1977 m880 no fuel pressure

[digitalchi]

Sooo this might be a long post but bare with me.

I have a 1977 m880. Iam currently rebuilding the engine(just getting parts together) with my cam with lifters, intake manifold, timing chain and gears and 4 barrel carb. But first i decided to drop the gas tank and clean it out.

All went well and i cleaned it out but i couldn't get the fuel sending unit out even after using a impact screwdriver so i left it alone. Reinstalled the tank and put about 8 gallons of fuel in and my truck started(using fuel that was already in the carb) It ran for about a min but i noticed no fuel was being pumped through the fuel filter and it cut off.

The fuel gadge works, I put a new fuel pump in i had laying around. But still no fuel going to carb. My question is could i have damaged the fuel sending unit causing it to not send fuel to the pump?

I just dropped the tank again and realized the line that send fuel to the pump was bone dry soo im guessing no fuel has even left the tank yet.

Just to recap with some cliffs.

1.cleaned out gas tank,fuel sending unit wouldn't come out
2.reinstalled gas tank truck started with fuel left in carb
3.Noticed as soon as it started no fuel was gushing through fuel filter.
4.put in new pump and still no pressure
5.dropped tank again and fuel lines were still dry

What could be causing this?

I plan on disconnecting the rubber hose and the fuel pump and routing it to a small jar with gas to see if the pump will suck gas through when cranking.

Thanks for any help.



most updated pic of engine i have new ones soon



and all my parts

[Williespeed]

D-chi

When you removed the fuel cell did you connect the fuel line to the correct spigot? there may be a vent spigot as well, is the fuel line pinched? try and blow through the spigot with an air compressor and air dart (little blower thingy) if you can hear the bubbles in the tank then you know you should be pulling fuel. Maybe have a friend listen for you. Your idea to place a temp fuel cell in to see if the pump is drawing is a good idea. I often have problems in my Van with the fuel pump pulling fuel from my Aux tank when I have run the main dry and don't have the vacuum pressure of road speeds to draw the fuel. But this was my fix for my PowerWagon
http://www.summitracing.com/parts/SUM-G3136/

[712edf]

I'd also add that if you don't seem to be making any progress in the tank area, look into where the pump bolts to the block. Is the cam driving the pump arm sufficently?
Bucky

[n1265]

On the bottom of the pickup tube there is a screen filter, there have been cases in the past where this filter will collapse and/or get sucked up into the pickup tube, restricting flow.


take the line off at the pump ( coming from the tank ) and blow it out to clear any obstruction. I would also remove the gas cap when doing this.

[digitalchi]

Ok so update

1. I discconected the rubber in line to the fuel pump and put some gas in a separate container and put the hose into it. When cranking the engine i got fuel pressure and it started right up.

So that mean the fuel pump is ok and the cam is driving the pump arm just fine.



2. I Blew air into the out line from the gas tank(circled in the pick below) that send fuel to the pump. When blowing air in i heard air bubbles which should mean there is no clog in the sock.



There only other problem should be a leak in the lines correct?

will test that tommorow.

thanks again for the help.

[n1265]

that would be the most likely trouble, however with as bad as that sending unit looks you might also have a pinhole leak in the pickup tube on the inside of the tank causing the pump to suck air.

Your problem has to be the line from the tank to the pump or the sending unit...

[n1265]

http://www.youtube.com/watch?v=MQ7hlabWg4E

It's a hard video to watch, but it will give you an idea of what your sending unit looks like inside the tank...

[Williespeed]

ya so it looks like it will be the pick up in the tank, as I think even a pinhole in the line would be quite noticeable unless its been awhile since you ran this rig. if you have some clear vinyl hose you could put it on the spigot and suck to see if you can siphon some fuel up from the tank if you can then hook everything back up and have some turn it over while you pour a small continuous stream of fuel into the carb. this should create enough vacuum to pull fuel from the tank about an 1/8th throttle and a steady low volume pour and it should pull fuel. sometimes it takes longer than you would expect for this to occur. up to a minute of run time before the fuel reaches the float bowls. the problem is a small fuel pump diaphragm isn't so efficient with air. fill the tank and try again.

[digitalchi]

OK sooo i fix it! turn outs there was a crack in the line right near the gas tank ever so small causing the pump to only suck air...instead of trying to find a line to replace it. I just found a longer rubber fuel line and routed it to the fuel sending unit.

The only problem now is i currently have toe straps holding up the gas tank temp. because i had to cut off the old straps with a sawsall because they were so rusty.

anyone know where i can find gas tank straps that will fit?? thanks

[DODGEBOYS]

SPECTOR gas tank supply has several universal-cut weld bent gas tank straps that work on old dodges