NO POWER 30mph top

[Bigred77]

I use my 68 m35a2 to haul a 1,100 gal water tank. Last water haul it started running like crap and would die at idle, very hard to start back up ((no fuel) 40sec crank no smoke) and wouldnt rev over 2,000rpm. It did this last month so I changed the fuel filters. shortly after, it did it again. so I changed only the primary filter AGAIN. It ran great for about 1 or 2 miles, then started running like crap till I shut it off while delivering the load. That took about 10 minutes, I got back in the truck, it started normally (for my deuce) cranking for about 5 sec at WOT. Then it ran fine for the .5 mile ride home. Do I have something clogging my tank / lines or do I have a transfer pump issue?

PLEASE HELP!!!
This is my bread and butter!

Thanks,
Ben

 

[BFR]

once it is running the truck should run fine with the intank pump off.

 

[Blood_of_Tyrants]

Is your in-tank lift pump working? If not you may have pinholes in the fuel line and be sucking n air.

 

[Bigred77]

I can hear the in tank transfer pump running

 

[BFR]

I have seen some pretty nasty crud covering the screen on the in tank pickup. I would pull the pump and take a look at the bottom of the tank and the bottom of the pichup and look for debris.

 

[gimpyrobb]

I just swapped my filters in the truck today, makes a huge difference. Fuel starvation even effects egts. I agree, since you have swapped filters, check the tank and pump. Might want to blow air from thr primary filter back to the tank to see if there is any crud in there.

 

[oilcan]

You don't have a mouse nest in the air cleaner, do you?
Could be some bad fuel, or junk getting knocked loose in the tank then plugging the filters.

 

[cranetruck]

After air and fuel filters have been confirmed in good condition (clean the air filter with low pressure compressed air), drain a few gallons of fuel from the fuel tank to make sure no water is present. My drain plug is a 9/16 Allen head, yours may be different.
Like mentioned above, check for pinched fuel line or air leak. Bleed fuel filters with bleeder on top of second/final fuel filter bracket.

 

[LanceRobson]

Even a cold engine should start, this time of year, in a few seconds with little or no throttle. A warm engine should need no throttle. Most, but not all will run without the in-tank pump. Some otherwise strong running trucks without leaks will gag and croak if the in-tank pump is out.

Take the fuel cap off with the master switch "ON", pull the fuel strainer and check if you can see or hear fuel running out of the return line. If you do, it's working (at least somewhat) and fuel is getting past all the filters. The pump should move a LOT more fuel then the engine can use, even at WOT, so you may want to check this with the engine running at high RPM, too.

After checking the fuel circuit for flow back to the tank, I'd carefully check the filter gaskets and sealing surfaces. Running well for a few minutes followed by fuel starvation is a classic gasket or sealing rim issue and it's aggravated by, but not caused by, low pressure from the in-tank pump.

Were the gaskets replaced and, if so, are you really sure all the old gaskets came out? The secondary and final filters are especially picky about any gasket problems. Sometimes there are wrinkles or galled spots in the gaskets that won't leak under pressure from the in-tank pump but which will suck air under the draw from the engine fuel pump.

Even the slightest bit of rotation of the filter can against the gasket while installing it can gall it enough to suck air. Sometimes a rust spot in the gasket channel can be a problem. The old gasket had conformed to it over time and the new gasket hasn't. You can use a mirror to check the gasket channels for crud or damage and should check them every time you put in a gasket.

Good luck

Lance

 

[GoHot229]

I changed the filters including the primary, and imediatly found a considerable amount of lost power now available. However I am running used motor oil, heating oil and some stale gasoline. In short order, say 10-20 miles again I could feel top speed reduced by what I assume the primary filter doing it's job and clogging up again. Once the tank is nearly empty, I will remove it and clean it out and install a new primary filter, which by the way was a NAPA # 3113. I have no way to adiquatly strain or filter the used motor oil so I will stick with new clean diesel from the gas stations, for me its just not a bargin running used oil at this time. I believe my top speed is limmited by the primary filter being cloged with contaminants at this point and starvation slowing top speed. While top speed is still satisfactory, it is not what it was with all new filters.

 

[cbvet]

FWIW- This time of year, I run a mix of about 60% FILTERED (1 micron) motor oil & 40% diesel.
The only differences I notice, is that it's more important to get the engine up to 180 degrees+ for it to run well, & it cranks about 3 revolutions before it starts.
Once up to temp, I have no problems.
Before winter sets in, I'll use up the 60 percent mix & go to about 20 percent mix for winter.
Haven't changed any filters in 5 years. Will probably do so this winter.

 

[WillWagner]

The thing that stands out is "normal cranking time for his truck, with WOT" . Sounds like a fuel pump. If you have done all the filters, i'd bet that's the issue.

 

[Bigred77]

I finaly found the problem (s)

#1) rubber hose inside of tank running from transfer pump to top of tank deteriorated clogging the primary filter.

#2) transfer pump made a internal fountain going nowhere inside the tank after the hose rotted off the pump.

#3) secondary filter rubber rolled and tore causing it to suck air after primary filter started clogging from the rotten hose.

The deuce is running and starting better than ever!

 

[Divemaster920]

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