M35a2 hard start when cold surging hunting and smoking

[Kellyrobins1977]

This last fall I purchased a 71 m35a2. It had been sitting for years. Truck started after 2 -3 try usually. It drove great when you floored the pedal. But had a bad hesitation in low to mid throttle. When the weather here in Arizona started getting colder. Starting became next to impossible in eaely mornings. But possible when it warmed up. I did the fdc bypass as well as the manifold heater bypass since I was suspecting diesel leaking into oil. I had changed the oil when I first got the truck and there was more oil then should of been. I also changed all fuel filters and air filter. Nothing changed the way it hesitated or started. Whats strange is the way the rpm goes up and down while idling when cold. It blows bluish smoke but clears after warming. I pulled the injectors and purchased a pop tester. Every injector was leaking and none would chater after the first few pumps of the tester. I purchased a used set of injectors since I thought that had to help. They came from a working truck and none of them leak. However only one actually chattered properly. After I installed them nothing changed. I cleaned the gas tank since it was full of rust but still runs like shit. What would be the next step? Pull the injection pump and check orings? Or could the lack of injector chattering cause this problem?

 

[GopherHill]

How is your lift pump in the fuel tank? Does it pump fuel to the filters?

 

[Kellyrobins1977]

How is your lift pump in the fuel tank? Does it pump fuel to the filters?

Seems to work ok. But I havent checked the pressure. If I turn off the fuel pump while it's still running, I don't notice any change in rpm or hear any difference in performance. Should it affect performance while idling?

 

[WillWagner]

Or possibly a giant restriction. There is a filter located under the alternator, did that get changed. Also, the hard fuel line that runs from the tank, to the filter under the alt and across the front of the frame, has a tendency to get crushed. That can cause restriction issues. Also, ef you hear the in tank pump working, sometimes the rubber hose on the pump, from the pick up to the pump, rots, cracks and can cause low low pressure fuel or a symptom like air in the fuel. The injection pump has a gear pump on it and it can suck air if the hose on the pick up is junk.

 

[Kellyrobins1977]

Or possibly a giant restriction. There is a filter located under the alternator, did that get changed. Also, the hard fuel line that runs from the tank, to the filter under the alt and across the front of the frame, has a tendency to get crushed. That can cause restriction issues. Also, ef you hear the in tank pump working, sometimes the rubber hose on the pump, from the pick up to the pump, rots, cracks and can cause low low pressure fuel or a symptom like air in the fuel. The injection pump has a gear pump on it and it can suck air if the hose on the pick up is junk.

I replaced the small rubber hose on the lift pump in the tank then I did the primary filter and the line running from the primary to the boost pump. Also 2 lines and filters after the boost pump. Didint change the line from the tank to primary but it looked ok. What should pressure be right after final filter? Also could the valves be suspect?

 

[V8srfun]

I wonder if you still have air in the system from when you replaced the injectors. Or if the new injectors are possibly faulty. Did I understand properly that the new to you set of used injectors did not pass pop test

 

[Kellyrobins1977]

] QUOTE
I wonder if you still have air in the system from when you replaced the injectors. Or if the new injectors are possibly faulty. Did I understand properly that the new to you set of used injectors did not pass pop test
[/.When I got the injectors I opened them up and cleaned them with carb cleaner. They had lots of carbon around nozzles so I ran a Qtip thru them and took a fine piece of copper wire to clear out the holes. Sprayed them down with wd40 , reassembled hooked them to the pop tester. All but one of them would chatter for the first 2-3 pumps . But then stopped chattering and would just spray a misty stream (I guess you could call it). I set them all to 3200psi. one of them chattered perfectly though. I was using diesel mixed with a little motor oil to test and a few of them I tested different ratios of oil to diesel mix. Nothing changed as far as them holding fuel or chattering. The only difference was more oil = less mist. Yea i purged the air from the bleeder valve on top of filters

 

[Kellyrobins1977]

When I got the injectors I opened them up and cleaned them with carb cleaner. They had lots of carbon around nozzles so I ran a Qtip thru them and took a fine piece of copper wire to clear out the holes. Sprayed them down with wd40 , reassembled hooked them to the pop tester. All but one of them would chatter for the first 2-3 pumps . But then stopped chattering and would just spray a misty stream (I guess you could call it). I set them all to 3200psi. one of them chattered perfectly though. I was using diesel mixed with a little motor oil to test and a few of them I tested different ratios of oil to diesel mix. Nothing changed as far as them holding fuel or chattering. The only difference was more oil = less mist. Yea i purged the air from the bleeder valve on top of filters

 

[V8srfun]

I would try to bleed them where the hard line attaches to the injectors but you may want to hear from someone more knowledgeable than me before you try that.

 

[Kellyrobins1977]

When I got the injectors I opened them up and cleaned them with carb cleaner. They had lots of carbon around nozzles so I ran a Qtip thru them and took a fine piece of copper wire to clear out the holes. Sprayed them down with wd40 , reassembled hooked them to the pop tester. All but one of them would chatter for the first 2-3 pumps . But then stopped chattering and would just spray a misty stream (I guess you could call it). I set them all to 3200psi. one of them chattered perfectly though. I was using diesel mixed with a little motor oil to test and a few of them I tested different ratios of oil to diesel mix. Nothing changed as far as them holding fuel or chattering. The only difference was more oil = less mist. Yea i purged the air from the bleeder valve on top of filters

I would try to bleed them where the hard line attaches to the injectors but you may want to hear from someone more knowledgeable than me before you try that.

