M35a2 in tank fuel pump

[JAYHAWK 1962]

Hello all. I have a 1971 am general m35a2 I am picking up with the understanding that it needs an intank fuel pump. I bought an entire replacement assembly from barstow equipment for only 60$ delivered!! What a deal!! Does any one know of any pitfalls I may encounter while changing out the pump. I have tested the replacement and seems to be working. I am figuring after all of the hook up is done the fuel system will have to be purged of air. truck does run when fuel is poured into engine (according to seller). Any help on this matter would be greately appreciated. thanks

 

[wsucougarx]

Hmm, engine should still run with the intank pump being inop. You may wish to clear up what "fuel is poured into engine" means. If the Injector Pump is toast then you're looking at a pretty hefty price for a new one:-0. There should be no pitfalls when installing the intank fuel pump. But FIRST!! Check to see if the fuse is blown on the old intank pump before going to the trouble of replacing the pump. It still may be good
Just make sure you clean the area around the tank before taking out the old pump. If you need to purge air out of the fuel system then you just need to open the valve on the secondary/final fuel pump housing. Crack open the valve, flip the accessory switch (don't start), get out watch the valve until fuel starts to come out, close valve, get back inside of truck, then try to start. Should fire right up after a few seconds. But the whole poured into engine thing needs to be cleared up

 

[GoHot229]

Hmm, engine should still run with the intank pump being inop. You may wish to clear up what "fuel is poured into engine" means. If the Injector Pump is toast then you're looking at a pretty hefty price for a new one:-0. There should be no pitfalls when installing the intank fuel pump. But FIRST!! Check to see if the fuse is blown on the old intank pump before going to the trouble of replacing the pump. It still may be good
Just make sure you clean the area around the tank before taking out the old pump. If you need to purge air out of the fuel system then you just need to open the valve on the secondary/final fuel pump housing. Crack open the valve, flip the accessory switch (don't start), get out watch the valve until fuel starts to come out, close valve, get back inside of truck, then try to start. Should fire right up after a few seconds. But the whole poured into engine thing needs to be cleared up

Yep, I'd check the fuse. When I got my Deuce it had the guage pannel stole and the old owner had bought another complete unit with all the nessesary guages etc. But none of the lights worked on the Deuce either, very verry dis-heartening to know I faced such an uphill battle before me to get all that functioning again. Well ALL of the bulbs were burnt out except one fillament in the whole lot of bulbs, so they were all replaced and WAL-AAA, lights! all the lights now functioned, high/low, emergency's, turns, all of it. Yep start with the simpelest stuff first like the fuse, and if nothing there, try cleaning the connections, having done that you can then determine the functionality of the in-tank pump.

 

[spicergear]

Be REALLY, REALLY careful pouring diesel fuel into a diesel engine to get it started or see if it runs. This 'gas' engine trick can spin your diesel to the moon rpm wise...in a matter of seconds. Diesels run on the amount of metered fuel. So a slosh of it down its throat may be 3 seconds worth of 2,800rpm right off the starter. Every part of the engine will love that...even some that previously weren't visable-

 

[Parker2]

The truck should run even if the lift pump is not working.
Something to think about.
If it is an injection pump problem, it can most likely be fixed easily and cheaply with good used parts.

 

[KaiserM109]

JAYHAWK 1962,
It sounds like you are new to SS; welcome.

I just went through the whole thing with fuel pumps:
http://www.steelsoldiers.com/deuce/38594-dead-fuel-pump-need-help-fast.html
http://www.steelsoldiers.com/deuce/19455-fuel-nozzle-leak.html
http://www.steelsoldiers.com/deuce/39073-leaking-flame-heater.html

The original pump in an M35A2 was an in-tank pump, as you probably already know. The advantage to an in-tank pump is that it does not have to suck on its input side. An in-line pump has to lift fuel by suction to the highest point in the line between the tank and the pump. If there is a leak it will suck air and you are in trouble. If the in-tank pump has a leak it will spray fuel but if there is enough fuel getting to the engine, it will still run.

$60 for a good in-tank pump is a real bargain, BUT there is no way of telling how good one is until it quits. It is a sealed (welded shut) motor and will sound just fine until it tosses a brush, like my original pump did. Olympic sells brand new pumps for around $225.

Long story short, because I am out of work and my truck was dead I put an in-line pump (see the first thread) to save bucks. I will definitely get a new one from Olympic when I have $$ to spare. Basically you get what you pay for. The head on the Carter pump I bought is 1/2 the size of the original pump.

You should only have to install the pump, check fuse, (5 AMP Slo blow or 10 AMP regular) and let the pump run for a minute. The fuse is under the molded cap held on by 3 nuts where the wire connects to the top of the tank. If the line has air in it, open the petcock at the top of the double fuel filters on the left-rear of the engine until you get fuel showing.

As wsucougarx said, the engine should run off of the injection pump, even with a dead in-tank or in-line pump, if there is no air in the lines. Pouring fuel straight into the engine sounds like a BAD idea on several counts. Not only does it sound dangerous, but it also sounds like a good way to get fuel into your crankcase.

Good luck and keep us posted,
Arlyn

 

[JAYHAWK 1962]

Thanks for the replies!! i am new to site and i appreciate all of the information you all have supplied. it is a whole lot easier to learn from people who have been there done that than wasting time tinkering around with half a clue. thanks all

 

[CHIEFSONN]

? with the in line fuel pump (the pump located on top of the fuel tank) when the the accessory switch and power switch ( on off). should you hear the pump running. if not how would i go about testing it if it is working. would i open the valve on the secondary fuel housing.bleeder valve.

 

[The King Machine]

With the main power switch turned on you should be able to hear the pump in the tank running.

 

[doghead]

Pulse type inline pumps stop when they build pressure. You wont hear that.

Measure or check for fuel pressure at the filters or IP.

 

[CHIEFSONN]

thank you for your reply ? how do i check or measure the pressure and with what sorry for the questions

 

[doghead]

Either a gauge in the bleeder hole threads, or just use your finger over it if you have any sense of that type of thing.

 

[westtek]

I drove my M35 for a couple years or so before I realized the lift pump wasn't working. Changed filters and had the system down. No start. Pulled the pump and it was just stuck. Freed it up and put it back in. Turned on the power and heard the pump for the first time. I bought a new pump to replace the stuck one. It's been 10 years and the original pump is still in it chugging away. New one is on the shelf waiting.
I listen for the pump every time I turn the power switch on now.

 

[m715]

While your pump is out replace the rubber fuel line on the pump.