First time poster with a VERY STRANGE problem

TCBoomer · May 6, 2004

Hi all,
I've been reading this NH forum for a few weeks now, and have really enjoyed it. I own a TC21D and have several questions to post to you guys. But first and most important...I'm trying to help a friend solve a strange problem with his skidsteer, and possibly someone here might have run into this before or advise me where else I could go. After I solve this problem, I look forward to participating here and maybe learn a thing or two. I plan to hang my hat here, so that is why I posted it here instead of somewhere else.

So here's the deal...machine is a Mighty Mac model 8C skidsteer/loader with the Orian gas engine. The electric fuel pump has just about died. It's an AC pump, and does run but very weak and won't supply enough fuel to run the tractor. If you fill the carb bowl...starts, runs and shuts off fine, or til it runs out of fuel. THe replacement pump is a Federal-Mogel/Carter brand. The problem with the new pump installed is the engine won't shut off with the key. Otherwise runs fine. If you cut the B+ to the pump or disconnect the voltage regulator feed to a terminal board (pump is wired from the same board) then the tractor will shut down (without using the key). Reinstalled the defective/weak pump again, fiil the carb bowl with fuel and it starts and runs until carb runs out of fuel. and again...it DOES shut off with the key, each and every time. Reinstall another new Fed Mog pump and same as before...can't shut it down with the key.

I really hope someone here can offer their .02 as to what might be causing this. I realize there are a few options...such as use a relay to power the pump and be able to shut down with the key, but the owner would really like to know why this new pump is causing this odd situation. He's a 'need to know' kinda guy<G>

BTW...sorry for the log winded first post...

So with that said...hope I can solve this riddle and start to talk about New Holland biz <VBG>

THanks to any and all...
Bob

Rip · May 6, 2004

Wecome to TBN and the NH forum.... many folks will be more than happy to help out and share experiences with you and your TC21.

While someone here might have a clue regarding your fuel pump problem, there is a greater chance on the Construction Equipment forum further down the listings. Try posting this there.

Rip

TCBoomer · May 6, 2004

THanks Rip...I'll post over there.

Soundguy · May 7, 2004

Any chance you can install a relay that is run off the key switch inline with the power to the fuel pump? That wat when the key switch is on.. it turns the relay on.. and lets the controler board tunr the fuel pump on.. then when you turn the key off, the relay goes off.. and then shuts down the fuel pump..?

A cobble yes.. but a decent cobble...

If you do go the relay rout.. diode compensate it so it doesn't throw any high KV back emf into any computers inthe system that may be sensitive to it..

That is as simple as taking a diode and installing it backwards across the relay coil contacts..it will be sitting parallel with the coil power contacts..in other words.. attatch the cathode of the relay on the incoming + power side of the coil. and the anode of the diode, on the side of the coil that goes to ground... and reverse emf will be shorted across the diode.. regular forward working voltage won't effect the diode..

A radioshack 1n914 diode will work fine.. 10 for a buck.. or used to be..

Hope this helps..

Soundguy

TCBoomer · May 8, 2004

Yes the relay would work, but my bud wanted to know what was behind the problem. Well sure enough...as luck would have it...both times he checked the resistance, he must have used the same direction with the connections. This time, checked it both ways and sure enough...2.4 ohms in one direction and OL the other. Thanks to 'bgott' at the construction equip site, he brought to my attention that the back feed could be the culprit.
While I've seen fan motors keep circuits alive, I've never seen it prevent an engine from shutting down.

Well, now that I found the answer here at TBN....I'm ready to chat about New Holland.<G>

BTW...thanks for the tip and part # for the diode.