I have a 99 7.3L with 199446 mls & on cold mornings it takes several on-off, on-off(wait to start light) & wont start. I end up using starting fluid. No, I haven't put a engine block warmer yet(wich is a good one?) How can I find out if I need to replace my glow plugs or my glow plug CONTROL MODULE?

Thanks

 

You truck already has a block warmer, look for a plug tucked in behind the grill by the tow hooks. Are you getting any white smoke when it does fire up? What kind of temps are you getting in your area?
BTW- Welcome to FTE, glad to have you aboard.

 

Don't us starting fluid ( big bang ) WD-40 instead.. Change the GPR first, than ohm out the GP if still no start! Are your batt. up to power! Takes alot of amps when the glowplugs come on and the starter work at the sametime! And Welcome to FTE... Also do you us fuel additives.

 

Welcome to FTE.

You need to get a multi-meter to check out the relay and the glow plugs. When the engine is cold, and the outside temperature is cold, set your multi-meter to read volts and check the voltage on the 2 big posts on the GPR (glow plug relay) With the engine off, you should see 12v on one post and 0 on the other. Then turn the key to the on position, and quickly check the voltage on the post that didn't have any power. You should now see 12 volts on that post for between 1 - 120 seconds. If not, then the relay is not energizing the glow plugs. With the key on, hold a screwdriver across the posts for 30 seconds (manually turning the relay on) then try to start. No power on the 2nd post when the key is first turned on means you need a new relay.

To check your glow plugs, look on top of the motor and find the long flat wire connector that plugs into the inboard side of each valve cover. Unplug the connector and you will see 9 pins inside (valve cover side) The front 2 pins, and the back 2 pins on each valve cover are your glow plugs. Set your multi-meter to ohms, place one lead on the battery ground, and check the ohm reading of each of the glow plug pins. You should see a reading between 0.6 - 2.0 ohms if the glow plugs are good.

 

Check out the following forum link.. and post #7 from Robin.. has a great pic and info on the GPR...
https://www.ford-trucks.com/forums/7...lot-chugs.html
Also, On my 99 when the GPR is working properly I get 11 volts until it kicks off.. If the engine is up to operating temperature, then the voltage goes back to normal at 14 volts. (all voltages are when the engine is idling)

 

Here is another great source for GPR info:
Welcome to guzzle's Stancor GPR replacement Mod Web Page

A buddy of mine was having those problems and he put in the big Stancor -- all good now!!

Also, we took apart his old relay, and it was pitted & corroded. It was nasty...

 

If you cant find it (they're hidden real well sometimes), look above the oil filter for a cord wrapped in orange tape. Follow that forward along the frame rail and you'll find the plug.


Welcome to FTE

 

On Guzzler's page, third pic down looks like he is replacing the black unit next to a brown identical unit. In the link before that (Clintbonnie's post) it looks like a brown unit.
Are there two GPRs?

 

There are 2 relays on your motor. The one toward the back (smaller one) is the GPR. The factory one is brown. Some of the ones from the auto parts stores are black. The color really doesn't make a difference.

 

Thanks Chris, sooooo...
What is the other one (black one on Guzzle's page)?
His page indicates the black is the GPR and unknown what the brown one is on his page.

Quick & dirty, I (we all) should check to see that it has batt voltage at the output terminal before the winter hits? Is that a good 'nuff check? I have 95k miles on the original GPR.

 

The bigger relay on your truck, the front one, is the AIH (air intake heater) relay. It's not really a critical relay, just used to minimize some smoke at idle on cold mornings. If money's tight you can use the AIH relay to run your glow plugs, and just ignore the AIH function. The earlier trucks did not even have one of these.

I wouldn't get too hung up on the color of the relays as much as the position (front or back). Checking the condition of your relay before winter hits is a good idea (if you live in a place that actually has a winter). I've never changed my GPR, but down in Texas, mine doesn't get as much exercise as the ones up North.

 

In a pinch on the trucks with an AIH, you can do the AIH delete (its not necessary anyway) and use the AIH relay as a GPR.

 

I did the AIH delete long ago.
Hmmm, wonder if I should clean up/remove the relay and wires for it.

But yep, I'll check the output voltage on the GPR tomorrow, been on there a long time!