Non electric mack engine

[Rockrunner]

I have a 92 Mack with Mack 300 hp engine it will run on either primed fuel filters but it won't pick up fuel new to Mack where is he fuel pump?

[Rockrunner]

Sorry it is a 1990 model Mack .

[MHfred]

E 6 ? The fuel pump is on the right hand side (passenger). I would pressurize the fuel tank with a a couple pounds air pressure to force it through the system while it cranks over with throttle applied.. You can use an old inner tube with the stem on it and put a 4 inch hose clamp to hold it on. Other people with more experience will have more ideas.

EDIT: I assume you have the shut down knob pushed in to the run position.

[umodelnut]

Pump is on the passenger side. Put air to the tank and crack open each injector one by one until you get fuel to them is another way.

[GreenGiant2]

where does your pick up line come off the tank. the tube in the tank could be cracked or broken and that will let you suck air instead of fuel. take the suction line off at the filter and put one into a clean container and see if the truck will run. that will tell you what the problem is.

gg2

[2stacksuperdog]

Your vent on the tank could also be plugged.

[Rockrunner]

Ok I will try these things this weekend the injection pump is on pass side the shut off valve is in. Even released the set screw and made sure the lever was fully open. The truck has a pneumatic blower on it and was running at 800 rpm when it started losing power. Drove it home and now it won't start changed both filters the fuel smells like turpentine or thinner I have owned the truck 2 years and not used it much except has a back up to my other blower truck maybe 5 times always started quick and ran good this was sudden. We had just put 20 gallons of diesel in it the day before. I primed the filters try to start then when I take the short filter off it is half empty. So we will try the clean container first I guess. Thanks

[Rockrunner]

Is there a transfer pump or fuel pump before the injection pump?

[j hancock]

Yes, the transfer pump is located on the pass. side of the block as well as the injection pump.

You can follow the hoses along the whole system and check their condition.

Jim

[blackdog2]

There are check valves in the transfer pump one under hand primer and one under 3/4 headed bolt you cant tell if they are bad.

[thomastractorsvc]

so what did you find out was your problem? my fuel transfer pump had a bad seals and was allowing fuel to drain back to the tank, replaced it and all is fine

[Rockrunner]

Just got in from checking it out this is what we did

Undo main hose from tank at filter blew into tank lots of bubbles, then pressurized tank, fuel came out hose tighten hose un did filter fuel came out filter, tried to start fuel out return line at tank. Made sure everything was Tightened up. Had to either to start. Runs.

Now it will not idle unless you use the throttle cable, and then the idle is rough, will not start with out either does not seem to be responsive with fuel peddle, on top of injection pump is the lines all lines loosed showed fuel and made engine idle rougher except one the 2 nd from back. Now going to try and figure out how to get that thing out and what is it called. Any more suggestion would be appreciated.

No fuel prime pump at injection pump. Bummers

Edited August 4, 2013 by Rockrunner

[thomastractorsvc]

Take a picture of the fuel injector set up, does the tach cable hook into the fuel line like this? If so got the answer to your problem and how to fix it

[Rockrunner]

My injection pump does not look like that it is not that clean yet here is a pic of mine

[Rockrunner]

[Rockrunner]

Not sure why they are upside down

[theakerstwo]

I don't know either but I hurt my neck trying to view that.

[thomastractorsvc]

you probably took with a cell phone, you need to orientate the phone before taken pics, I figured that out with my wife's phone

fixed it for ya

[thomastractorsvc]

mine was only clean because of the fuel leak so I pressured washed it. Made it a lot nicer to work on and when I was I wasn't afraid of getting crap in the fuel system.

the fuel transfer pump is hooked to the injector pump and runs like off a cam, pull the line off on the far side before it goes into the filter and crank it over with the fuel shut off pulled so the truck wont try and start to see if it is pumping fuel? sounds like what was happening to mine.

The pump is not a hard fix to replace a little pricy, just make sure its clean and take your time I was afraid I would break one of the 1/4 inch bolts that hold it on by always not knowing my own strength. I moved everything out of the way, filters etc... and still only took about 45 minutes taking my time.

[Rockrunner]

I have two filters on driver side long and short the fuel come from tank into short ( I guess primary) then to the side of injection pump i guess transfer pump, (which is where your tach is installed ) then out back to the other filter then back to injection pump so I should take line off after transfer pump that goes back to second filter? Sound like a good idea if the transfer is not pumping fuel than that's my problem.

[thomastractorsvc]

Exactly, the replacement fix for mine was a tach drive and a separate fuel transfer pump, it comes with a prime pump my original did not have a prime pump.

The tach adapter goes where the tack cable and transfer pump are in the picture and the transfer pumpw/primer goes on the injector pump had to take off a triangle plate and it bolted right on.

[br549]

ck the fuel pressure over flow valve, its at the front side of the pump where the line hooks and returns fuel to the tank, remove the nut and there is a spring, a ball, and a little hat for the ball, have seen several times the spring breaks and the truck can't hold fuel pressure.

[Rockrunner]

I have return pressure to tank. I pressure washed it today and I am working on it this weekend. My dad says it is the governor but I think it is the fuel pump, but because I have fuel return to tank he says governor. I guess we will find out this weekend

[br549]

If the spring is broke you will have most all of the fuel returning to the tank and truck cant build pressure, simple to ck.

[fxfymn]

Not trying to be a smarta.., but you have put a fuel pressure gauge on the system haven't you? Generally, that is one of the first steps in trying to diagnose fuel delivery issues. Not familiar with this system, but if there are check valves the system should hold pressure on the gauge when it is shut off.

Also, use WD-40 to run the engine, not ether. The WD-40 simulates diesel fuel and will not harm the engine like ether might. Just spray it into the air intake.