Going to try that right now. I'll post a video of it cold starting so you can see exactly what it's doing

 

[Kellyrobins1977]

I just noticed the new fuel line between the primary filter and booster pump has fuel on it. It's tight so I'm thinking maybe the booster pump is leaking. It's wet about 12" down the line and the booster pump has oil on it.

 

[Kellyrobins1977]

I just noticed the new fuel line between the primary filter and booster pump has fuel on it. It's tight so I'm thinking maybe the booster pump is leaking. It's wet about 12" down the line and the booster pump has oil on it. View attachment 824712View attachment 824713View attachment 824714

I just replaced the line and it was dry. I replaced the old one because it was wet just like it is now. Maybe it was the booster pump all along?

 

[V8srfun]

Definitely a leak there hopefully you found your problem!!!

 

[Kellyrobins1977]

Would be nice. I'm going to wait to start it up in the morning so I don't piss off my neighbors. I'll try bleeding the injectors but if that don't help then I'm pulling the pump. Probably will pull it regardless since it definitely looks like it's leaking. Thanks for all the responses from everyone on here!. I'll let you all know how it turns out.

 

[WillWagner]

If it starts and runs, it will bleed itself. No reason to bleed after it runs. It IS possible to introduce "air" into the system from a weak pintle spring. The compression overrides the pintle spring in the injector and lets compression INTO the fuel system. It will usually shut an engine off due to so much compression being pushed into the system. When a pintle injector is torn down, the only place carbon should be present is on the tip of the pintle and in the cavity of the nozzle. If the tapered portion of the pintle is dark, the spring pressure...pop off...is weak. You said the "new" injectors didn't pass the chatter test. I do not remember the low pressure spec, I THINK 10 psi?.

Find a way to divide the system in half, engine and chassis. Install a clear line looped like a roller coaster loop and a pressure gauge. Start it and run it, look for air in the clear looped line and check PSI. If all good, let it sit over nite and in the AM, see if the fuel is gone on either side of the loop. Top of the loop toward the tank, an issue on that side. Other way, an issue on the engine side, up to and including a fuel pump, but as simple as a washer on the filter cans. Usually, only one shot a day at this because every time the system is touched, it takes time to work the air out.

 

[M37M35]

It had been sitting for years...

Whats strange is the way the rpm goes up and down while idling...

Since the truck has been setting, another issue could be the fuel shut-off lever sticking.
Remove the cover where the engine stop cable goes into the injection pump and make sure the lever inside is moving freely. If it's gummed up and not moving freely, that will cause an erratic rpm issue.

 

[M37M35]

If it starts and runs, it will bleed itself.

This, If it's running, the injectors will bleed themselves.

Would be nice. I'm going to wait to start it up in the morning so I don't piss off my neighbors. I'll try bleeding the injectors but if that don't help then I'm pulling the pump. Probably will pull it regardless since it definitely looks like it's leaking. Thanks for all the responses from everyone on here!. I'll let you all know how it turns out.

Before you remove the booster pump, check the fuel stop lever like I mentioned above, and make sure your electric in-tank pump is giving you a few psi at the final filters.
If you turn the ignition on and let the in-tank pump run, can you hear and see fuel dumping back into the tank?
If you open the bleeders on top of the two filters on the side of the engine, does fuel come out?

If/when you end up removing the booster pump, get the rebuild kit and put new seals in it. When the seals go bad, it will dump fuel into your engine oil.
To remove the booster pump, you need to unbolt the engine and jack it up slightly to clear the steering box.

 

[Kellyrobins1977]

I wiped off the booster pump this morning started the fuel pump and watched for fuel leaking Didint see any so I started engine and checked again. No fuel leak as far as I could tell. Before I wiped down the pump I did a sniff test on the fluid that was on the hose. It didint smell like diesel it was more like oil. I do like the idea WillWagner has about testing for leaks, im going to try that. What kind of clear tubing should be used? I'm thinking I should change out the seals on the BP and HH then if it still not working, buy new injector nozzles. (if I can find them). I'm posting a video of the cold starting after a quick shot of starting fluid. Im also posting one of how it runs after warming and going through the rpm from idle to almost full throttle. Just curious what you guys think.

 

[WillWagner]

Just clear tubing from Home Defect works. Do it on the supply line to the booster pump. Any pressure will rupture the hose. You can check for air in the low pressure system by installing a shut off valve, like a WOG valve in the port where the bleeder is on the secondary fuel filter. On the outlet of the valve, instann a fitting with somewhere around .050 hole in it and a barb fitting. Attach a length of clear line to the barb and run the other end into a bucket of fuel. With the engine running, open the valve and see if there are air bubbles coming from the line into the bucket. It is normal for them to be there at first sstart but it shpuld be a solid stream as it runs. If you need a pic, leme know, I am an artist too

 

[Floridianson]

Myself if I suspect air in the system I just keep checking the bleed screw between the secondary and final. If it always has air when checked then there is a problem. With the booster IP pump putting out 30 min. psi at idle and 60 min. psi high idle if the fuel canisters were leaking it would show up. 3200 crack pressure for and injector is close to what my new two hole crack at which is 3500. I like the idea of checking the fuel control unit assemble for free movement and is quick and easy. Then maybe if the fuel control is free and you feel the injectors are cracking ok and good atomization ( big word for me ) then a simple fuel pressure check at the bleed screw. As said 30 min. idle and 60 min. at high idle. Another quick and easy is the Head fuel delivery valve just do not loose the spring. Not starting because no fuel? | SteelSoldiers