M1009 turns but no start

[CROM]

Over the past few weeks, my truck has been starting with more and more difficulty. I chalked it up the weather getting colder, but now I can't get it to fire at all. I followed the TM on "Cranks but will not start" and have a few questions.

I have half a tank of gas. I did an ohm check and found five bad glow plugs and replaced them. Still no start.

I am able to bleed with fuel filter with ease which should eliminate the fuel pump and lines as the culprit?

I get all eight glow plugs clicking and the wait light comes on and turns off like normal.

I have done the dogghead starter relay mod and voltage/load tested both batteries (both of which are charging now after attempts at starting)

My question has to do with making sure the fuel system is operating correctly. I understand that I would not be able to bleed the filter if the pump was not working but the tech manual mentions checking the fuel supply and return lines for problems. Is bleeding the filter a good check of this or is there more I need to look at?

Also, in a few related threads, I have seen a fuel drain back check mentioned in turning but no starting issues. How do I check/repair this issue?

Any help you gents could shoot out is, as always, most appreciated!

Oh, forgot to mention, I have a lower radiator hose heater that worked like a champ for me all last winter and still heats up now.

 

[original]

When you continuosly crank the engine, and it doesn't start, you should have unburnt fuel (smoke) coming out the exhaust. If the fuel (smoke) isn't coming out, make sure the pink/redwire on the injector pump has power. I've had this problem before and it always turns out to be a glow plug system issue. I would double check starter relay mod and change all eight glow plugs. Check to see if the plugs are getting power. The wait light working and the solenoid clicking correctly doesn't mean the plugs are working. Don't forget to check the fuses. That's all I have; hope it helps.

 

[CROM]

Thanks Original. Tomorrow is voltage check day. I just had time to do what I listed above before it got dark. I'll post what I find in the morn.

 

[CROM]

Looks like I have 12v on my GP relay when the truck is off. According to the tech manual, this means it's bad. However, it still clicks when I turn the key to the the plugs cycle. Is this a norman bad condition? Can the relay click and still be bad?

 

[CROM]

Also, when I jump the light blue wire from the GP module to ground and put the truck in the start position, the relay DOES NOT click. This is reassuring me that the relay is bad, but the fact that it clicks through when I turn the key with everything connected is making my eyes squint.....

 

[MakersTeleMark]

Are you seeing a drop in the voltmeter when cycling the plugs?

 

[CROM]

The voltmeter in the truck hasn't worked since I've owned it. Can put a meter directly on a glow plug to see if it's getting voltage?

 

[doghead]

Put the red probe on the bottom stud(output side) on the gp relay. Put the black probe to ground(engine or body)

Also, while the gp relay is energized, measure the input side(top side and see if there is a difference in voltage. If it is different, your relay is bad.

 

[CROM]

Ok, here's a pic of what I am assuming is the Glow Plug Relay. Doghead, you mention top and bottom studs, but what I am thinking is the relay has the studs next to each other. It is entirely possible I am taking measurments off of the completly wrong part. The TM pic is pretty bare (The tech manuals we have in the Air Force have colors and pictures and puzzles and someone comes and holds your hand while you look through it.)

I am assuming the relay is the compontent on the left?

 

[cpf240]

I am assuming the relay is the compontent on the left?

The black diamond shaped thing is the 12v buss. The silver cylinder next to the brake master cylinder is the GP relay.

Since it appears from that picture that the GP system is still in its 24v configuration, you should read 24v at the top post of the silver cylinder. The bottom post is connected to the GPs, and, if working correctly, should measure about 12v when the relay is energized. If it reads more than that, there may be some bad GPs in the system.

 

[doghead]

5, is the 12 volt junction/terminal. It supplies the whole vehicles 12v stuff(like a civilian vehicle has). It is also where we connect a new supply wire to resupply the gp relay with 12 volts, as a modification to protect the glow plugs from all burning out when one goes bad.

1,2,3,4 are terminals on your glow plug relay.

1, on your truck(stock) is 24 volts but it has a resistor in-line so when the glow plugs are on(and all good) the voltage will drop to 12 volts(unless one or more glow plugs are bad, then the voltage will vary)

4, is the output side of your glow plug relay. it will drop from 24 to 12 in about 2 seconds, after the relay closes) if all 8 glow plugs are good.

3, is the blue wire. It simply connects the relay coil to ground to activate the relay(controlled by your GP controller card).

2, is the pink wire that has 12 volts on anytime the key is on. It is the other side of the relay coil.

 

[cpf240]

Doghead said it way better than I did!

 

[CROM]

Well....that changes tings.

Ok, on the top port, I have 24V with the truck off. In the 'Run' position, I am getting 0-24V on the bottom port as the relay clicks (normal operation, I believe).

So, if the plugs are good and relay is good, do move onto the module next? I have the ablility at work to check all compontents on the board. If this check out ok, what next?

 

[doghead]

When the relay is activated (clicks), you should only have 12v at the bottom of the relay. Any more, and your glow plugs are bad.

any less that 12v and your relay is bad.

To test your glow plugs, unplug the wires and measure the gp for resistance. no resistance means they are bad. you should find 1-3 ohms. test all 8.

If your gps are all bad, i recommend you convert your gp supply to 12v to eliminate the possibility of one bad gp causing the others to all blow(in stock form it does this).

 

[CROM]

Thanks Doghead! Tomorrow when it's light I'll keep plugging. First thing I'll do is recheck all the glow plugs. I did just install 5 new ones, so if they're bad something is obviously wrong deeper back. I've read a few post on new glow plugs cooking and a few about the 12V bypass.

I'll post findings tomorrow, that's again for all the help.

 

[CROM]

Well here's a fun update. I finally found time work on the truck. Had some buddies come over and help me push it into the garage so I'm not freezing outside. Anyhow, first thing I did was re-check for continuity at the glow plugs. All are blown. On top of that, four of the ones I replaced are stuck inside the block. They unscrew fine, and aren't wedged in; but I'm assuming the ends have swollen and I cannot remove them.

I haven't pulled really hard on them yet as I don't want to break them off. Any suggestions on removing these?

 

[mistaken1]

Vice grips and a pry bar. Work slowly and maybe add a little lube. Search swollen glow plugs for other options.

 

[CROM]

I just picked up the gp removal tool from a buddy. I should be able to get them out, now. Still wondering why they went bad like that, though...

 

[Cliffinator]

Sounds like your GP resistor may be bad and your getting a 24v to the glow plugs instead of 12v like they should be getting, resulting in premature failure.

 

[CROM]

Well, even with the tool I broke off two plugs. Time to go fishing. I just remove the injector, to get at them, right?

Cliff - yeah, that's kind of what I'm figuring. I'm just going to bypass the thing with a manual switch.