In tank fuel pump

[johan77]

Hi guys,
recently i found out that the fuse for the fuel pump in the tank is blown. However the truck is starting and running perfectly fine, (when cold it takes about 25-30 sec to start up and idle). when i override the fuse , The pump is working (turning) when powered ( as well with auxilery power as with the accessory switch on in the cab) . there is no fuel coming out of the top vent screws on the final fuel filters, located behind the oil filters.
I try to rule out what may cause that. pump is not stuck, maybe the line from the pump to the top of the pump cover on the tank, but is this should be the case , the engine should also not start up , let alone running smoothly. so i assume the rubber hose is intact.
clogged primary fuel filter... I am gonna unscrew the feed line from the pump to the primary fuel filter and run the pump, if there is diesel coming out, working further towards the final filters. if there s no fuel the pump screen maybe clogged or the bottom part of the pump fell down (like i read in some other posts on SS) .
question : how does an m35a2 runs with clogged fuel filters ? according to me it runs but hessitates, or runs rough, also starting should be difficult,
i didnt do the filters yet is because it runs and starts just fine and never had ran on anything than diesel, the second part is that removing the pump is not that convenient on an M275 tractor, the cab is in the way, so the whole tank must be drained and removed from under the truck to have access to the pump in the tank.
another side note... when measuring the amps from the in tank pump.... it pulls 11.8 amps !!!! the fuse should be a 2amp slow blow. and when running the pump for about 5 minutes, the negative wire becomes warm, not yet hot , but warm, so something is not right .
Any more ideas ?
planning to check if it pumps fuel up to the first filter and i will go from there.
Thanks !!

 

[dmetalmiki]

Hi guys,
recently i found out that the fuse for the fuel pump in the tank is blown. However the truck is starting and running perfectly fine, (when cold it takes about 25-30 sec to start up and idle). when i override the fuse , The pump is working (turning) when powered ( as well with auxilery power as with the accessory switch on in the cab) . there is no fuel coming out of the top vent screws on the final fuel filters, located behind the oil filters.
I try to rule out what may cause that. pump is not stuck, maybe the line from the pump to the top of the pump cover on the tank, but is this should be the case , the engine should also not start up , let alone running smoothly. so i assume the rubber hose is intact.
clogged primary fuel filter... I am gonna unscrew the feed line from the pump to the primary fuel filter and run the pump, if there is diesel coming out, working further towards the final filters. if there s no fuel the pump screen maybe clogged or the bottom part of the pump fell down (like i read in some other posts on SS) .
question : how does an m35a2 runs with clogged fuel filters ? according to me it runs but hessitates, or runs rough, also starting should be difficult,
i didnt do the filters yet is because it runs and starts just fine and never had ran on anything than diesel, the second part is that removing the pump is not that convenient on an M275 tractor, the cab is in the way, so the whole tank must be drained and removed from under the truck to have access to the pump in the tank.
another side note... when measuring the amps from the in tank pump.... it pulls 11.8 amps !!!! the fuse should be a 2amp slow blow. and when running the pump for about 5 minutes, the negative wire becomes warm, not yet hot , but warm, so something is not right .
Any more ideas ?
planning to check if it pumps fuel up to the first filter and i will go from there.
Thanks !!

Some deuces run just fine without the in tank running.
Five ton trucks generally will not.
I f the bleed screws on the filters do not exude fuel, Well why would they?..The in tank pump is not running so not delivering any pressure.
The in tank pump is to help re prime the system after a filter change.
The high pressure pump then delivers to the injection pump.
No harm in changing ALL the filters, The first one under the right side of the truck. Also the secondary and primary filter.
The in tank pump might be clogged, But it has a magnetic 'drive' so no drag will be causing overheating.
Like the five ton trucks, Starting is extremely difficult on some trucks..And they do not run properly if the in tank pump is not delivering.
Remember then, The in tank pump COULD be running at any speed..if clogged.
And believe it..Clean pump diesel or not, They do get clogged over time.
....Sometimes.

 

[johan77]

Some deuces run just fine without the in tank running.
Five ton trucks generally will not.
I f the bleed screws on the filters do not exude fuel, Well why would they?..The in tank pump is not running so not delivering any pressure.
The in tank pump is to help re prime the system after a filter change.
The high pressure pump then delivers to the injection pump.
No harm in changing ALL the filters, The first one under the right side of the truck. Also the secondary and primary filter.
The in tank pump might be clogged, But it has a magnetic 'drive' so no drag will be causing overheating.
Like the five ton trucks, Starting is extremely difficult on some trucks..And they do not run properly if the in tank pump is not delivering.
Remember then, The in tank pump COULD be running at any speed..if clogged.
And believe it..Clean pump diesel or not, They do get clogged over time.
....Sometimes.

Thats the weird thing with mine, with the in tank pump not running and thus not delivering, it starts and runs without any problems.
When bleeding the filters with only the in tank pump running (not starting the truck) no fuel is coming out (on the top of the secondary and primary filter)

 

[NDT]

Way too much current being drawn by the pump, if it burns up, well having a fire in a fuel tank cannot be good.

 

[dmetalmiki]

Thats the weird thing with mine, with the in tank pump not running and thus not delivering, it starts and runs without any problems.
When bleeding the filters with only the in tank pump running (not starting the truck) no fuel is coming out (on the top of the secondary and primary filter)

As I already pointed out it won't. And most deuces start and run just fine without it. (In fact all my 1/2 ton deuces have a switch on the dash to turn off that pump once the engine is running to prevent wear.
You easily just purchase and fit a good in line 24 volt truck diesel fuel pump.
I have on two of mine, and my petrol GMC M135.