Cold start problem

[rebarwes]

I need help with my 753 Bobcat. Cold start glow plugs.

 

[DieselBound]

Do we get to guess what problems you're having?

 

[rebarwes]

Do we get to guess what problems you're having?

It just won稚 start In cold weather. I went to Bobcat supplier to buy new glow plugs and owner explained that there is a relay and timer. The relay is above the battery, a little hard to find..swaped the breaker no power to glow plugs . Not sure where timer is. Also tried to check ohm readings on plugs read 0. I do not have a book on this machine. Any help would be appreciated

 

[DieselBound]

OK, so you've got no power to the GPs. You say that you "swaped the breaker," do you mean you swapped the relay? Also, did you check whether you had any power to the GPs before you did anything?

I think that if you do a bit of searching you might be able to find an answer (or help).

I just searched and came up with this thread:

http://www.tractorbynet.com/forums/bobcat-construction-equipment/326860-bobcat-753-glow-plug-operation.html

 

[rebarwes]

Thanks for your reply..no I didn’t check but I will get my wife to turn key while I check it. Also that other post suggested to turn the key to left for gp. I have not tried that. Thank you..I am trying to get on to this. Still new!

 

[DieselBound]

If you've never dealt with a diesel before then any cold start issue will really cause you to pull your hair. But, once you realize that there's really not that much to GP systems, and that they really do do the job, then you'll be golden. I've got an old Ford IDI 7.3L diesel which can sit for months on end; I turn the key, wait for it's "wait to start" light go off, hit the starter and it always chugs to life. The previous owner burned out a starter because they couldn't get the GP system working correctly: I replaced a simple ($72) glowplug controller (only real piece of "electronics" on this truck), the fuel return lines and a set of glowplugs).

Where are you located? Location helps to understand what kind of environment equipment is being run in.

 

[rebarwes]

In the Western part of Maryland. Out where we are just between West Virginia and Pennsylvania. A little town of Frostburg, Md.

 

[rebarwes]

You hear of people twisting those glow plugs off and I am a little afraid to put a wrench on them. Put if it comes to that ,I will do that.

 

[DieselBound]

"Frostburg," and talking about "cold starts." :laughing: Anyway, yeah, you can see some colder temps there (I'm in a very moderate climate, GPs help, but one can get by in a pinch).

If you're looking to replace the GPs (had thought you'd already done that) then the best tool is patience. Start putting penetrating fluid around the bases. One could lightly tap on them from time to time . When going to put a socket to them make sure you're on them square. If you have a torque wrench I'd recommend using it so that you limit the amount of torque you're applying. No idea what the toque specs are for the ones you're dealing with, but I'd limit the extraction force/torque to no more than twice what the installation torque spec is. GPs that have been installed for a long time will end up bonding (threads locking) to the head. For example, my cars' GPs are spec'd at 11 ft-lbs; it's noted to not exceed about 25 ft-lbs for extraction: this is an aluminum head, which for sure one has to be careful with. While it may seem counter productive, often times FIRST TIGHTENING a nut/bolt/GP can help loosen an established bond; however, one has to be very CAREFUL not to exceed a safe torque; go very easy, stopping when there's movement or you hit that torque limit. If you had success in tightening (breaking any bonding) then add a little bit of penetrating fluid and remove! IF things won't budge do NOT FORCE, otherwise you'll break a GP and then be in for a lot of fun (use time/patience up-front lest you end up using a LOT of time and frustration later).

 

[ovrszd]

I try to patiently apply the KISS principle, Keep It Simple Stupid.

Sounds like you aren't sure how to activate the GPs using the ignition key? I'd educate myself on that procedure before I went any further. On my Kubota RTV it's simply holding the key in a certain position which lights the "Glow Plug" light on the dash. Time of holding the key is dependent on temperature. Usually 3 or 4 seconds.

If you are certain you are doing that part right then I'd start checking for power to the GPs. Again, I'd educate myself on how to analyze that. If no power there, then I'd start checking power back toward the ignition switch.

Do a Google search for this problem and maybe a search for a wiring diagram.

I would exhaust all of these search methods before replacing any parts. I'd never consider removing a GP until I had proven that it was defective. Normally if a GP goes bad the others still work. Engine might start a bit rough, but will usually start with one GP failing.

If you start blindly guessing and removing items you will most likely be headed in the opposite direction of a fix.

 

[ovrszd]

Here's the results of a simple Google search. Many images of wiring diagrams.

bobcat 753F wiring diagram - Google Search

 

[DieselBound]

Richard, yes, absolutely correct. In the thread that I linked to it mentioned the procedure for activating the GPs- the OP mentioned that he's going to look at that. I just added the GP replacement because it's "almost" a certainty that if this thing has been neglected that there's one or two bad GPs; everyone should be familiar with how to approach changing these.

 

[rebarwes]

Thanks for all suggestions. Not had time to check it out yet. I do want to get it working as I use it with my power angle snow plow. 36 out side right now and to be colder through weekend. Could snow anytime now. Thanks again. Harv

 

[ovrszd]

Richard, yes, absolutely correct. In the thread that I linked to it mentioned the procedure for activating the GPs- the OP mentioned that he's going to look at that. I just added the GP replacement because it's "almost" a certainty that if this thing has been neglected that there's one or two bad GPs; everyone should be familiar with how to approach changing these.

Good advice given by all. Hopefully the OP will figure out the problem and report back the results.