I did get it to run for another 15 minute stretch then shut it off. I went back out about an hr later and it started acting up again. Just like before it will run fine for a few minutes but then starts into a lean mis condition. If I shut it down and flip it back to run I hear the High pressure pump run for 3-4 seconds then I restart it and it will run good for a few minutes again. I know the High pressure pump works because if I unplug it it dies immediately . There is nothing else in the fuel feed system before the HP pump that it could be. I can see fuel flow through the filter at all times though sometimes the amount of fuel in the filter does go down but there is still fuel flowing into the filter from the vacuum pump. I have tried it with the fuel cap loose and there is no change.

I am not sure what the next step is. I down loaded the engine manual and I will have to study it some to see what I am missing. Right now I am leaning tward doing what mark said and install a low pressure electric fuel pump .

[thegary]

I disconected the fuel tank and ran a hose into a gas can. There was no improvement so that eliminates anything to do with the fuel pickup in the tank. I read the manual some today and i am beginning to think it might be something with the ECU sending wrong info to the injectors. I do not have the software for these EFI engines so it might be time to take it to a shop for repair. I have eliminated all the mechanical issues I think. It says something about it running open loop until it is warmed up then changing to closed loop .

[guajilloweld03]

My old trailblazer 301g is doing about same thing. Last time this happen, got a syringe and added a clear tubbing so to siphon fuel from bottom of tank. Then put this fuel in a clear bottle and looked to see if it would layer. Water on bottom and gas on top. Sure enough it had water. Then siphoned out the water and drained carb and was good to go.
Added some Seafoam gas treatment.
Some how think it has water again. The local small engine guy told me to use premium gas. With EFI give it a good cleaning.

[snoeproe]

Water was my first thought as well but he said he added iso propyl alcohol to his tank already. That takes care of the water in the tank, unless he has a gallon or 2 of water in the tank.

[thegary]

Water was my first thought as well but he said he added iso propyl alcohol to his tank already. That takes care of the water in the tank, unless he has a gallon or 2 of water in the tank.

Yes I eliminated anything to do with a fuel tank issue when I ran the machine from a portable container and still had the same problems. See post #21

[thegary]

I took it into a local repair shop . Now I wait for them to have time to look at it.