Glow plug problem.

[Davenj4f]

About a month ago I developed the "algae" problem. I know it isn't really algae, and subsequently solved the issue, but since then I started having bad starting problems. Once I get it started, it purrs just fine. I'm not measuring any voltage on the glow plugs with the key in the on position. After discussing this with a couple of other better informed friends, it was decided that the next thing to fix/replace was the glow plug relay. Well, that didn't fix the problem. So back at square one and don't know what or where to go from here. Any help would be tremendously appreciated.
BX-25D 3 years old, about 375 hours.
Dave

 

[cooksmtn]

Basic trouble shooting can be done with a simple test light, often easier than a DVM. Ground the pigtail on the test light, then start looking for power by probing with the tester, starting with the switch that operates the relay. Typical mechanical relay makes an audible click when activated. If relay activates, check for power on the incoming line and outgoing line. If power is at both terminals of the relay, check at the first glow plug.

If you have manually activated glow plugs, the circuit should be very simple, although it may be hard to trace wires when they disappear into a harness.

You can check glow plugs, individually, by disconnecting the power lead to each, hook the tester pig tail to the positive battery terminal, and touch the probe to each glow plug terminal. Glow plugs tend to fail as an "open", which will keep the tester from lighting. A functioning glow plug will ground the tester, causing its light to illuminate.

One or two non functioning glow plugs can make for very hard starting.

Good luck, let us know what you find.

 

[Roadworthy]

You may or may not measure voltage to the glow plugs. Some glow plugs short to ground when they fail while others go open. If you have the type that shorts to ground all voltage will drop across the controller. Try checking them individually. You can put an ammeter in series with each plug individually to see what it draws. You should probably use a twenty amp in series as well. I think about ten amps each is about right. If they draw nothing they are open. If they blow the fuse they are shorted. If they are open or shorted they will need replaced.

 

[Texasmark]

Glow plugs tend to fail as an "open".......

Voltage at the plug, pull the wire, with your DMM Ohm between wire terminal and chassis on lowest Ohm scale...just takes a second, nothing needs to be removed but the power lead......... no Ohms on the scale, bad glow plug. Get a reading go to the next one and repeat. I'd expect Ohm value of plug to be around 3-4 ohms (of continuity.....long way from open circuit reading).

 

[PILOON]

Very often the ignition switch can be making bad or week contacts.
I discovered that (certainly more often in open stations) that sun/heat dries up the lubricant inside the ignition switches.
My 'cure' is to spray WD40 into the key slot which results in softening that caked up grease.

Also a 'work around' is to wire a push switch into the glow plug circuit and bypassing the factory ignition.

Naturally that is after you have proven the plugs are good.

To confirm a good plug, remove the plug wire from the plug buss bar and measure the internal resistance of each which will read very low ohms, like around 10 ohms or even less.

If the plugs are proven good, then any way of powering them will heat them up.
(once knew a guy that simply made manual contact by touching 2 leads that he wired inside of his cab.)
On an old plow truck I used an old foot button type starter switch and counted off seconds.
Ran that plow that way for 3 years as the relay was very $$.

The only caution if U manually power the plugs is to keep the power cycle short, like mere seconds and certainly not over a minute.

 

[WranglerX]

Most expensive way to trouble shoot is randomly guessing what parts to replace, chances are you will replace several working part the are good before you stumble onto problem,...

Yes use test light and either start at glow plug and work back or glow plug "heat" switch and track voltages to where you either find it or lose it (depend on direction you take) and usually it will be problem, whether it is intermittent key switch or push button or glow plug "indicator" on dash or relay.... Use ohm meter to test continuity of glow plug with wire or buss bar disconnects from terminal to engine block....

I have probable $200 in analog and digital meters, and this is my first go too tool for basic "automotive" troubleshooting (non computer stuff)...

Dale

 

[Davenj4f]

About a month ago I developed the "algae" problem. I know it isn't really algae, and subsequently solved the issue, but since then I started having bad starting problems. Once I get it started, it purrs just fine. I'm not measuring any voltage on the glow plugs with the key in the on position. After discussing this with a couple of other better informed friends, it was decided that the next thing to fix/replace was the glow plug relay. Well, that didn't fix the problem. So back at square one and don't know what or where to go from here. Any help would be tremendously appreciated.
BX-25D 3 years old, about 375 hours.
Dave

Thanks to all who replied. Everyone is on the same page, thank goodness. Some of the suggestions I should have already done, but have never dealt with glow plugs before, but am learning fast.
I pulled the supply wire off the glow plugs and didn't get any voltage with the key ON. Without pulling the plugs out, and with the connector that goes between the plugs off, , I checked resistance. Had about 1.5 ohms each. The number varied slightly each time I checked, but always under 2 ohms.
Tomorrow I will try WD-40 in the switch. I had already thought about the switch, but not the WD-40.
I know, my bad buying the relay first. But my sources were fairly sure. Not going there again.
Have already considered a spring loaded toggle switch between the battery and the glow plugs. 2-3 seconds usually.
More tomorrow.
Thanks guys.

 

[PILOON]

Quote=
Have already considered a spring loaded toggle switch between the battery and the glow plugs. 2-3 seconds usually.

Careful, most toggle switches are only rated at 10 amps and 4 sure the plugs draw MUCH more.
A starter relay activated by spring loaded switch will work however.

Were U to monitor your battery while 'glowing the plugs' you'd see a serious voltage drop.
Those plugs really suck it up.

 

[WranglerX]

If going spring loaded toggle, also consider adding 30 amp (generic) auto relay with socket/pigtails...

 

[Roadworthy]

I got a heavy duty spring loaded toggle switch at the auto parts store. I think it was rated at fifty amps. I also replaced the glow resistor in series with the glow plugs. It drops the battery's twelve volts down to the (I think) 10.5 volts my glow plugs require. The resistance of the glow plugs changes as they warm up so a resistance check with an ohmmeter will be much lower than the resistance of a glow plug in use. I use four glow plugs (four cylinder engine) and I think the total draw is about forty amps. I turn on my key and look at the dash lights. When I hit the glow plug switch they do dim, but just a little bit.