glow plug replacement [Archive] - TheDieselGarage.com

: glow plug replacement


kkdiesel7
12-09-2007, 10:16 PM
so i have determined that replacing the glow plugs are needed. i put the ohm meter on each one getting no reading on 7 or 8 plugs i believe i did this test right any advice on testing would be helpful. i am worried however that my plugs may be carboned up and that i have read is a real bear. and if they break off then basically you have to pull the head which is extremely over my head. however i'm trying to do the glow plug replacement on my own.. ekkk... any tips tricks and advice would be extremely appreciated


2002 F250 7.3 6 position chip,ae intake, 4" lift.

John_G
12-09-2007, 11:48 PM
The 7.3L PSDs are not known for failing GPs, and they do not get stuck anything like they did in the 6.9L/7.3L IDI engines.

I find it almost impossible that you have 7 or 8 of 8 GPs bad. I have replaced three to date, since 1994 when the 7.3L PSD came out. It's possible, but it would be the first I have seen it.

Take a TEST LIGHT, any one will do. Connect the (normally ground) clip to a BATTERY POSITIVE source. Touch the tip of the test light to the tip of each GP. If the light lights, that GP is good, if not, it's DOA. That is the best test I know of.

kkdiesel7
12-10-2007, 12:20 AM
ok so say that i only have 1 or 2 that need replaced would that make a huge difference on cold starting. it WILL NOT start if its cold out unless plugged in and i just replaced the glow plug relay yesterday without results. also with the volt meter on dc i tested the output side sometimes however the output side aka one with 2 wires does not have volts most of the time though it does.... thanks

John_G
12-10-2007, 01:08 AM
On a powerstroke, one or two bad GPs will not typically cause a no-start condition. With the older IDI style engines, one will bad GP can kill it dead at 40*F!

When you measured your voltage, and it sounds like you did everything correctly, and it's working, how many volts were there (on the output stud)? You NEED to have the same as battery voltage, or at least within 1/2 volt. So if you get 11.5 at the battery (+), you need at LEAST 11.0 at the GPR output terminal.

Given that you just replaced the GPR, I would think this will be ok, but if it's low, check all you wiring back to the battery. You may just have a bad power connection.

Also, a weak starter may not spin the engine fast enough to get it to start. It turns over, just not fast enough. I have seen that before.

kkdiesel7
12-10-2007, 02:35 AM
i just did your test with the test light all glow plugs on the drivers side=dead
passenger side very front terminal was the only one that tested positive... dang thats prolly the reason for such cold starts ehhhh... after removing the valve cover is it smart to go ahead and put bp rust buster before even trying to turn the glow plugs? also has anyone had luck with the bosche glow plugs?? there available at the local autozone for like 15.00 cant buy motorcraft ones there and dont really want to go to the dealership....

jdydiesel
12-10-2007, 02:51 AM
Do not go with the aftermarket glowplugs. Stick with the Ford or international. I replaced allmine with the $8 units form krapen and had to replace tehm less then a year later. Something else that I found was the number 1 gp wire was loose on the krapen gp but not on the Ford unit. Spend the extra money and you will be ahead of the game.

pontiacross
12-10-2007, 02:53 AM
you can spray them down with pb blaster if you want but I dont think it would make any difference because thay probably have plenty of oil on them already to lube them up. I have never had any issues with getting them out.

John_G
12-10-2007, 02:58 AM
Yep, that would cause hard starting.

LOTS of people (technicians) believe that if on GP is bad, do 'em all. Well on the older engines that was sound advice, it's not on a Power Stroke.

In your case, I would bet that you have aftermarket GPs in there, which is why they are all dead. Aftermarket plugs simply do not last.'

Please let us know if they are OEM or aftermarket once you get them out!

kkdiesel7
12-10-2007, 05:49 AM
i'm looking forwards to finding this info out just as much as you. i bought this truck last december with 98,000 on it. the guy before me had a 6 position chip on it and did some mods. basically he burnt up the engine and ended up cracking the block i bought it from the dealer that he traded it off to. i found this info from the guy who traided it off. basically ford put in a new engine at 90,000 so i got it with 8,000 miles on it. but am finding i'm doing alot of the routine maint on a truck with a 100,000. such as new started, new alt, new batts, new gp relay, new serpentine belt, a few other things i'm too frustrated to think of right now. the truck runs great just a few things here and there. once i finally get all the little stuff about my truck fixed it'll be fine a dandy i hope. lol... basically i hope to keep it forever haha.. thanks for everyones advice!

gregrob
12-10-2007, 10:50 AM
1) there is a better test than using the test light like John mentioned, it's called an ohm meter. Just because a GP is good enough to turn on the bulb in a test light doesn't mean it is performing 100%, it just means it is not COMPLETELY burned out, but it could be making as much heat as a frog fart (very little). I don't remember what the resistance should be, but I can look it up for you.

