thought I might check in here as I am completely at a loss and need some help!

(my cummins is running fine!)

So I have a 1990 Massey Ferguson backhoe with a Perkins AT4.236 motor.

1st symptom was that when I throttled down to idle after running for a while, the motor would stall. sometimes would start right back up, sometimes would take a good bit of cranking. so I started shutting rpm's down very slowly, and once idle was attained without stalling, it would idle normally.

next, it stalled while running at full rpm. I was able to get it started a few times after that but it would not continue to run, and the throttle was sometimes responsive, sometimes not, so after a good deal of diagnostics, figured it was likely a fuel delivery problem.

I have replaced the lift pump, fuel filter, air filters, checked all fuel lines for flow, and had the injection pump rebuilt! none of these have fixed the problem. tried pulling air intake pipe off manifold in case something was wrong in air filter... no luck there. Have bled the fuel system to injectors multiple times.

When I reinstalled the injection pump (I had thought for sure that was going to be it https://www.dieseltruckresource.com/...lies/frown.gif), it started an ran for a couple seconds a few times then would die and then would not start again.

same thing after trying another fuel filter today. It started instantly, ran for a few seconds then stalled, and will not start again...

Anyone have any ideas???

I'm going to try to pull the exhaust/muffler next,
but when it started, there seemed to be a normal amount of smoke coming out, so I'm skeptical that's the cause.

could it be bad injectors? maybe it's flooding?? is it even possible to "flood" a diesel?

 

I would think if too much fuel is getting into one or more cylinders you'd see puffs of black smoke and the engine would run rough. My brother has a Massey of that vintage, but it's a farm tractor. It certainly sounds like a fuel problem to me, but you've really been thorough in what you've done. I wonder if this is a known Massy problem and if any of the tractor websites could help you out.

 

tried the "heavy equipment" and a few other forums... nothing too helpful so far. it was from advice there that I ended up rebuilding the inj pump.

These motors are in LOTS of different stuff... marine, equipment, tractors, etc... and I have been searching and reading through lots of forums with no luck so far.

 

Try getting a fuel gauge to install on the motor so you can see what your fuel pressure is. Also have you checked your fuel tank? I know that's simple but a lot of issues are simple. I've had a fuel cap keep one from running longer than 30 seconds. Not sure if it's gravity feed or pumped. But overflow can cause issues as well. Only other thing I could think of is a fuel line sucking air. I know there are some fuel lines that will not leak fuel but suck in air and cause rough smoky idle and hard start. Sounds like it got worse when you removed the pump and reinstalled causing a leak to get worse. Just giving you my thoughts. Maybe take a few pics of the pump and engine so se can see what you're talking about. I've heard good things about the small 3 and 4 cylinder Perkins and worked on an older fork lift that had a Perkins but not much experience otherwise. Good luck

Oh and I have seen the primer pump go bad and let air in the system, just another thought.

 

well, pulled the exhaust/muffler off today, but still no start. also sure it's not the tank cap. have tried with cap off... fuel is reaching the injection lines.

what do you mean by "overflow"?

After replacing all of the components, lift pump, fuel filter, and injection pump, the motor would always start but then shut down. For the little bit of time that it ran, it sounded fine.

I am a total loss. Only other thing I can think to do is keep trying to bleed it more, but I am getting a solid stream of fuel out the upper bleed screw on the injection pump when the supply is pressurized. I have bled three of the four lines, as the 4th is difficult to get to, but I am having a hard time believing that's relevant. I have run out of fuel once before, and I only had to bleed it to the filter and then crank for a little bit and it started.

I don't know how to check fuel pressure, but I was assuming that with a new lift pump and rebuilt injection pump, pressure to the injectors should be ok, wouldn't you think?

I have wondered if it could be the injectors, but that doesn't really seem to match the symptoms. When it was starting, it would run briefly and sounded totally normal, then would die. How could that happen if injectors were plugged up or something? I have gone through this process of having it start and run briefly and then shut down several times... and there is nothing that I can think of that can explain why sometimes it would start and sometimes not...

Now it won't start at all. No smoke of any color, no nothing.

 

trying to add some pics:

https://lh5.googleusercontent.com/-m...no/%5BUNSET%5D

https://lh4.googleusercontent.com/-u...no/%5BUNSET%5D

https://lh3.googleusercontent.com/-7...no/%5BUNSET%5D

https://lh3.googleusercontent.com/-e...no/%5BUNSET%5D

 

Got her running! Finally. It took several attempts at bleeding the fuel system.

Apparently these old Lucas CAV inj pumps are very sensitive to any air in there.
I bled everything from filter to pump to injection lines several times and was literally just about to give up when I tried one last time and she finally started... what a relief.

Thanks everyone for your suggestions!

 

Success!!!

 

Glad to hear it. I'm sure it'll last many years to come.

 

Or not.

Broke down again today. Same issue. Same symptoms. Fuel starvation until the engine grinds to a halt. This after I seriously believed I had fixed the problem. At this point I can't tell what I've actually fixed anymore.
But it does appear that air in the fuel system is causing the problem. Trying to get it started again, I bled both my engine and secondary fuel filters. Unscrewing the secondary fuel filter bleeder screw created a "whoosh" which indicates that air is being built up someone creating enough vacuum pressure to negate what the fuel pump can do. But why? And how to fix? The last palce I took it to tested for air leaks, replaced a portion of the fuel line they said was faulty and re-bled the fuel lines. I would have thoiught that would have fixed any air leaks issues.

***?!

 

The whoosh can either be air pushed out, or air sucked in.
With some of these Perkins engines the leak oil line from the injectors tees into the fuel supply line. An injector leaking exhaust gas into the return line causes the problem you describe.

Use a piece of transparent hose to connect injector return directly to the tank, plug the tee, and bleed air, run the engine and observe the return line for bubbles.

And if your Lucas pump has an electric shutdown solenoid, wire a small 12V bulb in parallel to it and install in the cab. (No power there - engine off)

 

In this case it's air coming out of the secondary filter. From that side of the fuel line, I would think the air leak is coming from the tank but who knows. It's definitely not any electrical component since I disengaged those a while back.

 

I don't know your installation, so I fly blind..

You can use transparent hose on the suction side and observe if there is air entering the fuel system. If the line collapses you have a suction side restriction.
Maybe I could help you more if you drew a diagram of your fuel system.
Perkins and Cummins deliver engines, but the fuel supply side is the responsibility of the vehicle (or machinery etc) manufacturer, the engine builders usually only supply the engine with the finest filter and tell the customer to "supply fuel here", and in some cases another port "that goes back into the fuel tank".