bad glow plugs or relay?

[90f250]

I've noticed on my truck that it doesn't matter if its cold or not, thhe wts light doesn't. come on, and the cycle time is about 2 eonds...every single time,?i have to cycle my key about 15 times...and then it hitbme that my old 6.9 cycled about 15 seconds initially ..and this doesn't

 

[OLDBULL8]

Check for 12 VDC on the battery side of the relay, if ya got it, then hook a VOM to the GP side, check for 8 to 12 VDC, if ya got it, relay is good, your GP's are then bad. Replace GP's with ZD9 Motorcraft/Beru for best life and results if needed.

 

[90f250]

Nice little.write up...ill have to try that tomorrow after work..thank you

 

[90f250]

Well either my relay is bad or my method of testing isn't good enough but being by my self i can't reach in and turn the key while holding the test prongs on it..

 

[90f250]

A question on this though...if my relay is bad..how would my gp's even come on?

 

[Zaggnutt]

Don't think they need to be cycling to have voltage to the relay. Just turn the key on and test. The symptoms you are describing are consistent with one or more bad gps (but don't rule out the relay yet). You can test each one with your voltage tester set to ohms. One tester on top of gp (with cap off, gp still screwed in) one grounded. May need to scratch through gunk on engine block to make a good ground. Ohm will be .01 - .03. I think it can be a little higher but you should see consistency. If ohm meter reads 0 you got a dead one.

In general it is probably best to replace all gps at once IF
1. You can afford it
2. You don't know what brand of gp is in there
3. They are not Motorcraft / Beru

 

[Zaggnutt]

If you can wait for them to ship, scan eBay. Somebody was just selling gps for $5 a piece which is roughly half price. Also, I like eBay better than say Amazon because you can find free shipping on parts.

 

[OLDBULL8]

You have to check the output voltage of the relay first to see if you have any.

Did you have 12 VDC on the battery side of the relay?

 

[90f250]

I had 12.46 volts on the battery side but i wasn't getting aanything on gp side so i did the best i could at setting my vom on my windshield and putting the test prongs on the gp side and grouund then got in the truck and cycled to see if it made a difference in voltage but i ddont think i had good enough connections... regarddless I don't think it could be bad glow plugs if the truck fires right up after i cycle it a few times, basically its not getting the "initial burn" ..and it leads me to believe the module under the solenoid is the bad part, i say that because the solenoidd clicks and everything and IMO if the solenoid itself went bad it either wouldn't click or would stay engaged which would either burn up the glow plugs because they were constantly on or wouldn't. send any power to them at all..thats my opinion as i have a general understanding pf how a solenoid works but I'm no pro so i could be wrong, regardless I'm going to order the relay assembly today and hopefully put it on friday since indiana should have a decent day friday...

 

[Zaggnutt]

I had 12.46 volts on the battery side but i wasn't getting aanything on gp side so i did the best i could at setting my vom on my windshield and putting the test prongs on the gp side and grouund then got in the truck and cycled to see if it made a difference in voltage but i ddont think i had good enough connections... regarddless I don't think it could be bad glow plugs if the truck fires right up after i cycle it a few times, basically its not getting the "initial burn" ..and it leads me to believe the module under the solenoid is the bad part, i say that because the solenoidd clicks and everything and IMO if the solenoid itself went bad it either wouldn't click or would stay engaged which would either burn up the glow plugs because they were constantly on or wouldn't. send any power to them at all..thats my opinion as i have a general understanding pf how a solenoid works but I'm no pro so i could be wrong, regardless I'm going to order the relay assembly today and hopefully put it on friday since indiana should have a decent day friday...

You have a bad glow plug. Just my $.02. Relay is not bad or it wouldn't cycle click. Controller underneath rarely malfunctions and would probably affect your relay.

Your glow plugs are connected together. If one is bad the relay senses it (I think it's the voltage, but you would have to do some research as I don't recall)

1 bad glow plug will cause the problem you are describing. It happened to me. It is a fact not a guess.

 

[OLDBULL8]

You have a bad glow plug. Just my $.02. Relay is not bad or it wouldn't cycle click. Controller underneath rarely malfunctions and would probably affect your relay.

Yes, the relay could be bad, even tho it energizes, the contact within it could be carboned up and not passing enough current/voltage to make the GP's glow (hot enough). That is why it's necessary to know what the voltage output is to make a determination if the relay is good or bad.

Your glow plugs are connected together. If one is bad the relay senses it (I think it's the voltage, but you would have to do some research as I don't recall)

The relay does not sense anything. It's the controller that senses, resistance and ambient temperature as to how long the glow cycle is.

1 bad glow plug will cause the problem you are describing. It happened to me. It is a fact not a guess.

From what 90F250 is saying, I believe the relay contacts are burnt. Relays are a lot cheaper than a controller, Azone stocks them as many other Auto stores, but you have to make sure you ask for one for a GP controller, they are different internally from a starter relay.
The initial current is 196 Amps at 12 VDC with all good GP's, then reduces to 135 Amps and 8.5 VDC for the duration of the cycle, however long that may be. If the relay cannot pass that amount of current, then it will short cycle.

 

[Zaggnutt]

From what 90F250 is saying, I believe the relay contacts are burnt. Relays are a lot cheaper than a controller, Azone stocks them as many other Auto stores, but you have to make sure you ask for one for a GP controller, they are different internally from a starter relay.
The initial current is 196 Amps at 12 VDC with all good GP's, then reduces to 135 Amps and 8.5 VDC for the duration of the cycle, however long that may be. If the relay cannot pass that amount of current, then it will short cycle.

I apologize for the mistake. 1 bad glow plug will still cause the short cycle. I agree with OLDBULL's assessment regarding testing. Testing will determine where to spend your money.

 

[90f250]

Ok i bought some aligator clips and wire to extend the leads...worked great, i have 9-10 volts while cycling kkey so i have a good relay? Which means bad glow plug correct? Now i need to test them

 

[BDOGONE]

Quick test: Use a cheap test light (bulb style not led) hook the clip to bat. positive terminal, remove the wire from a glow plug and touch the tester to the actual glow plug. If it lights up that one is good. Wiring must be disconnected from the glow plug to be tested. It's usually one or two dead ones.


Sent by wing, prayer & ATT

 

[Zaggnutt]

Ok i bought some aligator clips and wire to extend the leads...worked great, i have 9-10 volts while cycling kkey so i have a good relay? Which means bad glow plug correct? Now i need to test them

Does your voltmeter have an ohm setting or is it volts only?