M1009 has no power now that it's warmer in AZ?

Okay, this has probably been covered before but I've not found anything to reference yet.

I've been driving my M1009 for a couple months now, almost daily. It's been running great. About a year ago the same thing happened right around the same time of year.

What I did after the first time it happened:

I ran a camera into the fuel tank. The tank is clean like new and the filter sock looks to be in great shape.
Replaced the small section of tubing connecting the hard lines by the passenger door.
Replaced the fuel filter again (the rectangular one) just because. No sludge or anything in the previous two filters. I changed one when I bought it and another after about a year just because.
Replaced the fuel sending unit and hose.
Replaced the main hose to the IP off the fuel filter.
Replaced the fuel line going to the check valve at the IP.
Replaced the check valve at the IP, it was tired but not clogged. I've not found any particulates to speak of yet.
Made sure fuel was getting back to the tank through the return line.
Tested the "click" for the fuel cut off solenoid which seems to be working. I did not remove the cover for inspection.
Replaced the vacuum modulator while I was at it.
Replaced the throttle position switch.
Checked for vapor lock at the tank, not it.

Symptoms:
It has been running just fine in cooler weather, below 90 deg. This is the same thing that happened last year. After the above changes, it's been running great and I thought I'd fixed it but apparently not.
After it's warmed up to operating temp, it has no power like it's starving for fuel. I can push the pedal to the floor, it barely goes and will eventually stall out. I jumped the fuel cut off solenoid from the battery and started it but nothing changed. I imagine, if I start it up in the morning when it's cool there will be no issues.

Okay, so....what are your thoughts?

Thanks in advance! Scooter..

Injection timing? The DB2 injection pump first pressurizes the fuel to transfer pressure, 20 to 100 psi. Part of this flow is used to advance timing through a dash pot on the bottom of the pump. Since transfer pressure is a function of engine speed, a mechanical override is linked to the throttle shaft through a face cam and a lever. The lever should always press on the cam, if it doesn't, it could mean the dash pot is stuck, not moving to the passenger side. This will cause timing to be late.

Does the cold start timing advance cause an increase in engine noise when the engine is warm? Disconnect the electrical connector on the injection pump, then apply 12 volts to the terminal with engine running. What this does is advance timing by decreasing case pressure, thereby making the timing advance dash pot move further to the passenger side.

If so, a pump rebuild is needed

That is an odd set of symptoms.... when the air temp is over 90, is your engine running hotter?

Keith_J said:

Injection timing? The DB2 injection pump first pressurizes the fuel to transfer pressure, 20 to 100 psi. Part of this flow is used to advance timing through a dash pot on the bottom of the pump. Since transfer pressure is a function of engine speed, a mechanical override is linked to the throttle shaft through a face cam and a lever. The lever should always press on the cam, if it doesn't, it could mean the dash pot is stuck, not moving to the passenger side. This will cause timing to be late.

Does the cold start timing advance cause an increase in engine noise when the engine is warm? Disconnect the electrical connector on the injection pump, then apply 12 volts to the terminal with engine running. What this does is advance timing by decreasing case pressure, thereby making the timing advance dash pot move further to the passenger side.

If so, a pump rebuild is needed

Click to expand...

Thank you for the information, which terminal/wire are you referring to? The green one?

Scooter...

LT67 said:

That is an odd set of symptoms.... when the air temp is over 90, is your engine running hotter?

Click to expand...

It is strange, especially when it's been running fine. As for engine temp, I have no idea but I don't think so. I drive 45 minutes one way on the freeway to work and I've had zero issues. Engine temp, is another gauge install! I just installed a trans temp gauge on Monday and it's hovering around 150deg.

Scooter...

As suspected, it started right up with the standard increase in cold idle speed and regular power. Repositioned in my shop after the tow yesterday with no issues.

If the cold advance was getting stuck, I should have seen a lot of smoke out of the tailpipes right?

Scooter...

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I pulled the cap off the IP, it's very clean inside. I found a few small particulates but nothing frightening or unexpected from 1985. The fuel cut off and cold start solenoids activate when energized. Does the cold start solenoid have a spring return to the "open" position? Mine returns or drops open by gravity. Never mind, I found a picture of it and answered my own question, no spring. The fuel cut off activates fine when energized. However, when pushed manually it does have a little bit of a rough feel to it. it's not terrible but it might be enough to catch as the parts expand from heat. It's certainly not smooth.

While digging for a fuel cut off switch, look what I found at accurate diesel.


Another thing I forgot to mention is the return line check valve mounted on the top of the IP. The check ball is actually glass if you did not already know. Just because you can see light looking through it does not mean it's not stuck!

Scooter...

The green wire, yes. It comes from the thermal switch, to the injection pump and then to the high idle speed solenoid. To check the cold timing advance, disconnect at the pump so you only apply 12 volts to the cold timing advance.

Keith_J said:

The green wire, yes. It comes from the thermal switch, to the injection pump and then to the high idle speed solenoid. To check the cold timing advance, disconnect at the pump so you only apply 12 volts to the cold timing advance.

