acme66
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- Plains, Montana
My 1983 M925 has been a ball of fun the last few days. Last night while giving an offroad tour, after running flawlessly all day I felt a power loss and hesitation. I turned the truck around and refunded the money. Down hill it was idling fine. I started for home a trip of about 9 miles. On the highway it would run for about 12 seconds and die for three. Those numbers got worse as the miles ticked by. Less than a mile from home it would run for about a second and die for about 10 seconds. I could just keep it around 20mph. By the time I got to the drive way it would no longer idle. After sitting for a bit it started up and I was able to pull it in.
My first thought was fuel filter as I had run the tanks low enough to cause it to surge 3 days ago. I pull the filter and there is a little stuff on it but not much, it looked clean and when I cut out a section of the media I could see light through it. I put in a new one and reprimed the system. Did a test drive and bombed the truck around a while under heavy acceleration for a few miles and nothing seemed wrong.
This morning I start up the hill for tours and about 1/2 mile from home I get powerloss again. Bring it back home, pull the filter and work my way through the fuel system hose by hose all the way up to the pt pump. I can't find a thing. I checked the the manual shutoff is all the way open and the solenoid seems to be working fine though I haven't tried screwing it open and driving it. I have pressurized the tank, filter and lines to 2-3psi, no leaks. I pulled the small filter screen off the pt pump, I think the TMs call it AFC Fuel Pump Filter. I can see some stuff sticking to the little magnet inside but otherwise the filter is spotless. I have pulled the main supply hose from the pump and after pressurizing the tanks blasted 5 gallons of fuel into a bucket through it with no interruptions of flow. Both vent lines flow air with the tank pressurized, not much grant you but it seems adequate.
I am at a loss. I have yet to put the system back together and test the truck but since I never found anything actually wrong I can't see how this will be any better. I searched the forums but all similar accounts of trucks with powerloss resolved themselves after air leaks or filter work.
I am worried I damaged it running it low but the forums are full of stories of guys who ran out of fuel and the pump was fine, mine never got beyond surging before I added fuel to it. Will a pt pump fail like this? Giving power sometimes then just cutting out. I was SO sure it was either something in the tank plugging the pickup or a bad filter. I can look into the tank and it looks very clean with just a bit of stuff here or there on the bottom. Granted I can only see the front half of the baffle. Right now I am DOA and turning away business, can anyone shed some light? I would hate to just start throwing parts at it without some evidence of failure.
Your thoughts are appreciated.
Ken
UPDATE: I checked the return line check valve and it also was fine. Screwing in the solenoid override knob let me drive the truck normally for about 8 miles with no issues. Maybe I have an intermittent fault there. I am going to back the knob off and see if that induces failure again.
UPDATE 2: Screwed out the override knob and took the truck on a 16 mile ride with a big hill. No failure of the fuel system. The only change I can notice is that it now has more power. Doesn't accelerate any faster but up the hill I would have expected to pull it down into 4th didn't. Where before it would have been at 40mph it was holding 50. At this point I have no idea. I suppose that solenoid could have been sticking only partially open. From the moment I picked this truck up it has been a little dogish compared to the other two. I would like to say that solenoid has been sticking partialy closed since I picket it up from GL and screwing that knob in pushed it all the way open and now it works. At this point however I am so tired of beating my head against this wall I worry that I am grasping at straws and it is just waiting until I have a load of passengers to come and revisit me. If I ever find a definitive problem and solution I will update again.
My first thought was fuel filter as I had run the tanks low enough to cause it to surge 3 days ago. I pull the filter and there is a little stuff on it but not much, it looked clean and when I cut out a section of the media I could see light through it. I put in a new one and reprimed the system. Did a test drive and bombed the truck around a while under heavy acceleration for a few miles and nothing seemed wrong.
This morning I start up the hill for tours and about 1/2 mile from home I get powerloss again. Bring it back home, pull the filter and work my way through the fuel system hose by hose all the way up to the pt pump. I can't find a thing. I checked the the manual shutoff is all the way open and the solenoid seems to be working fine though I haven't tried screwing it open and driving it. I have pressurized the tank, filter and lines to 2-3psi, no leaks. I pulled the small filter screen off the pt pump, I think the TMs call it AFC Fuel Pump Filter. I can see some stuff sticking to the little magnet inside but otherwise the filter is spotless. I have pulled the main supply hose from the pump and after pressurizing the tanks blasted 5 gallons of fuel into a bucket through it with no interruptions of flow. Both vent lines flow air with the tank pressurized, not much grant you but it seems adequate.
I am at a loss. I have yet to put the system back together and test the truck but since I never found anything actually wrong I can't see how this will be any better. I searched the forums but all similar accounts of trucks with powerloss resolved themselves after air leaks or filter work.
I am worried I damaged it running it low but the forums are full of stories of guys who ran out of fuel and the pump was fine, mine never got beyond surging before I added fuel to it. Will a pt pump fail like this? Giving power sometimes then just cutting out. I was SO sure it was either something in the tank plugging the pickup or a bad filter. I can look into the tank and it looks very clean with just a bit of stuff here or there on the bottom. Granted I can only see the front half of the baffle. Right now I am DOA and turning away business, can anyone shed some light? I would hate to just start throwing parts at it without some evidence of failure.
Your thoughts are appreciated.
Ken
UPDATE: I checked the return line check valve and it also was fine. Screwing in the solenoid override knob let me drive the truck normally for about 8 miles with no issues. Maybe I have an intermittent fault there. I am going to back the knob off and see if that induces failure again.
UPDATE 2: Screwed out the override knob and took the truck on a 16 mile ride with a big hill. No failure of the fuel system. The only change I can notice is that it now has more power. Doesn't accelerate any faster but up the hill I would have expected to pull it down into 4th didn't. Where before it would have been at 40mph it was holding 50. At this point I have no idea. I suppose that solenoid could have been sticking only partially open. From the moment I picked this truck up it has been a little dogish compared to the other two. I would like to say that solenoid has been sticking partialy closed since I picket it up from GL and screwing that knob in pushed it all the way open and now it works. At this point however I am so tired of beating my head against this wall I worry that I am grasping at straws and it is just waiting until I have a load of passengers to come and revisit me. If I ever find a definitive problem and solution I will update again.
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