# Newbee to Diesels-Glow Plug quesiton



## Scottys (Nov 15, 2010)

Hi, I'm new to the forum and diesel equipment.
I've recently purchased (August) a used Cub Cadet compact tractor, Model 7304 with a belly mower and front end loader. It has a Diahatsu 30hp turbo diesel engine. It's my first diesel engine. I'm very happy with the tractor. It has run great and started easily while the weather was warmer.
Now that the temps are getting cooler here in Wisconsin (40-50 degs f), the tractor is hard to start. It cranks well but won't start easily. I don't intend to use it much in the winter but would like to be able to rely on it this fall and next spring (above 30degs). 
I've tried to determimed if there is something wrong with the glow plugs or their electrical circuit. Here' what I've done so far:
Turning the key to the glow plug position, I've tested and confirmed voltage (12vdc) at the plugs while the relay is closed. Afer about 5 seconds, the voltage drops to zero when the relay opens.

What do I check next? Is 5 seconds sufficient time to completely warm the plugs? How do I effectively test the glow plugs. The plugs are NSK brand. Sorry I don't have a part number at this time.

The circuit seems to consist of the ignition switch, a pre-heat timer relay, glow plug relay, a dash light indicator and 30 amp fuse. 

I'm quite handy with gas engines (cars, boats, motor cycles and small engines) and pretty mechanical inclined. But diesels are a bit foreign to me. Any help would be appreciated. Thanks.


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## Hoodoo Valley (Nov 14, 2006)

Welcome Scottys! I have direct injection, and hence, no glow plugs but wondered how many hours on it and the state of the fuel filters and air filter?


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## Scottys (Nov 15, 2010)

Unknown. The digital hour meter display is unreadable. It's a 2004 vintage tractor.
I do not know when the fuel filter and air filter were last changed. Although the air filter looks fairly clean and there is no visible water collection at the bottom of the filter bowl (poylcarbonite bowl).


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## Hoodoo Valley (Nov 14, 2006)

Wish I could be more help but I know very little about glow plugs, but someone else on here will sound off. Some super knowledgable folks on here. Too new a machine to have severe issues, but if you don't have it yet, I'd really consider a block heater. Well worth the money!


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## GreenFlyer (Feb 4, 2010)

Read your owner's manual regarding 'Starting in cold temperatures'. I am somewhat familiar with diesel engines and their cold starting procedures. If you have not already started a winter diesel treatment, do it. Do not count on diesel fuel treatments or the fuel filters to remove ice/water during the winter months. I am not familiar with Diahatsu diesels. If you are planning on using it during the winter and the engine model you have has a block heater available, get one. You mention that you live in Wisconsin. Unless you are storing it in a garage where the temperature will always be above 50 deg, you will need a block heater. And for heaven sakes, DO NOT rely on using ether to start your engine. If you do not absolutely have to use it, DO NOT. In the long run it will cost you. I have a JD 970 with a glow plug position on the ignition switch. I do not have the manual in front of me, but 10-15 seconds of 'glow plug' position is what I recall using the last time I used it,(2 or 3 yrs ago). Again, I am not familiar with your system, but 5 seconds seems like a short time for glow plugs, esp. if it is for very cold applications. Read the manual, fuel treatment, block heater, and keep the thing stored inside and/or covered if you can. Good luck!


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## Scottys (Nov 15, 2010)

GreenFlyer,
The owner's manual instructions for cold weather starting:
"Move the throttle handle to approximately the fFAST position, then follow the remaing normial engine starting instructions." Which are to turn the ignition key to the pre-heat positon, wait for the glow plug indicator light to go out then depress the start button."
Noted in the cold weather section is that Cub Cadet does offer an optional coolant heater. This will "aid in starting the tractor when the ambient temperature falls below 10deg F".


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## Scottys (Nov 15, 2010)

P.S.
I have been using fuel treatment since August (when I purchased the tractor).


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## rsmith335 (Jun 2, 2010)

You should be able to check the glow plugs with a AMP meter, you have voltage, but a burned out glow plug won't pull any AMPs. Good luck


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## Mickey (Aug 14, 2010)

Don't know anything specific about Diahatsu engines. Don't know what the spec'd time is for the glow plugs. My Yanmar is ~10 sec and there was a time when 1 min was more the norm. For the temps you are reporting I wouldn't have to use the GP's on the Yanmar.

As rsmith said, you can check the GP's to see if there is a short or open. If you are handly with a multimeter it wouldn't be hard to check each plug. Disconnect the wire leading to them. Check resistance between the center terminal and ground. They shouldn't be either ZERO resistance or infinite. I suspect they will be quite low resistance, 1-5 ohms. Any that reads either zero or infinite should be replaced.


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## Scottys (Nov 15, 2010)

rsmith335 and Mickey, 
Thanks for the tips.
How many amps would you expect a glow plug to pull?

Just another couple of notes:
The glow plugs remain for about 5 seconds and are controlled by a solid state timmer. I have no way of contolling their duration. Would it help to cycle the GPs several times before hitting the start button?

The glow plugs are located on the intake manifold right next to the injector, close to the cylinder head. Don't know if this is in anyway important in troubleshooting. I've seen diagrams where the GP is in the combustion chamber along with the injector.


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## rj'sbarn (Jul 30, 2008)

*glow plugs*

A glow plug is essentially a huge low resistance heating element. Just shy of a direct short to ground. You can test the glow plug with a multimeter by metering audible continuity to the connector on the plug and the surrounding cylinder head. Read the resistance on the display and look for glow plugs that have too little resistance or an open circuit. The glow plugs in my VW are 190-170 ohms as well as the ones in my 7.3L T444. Too low resistance and it heats up the wire supplying it more than the glow plug itself.
Cranking speed is also an issue in colder weather. Batteries have a harder time in lower temperatures supplying a full load of current. Since diesels rely on heat and compression alone, things have to be hot, fast and violent in that cylinder to get the party going. If your cranking speed is too low and your glow plugs dont get the precombustion chamber to 400 deg F(flashpoint of diesel) you will have a hard time starting. Cycling the cold start timer twice or 3 times probably wont do any damage and might get it to start but that would be one of the the last things I did. I have to over cycle the plugs in my 7.3 just because it's an old worn out engine and gets poor compression in the cold before she warms up.
I've had old rustbucket diesels I've had to use the wifes hairdryer to blow warm air in the air intake while she is cranking on it to pick up the slack for a cold battery or a bad set of glow plugs. Use the hairdryer if over cycling the plugs doesnt work.
Do everything you can to keep from shooting starting fluid at it!


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## Mahindra One (Aug 4, 2006)

*Can't find Discussion Groups*

I'm brand new to the forum and I'm sure it's me, but I can't find where to access the discussion groups. Help would be appreciated.


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## Mickey (Aug 14, 2010)

Scottys said:


> rsmith335 and Mickey,
> Thanks for the tips.
> How many amps would you expect a glow plug to pull?
> 
> ...


Are you saying the injectors are NOT shooting in to the cyl or precombustion chamber but into the manifold? Don't see how a diesel can operate with that design.


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## Hoodoo Valley (Nov 14, 2006)

I thought it sounded a bit weird for glow plugs. Wondered if mabe he had an intake heater instead of glow plugs. Is this a direct or indirect injection?


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