Click to expand...

Got it, I will do this next week once I get off work.

Thanks! Scooter...

Okay; so, I installed a new fuel cut off solenoid and checked the return check valve for debris and it was clean. It started up as usual with cold idle advance and sounded much better actually. I went inside so it could warm up and when I came back out it had stalled. I started it back up and it had a rough idle after it was warm. I jumped the wire as mentioned and nothing changed. I think I'm going to start looking into the tank sock again. It just acts as if it's not getting fuel. Notice the difference in solenoid length.

Keith_J, just may have hit the nail on the head....timing. I've never messed with the timing; so, I really don't know if it's correct. The gentleman I bought it from used it as a hunting rig which means he was hunting primarily in cooler weather and at a higher altitude. With no A/C, I'm sure he was not running around in the heat either. So, he probably never had any issues.

After switching the cut off solenoid out there was a notable difference in the tone and idle of the motor. There was also a much stronger exhaust odor and a bit more smoke than usual.

Scooter...

Ok, if you can put power to the cold timing advance solenoid (the one inside the injection pump) and it runs better, there is a good chance the timing chain has worn, creating sloppy timing. Or it could be a worn pump not making transfer pressure.
The transfer pump pressure rises with engine speed. This pressure along with metering valve are what vary the injection quantity. The pressure also advances timing, much like centrifugal advance in an old breaker points car distributor.

You can pull the oil fill tube and check pump gear backlash. Measure how many crank degrees of backlash, turn engine clockwise until the pump gear moves, then turn the engine crank counterclockwise. If that is more than 5 degrees, the timing chain should be replaced. Use a long breaker bar and pull the glow plugs to make life easier.

If the backlash is less than 5 degrees on the crank, the injection pump could be the problem. Try advancing it 2mm. There are lines on the pump and mounting bracket, see if these are lined up. Top of pump moved to the driver's side is advancing.

Okay, thank you.I'll take a look at that tomorrow. When the advance is energized there is no significant if any change to the motor.

Scooter...

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When the engine is warm, putting power to the solenoid should make it clatter.
That glass ball is a check valve, spring loaded. When the cold timing advance is energized, that pin holds the glass ball open, preventing case pressure from the spring. This loss of case pressure advances timing.

When the engine is cold, the clearance in the pressure advance is smaller since aluminium has 3 times the thermal expansion of steel..the piston is steel. Plus viscosity of diesel is greater when cold.
Got a non contact thermometer? I bet you have a hot pump issue.

Keith_J said:

When the engine is warm, putting power to the solenoid should make it clatter.
That glass ball is a check valve, spring loaded. When the cold timing advance is energized, that pin holds the glass ball open, preventing case pressure from the spring. This loss of case pressure advances timing.

When the engine is cold, the clearance in the pressure advance is smaller since aluminium has 3 times the thermal expansion of steel..the piston is steel. Plus viscosity of diesel is greater when cold.
Got a non contact thermometer? I bet you have a hot pump issue.

Click to expand...

Thanks Keith_J, I'm smelling what you're cooking. Can you expand on the hot pump issue? The troubles start when it's warmed up; however, I don't believe the engine is overheating at all. Are you saying the cold advance pin is getting stuck?

Scooter...

Current IP position.

Scooter...

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The dynamic timing is advanced by transfer pressure acting on a piston. It is retarded by preset spring force and the action of the face cam through the lever on the passenger side of the pump.

What could be happening is the fit of the piston in the bore has worn out, causing excessive bypass when the pump is warm and diesel viscosity low. A few overhaul shops line this bore with a steel sleeve to repair and reduce wear.

scooter421 said:

Thanks Keith_J, I'm smelling what you're cooking. Can you expand on the hot pump issue? The troubles start when it's warmed up; however, I don't believe the engine is overheating at all. Are you saying the cold advance pin is getting stuck?

Scooter...

Click to expand...

These n/a 6.2 diesels don't exactly run hot to begin with...

Had these symptoms on my 86 M1008; excessive blow by, 190 coolant temps, down on power, no heat coming out of the vents. Turns out the water pump was the culprit. Changed it out and now the engine never gets warmer than 150 degrees because of the blow by. The engine got a lil bit better when we put a new lift pump on, but the excessive blow by is why it's down on power because the engine is losing compression. Lol, on warm restarts it will not fire back up on it's own. I have to use a manual glow plug switch for a few seconds so it'll refire. Hope this helps..

Could be a worn engine, easy enough to compression test both cold and warm.

Keith_J said:

Could be a worn engine, easy enough to compression test both cold and warm.

Click to expand...

If the engine is not rattling like a metal trash can with rocks in it on a cold start, it's either a worn out engine, fuel issues or both. It should be a noisy lol.

I don't think it's the engine. When it runs, it runs good. Starts right up, burns no oil, Barely smoked at all until I changed out the fuel cut off solenoid. I'm confident it's the fuel delivery one way or another. It certainly could be the IP. The strange part is that it ran fine below 80deg ambient. Cold advance kicks in around that same temp right?

Scooter...

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