Help please. Got a used Lincoln 300G that won't run now

[learfxr]

Picked up a used 300G that was running and working, took it off the trailer and sat it in the truck bed and now won't start. Trying to diagnose the issue, any help would be greatly appreciated.

The fuel pump will not run. Been checking voltage at various places. Battery is good, power present at the on/off switch, power good at the circuit breaker, power supplied to the ecm. The ecm is not sending voltage out to the fuel pump? Not sure if the ecm is not seeing something it wants to see, or if it magically took a dump all of a sudden??

Any ideas why the ecm would stop telling the fuel pump to run? We ran power to the fuel pump and it will work, but can't start the motor that way, cause I'm sure the ecm isn't telling the injector to fire either.

Have a welding job in the morning and really trying to figure this out

Thanks guys

[aevald]

Hello learfxr, could certainly be a number of things that come into play here. First off, I believe you are taking a very methodical approach to finding the problem, that's a good thing. From the simple sound of things, if it was running before you unloaded it and it isn't now I would look for loose wires/connectors or something along that line. Maybe even a tripped breaker or something like that. Unfortunately, I am not that familiar with that particular machine so I am going on basics and probably not specifics. It might have a low oil level or pressure shut-down switch that isn't allowing it to start/run, see if you can verify these items and whether they have continuity or not depending upon their specific type(some require continuity in order to allow the engine to run, some are the opposite). There are likely others who are very familiar with this particular model machine and hopefully they will have some common issues that they can suggest for you to get you going. Best of luck and regards, Allan

[pigpen60]

check the ground cable. hook your testlight to the frame and check for continuity. or use a ohm meter and check between the frame and the battery post. may have more than one ground cable so look also does it have a murphy switch? just a guess. pigpen

[learfxr]

Well, spent hours working on it last night and I would swear it needed an ECM. I checked voltage and grounds at numerous places. The ECM wasn't putting out voltage to the fuel pump, made sure the ecm had power and ground. We checked the circuit breaker, removed wires from it one at a time and checked power.

Today a mechanic took a look at it, and determined it needed a new circuit breaker. While the new part is on order an inline fuse has been installed and it's running great. I have no idea how I missed that. I'm an aircraft mechanic and I'm not stranger to checking wiring issues. Bad circuit breakers can really kick your butt. I've seen them do the same thing in Lears. They check ok with a meter, but they are causing voltage drop across them and kills the circuit. I'm still scratching my head about how I got 12V at the ecm when the c/b was bad? Electrical systems can really drive ya crazy.

At least it's a $60 c/b and $70 labor, instead of $70 labor and $$$$ for an ECM


Thanks for the assistance guys. Was starting to feel pretty down about it last night. Looks like I need some more practice checking C/B's. Thought I had a good idea how to handle it.

[duaneb55]

Originally Posted by learfxr

Looks like I need some more practice checking C/B's. Thought I had a good idea how to handle it.

Glad you got it running learfxr (now I see where your user name comes from ).

Common mistake on the circuit breaker. Checks out 'OK' with a volt/ohmmeter but nothing when a load (fuel pump) is applied. No doubt you would have discovered the faulty CB if checking for voltage at its output with everything hooked up and attempting to start the unit. But then - Monday morning quarterbacking is easy.