glow plug test

[thomasinnv]

just curious, if a plug or two is bad, will it throw a code? how can each plug be tested to see if they are working or not?

the reason i ask is that the last few mornings has been cold (23 deg this morning) and i had to start the truck about 8 times or so before it would finally stay running. yes, i waited for the "wait to start" light each time. it would start without too much cranking, but it would lope really bad, like a huge cam in a gas engine, and then die after about 5 seconds or so. i was finally able to keep it running by pressing on the go pedal for about 10 seconds untill it smoothed out then it would idle.

i know diesels don't like cold weather, but at 23 deg with all glow plugs in working order it should still start and run ok, don't you think? thats why i'm thinking glow plugs...whadaya think?

[badazzstroker]

unplug the harness that goes in the valve cover there are 4 of the same color wires on each side i think that they are white but cant remember.take a 12v test light and put the clamp on your positive batt cable then take the test light and put it on each glowplug wire if it lights up your glowplug has at least some life in it but i bet you wont have to many of that happening from what i have read above.

[Kyle_1724]

I have a 2000 F350 and it was doing the same thing. It was very hard to start in the cold mornings. Very bad lope to it. Would take 5-8 times till she fired up. Talk to the local machanic and he said that I should replace the Glow plug relay. He said it was a cheap place to start. Went to Napa and bought a Glow plug relay for $70. Replaced it in my drivway in about 15 minutes and have not had a problem since. Works great. Starts right up in the cold mornings first try. you might want to try that before you pay Big $$ on new glow plugs. See if that works first. Hope this helps

Kyle

[Marty]

Using a light to test for power will not really do anything.

You'll need to get an OHM's reader on the plug and I forget the spec but for some reason 11 is screaming at me. Don't quote me though... it's been a LONG time since I had to know this info.

[Tree Killer]

Aren't glow plugs only 10-15$ each? Its been awhile since I bought um for my 89' 7.3

[Kyle_1724]

Well I'm not sure how much glow plugs are. I just didn't want to tackle that big of a job of replacing them. It was really easy to replace the relay instead. But mine ended up bad so it worked out for me

[Flinch]

Just tested mine and 5 were dead meat. Replaced 4 (all on one side) and starts easy.

Price for 8 totaled $99, Motorcraft brand. The bad ones were Bosch. Truck has 140k, so plugs have been replaced at least once since new.

Nope, they don't throw a code.

Take off the flat connectors on the valve covers. You are supposed to be able to push on 'em and presto - they release. After 1/2 hour I used a screwdriver and pried 'em apart. Was rewarded with a satisfying CRACK as splinters of the connector latch flew off somewhere. Maybe they wont stay connected - but if I have starting problems later, I'll start looking at the connectors first.

The female connector that is left has 9 (?) pins in it. Ground one end of your ohm-meter, and touch the outermost two pins on each end of the connector mounted on the covers. One pin at a time!

You should see from 0.5 to 1.7 ohms. Anything else and they are toast. No reading (infinite resistance) means they are burned out.

Replacing them rates as about a 5.5 on the learn-new-cusswords scale. A lot less than pulling a transfer case, and more than washing your cat.

The test for the glowplug relay is simple: ground one end of your voltmeter, turn the key to the on position, and quickly scurry to the front and touch the large exposed post. You should see somewhere near 12volts, and it should go to zero after from 20 seconds to 2 minutes. Anything else and replace the relay. (Ignore the two small posts. The other covered post is the +12v feed from the battery.)

Get the part# GPR109 (Not the more expensive GPR110) from NAPA. Cost me $33. It has a bit different mounting tabs, but fits after a little fiddling.

I actually ended up only replacing four on one side, as I had three good ones on the other. She starts great now in 20-30 degree temps.

Good luck

Flinch