2) You can get MOTORCRAFT glow plugs from Auto Zone for 2.99 a piece right now. Type ZD11 into the search on their website and print off the page, take it into the store in case they try to give you a different price. I would recommend replacing the relay as well, they're cheap. You can get a GPR109 from napa for around 20

gregrob
12-10-2007, 10:58 AM
A good gp will read btw 0.8-1.2 ohms.

You can unplug the 8-pin harness leading to each valve cover, and check the two outer most connections on each one. (the 4 inner pins are for the injectors)

Good luck

John_G
12-10-2007, 12:51 PM
I agree that you can measure the ohms in a GP, and know if it's shorted or has too much resistance.

I do not agree that that is a "better" test. Why? No modern ohm meter actually measures ohms, they calculate it. V = C x R, so the ohms is the voltage drop divided by the amps thru the circuit. Guess what, GPs work at 12V+ and 10A or more, your meter CANNOT supply that level of power (120W), typically they are closer to 0.05W (5V x 0.010A), so the ohms reading is not exactly accurate in a power circuit.

Using a regular (non LED) type test light, you actually get about 0.5A thru the GP circuit at 12V (6W), this is still not exactly like it's used, but a lot closer than what the multimeter can achieve.

But he's right, GP resistance can be measured, and there is a spec for it.

Squatch
12-10-2007, 01:41 PM
Don't forget that these trucks had problems with the UVC Harness coming loose. You will lose the glow plug circuits first then the injectors. There is a kit with locking clips that prevent the connector from coming loose. Even if you have some bad plugs and have the valve cover off put the clips in to prevent future issues

Part # 2C3Z-14A163-AB

kkdiesel7
12-10-2007, 09:16 PM
while changing the plugs should i replace the valve cover gasket while i'm at it? or is this something that shouldnt need replace unless in bad shape?

blindviper
12-10-2007, 09:50 PM
The 7.3L PSDs are not known for failing GPs, and they do not get stuck anything like they did in the 6.9L/7.3L IDI engines.

I find it almost impossible that you have 7 or 8 of 8 GPs bad. I have replaced three to date, since 1994 when the 7.3L PSD came out. It's possible, but it would be the first I have seen it.

Take a TEST LIGHT, any one will do. Connect the (normally ground) clip to a BATTERY POSITIVE source. Touch the tip of the test light to the tip of each GP. If the light lights, that GP is good, if not, it's DOA. That is the best test I know of.

Just did my neighbors truck. A 97 with 120k 7 of 8 plugs dead. I didn't believe they were dead at first until we got the covers off and the harnesses were good. 7 of the 8 wouldn't ohm at all. And its weird when I replaced mine when I did my injectors. I later found out mine were perfectly fine at 110k on them.

SlowRedTruck
12-10-2007, 10:36 PM
just did a early 99 at work had six bad glow plugs. Wouldnt start without being plugged in below 30 degrees.

fordboyyfm
12-11-2007, 12:21 AM
John i really diasagree, i see allot of 7.3s with bad glow plugs, stock original ford factory glow plugs. And it is best to check with an ohm meter, Like it was said above you will find out more testing with an ohm meter. Anything more than 5 ohms is considered too much, you could have a good glow plug but a bad connection thats causing it not to work properly but your test light will tell you its ok.

kkdiesel7
12-17-2007, 04:04 AM
after doing the replacement this weekend well not all at once hadta put the smack down on some honkers but anywho. replaced all 8 since they were all not showing a current with the test light. had to do it in stages and noticed a huge difference in cold starts even with just the drivers side bank going. i also found that the old glow plugs had ( WELLMAN) on them and the numbers of 6a843g138. so thats where i'm at to date thanks to everyone for your advice! it helps tremendous.

Beer Mod
12-17-2007, 04:12 AM
That's great! I'm glad you reported back, I may just do mine next weekend.