Deere 750C hard starting

eight · Feb 18, 2014

I have a 750C II that has become hard to start. It spins fast and will start after 20-30 seconds of cranking most of the time. Hot or cold makes no difference, sometimes I think it may be harder to start hot. Has been doing this for the past 250 hrs or so. Used to start with a bump of the key. Machine has almost 9000 hrs. Runs perfect once it starts.

Already tried:
New batteries
Rebuilt starter
New return line seals
New fuel supply line seals and o-rings
New fuel filters
Checked/Adjusted valve clearances

Any ideas?

Thanks

eight · Feb 18, 2014

One more thing. The machine thinks it has low alternator/battery voltage, usually reads 10-15v. Actually is somewhere around 28 volts. This does affect the fuel gauge, it reads lower than actual. Not sure if the hard starting could have something to do with this. Been doing it for at least a few hundred hours before the hard starting started.

Delmer · Feb 18, 2014

Are you getting fuel mist out of the exhaust while it's cranking? If not then check that the pump is getting voltage and clicking when the key is on. If it's clicking then try to prime the pump before you crank it and see if it starts faster, or if you get air out of the bleeders.

Deeretracks · Feb 18, 2014

Unscrew the top of the filter housing where the primer pump knob is, use a screwdriver to pop the black diaphragm out and clean all the crap out of it and the top of the housing. Also make sure the small diaphragm
(about 3/8" round) is still where it belongs in the center of the black piece.

wilko · Feb 18, 2014

If you shut it off and immediately try to restart it will it still start hard? If it does, how long do you have before it gets reluctant?

eight · Feb 18, 2014

I don't think I get fuel mist out the exhaust at first, then it does for 10 seconds or so and finally starts.
I have checked voltage to the pump, gets 24v with key on engine off. I have not checked it while cranking.
I haven't noticed clicking, will check tomorrow and also try priming it first. I have pressured up with the primer pump and checked for air out of the bleeders, no air.
I wonder if maybe the fuel shutoff solenoid is slow to open.

Will check out/clean the primer pump tomorrow.

Yes if I shut it off and immediately try to restart it will be hard to start.

steve.k · Feb 19, 2014

Check you lift pump on side of block. Likely worn and letting fuel leak back from main pump.Then it has to pressure system to main pump when you go to fire up again. I've had to change ours with less hrs than you. They are inexpensive ! Steve

eight · Feb 19, 2014

Primed it before trying to start today, no difference.

I do get smoke/mist out the exhaust right away, and I can hear the solenoid click. It's more like a puff of smoke, like maybe not from all the cylinders.

I remember replacing those lift pumps on old ford diesel pickups, they wouldn't start when it went bad. Guess that's the next part to throw at it. Cheap and easy to replace.

steve.k · Feb 19, 2014

If you have someone to watch take line off and spin over see how good it pumps?the only thing is its suppose to hold fuel against pump and they get weak and leak back. Then it's a delayed start. Could be that screen listed above also. They get really underpowered as those plug up also.

eight · Feb 19, 2014

There is no primer pump on the filter housings, just has a lever on the charge pump to prime. Charge pump does pressure up and will pump fuel out the bleed fitting on the filter housing. Of course that doesn't mean the fuel doesn't bleed back past the pump.

steve.k · Feb 19, 2014

The primer pump on filters is a little black round bulb on top of fiilter housing. It doesn't look like much but it does move. There are black collar similar to the one to remove filter. Spin that off and screen is under that. I beleive it's the rear filter.

Deeretracks · Feb 19, 2014

That's pretty strange, I've worked on tons of those machines and never saw one w/o a primer on the primary filter head.

steve.k · Feb 19, 2014

Yes I'm with Deeretracks. It should be there!

eight · Feb 19, 2014

Whatever these black plastic cap things are on top of both filters, they don't move.

http://img.photobucket.com/albums/v...694B741F-981-00000347BA0F9F52_zps665f124d.jpg

Deeretracks · Feb 19, 2014

Well you're right, there isn't a primer there. Weird! It was more of a pain anyway since the fuel tank level is higher than the engine all you had to do was open the bleeder to fill the filter. It was just a spot for debris to collect. It really does sound like a fuel supply issue. At 9000hrs I wouldn't hesitate to change the transfer pump. This may be a stupid question but are those the correct filters for the machine? A RE508633 should be a 30 micron primary filter but it looks like it's on the final filter housing. My 750c runs a re62424 150 micron primary and a re62419 5 micron final. I may be overlooking something though. EDIT* Nevermind I looked again that's the primary housing*

Deeretracks · Feb 19, 2014

As for the low voltage concern. Pull the monitor and alternator fuses out of the main fuse box and check for corrosion. I have to clean the fuse boxes every 1000hrs or so on our CII's the voltage display is one of the 1st things that acts up.

eight · Feb 20, 2014

When I pulled the monitor fuse the blades fell off. Guess I probably found my low voltage problem, now to dig out the blades.

I don't have an "alternator" fuse. Cleaned them all anyway.

eight · Jul 15, 2014

Machine is still hard to start. Have put another few hundred hours on it. I did replace the lift pump, no change. I guess the next thing to try would be the fuel shutoff solenoid? That and take another really good look at anywhere a seal could be in the fuel system.

Deere 750C hard starting

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