Oil & Fuel MF 135 1968 Fuel priming issue

[PerryW]

Hi Folks.

We've just completed what, to us at least, was a fairly major job - fitting a new shear coupler. That actually went surprisingly well once we'd found that was the problem (lost all drive following a lock-up with a mulcher).

While the old girl was in the shed we did some other routine maintenance including changing the fuel filters.

Last time we did this - it all went well. Just bled the injector pump while cranking over and she was good to go. This time though she doesn't want to know.

I've got diesel pumping happily though both bleed points on the pump without spluttering, so I'm guessing that I've got an air lock in the pipes to the injectors themselves? Does that sound reasonable?



I think that means loosening the nuts on the side of the injectors and cranking it over again (no manual lever on the lift pump on this model). I'm not sure though from what I've read and thought I'd check in for some advice here first.

If I do, do I do all three at the same time, just one or each one in sequence?

Many thanks

 

[PerryW]

UPDATE - She lives!
Had another go at cranking her over and this time, she started. All looks good.
I'd still be grateful though if anyone could help out with the right process for priming one of these - the manual I've got and everything I could find online all refer to versions with a manual lever on the lift pump

 

[thepumpguysc]

Once u get fuel to the bleed screw by the name plate on the pump.. it should squirt out w/ force.
Loosen ALL THE LINES AT THE INJECTORS {or as many as u can reach} & spin the engine, until fuel squirts out there & tighten..
Once the engine is running, loosen the bleed screw on the top cover of the inj. pump {if so equipped} until fuel comes out of IT & tighten.
When bleeding or just STARTING the engine, the throttle should be AT LEAST, 1/2 way to FULL THROTTLE..<< VERY IMPORTANT.
Good luck & I'm glad u gott'r started.

 

[Jerry/MT]

Hi Folks.

We've just completed what, to us at least, was a fairly major job - fitting a new shear coupler. That actually went surprisingly well once we'd found that was the problem (lost all drive following a lock-up with a mulcher).

While the old girl was in the shed we did some other routine maintenance including changing the fuel filters.

Last time we did this - it all went well. Just bled the injector pump while cranking over and she was good to go. This time though she doesn't want to know.

I've got diesel pumping happily though both bleed points on the pump without spluttering, so I'm guessing that I've got an air lock in the pipes to the injectors themselves? Does that sound reasonable?

View attachment 598161

I think that means loosening the nuts on the side of the injectors and cranking it over again (no manual lever on the lift pump on this model). I'm not sure though from what I've read and thought I'd check in for some advice here first.

If I do, do I do all three at the same time, just one or each one in sequence?

Many thanks

Bleeding a Diesel Fuel System


Start at the fuel outlet of the tank (inlet to the filter). Shut the tank valve, remove the line at the filter inlet and holding a suitable container to catch the diesel fuel, open the valve. You should have a CONTINUOUS rush/flow of fuel out of the line. If it dribbles or is intermittent, check the fuel cap for a blockage of the fuel vent or the strainer upstream of the valve for clogging. The strainer/screen is attached to the shut-off valve, and is positioned up inside the tank. You will have to drain the tank and pull the valve to clean the screen.
If you have good fuel flow at that point, reconnect the line and open the bleeder screw at the top of the filter. Turn on the tank valve and wait till you have a steady flow of fuel with no bubbles at the top of the filter, then close the bleeder screw.
Your pump may have a bleeder screw. If so, open that until fuel streams out with no bubbles, then close it. If you cannot identify the bleeder screw, loosen the inlet connection at the pump and purge air at that point.
Go back and make sure ALL the fittings in the fuel delivery system are tight so they cannot suck air.
Make sure the battery is fully charged. Loosen the fuel fittings at the injectors, either one at a time or all at once. Crank the engine till you see all fuel at the injector fittings and then tighten the fittings. If you do indvidual fittings, the engine will usually start before you get to the last fitting.
Alternatively, you can "tow-start" it to save wear and tear on your starter. Leave the injector lines cracked open at the injectors at first to purge the lines. Then tighten them up and she should start.
Your injection pump puts out a very small amount of fuel (high pressure/low volume). BE PATIENT. If the lines are totally empty, it takes a lot of cranking to fill them up.
sixbales & Jerry/MT

 

[PerryW]

Thanks! I'll print that and pin it up in the workshop for next time

 

[PatrickS2222]

Hi Perry, I've got a twin sister to yours - Dad bought it when I was 7 or 8 years old. Aside from being so useful and reliable, I'd never sell it because it's been "ours" since new.
As far as bleeding the fuel system goes, the lift pump should have a handle for manual priming and bleeding, but a lot of replacement lift pumps don't have this useful feature. It also relieves the poor starter motor of a lot of hard work. Remember to crank in 10sec bursts with 10sec pauses.
I have found this primer helps a lot when removing the air after changing filters because the fuel can be pumped into the filters, and the air released through the bleed screw on top of the second filter, without needing to crank the engine over. This prevents the transfer pump (inside the injector pump) from sucking the air along into the injector pump, causing the trouble you had.
That said, the next step to take in the situation you had was exactly what you did - open the lower bleeder on the pump and crank the engine until fuel appeared, GENTLY close it and repeat this with the upper bleeder. Then loosen the injector pipes, move to full throttle and crank over - this is the only way to clear air from here. When you see fuel, tighten pipes and crank another few seconds and it should start. After it starts, as ThePumpGuy stated, open them a bit again and release any further air. Remember, they're delicate.
Nevertheless, you got there. Any pics for us?

 

[DLTTrekkers]

Bleeding a Diesel Fuel System


Start at the fuel outlet of the tank (inlet to the filter). Shut the tank valve, remove the line at the filter inlet and holding a suitable container to catch the diesel fuel, open the valve. You should have a CONTINUOUS rush/flow of fuel out of the line. If it dribbles or is intermittent, check the fuel cap for a blockage of the fuel vent or the strainer upstream of the valve for clogging. The strainer/screen is attached to the shut-off valve, and is positioned up inside the tank. You will have to drain the tank and pull the valve to clean the screen.
If you have good fuel flow at that point, reconnect the line and open the bleeder screw at the top of the filter. Turn on the tank valve and wait till you have a steady flow of fuel with no bubbles at the top of the filter, then close the bleeder screw.
Your pump may have a bleeder screw. If so, open that until fuel streams out with no bubbles, then close it. If you cannot identify the bleeder screw, loosen the inlet connection at the pump and purge air at that point.
Go back and make sure ALL the fittings in the fuel delivery system are tight so they cannot suck air.
Make sure the battery is fully charged. Loosen the fuel fittings at the injectors, either one at a time or all at once. Crank the engine till you see all fuel at the injector fittings and then tighten the fittings. If you do indvidual fittings, the engine will usually start before you get to the last fitting.
Alternatively, you can "tow-start" it to save wear and tear on your starter. Leave the injector lines cracked open at the injectors at first to purge the lines. Then tighten them up and she should start.
Your injection pump puts out a very small amount of fuel (high pressure/low volume). BE PATIENT. If the lines are totally empty, it takes a lot of cranking to fill them up.
sixbales & Jerry/MT

Remember to pull the choke before opening the fuelsiseem and after bleeding the filters and inj pump push it back before starting .